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Case Study: Cost-Benefit Analysis of Renewable Energy Sources

In this article, we explore the European Union’s commitment to renewable energy and the rise of ‘prosumer’ economics, as well as the efficient land use and environmental impact of anaerobic digestion plants (ABPs) for renewable energy production. We will also examine a case study in Montenegro, highlighting the effectiveness of renewable energy investments in reducing greenhouse gas emissions and the pressing need for cost-effective emission reduction strategies within the energy sector.

Renewable energy refers to environmentally friendly sources of energy that can be naturally replenished. They have the advantage of causing minimal harm to the environment while producing electricity. Wind , solar , hydroelectric , and geothermal sources are examples of renewable sources that generate electricity. They are not only cleaner but also cheaper and easier to produce than any fossil fuel. 

Although there are expenses associated with harnessing these resources, their affordability enables scientists and engineers to exploit them effectively and facilitate the green transition.

EU’s Drive Towards Renewable Energy and ‘Prosumer’ Economics

The 27-member bloc conducted financial evaluations of green projects to determine their feasibility. It looked at things like cash flow (how money moves in and out), payback time (when you make back your initial investment), net present value (what future money is worth today), and internal rate of return (how profitable the investment is).

The analysis , published in 2021, found that if regular electricity users start generating their own power using renewable sources, they can become so-called “prosumers”: individuals who both consume and produce their own electricity using renewable sources. This approach can contribute to energy savings by reducing the distance electricity must travel from power plants to homes. The profitability of becoming a prosumer depends on factors such as setup costs, the amount of power consumed at home, and the surplus power sold back to the grid.

ABP Land Efficiency and Environmental Impact Assessment

A decade ago, a team of researchers at the University of Montenegro collaborated with the Ministry of Transport and Maritime Affairs to create a mode to evaluate and enhance the land requirements of anaerobic digestion plants (ABPs) while simultaneously minimising their environmental footprint. This comprehensive model was tailored to account for the distinct land requirements linked to ABPs, ensuring efficient land utilisation in the process.

To gauge the efficiency of land use in ABPs, these were compared to other energy sources like photovoltaic panels, onshore wind systems, and thermal power stations. The analysis revealed that ABPs are relatively efficient in terms of land utilisation for energy production.

Beyond land use, the evaluation of ABPs extends to their broader environmental footprint. This assessment encompasses factors such as greenhouse gas emissions, consumption of non-renewable resources, and the potential impacts of ABPs on local communities and ecosystems.

Matching the right renewable energy system to your energy needs is essential for both cost savings and environmental benefits and ensuring this alignment is crucial to maximise the associated benefits of using renewable energy sources.

You might also like: Renewables Will Dominate World’s Electricity Demand Through 2025, IEA Report Says

Assessing GHG Reduction in Montenegro: Analysis and Limitations

The aforementioned 2021 analysis includes a case study in Montenegro which focuses on the country’s significant dependence on imported liquid and gaseous fossil fuels. This reliance is closely linked to Montenegro’s energy sector, which heavily utilises imported fossil fuels for energy production, resulting in substantial greenhouse gas emissions (GHGs), a primary contributor to global warming.

Montenegro has significantly bolstered its investments in renewable energy sources from 2016 to 2021, resulting in a remarkable 20% reduction in GHG emissions. These notable achievements are particularly prominent within the energy sector. Currently, renewable energy sources contribute to around 35% of Montenegro’s overall energy production. Moreover, the nation has strategically crafted and implemented various initiatives aimed at elevating energy efficiency and curbing emissions, reinforcing its commitment to a sustainable and eco-friendly future.

To assess the economic feasibility of GHG reduction measures, the scientists behind the study conducted an economic analysis. Using a dataset spanning a decade, they calculated the present value of monetary units. Key economic indicators, such as net present value and benefit-cost ratio, were employed to evaluate the cost-effectiveness of various measures.

The analysis underscores the substantial positive impact of implementing economic and structural changes within the metal industry. These changes likely encompass improvements in energy efficiency, emissions reductions from industrial processes, and a potential transition to cleaner energy sources within the metal industry. As a result, emissions associated with this sector have significantly decreased, making a substantial contribution to the overall reduction in greenhouse gas emissions. However, the study also emphasises a crucial point: there is a pressing need for further greenhouse gas emissions reductions, particularly within the energy sector. This indicates that while progress has been made in the metal industry, there is still a need for additional emissions reductions at a broader scale, which may encompass the entire country or even global efforts.

This might involve a shift towards cleaner and more sustainable energy sources, enhanced energy efficiency practices, and the implementation of policies promoting renewable energy generation.

The study does have limitations, notably regarding the accuracy of investment cost estimates for certain measures. Future research should include cluster analysis to group measures based on their emissions impact. Additionally, addressing data limitations and conducting more precise analyses in specific areas of the research is essential.

Renewable energy resources offer an environmentally friendly and cost-effective solution for cleaner electricity generation. The efficient land use in (ABPs) for renewable energy production is a promising aspect, as ABPs demonstrate relatively low land requirements compared to other energy sources. However, it is crucial to assess their broader environmental impact, including greenhouse gas emissions and community effects. 

The case study in Montenegro highlights the effectiveness of renewable energy investments in reducing emissions, emphasising the need for cost-effective emission reduction strategies in the energy sector. Despite study limitations, these findings underscore the importance of advancing cleaner and sustainable energy systems globally, balancing power needs with environmental preservation.

You might also like: 7 Interesting Renewable Energy Facts

About the Author

Karnik Aswani

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renewable resources in buildings case study

a case study of two upcoming renewable energy alternatives that can be integrated into the building for optimal energy efficiency of the building. Read less

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• 1. BIOMASS AS A RENEWABLE RESOURCE: Application in Buildings case study
• 3. The most common biomass used is “woody” biomass comprising of trees and woody plants and leaves, grown in a forest, woodland, or rangeland environment that are the by-products of forest management. The biomass is typically burned as chips on a large-scale and wood pellets for small-scale applications. KETCHIKAN FEDERAL BUILDING Location: Ketchikan, Alaska Purpose: Hot water distribution system Application chosen: biomass heating technology by means of wooden pellet boiler system Boiler specifications: 1 million BTUs per hour Efficiency: 85.6%
• 6. METHODOLOGY The wood pellets are stored in a silo outside of the building and are augured into the building when the low-level signal is given from the fuel bin level sensor. The pellets automatically replenish the fuel bin and the conveyor stops when the upper level sensor is triggered.  The fuel is burned efficiently using staged combustion air injection. The hot flue gas travels through a bank of tubes where the heat is transferred to the water that surrounds the tube bundle. This is known as a “fire tube” design.  This boiler design is equipped with an automated mechanical cleaning system that periodically removes ash build-up from the tubes. This is done online to avoid interruptions in the heating process.
• 7. ENERGY ANALYSIS
• 8. CONCLUSION  environmental friendly system of heat generation. No wastage of fuels like diesel  additional energy savings in a building. Lower emissions of co2 Initial cost of execution is high. Can be installed only in places abundant with biomass sources
• 9. GEOTHERMAL ENERGY RESOURCE
• 11. GALT HOUSE EAST HOTEL AND WATERFRONT OFFICE BUILDINGS Location: Louisville, Kentucky Tag: largest Geothermal Heating and cooling system in the US Project description: 4,500 tons Geothermal Heat Power system 67 MM btu/hour heating
• 12. Heating and air conditioning is provided for 750 square foot hotel rooms, 1800 square foot apartments, square feet of meeting rooms, ballroom and public space, and square feet of office building totalling 1,740,000 square feet. The system can extract 2800 gallons per minute of ground water from four wells at and can either remove energy from the well water for heating or add heat to the well water from the air conditioning. The water is then discharged into a storm water system.  Construction and operation costs are extremely low compared to other systems commonly installed in a similar complex.
• 13. SYSTEM DESIGN For the Galt House East Hotel, ground water at 58'F is pumped into a 140,000 gallon reservoir under the mechanical room. Water from the reservoir is circulated through plate/ frame heat exchangers. This separates the ground water from closed loop circulation systems in the buildings. The closed loops are connected to water source heat pumps which can absorb heat from the loop water or reject heat into the loop water, depending on the requirement of that space. Any space can have heating or cooling at any time. During spring and fall, the use of thermal storage allows the controls to shut down the well pumps (sometimes for as long as a week). The Btu's stored in the reservoir during the day from air- conditioning can be used to heat the building at night
• 14. The pumps normally operate at 25% to30% of full load current due to water regulating valves and variable frequency drives on the circulating pumps. With 375hp pumps (three- 100hp pumps and one-75hp pump) running at70% less than full load, savings are $111,502 per year. Chemical emissions from cooling tower bleed and boiler blow down also are eliminated by the geothermal heat pump system Due to the reduction in power required, principle emissions from the power station were reduced by 7,870,0001b per year of COr; 44,000 Ib per year of SOr; 33,000 lb per year of NO,; and 5,500 lb per year particulate. EVALUATION STATISTICS
• 15. Comparative test results between Galt east hotel with the geothermal heating and cooling and Galt hotel with conventional heating and cooling systems

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The U.S. Department of Energy (DOE) Building America program has developed a series of technology-specific case studies and best practices guides that may be applicable to all climate zones.

Technology Solutions for New and Existing Homes

These case studies from Building America research teams and national laboratories describe energy-saving solutions for both new and existing homes, classified into four categories.

Building Envelope Solutions for Walls, Foundations, and Roofs

Project:  Advanced Extended Plate and Beam Wall System in a Cold-Climate House Technology Focus: Building envelope Profile: This case study describes the highly insulated (high-R) light-frame wall system, called the extended plate and beam (EP&B), for use above grade in residential buildings. 

Project: Apartment Compartmentalization with an Aerosol-Based Sealing Process Technology Focus: Air-sealing, building envelope Profile: In this case study, the Consortium for Advanced Residential Buildings team demonstrated the automated air-sealing and compartmentalization of buildings through the use of an aerosolized sealant developed by the Western Cooling Efficiency Center at University of California Davis.

Project : Application of Spray Foam Insulation Under Plywood and OSB Roof Sheathing Technology Focus: Insulation, existing homes with unvented cathedralized roofs Profile: Building Science Corporation conducted hygrothermal modeling and explorations of 11 in-service roof systems that used spray polyurethane foam to study the performance of this system for air-sealing in complex assemblies, particularly roofs.

Project: Capillary Break Beneath a Slab: Polyethylene Sheeting Over Aggregate Technology Focus: Foundation, water management Profile: In this project, IBACOS worked with a builder of single- and multifamily homes in southwestern Pennsylvania (climate zone 5) to understand its methods of successfully using polyethylene sheeting over aggregate as a capillary break beneath the slab in new construction.

Project: Cladding Attachment Over Mineral Fiber Insulation Board Technology Focus: Exterior insulation of wood-framed buildings, new and existing homes Profile: In this project, Building Science Corporation studied the performance of mineral fiber insulation sheathing as a viable solution for exterior insulation retrofits, and developed guidance for retrofit assembly for wood-frame roof and walls and for cast concrete foundations.

Project : Cladding Attachment Over Thick Exterior Insulating Sheathing Technology Focus: Exterior insulation, new and existing homes Profile: Building Science Corporation investigated the benefits—and limitations—of adding insulation to the exterior of buildings as an effective means of increasing the thermal resistance of wood-framed walls and mass masonry wall assemblies.

Project: Cold Climate Foundation Wall Hygrothermal Research Facility Technology Focus: Building envelope and wall systems Profile: This case study describes the University of Minnesota’s Cloquet Residential Research Facility in northern Minnesota, which features more than 2,500 ft 2   of below-grade space for building systems foundation hygrothermal research.

Project: Complete and Fully Aligned Air Barrier Technology Focus: Air-sealing, insulation Profile: This research project, conducted by Pacific Northwest National Laboratory , focused on eliminating excessive humidity in the attic of a multi-floor, single-family home that was causing condensation and water damage along the roof and eaves.

