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By, Manoj Acharya Madan Bhandari Memorial Academy
Pokhara University solutions : https://manojac122.blogspot.com/2023/08/energy-energy-engineering-model.html
Universal Engineering Collage : https://highgradeschoolar.blogspot.com/2023/09/energy-engineering-assessment-question.html
Internal Assesment of Oxford Collage
1 a) What are the various causes of Global Energy crisis? How green hydrogen is one of the solutions?
Ans: The global energy crisis is a complex issue with various interrelated causes. Some of the key factors contributing to the energy crisis include:
1. Growing Energy Demand: The world's population is increasing, and as developing countries industrialize and improve their living standards, the demand for energy continues to rise. This increased demand puts pressure on existing energy resources.
2. Fossil Fuel Depletion: Traditional fossil fuels like coal, oil, and natural gas are finite resources, and their extraction becomes more challenging and expensive as reserves deplete. This can lead to price volatility and supply disruptions.
3. Geopolitical Tensions: Geopolitical conflicts in regions rich in energy resources can disrupt the supply chain, leading to energy shortages. Political instability in major oil-producing regions, for example, can have a significant impact on global energy markets.
4. Environmental Concerns: The environmental impact of burning fossil fuels, including greenhouse gas emissions and climate change, has led to a global push for cleaner and more sustainable energy sources.
5. Infrastructure Challenges: Aging energy infrastructure in many parts of the world can result in energy losses during transmission and distribution, making it harder to meet rising demand.
6. Resource Constraints: The availability of certain resources required for energy production, such as rare earth metals for renewable technologies or uranium for nuclear power, can be limited.
Green hydrogen is emerging as a potential solution to some of these challenges. Green hydrogen is produced through a process called electrolysis, where water is split into hydrogen and oxygen using electricity, typically sourced from renewable energy sources like wind or solar power. Here's how green hydrogen can help address the energy crisis:
1. Clean Energy Source: Green hydrogen is a clean and sustainable energy carrier. When burned or used in fuel cells, it emits only water vapor as a byproduct, making it an environmentally friendly option.
2. Energy Storage: Hydrogen can be used for energy storage, helping to address the intermittent nature of renewable energy sources like wind and solar. Excess electricity generated during periods of high renewable output can be used to produce hydrogen, which can be stored and then converted back to electricity when needed.
3. Diversification of Energy Sources: Incorporating green hydrogen into the energy mix can reduce dependency on fossil fuels and enhance energy security.
4. Decentralization: Hydrogen production can be decentralized, allowing for more localized energy production and reducing transmission losses.
5. Industrial and Transportation Applications: Green hydrogen can be used in various sectors, including industry and transportation, as a clean alternative to fossil fuels, helping to reduce emissions.
However, it's important to note that there are challenges to widespread adoption of green hydrogen, including the high cost of electrolysis and the need for further infrastructure development. Additionally, the efficiency of electrolysis and the availability of renewable energy sources are critical factors in determining the environmental benefits of green hydrogen.
In conclusion, while green hydrogen holds promise as a solution to the global energy crisis, it is not a silver bullet. It should be part of a broader strategy that includes energy efficiency measures, renewable energy deployment, and sustainable practices to address the complex challenges of energy security and environmental sustainability.
b) What are the various modes of heat transfer? Explain radial heat conduction through tubes.
Ans:There are three main modes of heat transfer: conduction, convection, and radiation. Let's focus on conduction and explain radial heat conduction through tubes.
**1. Conduction:** Conduction is the transfer of heat through a material without the movement of the material itself. It occurs when there is a temperature gradient within a solid object, and heat flows from the hotter region to the colder region. Heat conduction is governed by Fourier's Law of Heat Conduction, which states that the rate of heat transfer through a material is directly proportional to the cross-sectional area, the temperature difference, and inversely proportional to the distance over which the heat travels.
**Radial Heat Conduction Through Tubes:**
Radial heat conduction through tubes, often referred to as radial heat conduction or cylindrical heat conduction, occurs when heat flows through the walls of a cylindrical or tubular structure, such as pipes, tubes, or cylinders. This is a common scenario in various engineering applications, including heat exchangers, boilers, and pipelines. In this context, heat is transferred from the inner surface of the tube to the outer surface, or vice versa, due to a temperature gradient.
The governing equation for radial heat conduction through tubes is similar to Fourier's Law, but it's adapted to the cylindrical geometry. The equation for steady-state radial heat conduction can be written as:
Key points to note about radial heat conduction through tubes:
1. Heat flows from the hotter inner surface to the cooler outer surface or vice versa, depending on the temperature gradient.
2. The logarithmic term (\(ln(r_2/r_1)\)) in the equation accounts for the cylindrical geometry of the tube. It represents the natural logarithm of the ratio of the outer radius to the inner radius.
3. Insulating materials with low thermal conductivity are often used as tube coatings or insulating layers to reduce heat loss or gain.
4. Engineers and designers need to consider the thermal properties of the material, tube geometry, and temperature differentials when analyzing and designing systems involving radial heat conduction through tubes.
Understanding radial heat conduction is essential for efficiently designing and optimizing systems where heat transfer through cylindrical structures is a critical factor.