Project: Cost Analysis of Roof-Only Air-Sealing and Insulation Strategies on 1-1/2 Story Homes in Cold Climates Technology Focus: Roof, air-sealing, insulation Profile: This project describes the use of the External Thermal and Moisture Management System developed by the NorthernSTAR Building America Partnership for deep energy retrofits. It is effective in reducing energy loss through the building envelope, improving building durability, reducing ice dams, and providing opportunities to improve occupant comfort and health.

Project: Durable Interior Foundation Insulation Retrofits for Cold Climates Technology Focus: Foundations Profile: This approach by the NorthernSTAR Building America Partnership team addresses thermal and moisture management for basements from the interior face of the wall without disturbing the exterior soil and landscaping.

Project: Excavationless: Exterior-Side Foundation Insulation for Existing Homes Technology Focus: Insulation, foundations Profile: This project describes an innovative, minimally invasive foundation insulation upgrade technique on an existing home that uses hydrovac excavation technology combined with a liquid insulating foam. Cost savings over the traditional excavation process ranged from 23% to 50%.

Project: Field Trial of an Aerosol-Based Enclosure Sealing Technology Technology Focus: Insulation Profile: This project demonstrated a new method for sealing building envelope air leaks using an aerosol sealing process developed by the Western Cooling Efficiency Center at the University of California-Davis, which is part of the U.S. Department of Energy’s Building America research team Alliance for Residential Building Innovation. Developed in a laboratory setting, this process was applied to six single-family homes in this study and involved pressurizing a building while applying an aerosol sealant to the interior. 

Project: High-Performance Walls in Hot-Dry Climates Technology Focus: Walls Profile: In this project, the Alliance for Residential Building Innovation team worked with California builders to to implement wall assemblies meeting a U-value lower than 0.050 Btu/h-ft2-°F. The team observed and documented construction methods and obtained construction costs from builders to inform cost estimates for a range of advanced wall system types and insulation types.

Project: Hygrothermal Performance of a Double-Stud Cellulose Wall Technology Focus: Walls Profile: In this project, the Consortium for Advanced Residential Buildings research team monitored a double-stud assembly in climate zone 5A to determine the accu­racy of moisture modeling and make recommendations to ensure durable and efficient assemblies..

Project: Initial and Long-Term Movement of Cladding Installed Over Exterior Rigid Insulation Technology Focus: Insulation, walls Profile: This research conducted by Building Science Corporation evaluated the system mechanics and long-term performance of the use of wood furring strips attached through the insulation back to the structure to provide a convenient cladding attachment location for exterior insulation.

Project: Innovative Retrofit Foundation Insulation Strategies Technology Focus: Foundation insulation Profile: In this project, the NorthernSTAR Building America Partnership evaluated a retrofit insulation strategy for foundations that is designed for use with open-core concrete block foundation walls. The three main goals were to improve moisture control, improve occupant comfort, and reduce heat loss..

Project: Insulated Siding Retrofit in a Cold Climate Technology Focus: Exterior building envelope Profile: In this study, the Building America Partnership for Improved Residential Construction worked with Kinsley Construction Company to evaluate the real-world performance of insulated siding when applied to an existing home.

Project : Insulating Concrete Forms Technology Focus: Building envelope Profile: This Pacific Northwest National Laboratory project investigated insulating concrete forms—rigid foam, hollow walls that are filled with concrete for highly insulated, hurricane-resistant construction.

Project: Interior Foundation Insulation Upgrade - Madison Residence Technology Focus: Building envelope Profile: This basement insulation project included a dimple mat conveying inbound moisture to a drain tile, airtight spray polyurethane foam wall and floor insulation, and radiant floor heat installation..

Project: Interior Foundation Insulation Upgrade - Minneapolis Residence Technology Focus: Building envelope Profile: This interior foundation project employed several techniques to improve performance and mitigate moisture issues: dimple mat; spray polyurethane foam insulation; moisture and thermal management systems for the floor; and paperless gypsum board and steel framing.

Project: Investigating Solutions to Wind Washing Issues in Two-Story Florida Homes; Phase 2 - Southeastern United States Technology Focus: Attic-floor cavity intersections Profile: The Building America Partnership for Improved Residential Construction team investigated wind washing in 56 homes and developed recommendations for cost-effective retrofit solutions and information that can help avoid these problems in new construction.

Project : Moisture Durability of Vapor Permeable Insulation Sheathing Technology Focus: Exterior insulation, existing homes with vapor open wall assemblies Profile :   The Building Science Corporation team researched some of the ramifications of using exterior, vapor permeable insulation on retrofit walls with vapor permeable cavity insulation.

Project : Moisture Management of High-R Walls Technology Focus: Exterior insulation, existing homes with vapor open wall assemblies Profile: This project by the Building Science Corporation team focuses on how eight high-R walls handle the three main sources of moisture—construction moisture, air leakage condensation, and bulk water leaks.

Project: Monitoring of Double-Stud Wall Moisture Conditions in the Northeast Technology Focus: Exterior insulation Profile: Building Science Corporation monitored moisture conditions in double-stud walls from 2011 through 2014 at a new production house; three double stud assemblies were compared..

Project : Predicting Envelope Leakage in Attached Dwellings Technology Focus: Building envelope, multifamily housing Profile: The Consortium for Advanced Residential Buildings team analyzed blower door test results from 236 attached dwelling units in 17 apartment complexes, in efforts to create a simplified tool for predicting air leakage to the outside in attached housing.

Project : Preventing Thermal Bypass Technology Focus: Fully aligned air and thermal barriers Profile: This project highlights the importance of continuous air barriers in full alignment with insulation to prevent thermal bypasses and achieve high energy performance, and recommends use of ENERGY STAR's Thermal Bypass Inspection Checklist.

Project: Project Overcoat: Airtightness Strategies and Impacts for 1-1/2 Story Homes Technology Focus: Building envelope; roof/attic air-seal and insulation Profile: The NorthernSTAR team studied the effectiveness of the External Thermal Moisture Management System as a solution for improving airtightness in a roof-only application and compared the results to more than 250 roof-only, interior-applied energy retrofits on 1-½ story homes.

Project: Stand-Off Furring in Deep Energy Retrofits Technology Focus: Exterior wall envelope Profile: This research project, conducted by IBACOS and GreenHomes America, investigated cost-effective deep energy retrofit solutions for improving the building shell exterior while achieving a cost-reduction goal, including reduced labor costs to reach a 50/50 split between material and labor..

Project : Stud Walls with Continuous Exterior Insulation for Factory Built Housing Technology Focus: Walls for factory built housing Profile :  This profile describes the Advanced Envelope Research project, managed by ARIES Collaborative , which will provide factory homebuilders with high-performance, cost-effective alternative envelope designs that will meet stringent energy code requirements.

Project: Taped Insulating Sheathing Drainage Planes Technology Focus: Building envelope Profile: The energy efficiency-based financial benefits of adding exterior insulation are well accepted by the building industry, and using exterior insulation as the drainage plane is the next logical step. This project by Building Science Corporation focuses on the field implementation of taped board insulation as the drainage plane in both new and retrofit residential applications.

Low-Load Heating, Ventilating, and Air Conditioning

Project:  Supplemental Ductless Mini-Split Heat Pump in the Hot-Humid Climate Technology Focus: HVAC Profile: In this project, the Building America Partnership for Improved Residential Construction team studied the effects of mini-split heat pumps in six central Florida homes.

Project:  The Impact of Thermostat Placement in Low-Load Homes in Sunny Climates Technology Focus: Thermostat Placement Profile: In this project, Building America team IBACOS has found that low-load homes (zero energy ready homes) have differing room-to-room load densities and highly variable load densities throughout the day and year because of solar gains and internal gains.

Project: Advanced Boiler Load Monitoring Controls Technology Focus: HVAC Profile: In this project, the Building America team Partnership for Advanced Residential Retrofit installed and monitored an ALM aftermarket controller, the M2G from Greffen Systems, at two Chicago area multifamily buildings with existing OTR control..

Project: Balancing Hydronic Systems in Multifamily Buildings Technology Focus: Space heating Profile: In this project, the Partnership for Advanced Residential Retrofit team and Elevate Energy explored cost-effective distribution upgrades and balancing measures in multifamily hydronic systems, providing a resource to contractors, auditors, and building owners on best practices to improve tenant comfort and lower operating costs..

Project: Boiler Control Replacement for Hydronically Heated Multifamily Buildings Technology Focus: HVAC controls Profile: The Advanced Residential Integrated Solutions Collaborative partnered with Homeowners' Rehab Inc., a nonprofit affordable housing owner, to upgrade the central hydronic heating system in a 42-unit housing development, reducing heating energy use by an average of 19%.

Project : Buried and Encapsulated Ducts Technology Focus: HVAC systems, duct work and attic insulation Profile: In a study of three single-story houses in Florida, the Consortium for Advanced Residential Buildings team investigated the strategy of using buried and/or encapsulated ducts to reduce duct thermal losses in existing homes.

Project: Calculating Design Heating Loads for Superinsulated Buildings Technology Focus: HVAC systems Profile: The Consortium for Advanced Residential Buildings team monitored the energy use of three homes in the EcoVillage community in climate zone 6 to evaluate the accuracy of two different mechanical system sizing methods for low-load homes..

Project: Ducts in Conditioned Space in a Dropped Ceiling or Fur-down Technology Focus: HVAC systems, ducts Profile: This case study examines an inexpensive, quick and effective method of building a fur-down or dropped ceiling chase, which brings the duct system into the interior of the house to reduce air leakage and improve durability and indoor air quality homes.

Project: Ducts Sealing Using Injected Spray Sealant Technology Focus: HVAC duct sealing Profile: In this project, the Raleigh Housing Authority worked with the Advanced Residential Integrated Solutions Collaborative to determine the most cost-effective ways to reduce duct leakage in its low-rise housing units.

Project: Evaluation of Ventilation Strategies in New Construction Multifamily Buildings Technology Focus: HVAC systems Profile: This research effort, conducted by the Consortium for Advanced Residential Buildings, included several weeks of building pressure monitoring to validate system performance of four different strategies for providing make-up air to apartments.

Project: Homeowner's Guide to Window Air Conditioner Installation for Efficiency and Comfort Technology Focus: HVAC systems Profile: This step-by-step guide developed by the National Renewable Energy Laboratory describes proper installation of window air conditioning units, in order to improve energy efficiency, save money, and improve comfort for homeowners.

Project: Hydronic Systems: Designing for Setback Operation Technology Focus: Space heating, water heating Profile: This guide, developed by Consortium for Advanced Residential Buildings , provides step-by-step instructions for heating contractors and hydronic designers for selecting the proper control settings to maximize system performance and improve response time when using a thermostat setback..

Project : Improving Comfort in Hot-Humid Climates with a Whole-House Dehumidifier Technology Focus: HVAC systems, humidity control Profile : Researchers from the Consortium of Advanced Residential Buildings team monitored the operation of two AC systems coupled with a whole-house dehumidifier for a 6-month period, to study how comfort can be improved while reducing utility costs.

Project: Improving the Field Performance of Natural Gas Furnaces Technology Focus: HVAC systems, natural gas furnaces Profile: In this study, the Partnership for Advanced Residential Retrofit team examined the impact that common installation practices and age-induced equipment degradation may have on the installed performance of natural gas furnaces, as measured by steady-state efficiency and AFUE.

Project: Low-Load Space Conditioning Needs Assessment, Northeast and Mid-Atlantic Technology Focus: HVAC Profile: In this project, the Consortium for Advanced Residential Buildings team compiled and analyzed the data from 941 multifamily buildings in the Northeast and Mid-Atlantic regions to outline the heating and cooling design load characteristics of low-load dwellings.

Project :   New Insights for Improving the Designs of Flexible Duct Junction Boxes Technology Focus: HVAC, duct design Profile:  IBACOS explored the relationships between pressure and physical configurations of flexible duct junction boxes by using computational fluid dynamics simulations to predict individual box parameters and total system pressure, thereby ensuring improved HVAC performance.

Project : Optimizing Hydronic System Performance in Residential Applications Technology Focus: Space heating, water heating Profile: In this project, the Consortium for Advanced Residential Buildings team worked with industry partners to develop hydronic system designs that would address performance issues and result in higher overall system efficiencies and improved response times.

Project: Properly Sized and Located Return Air Inlet Technology Focus: HVAC systems, ducts Profile: For this project, Pacific Northwest National Laboratory researchers improved the duct systems in an existing home to increase safety, comfort and energy performance of HVAC equipment.

Project: Raised Ceiling Interior Duct System Technology Focus: HVAC systems, ducts Profile: This project describes a Habitat for Humanity builder’s efforts to construct a home to new DOE Zero Energy Ready Home standards using a fur-up or raised ceiling chase.

Project: Sealed Air Return Plenum Retrofit Technology Focus: HVAC systems Profile: In this project, Pacific Northwest National Laboratory researchers greatly improved indoor air quality and HVAC performance by replacing an old, leaky air handler with a new air handler with an air-sealed return plenum with filter; they also sealed the ducts, and added a fresh air intake.

Project: Selecting Ventilation Systems for Existing Homes Technology Focus: HVAC systems Profile: This research effort by the Consortium for Advanced Residential Buildings team evaluated four different strategies for provide make-up air to multifamily residential buildings in order to help contractors and building owners choose the best ventilation systems.

Project: Steam System Balancing and Tuning for Multifamily Residential Buildings Technology Focus: HVAC systems, steam heating distribution system and controls Profile: The Partnership for Advanced Residential Retrofit team conducted a study to identify best practices, costs, and savings associated with balancing steam distribution systems through increased main line air venting, radiator vent replacement, and boiler control system upgrades.

Project: Ventilation System Effectiveness and Tested Indoor Air Quality Impacts Technology Focus: HVAC systems, whole-building dilution ventilation Profile: The Building Science Corporation tested the effectiveness of various ventilation systems at two unoccupied, single-family lab homes at the University of Texas at Tyler. 

Components for Water Heating and Space Conditioning

Project: Addressing Multifamily Piping Losses with Solar Hot Water Technology Focus: Water heating Profile: Sun Light & Power, a San Francisco Bay Area solar design-build contractor, teamed with Building America partner the Alliance for Residential Building Innovation (ARBI) to study this heat-loss issue. The team added three-way valves to the solar water heating systems for two 40-unit multifamily buildings.

Project: Air-to-Water Heat Pumps with Radiant Delivery in Low Load Home Technology Focus: Water heating Profile: Researchers from Alliance for Residential Building Initiative worked with two test homes in hot-dry climates to evaluate the in-situ performance of air-to-water heat pump systems, an energy efficient space conditioning solution designed to cost-effectively provide comfort in homes with efficient, safe, and durable operation.

Project: Foundation Heat Exchanger Technology Focus: HVAC and water heating Profile: The foundation heat exchanger, developed by Oak Ridge National Laboratory , is a new concept for a cost-effective horizontal ground heat exchanger that can be connected to water-to-water or water-to-air heat pump systems for space conditioning as well as domestic water heating.

Project: Ground Source Heat Pump Research, TaC Studios Residence Technology Focus: Heating and cooling systems Profile: This case study describes the construction of a new test home that demonstrates current best practices for the mixed-humid climate, including a high performance ground source heat pump for heating and cooling, a building envelope featuring advanced air sealing details and low-density spray foam insulation, and glazing that exceeds ENERGY STAR requirements.

Project: Heat Pump Water Heater Retrofit Technology Focus: Water heating Profile: In this project, Pacific Northwest National Laboratory studied heat pump water heaters, an efficient, cost-effective alternative to traditional electric resistance water heaters that can improve energy efficiency by up to 62%.

Project: Long-Term Monitoring of Mini-Split Ductless Heat Pumps in the Northeast Technology Focus: Mini-split heat pumps Profile: In this project, Building Science Corporation evaluated the long-term performance of mini-split heat pumps (MSHPs) in 8 homes during a period of 3 years. The work examined electrical use of MSHPs, distributions of interior temperatures and humidity when using simplified (two-point) heating systems in high-performance housing, and the impact of open-door/closed-door status on temperature distributions..

Project: Performance of a Heat Pump Water Heater in the Hot-Humid Climate Technology Focus: Water heating Profile: For a 6-month period, the Consortium for Advanced Residential Buildings team monitored the performance of a heat pump water heater, discovering that it performed 144% more efficiently than a traditional electric resistance water heater and could save approximately 64% on annual water heating costs.

Project: Replacement of Variable Speed Furnace Motors Technology Focus: HVAC systems Profile: In this project, the Consortium for Advanced Residential Buildings  team tested the Concept 3 replacement motors for residential furnaces in eight homes in and near Syracuse, New York, to test how these brushless, permanent magnet motors can use much less electricity than their permanent split capacitor predecessors.

Project: Replacing Resistance Heating with Mini-Split Heat Pumps Technology Focus: HVAC systems Profile: In this project, the Advanced Residential Integrated Solutions team investigated the suitability of mini-split heat pumps for multifamily retrofits.

Project: Retrofit Integrated Space and Water Heating Field Assessment Technology Focus: HVAC and water heating Profile: The NorthernSTAR team analyzed combined (combi) condensing water heaters or boilers and hydronic air coils to provide high- efficiency domestic hot water and forced air space heating.

Indoor Air Quality Solutions

Project:  Design Guidance for Passive Vents in New Construction, Multifamily Buildings Technology Focus: Passive vents Profile: In this project, Consortium for Advanced Residential Buildings constructed the following steps, which outline the design and commissioning required for these passive vents to perform as intended.

Project: Air Leakage and Air Transfer Between Garage and Living Space Technology Focus: Building and garage ventilation Profile: In this project, Building Science Corporation worked with production homebuilder K. Hovnanian to conduct testing at a single-family home to measure the garage and house air leakage and pressure relationships and the garage-to-house air leakage.

Project: Combustion Safety for Appliances Using Indoor Air Technology Focus: HVAC systems and appliance safety Profile: In this case study, the Partnership for Advanced Residential Retrofit team provides guidance on how to assess and carry out the combustion safety procedures for appliances and heating equipment that uses indoor air for combustion in low-rise residential buildings.

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​ Introduction To Energy Resources  ​

 guess the energy source ​,   ​ quick case study   - fuelwood in ledc's  ​, ​case study h.e.p - china .

Case Study Thermal Power Station - England

Environmental Studies

Lesson 6. ENERGY RESOURCES

• The very original form of energy technology probably was the fire, which produced heat and the early man used it for cooking and heating purposes.
• Wind and hydropower has also been used. Invention of steam engineers replaced the burning of wood by coal and coal was further replaced by oil.
• The oil producing has started twisting arms of the developed as well as developing countries by dictating the prices of oil and other petroleum products.
• Energy resources are primarily divided into two categories viz. renewable and non-renewable sources.
• Renewable energy resources must be preferred over the non-renewable resources.
• It is inevitable truth that now there is an urgent need of thinking in terms of alternative sources of energy, which are also termed as non-conventional energy sources which include:
• Solar energy needs equipments such as solar heat collectors, solar cells, solar cooker, solar water heater, solar furnace and solar power plants .
• Wind energy
• Hydropower, Tidal energy, ocean thermal energy, geothermal energy, biomass, biogas, biofuels etc.
• The non renewable energy sources include coal, petroleum, natural gas, nuclear energy.
• 69% is from coal (thermal power),
• 25% is from hydel power,
• 4% is from diesel and gas,
• 2% is from nuclear power, and
• Less than 1% from non- conventional sources like solar, wind, ocean, biomass, etc.
• Accelerated exploitation of domestic conventional energy resources, viz., oil, coal, hydro and nuclear power;
• Intensification of exploration to achieve indigenous production of oil and gas;
• Efficient management of demand of oil and other forms of energy;
• To formulate efficient methods of energy conservation and management;
• Optimisation of utilisation of existing capacity in the country
• Development and exploitation of renewable sources of energy to meet energy requirements of rural communities;
• Organisation of training for personnel engaged at various levels in the energy sector.
• Government private partnership to exploit natural energy resources
• The resources that can be replenished through rapid natural cycles are known as renewable resource.
• These resources are able to increase their abundance through reproduction and utilization of simple substances.
• Examples of renewable resources are plants (crops and forests),and animals who are being replaced from time to time because they have the power of reproducing and maintain life cycles.
• Some examples of renewable resources though they do not have life cycle but can be recycled are wood and wood-products, pulp products, natural rubber, fibres (e.g. cotton, jute, animal wool, silk and synthetic fibres) and leather.
• In addition to these resources, water and soil are also classified as renewable resources. Solar energy although having a finite life, as a special case, is considered as a renewable resource in as much as solar stocks is inexhaustible on the human scale.
• The resources that cannot be replenished through natural processes are known as non-renewable resources.
• These are available in limited amounts, which cannot be increased. These resources include fossil fuels (petrol, coal etc.), nuclear energy sources (e.g. uranium, thorium, etc). metals (iron, copper, gold, silver, lead, zinc etc.), minerals and salts (carbonates, phosphates, nitrates etc.).
• Once a non-renewable resource is consumed, it is gone forever. Then we have to find a substitute for it or do without it.
• Non-renewable resources can further be divided into two categories, viz. Recyclable and non-recyclable

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• ORIGINAL ARTICLE
• Open access
• Published: 06 March 2017

A case study of a procedure to optimize the renewable energy coverage in isolated systems: an astronomical center in the North of Chile

• H. Abos 2 ,
• M. Ave   ORCID: orcid.org/0000-0001-7386-4828 1 &
• H. Martínez-Ortiz 2  

Energy, Sustainability and Society volume  7 , Article number:  7 ( 2017 ) Cite this article

11k Accesses

2 Citations

Metrics details

Renewable energy resources show variabilities at different characteristic time scales. For a given resource and demand pro le, there is an absolute maximum achievable coverage (when limiting the fraction of energy lost during production and delivery to a reasonable value). To reach larger coverage factors, two plausible paths can be taken: a mix of resources with different time variabilities and/or an energy storage system. The case treated in this paper is the electricity supply of an Astronomical Center in the North of Chile. The economical feasibility of both possibilities is explored and compared to a grid connected alternative.

First, data from local weather stations was collected to have a realistic evaluation of the variability of the solar/wind resource at all time scales. Then, we developed a scalable design of a solar/wind plant and a pumped hydro energy storage system. The free parameters of the design are the maximum installed power for each resource and the capacity of the storage system. Finally, the electricity production is calculated to determine the coverage factor and losses for different values of these parameters.

We found that a coverage factor of 64% is economically feasible for systems without storage. The associated total losses are 24%. To reach larger coverage factors is not economically possible and a storage system must be introduced. If this is done, there is a quantum increase of the total cost of about 30%. However, losses are reduced to about 5% and the coverage factor reaches almost 90%. The cost increase is marginally economically feasible, but it has some other advantages: the consumer is independent of the volatility of electricity prices, and is more sustainable.

The time variability of renewable energy resources difficults reaching coverage levels larger than 60%. Energy storage systems are a requirement. Periods of zero net production seem unavoidable unless the renewable energy and storage system are largely overdimensioned. Back up systems based on fossil fuels seem to be unavoidable. Both the energy storage and back up system add an extra cost that has to be paid if such high coverage levels are a requirement.

The case treated in this paper is the electricity supply of an Astronomical Center in the North of Chile. The ESO is the European Organization for Astronomical research in the Southern hemisphere. It operates the VLT (very large telescope), located at Cerro Paranal in the Atacama desert, North of Chile. The E-ELT (European extremely large optical/infrared telescope) in Cerro Armazones (20 km away from Cerro Paranal) is in advanced design phase and will be the largest optical telescope in the world. Finally, the CTA collaboration (Cherenkov Telescope Array) has chosen the Armazones-Paranal site for construction of its Southern Observatory.