2 a) Windows provide daylight and natural ventilation inside the room. However, it contributes significantly to the building cooling load compared to the external walls and roof of the building. Consider a room of a building located in Chitwan with west- facing external wall incorporating a window. The thickness and thermal conductivity of the glass window is 3.2 mm and 0.92 W/mK, respectively. Transmissivity and absorptivity of the glass at 60° incident angle are 0.75 and 0.11, respectively. The average incident solar radiation on the west wall is 680 W / (m ^ 2) and the ambient temperature is 39 °C in the summer month of May in Chitwan at 4.00 p.m. The room is maintained at 27 °C to achieve thermal comfort. The average heat transfer coefficients associated with the inner and outer surfaces of the window are 7.69 W / (m ^ 2) * K and 25 W / (m ^ 2) * K respectively.
Calculate the heat flux through the window and temperatures of the inner and outer surfaces of the window considering steady state condition.
Ans::
b) To maintain the comfort environment in a room that has one external wall (west wall exposed to the ambient), a layer of XPS insulation of 50 mm is given between two brick layers of 115 mm each. The brick wall is plastered with 15-mm-thick cement plaster on inside and outside surfaces. The thermal conductivities of insulation, brick layer, and plaster layer are 0.028 W/mK, 0.85 W/mK, and 0.72 W/mK, respectively The average heat transfer coefficients of inner and outer walls are 7.69 W/m²K and 25.0 W/m²K, respectively. The room with exposed west wall of 5.0 x 3.5 m is maintained at 27 °C to achieve thermal comfort. On a typical day in May at 4.00 p.m. in Chitwan, the incident solar radiation on the west wall is 680 W/m² and ambient temperature is 39 °C. The absorptivity of the exposed surface of the plaster is 0.65. Determine the heat transfer rate through the wall and temperatures of the inner and outer surfaces of the wall assembly and overall heat transfer coefficient considering steady state condition.
3 a) What are solar collectors? Describe standalone or off-grid PV-system with schematic 7
diagram
Ans:
Solar collectors are devices that absorb solar radiation and convert it into thermal energy. This thermal energy can then be used to heat water, air, or other fluids. Solar collectors are typically used in solar heating systems, but they can also be used to generate electricity in solar thermal power plants.
There are two main types of solar collectors: flat-plate collectors and evacuated tube collectors. Flat-plate collectors are the simplest and most common type of solar collector. They consist of a metal absorber plate that is covered by a transparent glass or plastic cover. The absorber plate is typically made of copper or aluminum, and it is painted black to maximize absorption of solar radiation.
Evacuated tube collectors are more efficient than flat-plate collectors, but they are also more expensive. Evacuated tube collectors consist of a series of glass tubes that contain a vacuum inside. The absorber plate is located inside the vacuum tube, and it is coated with a special material that absorbs solar radiation very efficiently.
Standalone or Off-Grid PV-System
A standalone or off-grid PV-system is a solar power system that is not connected to the electrical grid. This type of system is typically used in remote locations where there is no access to the grid, or in areas where the grid is unreliable.
Off-grid PV-systems typically consist of the following components:
- Solar panels: Solar panels convert sunlight into electricity.
- Charge controller: The charge controller regulates the flow of electricity from the solar panels to the batteries.
- Batteries: Batteries store the electricity generated by the solar panels.
- Inverter: The inverter converts the DC electricity stored in the batteries to AC electricity, which can be used to power appliances and lights.
Schematic Diagram of a Standalone or Off-Grid PV-System
The following schematic diagram shows a typical standalone or off-grid PV-system:
[Schematic diagram of a standalone or off-grid PV-system]
The solar panels are connected to the charge controller, which is connected to the batteries. The inverter is connected to the batteries, and the loads are connected to the inverter.
The charge controller regulates the flow of electricity from the solar panels to the batteries to prevent the batteries from being overcharged. The batteries store the electricity generated by the solar panels for use at night or on cloudy days. The inverter converts the DC electricity stored in the batteries to AC electricity, which can be used to power appliances and lights.
Advantages of Standalone or Off-Grid PV-Systems
Standalone or off-grid PV-systems offer a number of advantages, including:
- Energy independence: Off-grid PV-systems allow you to generate your own electricity, so you are not dependent on the electrical grid.
- Reliability: Off-grid PV-systems are very reliable, and they can continue to provide electricity even during power outages.
- Environmental benefits: Off-grid PV-systems are a clean and renewable source of energy.
Disadvantages of Standalone or Off-Grid PV-Systems
Standalone or off-grid PV-systems also have some disadvantages, including:
- Cost: Off-grid PV-systems can be expensive to install.
- Maintenance: Off-grid PV-systems require regular maintenance, such as cleaning the solar panels and checking the batteries.
- Storage: Off-grid PV-systems require batteries to store electricity for use at night or on cloudy days. Batteries can be expensive to replace.
Overall, standalone or off-grid PV-systems are a good option for people who want to generate their own electricity and be independent of the electrical grid. However, it is important to weigh the advantages and disadvantages carefully before deciding whether to install an off-grid PV-system.
4. a) What are biomass fuel crops? Explain anaerobic fermentation of biogas production .
Ans:**Biomass Fuel Crops:**
Biomass fuel crops are plants that are specifically grown and harvested for the purpose of producing biofuels. These crops are cultivated to extract energy from their organic matter, which can be converted into various forms of bioenergy, such as biofuels and biogas. Unlike fossil fuels, which are finite and contribute to greenhouse gas emissions when burned, biomass fuels are considered renewable and are part of a sustainable energy strategy.