When the two new observatories enter in operation, the peak power demand of the Armazones-Paranal site is estimated to be ∼ 8.5 MW and the total annual energy consumption ∼ 70 GWh. Currently, the VLT is generating its own electricity using fossil fuel-based generators.

The two main characteristics of this consumption center are the strong requirements on the stability of the electricity supply, and the relatively large power demanded. Due to these two factors, the use of liquid fossil fuels is economically un-viable. The only two non-renewable solutions plausible are connection to the Chilean national grid or self production of electricity using generators run with natural gas from a nearby pipeline.

The main renewable energy resources available at the site are wind and solar. In this work, we consider a wind-solar PV plant with Pumped Hydro Energy Storage (PHES). We calculate the coverage factor for different values of total Power, Maximum Energy Storage and wind to solar fraction to find energy systems that maximize coverage but with costs below the non-renewable energy solutions. Embedded in this procedure is the fact that renewable energy time variability can be diminished by considering a mixture. An important ingredient of this procedure is the relative cost of each technology. Government estimates are taken when possible.

Additionally, a concentrated solar power (CSP) plant with thermal energy storage is analyzed. This technology is considered separately since the storage system cannot be used by the wind farm.

The design of the systems is not detailed but all sources of inefficiencies are taken into account. The wind and solar input data used is from local weather stations, which provides realistic time series that account for all possible sources of the variability of the resources. Overall, the estimates of electricity production and cost are as realistic as possible so they can be used as a guide if such energy systems are eventually implemented. The total cost of each system includes operation and maintenance over the 25 year lifetime of the astronomical center.

The paper is organized as follows: in “ Energy demand ” section, the energy demand is described; in “ Non-renewable energy systems ” section, the non-renewable energy systems and their cost are analyzed; in “ Renewable energy resources available in the site: solar and wind ” section, the solar and wind data used in our calculations is described; in “ Renewable energy systems ” section, the methodology to calculate the time series of electricity production for the Wind-Solar PV plant with PHES is presented, together with a modular design of each of the subsystems and their cost; in “ Results ” section, an algorithm to find the optimum system is presented and compared to the non-renewable energy alternatives. The CSP with thermal storage design and cost are presented in the Appendix .

Energy demand

The energy demand of the VLT is known [ 1 ]. The power demand changes from day to night but is rather constant along the year (less than 5% variability). The projected E-ELT (CTA) consumption is taken from ESO estimates [ 2 ]. All the sub-systems, including lodging, offices and workshops are included. A simplified model is adopted: a constant power with different day/night values. The start/end for day/night will be calculated using the sunrise and sunset, even though the start/end of astronomical observations is typically later/earlier.

Table 1 shows a summary of the site energy demand. Night consumption is smaller than day for the E-ELT and VLT due to the strict thermal control system.

All observatories work in slow tracking mode during the night. In between observational windows, telescopes are re-positioned to track new objects. The instantaneous power required for re-positioning is large compared to the average power: 700, 3200, and 2000 kW for the VLT, CTA, and E-ELT compared to 1000, 2750, and 4250 kW. However, the total energy for repositioning is small (<5%). The extra power for repositioning can be supplied by energy storage systems with extremely fast responses like flywheels, STATCOMs or a battery system.

Non-renewable energy systems

Connection to the chilean electrical network.

The grid connection alternative envisages the connection of the Armazones-Paranal site to the Paposo substation. It requires the construction of a ∼ 60 km 66 kV line, one 220–66 kV transformer (at Paposo) and one 66–23 kV substation (located halfway between Cerro Armazones and Paranal). The projected investment cost or CAPEX is 12.5 MUSD ( ∼ 11 M e ). The OPEX is calculated multiplying the total annual energy consumed (70 GWh) by a nominal price. Two cases are considered: no inter-annual increase and 1% inflation.

The electrical network in Chile consist of four independent networks, the two most important being Sistema Interconectado Central (SIC) and Sistema Interconectado del Norte Grande (SING). The electricity market is liberalized but there is a distinction between regulated ( P < 2000 kW) and special clients ( P > 2000 kW). Special clients can negotiate directly electricity prices with the producers and/or produce its own energy. Regulated clients are subject to prices fixed twice a year by the government based on the liberalized market prices. Figure 1 shows the time evolution of the mean market price in Chile for the SING/SIC in Chilean Pesos per kWh and e per MWh [ 3 ]. Prior the 2007 crisis, prices were around 40 e /MWh, and during the last 5 years have been stable around 80 e /MWh with 15% oscillations. This is the nominal price that will be considered in this work.

Time evolution of the mean market electricity price in Chile for the SING/SIC in Chilean Pesos per kWh and e per MWh

Multifuel generators

A 8.5 MW combined cycle gas turbine (CCGT) is considered in this case: it has high efficiencies ∼ 55% and fast time responses. Since there is already a 2.5 MW generator with these characteristics in the site, it will be only necessary to upgrade it with 6 MW more. We consider an investment cost of 1000 e /kW, i.e., a CAPEX of ∼ 6 M e . Natural Gas supplied by Gas Atacama, whose pipeline passes through the middle of the Armazones-Paranal site, can be used to run these generators. The expected connection cost is ∼ 2.5 M e : a gas sub-station, a low capacity (7000 m 3 per day) 5-km pipeline and a low capacity tank for regulation. In total, the CAPEX of the back-up system is 8.5 M e .

The OPEX is mainly due to the purchase of natural gas. The natural gas prices are high in Chile. The projections from the Chilean government are taken to correct the world market prices to the special case of Chile. The following equation is adopted to estimate the time-dependent price of a kWh generated by CCGT:

where C gas is given by (1+ f N years )·9, N years is the number of years since 2015 and f takes into account the interannual increase of prices. We consider two values: f =0.01 and f =0.1. This equation yields 0.07 e /kWh for 2015.

Due to the strong requirements on the stability of the supply, this system is also a requirement for all renewable energy systems considered.

Cost estimation

The total cost normalized to year 0 is estimated using:

where k is the interest rate, 3%. The lifetime of the observatories and the renewable energy system is taken as 25 years. Table 2 shows the results.

Renewable energy resources available in the site: solar and wind

The Armazones-Paranal site is located in the Atacama desert, 130 km south from Antofagasta and 1200 km north of Santiago de Chile. The Cerro Paranal and Cerro Armazones have a height of 2635 and 3000 m respectively, and they are 22 km apart. The Cerro Paranal is 15 km away from the coast.

The topography in the North of Chile is dominated by the Central Andes, characterized by four topographical segments from West to East: the coast mountain range, the central hollow, the pre Cordillera, and the Cordillera. The Armazones-Paranal site is located in the coast mountain range, 20–40 km wide and with mean heights of 1500–2000 m. The coast mountain range falls rapidly into the sea with active segments of sea abrasion where sea cliffs are present and inactive segments where there is an emerged platform.

The climate is typical of a desert region: day/night thermal differences of up to 10 o C , rainfall smaller than 30 mm and relative humidities in the 5–20% range. The average temperature is ∼ 15 with ∼ 5 o C seasonal variations.

The solar resource

The solar resource is characterized using the 2011 data from a weather station installed in the area [ 4 ]. The measurements available are global and diffuse irradiance in horizontal plane and one axis tracking mode (North-South orientation), temperature. Only 25 days have missing measurements. This data is directly used in the estimation of the electricity production of a solar based renewable energy system. This data contains all sources of time variability and in that sense is more suited for our purpose than satellite based models.

In some special cases, e.g., for missing data periods or to evaluate the inter-annual variability of a wind-solar plant, a simplified model of solar irradiance is used:

where I G is the global solar irradiance incident on a surface that subtends an angle Φ with the sun direction, f d is the fraction of diffuse irradiance and I D is the direct irradiance in the sun direction:

where θ s is the solar zenith angle, I 0 the irradiance when the sun is in the zenith and τ is an atmospheric extinction parameter. Adopting f d =0.05, I 0 =1200 W/m 2 1 and τ =0.1, a good description of the data is found. 2

Figure 2 shows the global irradiance incident on a horizontal and a one-axis tracking surface from data (dashed lines) compared to the model (solid lines) for the 23rd of June 2011. Figure 3 shows the same for the accumulated day irradiance. 34 days out of the 340 analyzed has a predicted irradiance 10% larger than measured (“Cloudy Days”) but only 5 are consecutive.

Global irradiance incident on a horizontal and a one-axis tracking surface from data ( dashed lines ) compared to the model ( solid lines ) for the 23rd of June 2011

Same as Fig. 2 but for the accumulated day irradiance

The temperature is also an important factor that determines the performance of solar plants. The weather station temperature time series is used in our calculations.

The wind resource

Wind and speed direction from the VLT meteo mast is used to characterized the wind resource [ 5 ]. Measurements at 10 and 30 m from the last 15 years exist. Table 3 shows the average wind speeds at 30 m for the last 10 years. Figure 4 shows the wind speed distribution for the year 2011 at 30 m.

Wind speed distribution at 30 m in Cerro Paranal for the year 2011

Renewable energy systems

In this section, the methodology to calculate the time series of electricity production for the wind-solar PV plant with PHES is presented. Then, a modular design of each of the subsystems is described. Finally, the procedure to calculate the cost given any value of installed power, wind to solar fraction and size of the storage system is described.

Electricity production time series: methodology

The following definitions will be adopted:

P P ( t ) MW : time series of power produced by solar/wind plant.

P D ( t ) MW : time series of power demand.

P A ( t ) MW : time series of power available to satisfy the demand (either from wind/solar plant or storage system).

E S and E MSC MWh: storage level and maximum storage capacity.

P to store and P \(_{max}^{to~store}\) : power to store and maximum instantaneous power that the storage system is able to store.

s 1 /s 2 : efficiency of the storage system to store/deliver electricity. It can depend on load.

t 1 /t 2 /t 3 : transport efficiencies (transformer and lines) between solar/wind plant-storage system (t 1 ), storage system-demand site (t 2 ) and solar/wind plant-demand site (t 3 ). t 1 /t 2 /t 3 depends on the location of each subsystem and transmission line type. For our case and using standard calculations they are: 97, 97.5, and 98%.

Time series are calculated in 10 min intervals. If P P > P D energy is stored with efficiency s 1 × t 1 , unless P to store > P \(_{max}^{to~store}\) or the storage system is full. If P P < P D energy is extracted from the storage system with efficiency s 2 × t 2 until depleted. The efficiency t 3 is also applied to the fraction of P P that directly satisfy the demand.

E \(_{loss}^{Stg}\) accounts for the energy lost because of P \(_{max}^{to~store}\) and E MSC . E \(_{loss}^{Eff}\) accounts for losses due to s 1 / s 2 . E \(_{loss}^{Transport}\) accounts for losses in transport. E \(_{loss}^{Avail}\) accounts for availability: it is included assuming that on the 15th day of each month all systems are stopped for maintenance (3.3%). It is only applied to the annual energy production.

E P , E D , and E A are the annual sum P P , P D , and P A . Other definitions:

f cover =E A /E D : energy coverage.

\(f_{loss}^{Stg}\) = E \(_{loss}^{Stg}\) /E P : energy loss due to storage size and storage maximum power.

\(f_{loss}^{All}\) =( E \(_{loss}^{Stg}\) + E \(_{loss}^{Eff}\) + E \(_{loss}^{Transport}\) + E \(_{loss}^{Avail.}\) )/ E P : total energy loss.

Solar PV plant

We present a modular design of a solar PV plant. The unit cells corresponds to ∼ 1 MWp. The components of the Solar PV plant selected are the following:

Solar panels: Jinko Solar JKM300M. This is a silicon poly-crystalline 300 Wp panel. These modules have the IEC61215 certification which is the standard in Europe.

Inverter/transformer: the Sunny Central SC1000MV. This is a central inverter optimal for large system where production is uniform across the array

Trackers: the ExoSun ExoTrackHZ, suitable for large plants deployed in flat areas. This is a one axis tracker (axis orientation North-South).

The number of panels to be placed in series is calculated using: N series = V op,inv / V mpp,panel , where V op,inv is 450–820 V and V mpp,panel is 35–40 V depending on irradiance. This gives between 11 and 23 panels per string . The open circuit voltage of a string ( N series x45 V) should not exceed the maximum operating voltage of the inverter (880 V). For that reason 18 panels per string are chosen. 30 string s will be connected to a tracker forming a block , fulfilling the tracker specifications. All strings within a block are connected in parallel to an inverter. The number of blocks to be connected in parallel to reach the nominal inverter power is given by \(\frac {P_{inverter}}{N_{blocks}\times 30 \times 18 \times P_{nom,panel}}\) . This yields six blocks per inverter, which also complies with the restriction that the short circuit current does not exceed the maximum allowable current of the inverter.

Each string is a 2 x 18 m rectangle. 30 of them are placed consecutively (with a spacing of 7 m) to form a block. The spacing is chosen to minimize shading losses. 3 x 3 blocks are placed side by side to minimize DC cabling forming a unit cell, a rectangle of ∼ 280 x 64 m.

The power produced by the solar PV plant in a given time period is given by:

where I G ( Φ ) is the global solar irradiance on a surface with an incidence angle Φ , I stc the irradiance in standard conditions 1000 W/m 2 , the factors f therm . and f shading take into account the thermal and shading losses that depend on irradiance, ambient temperature and sun position, the factor f cte are losses that have no dependencies on the time period considered. The angle Φ is calculated for each period so the solar vector lies within the plane perpendicular to the aperture. The only exception is when the required solar panel elevation is smaller than what trackers allow (40 o , since trackers can rotate ±50 o ). In that case, the incidence angle is calculated for a fixed elevation of 40 o .

The thermal losses are calculated using:

where g is the thermal losses coefficient (0.4% per o C ), T std is the temperature in standard conditions (25 o C ) and T panel is the panel temperature that can be calculated using:

where T c is the characteristic temperature of the panel, 45 o C in our case, and T ambient is the ambient temperature taken from the weather station.

The shading losses are estimated by geometric calculations for each time period considered. The constant losses are 7%, see Table 4 .

Panel degradation is 20% over 25 years. Only the production of the first year is calculated. To maintain it over 25 years, extra power will be deployed that will be accounted in the OPEX of the plant.

Using the meteo-mast data and a topographic map of the area, we followed the standard procedure to design a wind farm. The software WASP is used to generate a wind resource map (WRG), see Fig. 5 . Then, the OpenWind Software is used to design wind farms with two, five, and ten turbines. The location is 15 km to the west of Cerro Paranal in the Coastal Cliff, where the wind power density is the highest. The wind turbine chosen is the Alstom ECO 80 2.0 Class 2. It is a pitch regulated 2 MW wind turbine, with a hub height of 80 m, a cut-in wind of 4 m/s and a cut-off wind of 25 m/s.

Map of the wind power density to the west of Cerro Paranal. The wind power density is higher in the pink areas . We also show the wind direction rose at the location of the Cerro Paranal. The areas with high wind density on the left correspond to the Coastal Cliff, about 15 km away from the Cerro Paranal

The mentioned software does not provide a time series of the produced electricity. This is a problem for our study: an storage system cannot be dimensioned without them. To overcome this problem, we use the following assumption to characterized the time series:

where P Turbine is the turbine power as a function of air density and wind speed at hub height:

where v 30 ( t ) is the measured temporal series of the meteo mast at 30 m, f vertical is a factor to extrapolate measurements to different heights:

and f horizontal is a factor that takes into account the geographical variations of the wind speed. The value of f horizontal is adjusted so Eq. 8 gives the same duty factor as OpenWind.

The PV and Wind plant requires an electricity based storage system that fulfills the following criteria:

Power: ∼ 10 MW.

Discharge time at output power: more than 12 h.

Response time: ∼ 10–30 min.

Lifetime 25 years.

Efficiency: high, at least 75%.

Technologically mature.

The only technology that matches these criteria is the pumped hydro energy storage (PHES). The site is located in the Atacama desert where water is scarce. Due to the proximity to the coast, there is the possibility to use sea water as storage medium. However, due to the size of the facility and plausible technological and environmental problems, it is advised the use of desalinated water either self produced or bought.

The PHES plant consist in an upper and lower water reservoir connected by penstocks, and a system of turbines and pumps than convert gravitational energy into electricity or vice versa. The system is closed, so filling of the reservoirs has to be done only once. A separate turbine and pumping system is planned, so typical elapsed times to go from pumping to full load generation are of the order of minutes. Water evaporation 4 and filtration of water are important and will be taken into account in the design. P \(_{max}^{to~store}\) is fixed to 14 MW, so hydraulic losses does not severely affect the design.

The hydro power in W is given by:

where ρ is the water density in kg/m 3 , g is the gravity acceleration constant in m/s 2 , Q is the water flow rate through the penstocks in m 3 /s, and δ h n is the net height difference given by:

where δ h g is the gross height difference and δ h ( Q ) are the hydraulic losses in the whole system that depend on the flow rate. The electric power in generation mode is given by:

where η turb and η gen is the efficiency of the turbine (that depends on load) and the generator. The electric power in storage mode is given by:

where η pump and η mot is the efficiency of the pump system (that depends on load) and the motor.

The required value of P e turb / P e pump is 8.5/14 MW.

The design of the system proceeds in two phases:

Site selection.

Plant design.

The site selection implies indirectly choosing two important variables: δ h g and penstock length. The second variable is crucial when determining the hydraulic losses, and is an important contributor to the total cost of the system. As a general rule, larger values of δ h g and smaller penstock length yield smaller investment costs. However, other factors have been analyzed:

Existence of infrastructures like roads and transmission lines.

Existence of hydro resources or possibilities to obtain them.

Earthquake risks.

Detritus removal: short but intense rainfalls can generate detritus removal that can affect the integrity of the PHES.

Topographic maps have been used to choose four possible sites. All sites have similar availability of water/infrastructures and geological risks. Therefore, the site with larger height difference and the smaller penstock length was chosen. Figure 6 shows a detailed topographic map of the site. It is located in the Coastal Cliff, close to the Wind Farm location.

3D map of the selected PHES site together with the elevation contour

Our choice for the turbine system is the use of two Pelton turbines with one injector that can work in parallel to provide the maximum power. The Pelton turbines can work up to 10% of the nominal load, have efficiencies around 90% and are adequate for the site height differences and required nominal flows. The turbines will be coupled to two generators with nominal power 5 MW, AC output voltage of 6 kV and 98% efficiency.

Regarding the pumping system configuration, our choice is the use of multistage centrifugal pumps: 6 of 2 MW and 2 of 0.5 MW. To simplify the calculations an efficiency of 90% for all loads is considered. The motors that drive the pumps work at 6 kV with an efficiency of 98%.

Steel penstocks have rugosities of ∼ 0.6 mm. The hydraulic losses are calculated using standard formulas for different pipe diameters. For each case, the nominal flow rate in production and storage mode is calculated by solving iteratively Eq. 13 /Eq. 14 . The hydraulic losses drop below 5% in both modes at nominal conditions for a tube diameter of 0.85 m. Losses because of other hydraulic components like valves, bypasses, contractions/expansions, etc. are small (10% of Penstock losses) and taken into account. Table 5 gives the final nominal flow rate and hydraulic losses in both modes. Using these calculations the storage efficiencies s 1 and s 2 are calculated.

The penstock wall thickness required to withstand the hydrostatic pressure is given by:

where e s is extra thickness in meters to allow for corrosion, k f is the weld efficiency (0.9), D is the pipe diameter in meters, σ f is the allowable tensile stress in Pascals (1400 kgf/cm 2 , i.e., 1.373 10 5 Pa) and P is the hydrostatic pressure in Pascals. Since the hydrostatic pressure changes from the upper to the lower reservoir, the penstock is built in sections of 100 m with decreasing thickness (10–30 mm). The total weight of the penstock is ∼ 1000 tons.

The surge pressure for the water-hammer effect at the pumping nominal load is 450 m, which would require a substantial increase of the thickness walls that would yield to a doubling of the total penstock weight, i.e. its cost. For that reason, the installation of a surge tower or relief valves is necessary.

The free parameter of the design is the maximum storage capacity, E MSC MWh. For a given value of E MSC , the volume of the water reservoirs is calculated by multiplying the flow rate in generation mode by E MSC /8.5 h, adding a 20% safety margin. In the selected site, there is room for reservoirs with storage capacities up to 1000 MWh.

The reservoirs will be constructed following the scheme of an Earth/Rock filled dam. The depth of the reservoir will be 14 m, leaving 1.3 m between the maximum water level and the top of the dam. The digged material will be reused to build the trapezoidal perimetral dike (3:1), which fixes the dimensions of the reservoir. The surface in contact with the water and the air-water layer is covered by a geotextile cloth.

To build and maintain the upper reservoir it is necessary to construct a 12 km access road. In the case of the lower reservoir there is a nearby access road, so only a short and flat connection to it is necessary. It will be also necessary to build a housing for the electromechanical equipment.

The total cost after 25 years of the wind-solar PV plant with PHES storage is estimated using Eq. 2 . The CAPEX in that equation has the following components:

Solar PV and wind plant: total power installed times a unitary cost of 1,700 e /kW.

PHES: the cost of a PHES system with E MSC =110 MWh is estimated to be 26.4 M e . Table 6 shows a breakdown. The PHES cost for different values of E MSC is estimated using:

where C 1 =3.8 M e is the baseline cost of water and reservoir and C 2 =19.51 M e is the cost of the rest of the subsystems.

Back up system: 8.5 M e .

Electrical infrastructures: 3.5 M e , see Table 7 .

The OPEX has the following components:

Insurance and O&M: we assume 2% of CAPEX with 3% inter annual increase.

Gas purchases: (1− f cover )·70 GWh times the unitary price given by Eq. ??.

Solar PV: the required annual enhancement of the power installed to reach the same nominal production as the first year 5 .

The electricity production is simulated for the following parameters:

P total MW : 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, and 40.

f solar : 0, 0.25, 0.5, 0.75, and 1.

E MSC MWh: 0, 20, 40, 60, 80, 100, 120, 240, 480, 1000.

An example of the time series is shown in Fig. 7 for P total =20 MW, f solar =0.5 and E MSC =100 MWh. For each simulated case, the annual value of f cover and \(f_{loss}^{All}\) is calculated. The left (right) panel in Fig. 8 show an example: f cover ( \(f_{loss}^{All}\) ) as a function of the total installed power for E MSC =0 MWh and three cases of f solar , 0, 0.5, and 1. For this value of E MSC , the optimum system in terms of coverage is neither purely wind or solar, but a mixture. \(f_{loss}^{All}\) for small P total is due to availability and transport.

An example of the time series of electricity production for P total =20 MW, f solar =0.5 and E MSC =100 MWh

f cover and \(f_{loss}^{All}\) as a function of the total installed power for E MSC =0 MWh and three cases of f solar , 0, 0.5, and 1

On the basis of the costs shown in Table 2 , we select two target maximum costs: 100 and 130 M e . For each simulated case, the total cost over 25 years is calculated as in “ Cost estimation ” section. The case with a cost below the target and with maximum coverage is kept. The two cases selected for the two targets are shown in Table 8 . The coverage factors are as large as 64 and 88%. It should be mentioned that the losses for the high cost target are driven by the storage efficiency, transport losses, and availability.

Finally, the case of a concentrated solar power (CSP) plant with thermal energy storage is analyzed. This technology is considered separately since the storage system cannot be used simultaneously by the Wind farm 6 . The design and costs are presented in Appendix . The total cost is 124 M e and f cover 72.5%. This alternative is within the high cost target, but it has lower coverage factor than the case presented in this section.

1 I 0 is only 12% smaller than the irradiance outside the atmosphere (1370 W/m 2 ), which is an indicator of the quality of the site.