Common examples of biomass fuel crops include:
1. **Corn (Maize):** Used to produce ethanol, which is blended with gasoline as a biofuel.
2. **Sugarcane:** Used for ethanol production, particularly in countries like Brazil.
3. **Switchgrass:** A native North American grass species that can be converted into cellulosic ethanol.
4. **Miscanthus:** A fast-growing grass that is used for biofuel production.
5. **Jatropha:** A non-edible plant whose seeds can be converted into biodiesel.
6. **Algae:** Certain types of algae can be used to produce biofuels, such as biodiesel and biogas.
7. **Woody Biomass:** Trees and woody plants can be used for bioenergy in the form of wood pellets, chips, or directly burned as biomass.
These biomass crops are typically chosen based on their high energy yield, ease of cultivation, and suitability for the local climate and soil conditions. The organic material from these crops can be converted into biofuels through processes like fermentation (for ethanol), pyrolysis (for bio-oil), or anaerobic digestion (for biogas).
**Anaerobic Fermentation for Biogas Production:**
Anaerobic fermentation is a biological process that occurs in the absence of oxygen, where microorganisms break down organic matter to produce biogas, a mixture of primarily methane (CH4) and carbon dioxide (CO2). This process is commonly used in the treatment of organic waste materials, such as agricultural residues, food waste, and sewage sludge, to both reduce waste volume and produce a renewable source of energy.
Here's how the anaerobic fermentation process works for biogas production:
1. **Collection of Organic Matter:** Organic materials, such as crop residues, animal manure, or sewage sludge, are collected and loaded into an anaerobic digester or biogas reactor.
2. **Anaerobic Digestion:** The digester is sealed to create an oxygen-free environment. This prevents aerobic decomposition and promotes anaerobic fermentation. Inside the digester, a consortium of microorganisms, including bacteria and archaea, break down the organic matter through a series of biological reactions.
3. **Biogas Production:** As a result of anaerobic fermentation, the microorganisms produce biogas, primarily consisting of methane (CH4) and carbon dioxide (CO2), along with trace amounts of other gases. Methane is the main component of biogas and can be used as a renewable energy source.
4. **Digestate:** After the digestion process is complete, what remains is a nutrient-rich residue called digestate. This material can be used as a valuable organic fertilizer.
5. **Biogas Utilization:** The biogas produced can be captured, cleaned, and used as a source of renewable energy for various applications, including electricity generation, heating, or as a vehicle fuel.
Anaerobic fermentation offers several advantages, including waste management, renewable energy production, and the reduction of methane emissions from organic waste decomposition in landfills. It is considered an environmentally sustainable way to manage organic waste while simultaneously harnessing the energy potential of biomass.
5 a) Describe the basic component of wind turbine.
Ans: Wind turbines are complex machines designed to capture kinetic energy from the wind and convert it into mechanical power or electricity. They consist of several key components that work together to harness wind energy efficiently. Here are the basic components of a typical horizontal-axis wind turbine:
1. **Rotor Blades:** The rotor blades are perhaps the most visible part of a wind turbine. They are long, aerodynamic structures that capture the kinetic energy from the wind. Modern wind turbines typically have two or three rotor blades. The shape and design of these blades are carefully engineered to maximize energy capture and minimize drag.
2. **Hub:** The hub is the central component to which the rotor blades are attached. It connects the blades to the main shaft and allows them to rotate. The hub contains a pitch control mechanism that can change the angle of the blades to optimize their performance in varying wind conditions.
3. **Nacelle:** The nacelle is the housing that sits atop the tower and contains most of the wind turbine's critical components. It houses the generator, gearbox (in some designs), yaw drive (which rotates the turbine to face the wind), and various control systems. The nacelle is designed to be aerodynamic and weather-resistant.
4. **Generator:** The generator is responsible for converting the mechanical energy from the rotating shaft into electrical energy. Most modern wind turbines use synchronous generators, although some may employ asynchronous generators. The generator produces electricity when the rotor blades spin.
5. **Gearbox (Optional):** In some wind turbine designs, a gearbox is used to increase the rotational speed of the generator to match the optimal speed for electricity generation. This allows for a smaller, more efficient generator.
6. **Yaw System:** The yaw system is responsible for turning the entire nacelle and rotor assembly to face the oncoming wind. Wind direction can change, so the yaw system ensures that the blades are always facing into the wind to maximize energy capture.
7. **Tower:** The tower is the tall structure that supports the nacelle and rotor assembly. It elevates the turbine to a height where wind speeds are typically higher and more consistent. Tower height can vary depending on the wind resource and turbine design.
8. **Anemometer and Wind Vane:** These instruments are mounted on the nacelle to measure wind speed and direction. The data collected is used by the control system to adjust the blade pitch and yaw orientation for optimal performance.
9. **Control System:** The control system includes sensors, computers, and software that monitor and manage the operation of the wind turbine. It adjusts the blade pitch, rotor speed, and yaw orientation to maximize energy capture and protect the turbine in extreme conditions.
10. **Brakes and Safety Systems:** Wind turbines are equipped with brakes that can stop the rotor in the event of high winds or emergencies. They also have various safety systems to protect against over-speeding, icing, and other potential issues.