2 The electricity production using the model and the raw data for the reference year agrees within 5%.

3 α =0.08 from the ratio of the measurements at 10 and 30 m. A conservatively smaller value is taken: measurements at 10 m can be affected by the surrounding buildings

4 According to our estimations, it can be severe, reducing the water level by almost 3 m per year.

5 It is calculated assuming: PV system prices will decrease at a rate of 20% over 25 years; PV module degradation is 20% over 25 years.

6 Electricity from the Wind Farm would have to be converted into thermal energy. To convert back to electricity the efficiency is given by the steam turbine, ∼ 32%.

Concentrated solar power (CSP) plant with thermal energy storage

The CSP is a technology that needs to be considered when there is plenty available land, the cloudy fraction is small and the fraction of direct irradiance is high. The dessert characteristics of the site fulfill these three criteria. The technology considered in this work is the parabolic trough collectors (PTC), widely considered in a stage of maturity.

In a CSP plant, an oil is heated in the solar field from 293 o C to 393 o C and sent either to the thermal storage system or to a heat exchanger that produces water vapour at 380 o C and 104 bar. The vapour is then conducted to a steam turbine coupled to a generator. After the turbine, the vapour is taken to a condenser and fed again into the loop. Due to the scarcity of water in the site, aerocondensers are considered. The efficiency to convert thermal energy into electricity depends on the nominal power of the turbine and for a 10 MW steam turbine is ∼ 32%.

The solar field is an array of PTCs. The mirrors have a one axis tracking system (North-South) that ensures that at all moments the solar vector lies within the plane perpendicular to the aperture of the collector. Alignment is a strong requirement in PTCs, and also cleaning.

The PTCs have lengths between 100 and 150 m. The 8 module EuroTrough collector with PTR-70 Schott tubes is selected. N series of these modules are placed in series to form a group. N parallel groups are connected in parallel in central feeding configuration to minimize pipe lengths. The separation between rows of collectors is three times the width of the parabola to ensure that annual shadowing losses are below 1%.

The thermal power captured by the collector is given by:

where \(\eta _{opt \phi =0^{0}}~K(\Phi)\phantom {\dot {i}\!}\) is a parameterization of the optical and geometrical losses of the collector, A c is the aperture area, I D is the direct irradiance in W/m 2 at the period considered, F e is a factor that takes into account the dirt in the mirrors (0.95), and P losses are the thermal losses parameterized with its dependence on the temperature difference between the fluid and the ambient, as well as on the direct irradiance and incidence angle.

The collected power can also be written as:

where Q m is the fluid mass flow in kg/s, C p is the specific heat in J/K Kg and T in /T out is the start/final temperature of the fluid. The thermal fluid chosen is an oil called Therminol VP1. Its maximum working temperature is 398 o and solidification temperature is 12 o . This fluid has to be pressurized to 10.5 bar so it is not gas phase at the maximum working temperature. The specific heat and density depends on temperature and is taken from a parameterization provided by the manufacturer.

N series of collectors have to rise the fluid temperature from T in =293 o C to T out =393 o C. The necessary value of Q m is calculated iteratively by equating Eqs. 17 and 18 in 1 m intervals.

The fluid must circulate in a regime turbulent enough to avoid thermal gradients between the external/internal face of the tube that can cause fractures. The optimum value of N series is calculated by imposing a condition on the Reynolds number of the circulating fluid for the time of maximum direct irradiance. In our design, N series must be 4.

The hydraulic losses are calculated for each configuration of the system ( N series , N parallel ) and time period considered using the oil and tube characteristics and ambient conditions. Losses in the pipes that connect the collectors with the heat exchanger and the losses in the pump are also taken into account. 7 .

The required electrical pumping power is given by:

where η m ( ∼ 70%) and η e ( ∼ 99%) are the mechanical and electrical efficiency of the pump.

The electrical power produced by the plant is given by:

where η is the efficiency to convert thermal to electrical energy (32%). The storage efficiencies considered are s 1 = s 2 =96% (Round trip efficiency of 92%). Transport losses are only applicable to t 3 (2%). The availability is included as described before.

The electricity production described in “ Electricity production time series: methodology ” section is calculated in 10 min intervals during a period of 48 hours around the summer solstice. N parallel is increased until f cover =100%. The required value of N parallel is 33. E MSC is given by the maximum storage level during the design period (100 MWh).

The storage system must be able to store 100 MWh, i.e., 312 MWth. This capacity is increased by a safety margin of 8%, i.e., 337.5 MWhth. The temperature in the hot/cold tank corresponds to the temperature of the oil before/after the heat exchanger. Nitrate salt (60% by weight NaNO 3 and 40% KNO 3 ) is considered as storage medium. The mass required can be calculated using:

which yields 8530 tons of salt to store 337.5 MWth. The corresponding volume of the hot and cold tank is different due to temperature. The volume required for the cold/hot tank is 4471 and 4618 m 3 . Fast fluctuations of the solar resource are easily tracked by the thermal storage system by controlling the flow from the solar field that is diverted to the heat exchanger of the storage system.

The electricity production is then calculated for the whole year. The results are shown in Table 9 together with the main design parameters.

A flat area is necessary to ease installation of the solar field. A possible site has been found 10 km away from Cerro Paranal. The access road to the Cerro Paranal passes by the solar field, so no extra civil works are planned. For electrical infrastructures and their cost, see Table 10 .

The investment cost (CAPEX) of the CSP plant is estimated to be 58.5 M e . Table 11 shows the breakdown. The OPEX considered is 2% of the CAPEX with a 3% inter annual increase. The total cost after 25 years normalized to year 0 is 124 M e .

Abbreviations

British thermal unit

Capital expenditure

Combined cycle gas turbine

• Concentrated solar power

Cherenkov telescope array

European extremely large telescope

European southern observatory

Million US dollars

Open software to design Wind Farms

Operating expenditure

Pumped hydro energy storage

• Photovoltaic

Parabolic Trough Collectors

Sistema interconectado central

Sistema interconectado del Norte Grande

Static synchronous compensator

Very large telescope

Wind energy industry-standard software

Wind Resource Map (Power density)

Interest rate

Global solar irradiance in a surface W/m 2

Direct irradiance in the sun direction

Diffuse irradiance in a surface expressed as a fraction of the direct irradiance

Angle subtended by the normal of a surface with the sun direction

Solar zenith angle

Atmospheric extinction parameter

Time series of power produced by solar/wind plant in MW

Time series of power demand in MW

Time series of power available to satisfy the demand in MW

Annual sum P P ,P D and P A E S and E MSC : Storage Level and Maximum Storage Capacity in MWh

Power to store and Maximum Instantaneous Power that the storage system is able to store

Efficiency of the storage system to store/deliver electricity

Transport efficiencies (transformer and lines) between solar/wind plant-storage system (t 1 ), storage system-demand site (t 2 ) and solar/wind plant-demand site (t 3 )

Energy lost during storage operations due to P \(_{max}^{to~store}\) and E MSC

Energy lost during storage operations due to s 1 / s 2

Energy lost due to transport inefficiencies

Energy lost due to operation and maintenance (availability)

E A /E D energy coverage

E \(_{loss}^{Stg}\) /E P , energy loss due to storage size and storage maximum power

(E \(_{loss}^{Stg}\) +E \(_{loss}^{Eff}\) +E \(_{loss}^{Transport}\) +E \(_{loss}^{Avail.}\) )/E P , total energy loss

The irradiance in standard conditions 1000 W/m 2

Watt Peak, solar panel power for I stc

The solar panel temperature in standard conditions (25 o C )

Solar panel losses, thermal, shading and those that do not depend on solar irradiance

Solar panel thermal loss coefficient

Inverter input voltage range

Solar panel volage at maximum power

Wind speed at hub height

Wind speed height coefficient

Air density

Water density

Gravity acceleration constant

Water flow rate through the penstocks in m 3 /s

Net height difference between upper and lower reservoir in a PHES

Gross height difference

Q dependent hydraulic losses

Efficiencies of turbine, generator, pump and motor in a PHES

Hydro power

Electrical power

Penstock diameter

Length of penstock

Penstock weld efficiency

Allowable tensile stress in Pascals

Hydrostatic pressure in penstock

PTC thermal losses

PTC losses due to dirtying

Thermal power captured by a PTC

Optical and geometrical losses of the collector

Specific heat of PTC thermal fluid

Mass flow in kg/s of the thermal fluid

Temperature in/out of the thermal fluid

Towards a Green Observatory. https://www.eso.org/sci/libraries/SPIE2010/7737-73.pdf . Accessed Feb 2017.

The E-ELT construction proposal. http://www.eso.org/public/products/books . Accessed Feb 2017.

Comision Nacional de Energia de Chile. www.cne.cl. Accessed Feb 2017.

Ministerio de Energía de Chile. http://antiguo.minenergia.cl . Accessed May 2015.

European Southern Observatory. http://archive.eso.org . Accessed Feb 2017.

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Acknowledgements

This work would not be possible without the financial support of the CNPq, FAPESP (PROCESSO 2015/15897-1) and the resources of the Instituto de Física de São Carlos. We thank Vitor de Souza for the careful reading of the manuscript, Eduardo Zarza for his guidance with CSP technology, Marcos Blanco for providing the WASP simulations needed to estimate the Wind Resource, Marc Sarazin for his help with the Wind data and ESO water supply, and Natalia Serre for all the information she provided concerning CTA power supply. Finally, we also thank all the Escuela de Organizacion Industrial (EOI) staff for their support.

Authors’ contributions

All authors contributed to the development of the work. The corresponding author prepared the manuscript, but all authors read and approved the final manuscript.

Competing interests

The authors declare that they have no competing interests.

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Abos, H., Ave, M. & Martínez-Ortiz, H. A case study of a procedure to optimize the renewable energy coverage in isolated systems: an astronomical center in the North of Chile. Energ Sustain Soc 7 , 7 (2017). https://doi.org/10.1186/s13705-017-0109-0

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Received : 25 November 2016

Accepted : 10 February 2017

Published : 06 March 2017

DOI : https://doi.org/10.1186/s13705-017-0109-0

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Amazon Net Present Value

Middle east turnaround, pestel case analysis, shared leadership, personalization marketing, channel management, human resource management and artificial intelligence, customer journey design principles & solution, forecasting & risk management in real estate, diamond energy resources net present value (npv) / mba resources.

• Diamond Energy Resources
• Finance & Accounting / MBA Resources

Introduction to Net Present Value (NPV) - What is Net Present Value (NPV) ? How it impacts financial decisions regarding project management?

NPV solution for Diamond Energy Resources case study

At Oak Spring University , we provide corporate level professional Net Present Value (NPV) case study solution. Diamond Energy Resources case study is a Harvard Business School (HBR) case study written by Lena Chua Booth. The Diamond Energy Resources (referred as “Coal Agus” from here on) case study provides evaluation & decision scenario in field of Finance & Accounting. It also touches upon business topics such as - Value proposition, Budgeting, Costs. The net present value (NPV) of an investment proposal is the present value of the proposal’s net cash flows less the proposal’s initial cash outflow. If a project’s NPV is greater than or equal to zero, the project should be accepted.

NPV = Present Value of Future Cash Flows LESS Project’s Initial Investment

Case description of diamond energy resources case study.

Agus Halim, the CEO of PT Diamond Energy Resources Indonesia, a wholly owned subsidiary of an Australian based mining company, was contemplating whether to invest in a new coal mine near East Kalimantan, Indonesia. His consultant had prepared a preliminary acquisition plan that includes a capital budget with verified mineable surface coal reserves and projected coal prices. This acquisition would add to Diamond's coal reserves and position itself as an important player in the coal export market in Indonesia. Before getting the green light from his parent firm, Agus needed to ensure this investment would create value for the firm. He also needed to convince his local banker to provide the necessary financing in a challenging environment with very volatile commodity prices.

Case Authors : Lena Chua Booth

Topic : finance & accounting, related areas : budgeting, costs, calculating net present value (npv) at 6% for diamond energy resources case study, the net present value at 6% discount rate is 2649300.