These are the fundamental components of a horizontal-axis wind turbine, which is the most common type of wind turbine used for electricity generation. Vertical-axis wind turbines (VAWTs) have a somewhat different design, but they also consist of rotor blades, a generator, and other essential components to capture wind energy.
b) At a project site, the head available is 160 m of water at a flow rate of 0.005m³/s. The loss in pipeline is taken as 10% and overall efficiency of turbine is 95%. Design a suitable turbine and assume the required coefficients.
Ans:
6. a) What are the criteria for the selection of HVAC systems?
Ans:The selection of an HVAC (Heating, Ventilation, and Air Conditioning) system is a critical decision for any building or facility, as it directly impacts indoor comfort, energy efficiency, and operating costs. Several criteria should be considered when selecting an HVAC system to ensure it meets the specific needs and requirements of the building or space. Here are the key criteria for the selection of HVAC systems:
1. **Building Type and Use:**
- Consider the type of building (e.g., residential, commercial, industrial, healthcare, educational) and its intended use. Different building types may have unique HVAC requirements.
2. **Climate and Location:**
- Evaluate the local climate, temperature extremes, humidity levels, and seasonal variations. HVAC systems should be selected to cope with the climate conditions of the region.
3. **Load Calculation:**
- Conduct a thorough load calculation to determine the heating and cooling loads of the space. This includes factors like insulation, windows, occupancy, and equipment. The load calculation helps determine the system's capacity requirements.
4. **Energy Efficiency:**
- Prioritize energy-efficient HVAC systems to minimize operating costs and reduce environmental impact. Look for systems with high SEER (Seasonal Energy Efficiency Ratio) or EER (Energy Efficiency Ratio) ratings for cooling and high AFUE (Annual Fuel Utilization Efficiency) ratings for heating.
5. **System Type:**
- Choose the appropriate HVAC system type, such as central HVAC, ductless mini-split systems, rooftop units, heat pumps, or geothermal systems, based on the building's size, layout, and usage patterns.
6. **Zoning and Control:**
- Consider the need for zoning capabilities and advanced control systems. Zoning allows for customized temperature control in different areas of the building, improving comfort and energy efficiency.
7. **Ventilation and Indoor Air Quality (IAQ):**
- Evaluate the system's ability to provide adequate ventilation and maintain indoor air quality. Systems should include air filtration, humidity control, and fresh air intake as needed.
8. **Maintenance and Serviceability:**
- Assess the ease of maintenance and accessibility for servicing the HVAC system. Easy maintenance can extend the system's lifespan and reduce downtime.
9. **Cost and Budget:**
- Evaluate the initial cost of the HVAC system, including equipment, installation, and any necessary modifications to the building's infrastructure. Consider long-term operating costs, including energy consumption and maintenance.
10. **Scalability and Future Expansion:**
- Determine whether the HVAC system can accommodate future changes or expansions to the building. This is crucial for commercial and industrial facilities that may undergo growth or renovations.
11. **Environmental Impact:**
- Consider the environmental impact of the HVAC system, including its refrigerants and emissions. Choose systems with environmentally friendly refrigerants and low greenhouse gas emissions.
12. **Local Codes and Regulations:**
- Ensure compliance with local building codes, energy efficiency standards, and environmental regulations that may influence the choice of HVAC equipment and installation practices.
13. **Manufacturer and Installer Reputation:**
- Select reputable HVAC equipment manufacturers and experienced installation contractors who can provide quality products and services.
14. **Warranty and Support:**
- Review the warranties offered by the manufacturer and consider post-installation support and service agreements.
15. **User Comfort and Feedback:**
- Gather feedback from potential users or occupants of the building to ensure that the selected HVAC system meets their comfort preferences.
The selection of an HVAC system should be a well-informed decision that balances performance, efficiency, comfort, and cost. It's often beneficial to work with HVAC professionals and engineers who can perform detailed calculations and provide recommendations tailored to the specific needs of the project.
7. Write short note on (Any Two):
a. Refrigeration Cycle
b. Scope of energy engineering for civil engineers
c. Climatic Change Models
**a. Refrigeration Cycle:**
The refrigeration cycle is a thermodynamic process that forms the basis for cooling and air conditioning systems. It allows for the transfer of heat from a low-temperature environment (interior of a refrigerator or air-conditioned space) to a high-temperature environment (the surroundings). This cycle is essential for maintaining comfortable indoor temperatures, preserving food, and various industrial processes. Here's a brief overview of the basic components and stages of a typical vapor-compression refrigeration cycle:
1. **Compression:** The cycle starts with the compressor, which raises the pressure and temperature of the refrigerant gas. As the gas is compressed, it becomes hotter and more pressurized.
2. **Condensation:** The hot, high-pressure gas then flows to the condenser coil, where it releases heat to the surrounding air (or water) and undergoes a phase change from a gas to a liquid. This is when heat is removed from the refrigerant.
3. **Expansion:** The high-pressure liquid refrigerant enters an expansion valve or throttle valve, where its pressure is rapidly reduced. This causes the refrigerant to expand and partially vaporize, resulting in a mixture of liquid and vapor at a lower temperature and pressure.
4. **Evaporation:** The low-pressure, low-temperature refrigerant enters the evaporator coil or evaporator, typically located inside the space to be cooled. Here, it absorbs heat from the surroundings (cooling the indoor air) and evaporates back into a gas.