In isolation the NPV number doesn't mean much but put in right context then it is one of the best method to evaluate project returns. In this article we will cover -

Different methods of capital budgeting

Capital Budgeting Approaches

Methods of Capital Budgeting

There are four types of capital budgeting techniques that are widely used in the corporate world – 1. Net Present Value 2. Profitability Index 3. Internal Rate of Return 4. Payback Period

Apart from the Payback period method which is an additive method, rest of the methods are based on Discounted Cash Flow technique. Even though cash flow can be calculated based on the nature of the project, for the simplicity of the article we are assuming that all the expected cash flows are realized at the end of the year. Discounted Cash Flow approaches provide a more objective basis for evaluating and selecting investment projects. They take into consideration both – 1. Magnitude of both incoming and outgoing cash flows – Projects can be capital intensive, time intensive, or both. Coal Agus shareholders have preference for diversified projects investment rather than prospective high income from a single capital intensive project. 2. Timing of the expected cash flows – stockholders of Coal Agus have higher preference for cash returns over 4-5 years rather than 10-15 years given the nature of the volatility in the industry.

Formula and Steps to Calculate Net Present Value (NPV) of Diamond Energy Resources

NPV = Net Cash In Flowt1 / (1+r)t1 + Net Cash In Flowt2 / (1+r)t2 + … Net Cash In Flowtn / (1+r)tn Less Net Cash Out Flowt0 / (1+r)t0 Where t = time period, in this case year 1, year 2 and so on. r = discount rate or return that could be earned using other safe proposition such as fixed deposit or treasury bond rate. Net Cash In Flow – What the firm will get each year. Net Cash Out Flow – What the firm needs to invest initially in the project. Step 1 – Understand the nature of the project and calculate cash flow for each year. Step 2 – Discount those cash flow based on the discount rate. Step 3 – Add all the discounted cash flow. Step 4 – Selection of the project

Why Finance & Accounting Managers need to know Financial Tools such as Net Present Value (NPV)?

In our daily workplace we often come across people and colleagues who are just focused on their core competency and targets they have to deliver. For example marketing managers at Coal Agus often design programs whose objective is to drive brand awareness and customer reach. But how that 30 point increase in brand awareness or 10 point increase in customer touch points will result into shareholders’ value is not specified. To overcome such scenarios managers at Coal Agus needs to not only know the financial aspect of project management but also needs to have tools to integrate them into part of the project development and monitoring plan.

Calculating Net Present Value (NPV) at 15%

After working through various assumptions we reached a conclusion that risk is far higher than 6%. In a reasonably stable industry with weak competition - 15% discount rate can be a good benchmark.

The Net NPV after 4 years is 432350

(10439609 - 10007259 )

Calculating Net Present Value (NPV) at 20%

If the risk component is high in the industry then we should go for a higher hurdle rate / discount rate of 20%.

The Net NPV after 4 years is -537814

At 20% discount rate the NPV is negative (9469445 - 10007259 ) so ideally we can't select the project if macro and micro factors don't allow financial managers of Coal Agus to discount cash flow at lower discount rates such as 15%.

Acceptance Criteria of a Project based on NPV

Simplest Approach – If the investment project of Coal Agus has a NPV value higher than Zero then finance managers at Coal Agus can ACCEPT the project, otherwise they can reject the project. This means that project will deliver higher returns over the period of time than any alternate investment strategy. In theory if the required rate of return or discount rate is chosen correctly by finance managers at Coal Agus, then the stock price of the Coal Agus should change by same amount of the NPV. In real world we know that share price also reflects various other factors that can be related to both macro and micro environment. In the same vein – accepting the project with zero NPV should result in stagnant share price. Finance managers use discount rates as a measure of risk components in the project execution process.

Sensitivity Analysis

Project selection is often a far more complex decision than just choosing it based on the NPV number. Finance managers at Coal Agus should conduct a sensitivity analysis to better understand not only the inherent risk of the projects but also how those risks can be either factored in or mitigated during the project execution. Sensitivity analysis helps in –

What are the key aspects of the projects that need to be monitored, refined, and retuned for continuous delivery of projected cash flows.

What are the uncertainties surrounding the project Initial Cash Outlay (ICO’s). ICO’s often have several different components such as land, machinery, building, and other equipment.

What can impact the cash flow of the project.

What will be a multi year spillover effect of various taxation regulations.

Understanding of risks involved in the project.

Some of the assumptions while using the Discounted Cash Flow Methods –

Projects are assumed to be Mutually Exclusive – This is seldom the came in modern day giant organizations where projects are often inter-related and rejecting a project solely based on NPV can result in sunk cost from a related project. Independent projects have independent cash flows – As explained in the marketing project – though the project may look independent but in reality it is not as the brand awareness project can be closely associated with the spending on sales promotions and product specific advertising.

Negotiation Strategy of Diamond Energy Resources

References & further readings.

Lena Chua Booth (2018) , "Diamond Energy Resources Harvard Business Review Case Study. Published by HBR Publications.

Case Study Solution & Analysis

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ORIGINAL RESEARCH article

This article is part of the research topic.

GIS and MCDM Techniques as Tools for Navigating to a Greener Future by Harnessing Onshore and Offshore Wind Energy

Wind farm site selection using GIS-based mathematical modeling and fuzzy logic tools: A case study of Burundi Provisionally Accepted

• 1 University of Rwanda, Rwanda
• 2 University of Mauritius, Mauritius

The final, formatted version of the article will be published soon.

The electricity generated from nuclear plants and petroleum-based products has a negative influence on the environment as a whole. It has shown the utility to search out and promote the utilization of renewable, environmentally friendly, and sustainable energy sources such as solar, wind, and geothermal. Nowadays, Wind energy resource has quickly emerged as the world's fastest-growing energy source. However, the selection of the most suitable places for developing a wind farm is a crucial challenge that can be seen as a problem of site selection, which involves numerous conflicting variables. Therefore, it is classified as an MCDM (multi-criteria decision-making) problem. The main objective of this research is to determine the best locations in Burundi for the installation of wind farms. The Fuzzy Analytic Hierarchy Process (FAHP) was used to weigh the criteria considering their relative importance. This study considers several key factors when determining the optimal location for a wind farm. These factors include wind speed, slope, proximity to the grid network, distance to roads, and land use/land cover (LULC). Furthermore, a geographic information system (GIS) is utilized to generate the final suitability wind farm locations map. The obtained results indicate that 20.91% of the whole study area is suitable nevertheless, only 1.96% is tremendously suitable for wind turbine placement. The western part of Burundi is the optimal area for constructing a wind farm, and the most is in Lake Tanganyika.

Keywords: Fuzzy theory, Wind farm location, decision-making, Fuzzy-analytic hierarchy process, restriction factors

Received: 10 Dec 2023; Accepted: 15 Apr 2024.

Copyright: © 2024 Placide and Lollchund. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mx. GATOTO Placide, University of Rwanda, Kigali, Rwanda

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All-electric vehicles, as well as PHEVs operating in all-electric mode, do not produce tailpipe emissions. However, there are emissions associated with the majority of electricity production in the United States. See the emissions section for more information on local electricity sources and emissions.

According to the U.S. Energy Information Administration, most of the nation's electricity was generated by natural gas, renewable sources, coal, and nuclear energy in 2022. Renewable sources of electricity include wind, hydropower, solar power, biomass, and geothermal. Together, these sources generated about 20% of the country's electricity in 2022 .

To produce electricity, a turbine generator set converts mechanical energy to electrical energy. In the cases of natural gas, coal, nuclear fission, biomass, petroleum, geothermal, and solar thermal, the heat that is produced is used to create steam, which moves the blades of the turbine. In the cases of wind power and hydropower, turbine blades are moved directly by flowing wind and water, respectively. Solar photovoltaic panels convert sunlight directly to electricity using semiconductors.

The amount of energy produced by each source depends on the mix of fuels and energy sources used in your area. To learn more, see the emissions section . Learn more about electricity production from the U.S. Department of Energy's Energy Information Administration .

Electricity Transmission and Distribution

Electricity in the United States often travels long distances from generating facilities to local distribution substations through a transmission grid of nearly 160,000 miles of high-voltage transmission lines. Generating facilities provide power to the grid at low voltage, from 480 volts (V) in small generating facilities to 22 kilovolts (kV) in larger power plants. Once electricity leaves a generating facility, the voltage is increased, or "stepped up," by a transformer (typical ranges of 100 kV to 1,000 kV) to minimize the power losses over long distances. As electricity is transmitted through the grid and arrives in the load areas, the voltage is stepped down by substation transformers (ranges of 70 kV to 4 kV). To prepare for customer interconnection, the voltage is lowered again (residential customers use 120/240 V; commercial and industrial customers typically use 208/120 V, or 480/277 V).

Electric Vehicles and Electricity Infrastructure Capacity

Demand for electricity rises and falls, depending on time of day and time of year. Electricity production, transmission, and distribution capacity must be able to meet demand during times of peak use; but most of the time, the electricity infrastructure is not operating at its full capacity. As a result, EVs are unlikely to require expanded grid capacity.

Although increasing demand associated with charging EVs is not likely to strain much of our existing generation resources, high coincident peaks of EV charging in concentrated locations could strain nearby distribution equipment . According to a U.S. Department of Energy report , planning and forecasting for EVs should include assessments of the micro or distribution circuit level since the impacts and infrastructure investments needed will be highly localized. Advanced grid planning and solutions, such as smart charge management, will be important to ensure existing electrical infrastructure can safely support areas with large increases in demand related to EVs depending on when, where, and at what power level the vehicles are charged.

According to deployment models developed by researchers at the National Renewable Energy Laboratory (NREL), the diversity of household electricity loads and EV loads should allow introduction and growth of the EV market while "smart grid" networks expand. Smart grid networks allow for two-way communication between the utility and its customers, and sensing along transmission lines through smart meters, smart appliances, renewable energy resources, and energy efficient resources. Smart grid networks may provide the capability to monitor and protect residential distribution infrastructure from any negative impacts due to increased vehicle demand for electricity because they promote charging during off-peak periods, and reduce costs to utilities, grid operators, and consumers.

The NREL analysis also demonstrated the potential for synergies between EVs and distributed sources of renewable energy. For example, small-scale renewables, like solar panels on a rooftop, can both provide clean energy for vehicles and reduce demand on distribution infrastructure by generating electricity near the point of use. For utilities to fully realize the benefits of these technologies, smart charge management must be deployed to influence EV charging.

Utilities, vehicle manufacturers, charging equipment manufacturers, and researchers are working to ensure that EVs are smoothly integrated into the U.S. electricity infrastructure. Some utilities offer lower rates at off-peak times to encourage residential vehicle charging when electricity demand is lowest. Vehicles and many types of charging equipment (also known as electric vehicle supply equipment or EVSE) can be programmed to delay charging to off-peak times. "Smart" models are even capable of communicating with the grid, load aggregators , or facility/home owners, enabling them to charge automatically when electricity demand and prices are best; for example when prices are lowest, aligned with local distribution needs (such as temperature constraints), or aligned with renewable generation.

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• Maryland State Fleet Commits to Zero-Emission Vehicles
• Electric Vehicles in Rural Communities

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Healthy Living with Diabetes

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How can I plan what to eat or drink when I have diabetes?

How can physical activity help manage my diabetes, what can i do to reach or maintain a healthy weight, should i quit smoking, how can i take care of my mental health, clinical trials for healthy living with diabetes.

Healthy living is a way to manage diabetes . To have a healthy lifestyle, take steps now to plan healthy meals and snacks, do physical activities, get enough sleep, and quit smoking or using tobacco products.

Healthy living may help keep your body’s blood pressure , cholesterol , and blood glucose level, also called blood sugar level, in the range your primary health care professional recommends. Your primary health care professional may be a doctor, a physician assistant, or a nurse practitioner. Healthy living may also help prevent or delay health problems  from diabetes that can affect your heart, kidneys, eyes, brain, and other parts of your body.