5. **Return to Compressor:** The vaporized refrigerant is then returned to the compressor to repeat the cycle.
This continuous cycle of compression, condensation, expansion, and evaporation allows the refrigeration system to maintain a lower temperature inside the conditioned space than the surrounding environment. The refrigerant acts as a heat transfer medium, absorbing heat from the indoor space and releasing it outside, creating a cooling effect.
**b. Scope of Energy Engineering for Civil Engineers:**
Energy engineering is a multidisciplinary field that plays a crucial role in addressing energy-related challenges and improving sustainability. Civil engineers, with their expertise in infrastructure and construction, have an essential role to play in the field of energy engineering. Here's a brief overview of the scope of energy engineering for civil engineers:
1. **Energy-Efficient Building Design:** Civil engineers can design and construct energy-efficient buildings by incorporating features such as improved insulation, energy-efficient HVAC systems, passive solar design, and renewable energy integration (e.g., solar panels).
2. **Renewable Energy Projects:** Civil engineers can work on the planning, design, and implementation of renewable energy projects, including solar farms, wind farms, and hydropower installations.
3. **Energy Audits and Retrofitting:** Civil engineers can perform energy audits on existing buildings and infrastructure to identify areas for energy savings. They can then oversee retrofitting projects to improve energy efficiency.
4. **Infrastructure for Electric Vehicles:** As electric vehicles become more common, civil engineers can design and develop charging infrastructure, including charging stations in parking lots and along roadways.
5. **Smart Grids and Energy Distribution:** Civil engineers can contribute to the development of smart grids and efficient energy distribution systems that incorporate advanced technologies for monitoring and managing energy consumption.
6. **Environmental Sustainability:** Civil engineers can work on projects aimed at reducing the environmental impact of energy production and consumption, including carbon capture and storage (CCS) and sustainable urban planning.
7. **Energy Policy and Regulation:** Some civil engineers may engage in energy policy and regulatory roles, helping shape energy-related legislation and standards.
8. **Energy Management:** Civil engineers can work in energy management roles within organizations, focusing on optimizing energy use in facilities and industrial processes.
9. **Research and Development:** Civil engineers can engage in research and development activities related to new energy-efficient technologies and materials.
In summary, civil engineers have a broad scope in the field of energy engineering, contributing to sustainable infrastructure, energy-efficient building design, renewable energy projects, and the development of innovative solutions to meet the world's growing energy needs while minimizing environmental impact.
**c. Climatic Change Models:**
Climatic change models, often referred to as climate models or climate simulations, are computer-based tools used by climate scientists and researchers to simulate and predict changes in Earth's climate system. These models are critical for understanding past climate variations, assessing current trends, and making projections about future climate change. Here's an overview of climatic change models:
1. **Types of Models:**
- Climate models can be divided into various categories, including General Circulation Models (GCMs), Earth System Models (ESMs), and Regional Climate Models (RCMs). GCMs are global-scale models that simulate climate processes at a large scale, while ESMs include additional components to simulate interactions between the atmosphere, oceans, land, and ice. RCMs focus on specific regions and provide higher-resolution data.
2. **Components:** Climate models simulate various components of the Earth's climate system, including the atmosphere, oceans, land surface, ice sheets, and vegetation. These components interact with each other through complex physical and chemical processes.
3. **Data Input:** Climate models rely on historical climate data and observations as input to initialize the model and validate its performance. These data sources include temperature records, satellite observations, and measurements of greenhouse gas concentrations.
4. **Physical Processes:** Models incorporate mathematical representations of physical processes such as radiative forcing (interaction of sunlight and heat with the Earth's surface and atmosphere), heat transfer, cloud formation, precipitation, ocean circulation, and more.
5. **Scenarios:** Climate models can run simulations under different greenhouse gas emission scenarios, such as business-as-usual emissions or scenarios with aggressive emissions reductions. These scenarios help project various possible future climate outcomes.
6. **Validation:** Model output is compared to observed climate data to assess the model's accuracy and reliability. Model validation is an ongoing process to improve the models' performance.
7. **Projections:** Climate models are used to make projections about future climate change, including temperature increases, sea-level rise, changes in precipitation patterns, extreme weather events, and more. These projections are vital for policymakers, scientists, and governments to make informed decisions about climate mitigation and adaptation strategies.
8. **Policy and Decision Support:** Climate models inform policy decisions at the international, national, and local levels. They are used in climate assessments, impact studies, and risk assessments to guide actions aimed at addressing climate change.
Overall, climatic change models are essential tools for understanding the complex interactions within Earth's climate system and for predicting the potential consequences of human-induced climate change. They provide valuable insights for addressing the global challenges posed by climate change.
NEC (Nepal Engineering Collage )
1a) How can Nepal Shift towards secure and sustaniable energy sources at present ?
Ans : Nepal has a significant potential for renewable energy development, including hydropower, solar, wind, and biomass. By shifting towards secure and sustainable energy sources, Nepal can improve energy access, reduce air pollution, and mitigate climate change.
Here are some specific steps that Nepal can take to shift towards secure and sustainable energy sources:
- Expand hydropower generation. Hydropower is Nepal's largest source of renewable energy, accounting for over 90% of the country's electricity generation. Nepal has the potential to generate over 40,000 MW of hydropower, but only a small fraction of this potential has been developed. By expanding hydropower generation, Nepal can increase its energy security and reduce its reliance on fossil fuels.
- Develop solar and wind energy. Nepal has a high potential for solar and wind energy development. The country receives an average of 4-6 kWh/m2/day of solar radiation, and its mountainous regions have strong wind resources. By developing solar and wind energy, Nepal can diversify its energy mix and reduce its reliance on hydropower.
- Promote energy efficiency. Energy efficiency is one of the most cost-effective ways to reduce energy consumption and greenhouse gas emissions. Nepal can promote energy efficiency through a variety of measures, such as building codes, energy audits, and public awareness campaigns.
- Support the development of renewable energy technologies. Nepal can support the development of renewable energy technologies by providing subsidies and tax breaks for renewable energy projects, and by funding research and development in renewable energy technologies.
- Strengthen the institutional and regulatory framework for renewable energy. Nepal can strengthen the institutional and regulatory framework for renewable energy by developing clear and transparent policies and regulations, and by creating a supportive investment environment for renewable energy projects.
In addition to these steps, Nepal can also learn from the experiences of other countries that have successfully transitioned to renewable energy sources. For example, countries such as Costa Rica and Denmark have been able to generate over 90% of their electricity from renewable sources.
By taking these steps, Nepal can shift towards secure and sustainable energy sources, and create a more sustainable future for its people.
b) . As a civil engineer what role can you play to increase energy efficency in a building amidst (बीचमा) climate change ?
Ans: As a civil engineer, I can play a significant role in increasing energy efficiency in buildings amidst climate change. Here are some specific ways that I can do this:
- Design buildings that are energy efficient from the start. This includes considering factors such as building orientation, envelope insulation, and window design. I can also use energy modeling software to simulate the energy performance of a building and identify areas where energy efficiency can be improved.
- Use energy-efficient materials and construction methods. This includes using materials with high insulation properties, such as recycled cotton insulation or cellulose insulation, and using construction methods that minimize air leaks.
- Incorporate renewable energy systems into buildings. This includes installing solar panels, wind turbines, or geothermal heating and cooling systems. By incorporating renewable energy systems into buildings, I can help to reduce their reliance on fossil fuels and reduce their greenhouse gas emissions.
- Retrofitting existing buildings to make them more energy efficient. This can include adding insulation, upgrading windows, and installing energy-efficient appliances and lighting.
In addition to these specific measures, I can also play a role in increasing energy efficiency in buildings by advocating for policies and regulations that support energy efficiency. I can also educate the public about the importance of energy efficiency and how to make their homes and businesses more energy efficient.
By taking these steps, I can help to make buildings more energy efficient and reduce their impact on the environment. This is especially important in the context of climate change, as buildings are a major source of greenhouse gas emissions.
Here are some specific examples of energy-efficient building design features that I can incorporate into my projects:
- Passive solar design: This involves designing buildings to take advantage of natural sunlight and heat. For example, I can orient buildings so that they receive maximum sunlight during the winter months, and I can design buildings with large south-facing windows.
- High-performance insulation: I can use high-performance insulation in the building envelope to reduce heat loss in the winter and heat gain in the summer. This will help to reduce the energy needed to heat and cool the building.
- Air-tight construction: I can use air-tight construction methods to minimize air leaks in the building envelope. This will also help to reduce the energy needed to heat and cool the building.
- Energy-efficient appliances and lighting: I can install energy-efficient appliances and lighting in the building. This will help to reduce the building's energy consumption.
- Renewable energy systems: I can incorporate renewable energy systems into the building, such as solar panels, wind turbines, or geothermal heating and cooling systems. This will help to reduce the building's reliance on fossil fuels and reduce its greenhouse gas emissions.
I believe that civil engineers have a responsibility to design buildings that are energy efficient and sustainable. By taking the steps outlined above, we can help to reduce the environmental impact of buildings and create a more sustainable future for all.
3 a) How solar thermal energy be converted in to electrical energy ? Explain the working with schematic digram.
Ans : Solar thermal energy can be converted into electrical energy using a solar thermal power plant. A solar thermal power plant uses concentrated sunlight to heat a fluid, such as water or oil. The heated fluid then turns a turbine, which generates electricity.
Here is a schematic diagram of a solar thermal power plant:
The main components of a solar thermal power plant are:
- Solar collectors: The solar collectors concentrate the sunlight onto the receiver.
- Receiver: The receiver absorbs the concentrated sunlight and heats the fluid.
- Heat exchanger: The heat exchanger transfers the heat from the fluid to a working fluid.
- Turbine: The turbine is turned by the working fluid, which generates electricity.
- Generator: The generator converts the mechanical energy from the turbine into electrical energy.
The solar collectors can be parabolic troughs, linear Fresnel reflectors, or heliostats. Parabolic troughs are long, curved mirrors that concentrate the sunlight onto a tube running along the center of the trough. Linear Fresnel reflectors are flat mirrors that are arranged in rows and concentrate the sunlight onto a receiver at the top of the row. Heliostats are flat mirrors that track the sun and reflect its light onto a receiver.
The receiver is typically a black tube that is filled with a fluid. The fluid absorbs the concentrated sunlight and heats up. The heated fluid then flows through the heat exchanger, where it transfers its heat to the working fluid.