Making lifestyle changes can be hard, but starting with small changes and building from there may benefit your health. You may want to get help from family, loved ones, friends, and other trusted people in your community. You can also get information from your health care professionals.

What you choose to eat, how much you eat, and when you eat are parts of a meal plan. Having healthy foods and drinks can help keep your blood glucose, blood pressure, and cholesterol levels in the ranges your health care professional recommends. If you have overweight or obesity, a healthy meal plan—along with regular physical activity, getting enough sleep, and other healthy behaviors—may help you reach and maintain a healthy weight. In some cases, health care professionals may also recommend diabetes medicines that may help you lose weight, or weight-loss surgery, also called metabolic and bariatric surgery.

Choose healthy foods and drinks

There is no right or wrong way to choose healthy foods and drinks that may help manage your diabetes. Healthy meal plans for people who have diabetes may include

• dairy or plant-based dairy products
• nonstarchy vegetables
• protein foods
• whole grains

Try to choose foods that include nutrients such as vitamins, calcium , fiber , and healthy fats . Also try to choose drinks with little or no added sugar , such as tap or bottled water, low-fat or non-fat milk, and unsweetened tea, coffee, or sparkling water.

Try to plan meals and snacks that have fewer

• foods high in saturated fat
• foods high in sodium, a mineral found in salt
• sugary foods , such as cookies and cakes, and sweet drinks, such as soda, juice, flavored coffee, and sports drinks

Your body turns carbohydrates , or carbs, from food into glucose, which can raise your blood glucose level. Some fruits, beans, and starchy vegetables—such as potatoes and corn—have more carbs than other foods. Keep carbs in mind when planning your meals.

You should also limit how much alcohol you drink. If you take insulin  or certain diabetes medicines , drinking alcohol can make your blood glucose level drop too low, which is called hypoglycemia . If you do drink alcohol, be sure to eat food when you drink and remember to check your blood glucose level after drinking. Talk with your health care team about your alcohol-drinking habits.

Find the best times to eat or drink

Talk with your health care professional or health care team about when you should eat or drink. The best time to have meals and snacks may depend on

• what medicines you take for diabetes
• what your level of physical activity or your work schedule is
• whether you have other health conditions or diseases

Ask your health care team if you should eat before, during, or after physical activity. Some diabetes medicines, such as sulfonylureas  or insulin, may make your blood glucose level drop too low during exercise or if you skip or delay a meal.

Plan how much to eat or drink

You may worry that having diabetes means giving up foods and drinks you enjoy. The good news is you can still have your favorite foods and drinks, but you might need to have them in smaller portions  or enjoy them less often.

For people who have diabetes, carb counting and the plate method are two common ways to plan how much to eat or drink. Talk with your health care professional or health care team to find a method that works for you.

Carb counting

Carbohydrate counting , or carb counting, means planning and keeping track of the amount of carbs you eat and drink in each meal or snack. Not all people with diabetes need to count carbs. However, if you take insulin, counting carbs can help you know how much insulin to take.

Plate method

The plate method helps you control portion sizes  without counting and measuring. This method divides a 9-inch plate into the following three sections to help you choose the types and amounts of foods to eat for each meal.

• Nonstarchy vegetables—such as leafy greens, peppers, carrots, or green beans—should make up half of your plate.
• Carb foods that are high in fiber—such as brown rice, whole grains, beans, or fruits—should make up one-quarter of your plate.
• Protein foods—such as lean meats, fish, dairy, or tofu or other soy products—should make up one quarter of your plate.

If you are not taking insulin, you may not need to count carbs when using the plate method.

Work with your health care team to create a meal plan that works for you. You may want to have a diabetes educator  or a registered dietitian  on your team. A registered dietitian can provide medical nutrition therapy , which includes counseling to help you create and follow a meal plan. Your health care team may be able to recommend other resources, such as a healthy lifestyle coach, to help you with making changes. Ask your health care team or your insurance company if your benefits include medical nutrition therapy or other diabetes care resources.

Talk with your health care professional before taking dietary supplements

There is no clear proof that specific foods, herbs, spices, or dietary supplements —such as vitamins or minerals—can help manage diabetes. Your health care professional may ask you to take vitamins or minerals if you can’t get enough from foods. Talk with your health care professional before you take any supplements, because some may cause side effects or affect how well your diabetes medicines work.

Research shows that regular physical activity helps people manage their diabetes and stay healthy. Benefits of physical activity may include

• lower blood glucose, blood pressure, and cholesterol levels
• better heart health
• healthier weight
• better mood and sleep
• better balance and memory

Talk with your health care professional before starting a new physical activity or changing how much physical activity you do. They may suggest types of activities based on your ability, schedule, meal plan, interests, and diabetes medicines. Your health care professional may also tell you the best times of day to be active or what to do if your blood glucose level goes out of the range recommended for you.

Do different types of physical activity

People with diabetes can be active, even if they take insulin or use technology such as insulin pumps .

Try to do different kinds of activities . While being more active may have more health benefits, any physical activity is better than none. Start slowly with activities you enjoy. You may be able to change your level of effort and try other activities over time. Having a friend or family member join you may help you stick to your routine.

The physical activities you do may need to be different if you are age 65 or older , are pregnant , or have a disability or health condition . Physical activities may also need to be different for children and teens . Ask your health care professional or health care team about activities that are safe for you.

Aerobic activities

Aerobic activities make you breathe harder and make your heart beat faster. You can try walking, dancing, wheelchair rolling, or swimming. Most adults should try to get at least 150 minutes of moderate-intensity physical activity each week. Aim to do 30 minutes a day on most days of the week. You don’t have to do all 30 minutes at one time. You can break up physical activity into small amounts during your day and still get the benefit. 1

Strength training or resistance training

Strength training or resistance training may make your muscles and bones stronger. You can try lifting weights or doing other exercises such as wall pushups or arm raises. Try to do this kind of training two times a week. 1

Balance and stretching activities

Balance and stretching activities may help you move better and have stronger muscles and bones. You may want to try standing on one leg or stretching your legs when sitting on the floor. Try to do these kinds of activities two or three times a week. 1

Some activities that need balance may be unsafe for people with nerve damage or vision problems caused by diabetes. Ask your health care professional or health care team about activities that are safe for you.

Stay safe during physical activity

Staying safe during physical activity is important. Here are some tips to keep in mind.

Drink liquids

Drinking liquids helps prevent dehydration , or the loss of too much water in your body. Drinking water is a way to stay hydrated. Sports drinks often have a lot of sugar and calories , and you don’t need them for most moderate physical activities.

Avoid low blood glucose

Check your blood glucose level before, during, and right after physical activity. Physical activity often lowers the level of glucose in your blood. Low blood glucose levels may last for hours or days after physical activity. You are most likely to have low blood glucose if you take insulin or some other diabetes medicines, such as sulfonylureas.

Ask your health care professional if you should take less insulin or eat carbs before, during, or after physical activity. Low blood glucose can be a serious medical emergency that must be treated right away. Take steps to protect yourself. You can learn how to treat low blood glucose , let other people know what to do if you need help, and use a medical alert bracelet.

Avoid high blood glucose and ketoacidosis

Taking less insulin before physical activity may help prevent low blood glucose, but it may also make you more likely to have high blood glucose. If your body does not have enough insulin, it can’t use glucose as a source of energy and will use fat instead. When your body uses fat for energy, your body makes chemicals called ketones .

High levels of ketones in your blood can lead to a condition called diabetic ketoacidosis (DKA) . DKA is a medical emergency that should be treated right away. DKA is most common in people with type 1 diabetes . Occasionally, DKA may affect people with type 2 diabetes  who have lost their ability to produce insulin. Ask your health care professional how much insulin you should take before physical activity, whether you need to test your urine for ketones, and what level of ketones is dangerous for you.

Take care of your feet

People with diabetes may have problems with their feet because high blood glucose levels can damage blood vessels and nerves. To help prevent foot problems, wear comfortable and supportive shoes and take care of your feet  before, during, and after physical activity.

If you have diabetes, managing your weight  may bring you several health benefits. Ask your health care professional or health care team if you are at a healthy weight  or if you should try to lose weight.

If you are an adult with overweight or obesity, work with your health care team to create a weight-loss plan. Losing 5% to 7% of your current weight may help you prevent or improve some health problems  and manage your blood glucose, cholesterol, and blood pressure levels. 2 If you are worried about your child’s weight  and they have diabetes, talk with their health care professional before your child starts a new weight-loss plan.

You may be able to reach and maintain a healthy weight by

• following a healthy meal plan
• consuming fewer calories
• being physically active
• getting 7 to 8 hours of sleep each night 3

If you have type 2 diabetes, your health care professional may recommend diabetes medicines that may help you lose weight.

Online tools such as the Body Weight Planner  may help you create eating and physical activity plans. You may want to talk with your health care professional about other options for managing your weight, including joining a weight-loss program  that can provide helpful information, support, and behavioral or lifestyle counseling. These options may have a cost, so make sure to check the details of the programs.

Your health care professional may recommend weight-loss surgery  if you aren’t able to reach a healthy weight with meal planning, physical activity, and taking diabetes medicines that help with weight loss.

If you are pregnant , trying to lose weight may not be healthy. However, you should ask your health care professional whether it makes sense to monitor or limit your weight gain during pregnancy.

Both diabetes and smoking —including using tobacco products and e-cigarettes—cause your blood vessels to narrow. Both diabetes and smoking increase your risk of having a heart attack or stroke , nerve damage , kidney disease , eye disease , or amputation . Secondhand smoke can also affect the health of your family or others who live with you.

If you smoke or use other tobacco products, stop. Ask for help . You don’t have to do it alone.

Feeling stressed, sad, or angry can be common for people with diabetes. Managing diabetes or learning to cope with new information about your health can be hard. People with chronic illnesses such as diabetes may develop anxiety or other mental health conditions .

Learn healthy ways to lower your stress , and ask for help from your health care team or a mental health professional. While it may be uncomfortable to talk about your feelings, finding a health care professional whom you trust and want to talk with may help you

• lower your feelings of stress, depression, or anxiety
• manage problems sleeping or remembering things
• see how diabetes affects your family, school, work, or financial situation

Ask your health care team for mental health resources for people with diabetes.

Sleeping too much or too little may raise your blood glucose levels. Your sleep habits may also affect your mental health and vice versa. People with diabetes and overweight or obesity can also have other health conditions that affect sleep, such as sleep apnea , which can raise your blood pressure and risk of heart disease.

NIDDK conducts and supports clinical trials in many diseases and conditions, including diabetes. The trials look to find new ways to prevent, detect, or treat disease and improve quality of life.

What are clinical trials for healthy living with diabetes?

Clinical trials—and other types of clinical studies —are part of medical research and involve people like you. When you volunteer to take part in a clinical study, you help health care professionals and researchers learn more about disease and improve health care for people in the future.

Researchers are studying many aspects of healthy living for people with diabetes, such as

• how changing when you eat may affect body weight and metabolism
• how less access to healthy foods may affect diabetes management, other health problems, and risk of dying
• whether low-carbohydrate meal plans can help lower blood glucose levels
• which diabetes medicines are more likely to help people lose weight

Find out if clinical trials are right for you .

Watch a video of NIDDK Director Dr. Griffin P. Rodgers explaining the importance of participating in clinical trials.

What clinical trials for healthy living with diabetes are looking for participants?

You can view a filtered list of clinical studies on healthy living with diabetes that are federally funded, open, and recruiting at www.ClinicalTrials.gov . You can expand or narrow the list to include clinical studies from industry, universities, and individuals; however, the National Institutes of Health does not review these studies and cannot ensure they are safe for you. Always talk with your primary health care professional before you participate in a clinical study.

This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by NIDDK is carefully reviewed by NIDDK scientists and other experts.

NIDDK would like to thank: Elizabeth M. Venditti, Ph.D., University of Pittsburgh School of Medicine.

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