The working fluid is typically a liquid or a gas that has a low boiling point. When the working fluid is heated, it vaporizes and expands. The expanding working fluid turns the turbine, which generates electricity.
The generator converts the mechanical energy from the turbine into electrical energy. The electricity is then transmitted to the grid.
Solar thermal power plants are a reliable and efficient way to generate electricity from solar energy. They can operate 24 hours a day, even when the sun is not shining. This is because they can store heat energy from the sun and use it to generate electricity at night.
Solar thermal power plants also have a low environmental impact. They do not produce any greenhouse gases or other pollutants.
Solar thermal power plants are becoming increasingly popular around the world. As the cost of solar energy continues to decline, solar thermal power plants are expected to play an increasingly important role in meeting the world's energy needs.
OR
or Explain the working of wind-solar hybrid system with proper schematic digram
A wind-solar hybrid system combines both wind turbines and solar panels to generate electricity from renewable sources. This integration allows for a more consistent and reliable power generation, as it takes advantage of the complementary nature of wind and solar energy resources. Here's an explanation of how a wind-solar hybrid system works, along with a simplified schematic diagram:
**Working of a Wind-Solar Hybrid System:**
1. **Wind Turbines**: Wind turbines are designed to convert the kinetic energy of moving air (wind) into mechanical energy. This mechanical energy is then used to generate electricity through a generator. The key components of a wind turbine include the rotor (blades), the nacelle (housing the generator and other components), and the tower.
2. Solar Panels: Solar panels, also known as photovoltaic (PV) panels, capture sunlight and convert it directly into electricity through the photovoltaic effect. Solar panels consist of multiple solar cells connected in series and parallel to generate usable electrical power.
3. Inverters: Both wind turbines and solar panels produce electricity in different forms. Wind turbines generate alternating current (AC) electricity, while solar panels generate direct current (DC) electricity. Inverters are used to convert the electrical output from these sources into a consistent form of electricity that can be used in homes or sent to the grid.
4. Charge Controller and Battery: Many wind-solar hybrid systems incorporate energy storage in the form of batteries. This allows excess electricity generated by wind and solar to be stored for use when the wind isn't blowing, and the sun isn't shining. A charge controller manages the charging and discharging of the batteries to prevent overcharging or over-discharging.
5. Grid Connection (Optional): In some cases, wind-solar hybrid systems are connected to the grid. When the system generates more electricity than is needed, the excess can be fed back into the grid, allowing the owner to earn credits or compensation for the excess energy.
**Schematic Diagram of a Wind-Solar Hybrid System:**
Below is a simplified schematic diagram of a wind-solar hybrid system.
```
|----------|
Wind Turbine | Inverter | AC Load
--------- |----------| |
| | | |
| Blades |---| |------------------|
| | | |
| | | |------------------|
--------- | Battery Bank | DC Load
| --------- |
| | | |
| | Charge|<-----|
| |Controller|
| | |
| ---------
|
Solar Panels |
--------- |
| | |
| PV |----|
| Array |
| |
---------
```
In this schematic:
- The wind turbine and solar panels are connected to their respective inverters.
- The inverters convert the electricity from DC (solar panels) and AC (wind turbine) to a consistent AC form.
- The AC load receives power directly from the inverters when both wind and solar resources are available.
- Excess electricity can be directed to charge a battery bank through a charge controller.
- During periods when wind and solar resources are insufficient, the battery bank can supply power to the DC and AC loads.
- Optionally, excess energy can be sent to the grid or pulled from the grid when needed.
This hybrid system ensures a more stable and reliable energy supply by leveraging the strengths of both wind and solar power sources, making it a valuable renewable energy solution
5 a) What are the differient types of wind machines ? Wow do lift type of machine generate power ?
Ans :Wind machines, also known as wind turbines, come in various types and designs, each with its own way of harnessing wind energy. One common classification of wind turbines is based on their axis of rotation, which results in two primary categories: horizontal-axis wind turbines (HAWTs) and vertical-axis wind turbines (VAWTs). Within these categories, there are different designs and variations. Let's explore these types and how lift-type wind machines generate power:
**1. Horizontal-Axis Wind Turbines (HAWTs):**
HAWTs are the most common type of wind turbines and have a horizontal rotor shaft. They come in various sizes and designs, including:
- **Upwind Wind Turbines:** These turbines have the rotor (blades) located upwind of the tower. The wind flows over the blades before reaching the tower. Most modern large-scale wind turbines are upwind designs.
- **Downwind Wind Turbines:** In downwind turbines, the rotor is located downwind of the tower. The wind first encounters the tower before reaching the rotor. Downwind turbines are often smaller and less common in large-scale applications.
**2. Vertical-Axis Wind Turbines (VAWTs):**
VAWTs have a vertical rotor shaft and come in various shapes, including:
- **Darrieus Wind Turbines:** Darrieus turbines have a characteristic "eggbeater" shape with curved blades. They rely on lift forces to generate power. As the wind flows over the curved blades, it creates a pressure difference between the convex and concave sides, generating lift and causing the rotor to spin. Darrieus turbines are often used in small-scale and urban applications.
- **Savonius Wind Turbines:** Savonius turbines have a distinctive "S" shape and consist of two or three curved blades. They rely on drag rather than lift to rotate. The wind pushes against the concave side of the blades, causing them to spin. Savonius turbines are less efficient than some other types but are known for their simplicity and reliability.
**How Lift-Type Wind Machines Generate Power:**
Lift-type wind machines, such as Darrieus VAWTs, generate power through the principles of aerodynamics and the generation of lift forces. Here's a simplified explanation of how they work:
1. When the wind flows over the curved blades of a Darrieus turbine, it encounters a difference in air pressure between the convex (curved outward) and concave (curved inward) sides of the blades.
2. This pressure difference creates lift, similar to the lift generated by an airplane wing. As a result, the blades start to rotate.
3. The rotational motion of the blades is transferred to a generator, which converts mechanical energy into electrical energy.
4. The generated electricity is then either used locally or fed into the electrical grid.
While lift-type wind turbines like Darrieus designs have certain advantages, such as omnidirectional wind capture, they also face challenges in terms of efficiency and startup torque. As a result, they are often used in smaller-scale applications or as experimental designs. Most large-scale wind farms employ horizontal-axis wind turbines due to their higher efficiency and power output.
Write short notes on :
Planetory wind
Green house gases
Refrigeranation cycle
Solar water heating system
Sure, here are short notes on each of the topics you mentioned:
**Planetary Wind:**
Planetary winds are large-scale wind patterns that occur due to the Earth's rotation and the differential heating of its surface. There are several key planetary wind belts, including the trade winds, westerlies, and polar easterlies, which circulate air across the globe. These winds play a crucial role in weather patterns, ocean currents, and navigation. The Coriolis effect, a result of the Earth's rotation, influences the direction of these winds, causing them to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
**Greenhouse Gases:**
Greenhouse gases are atmospheric gases, such as carbon dioxide (CO2), methane (CH4), and water vapor (H2O), that trap heat from the sun and prevent it from escaping into space. This natural greenhouse effect is essential for maintaining Earth's temperature within a range suitable for life. However, human activities, especially the burning of fossil fuels, have increased the concentration of greenhouse gases in the atmosphere, leading to enhanced greenhouse effect, global warming, and climate change.
**Refrigeration Cycle:**
The refrigeration cycle is a thermodynamic process used in refrigeration and air conditioning systems to transfer heat from a cooler space to a warmer one. It operates on the principles of compression, condensation, expansion, and evaporation. In a typical refrigeration cycle, a refrigerant circulates through a closed system, changing from a gas to a liquid and back again. The cycle removes heat from the space being cooled and releases it outside. This process allows for temperature control and cooling in various applications, including refrigerators, air conditioners, and industrial cooling systems.
**Solar Water Heating System:**
A solar water heating system uses energy from the sun to heat water for residential or commercial use. It typically consists of solar collectors (such as flat-plate collectors or solar thermal tubes) installed on rooftops or other suitable locations. These collectors absorb sunlight and convert it into heat, which is transferred to a fluid (usually water or a heat-transfer fluid) in the system. The heated fluid is then used to warm domestic or industrial water. Solar water heating systems can be active (with pumps to circulate the fluid) or passive (relying on natural convection). They are an environmentally friendly and cost-effective way to reduce energy consumption for water heating.
1) Discuss the present energy situation of koshi provience and explore the potential role of the proviencial government in resolving energy related difficulties .
The present energy situation in Koshi Province is mixed. On the one hand, the province has a significant potential for renewable energy development, including hydropower, solar, and wind energy. On the other hand, the province is still heavily reliant on fossil fuels, and its energy infrastructure is underdeveloped.
One of the biggest challenges facing Koshi Province is its high rate of energy poverty. According to the World Bank, over 50% of the province's population does not have access to electricity. This is a major obstacle to economic development and social welfare.
Another challenge facing Koshi Province is its reliance on imported fossil fuels. The province imports over 90% of its petroleum products. This makes the province vulnerable to fluctuations in global oil prices and can lead to energy shortages.
The provincial government of Koshi Province has a number of roles to play in resolving the province's energy-related difficulties. These roles include:
- Developing and promoting renewable energy. The provincial government can develop and promote renewable energy by providing subsidies and tax breaks for renewable energy projects, and by investing in research and development in renewable energy technologies.
- Improving energy efficiency. The provincial government can improve energy efficiency by developing and enforcing energy-efficient building codes, and by promoting energy-efficient appliances and lighting.
- Expanding access to electricity. The provincial government can expand access to electricity by investing in rural electrification projects and by providing subsidies to low-income households.
- Reducing reliance on imported fossil fuels. The provincial government can reduce reliance on imported fossil fuels by promoting renewable energy and improving energy efficiency.
- Develop a provincial energy plan. This plan should identify the province's energy needs and resources, and it should outline a strategy for developing and promoting renewable energy, improving energy efficiency, and expanding access to electricity.
- Establish a provincial energy development fund. This fund could be used to provide subsidies and tax breaks for renewable energy projects, and to invest in research and development in renewable energy technologies.
- Develop and enforce energy-efficient building codes. These codes should require new buildings to be constructed using energy-efficient materials and construction methods.
- Promote energy-efficient appliances and lighting. The provincial government can do this by providing subsidies for energy-efficient appliances and lighting, and by raising awareness of the benefits of energy efficiency.
- Invest in rural electrification projects. These projects can help to bring electricity to rural communities that are currently without it.
- Provide subsidies to low-income households. This can help low-income households to afford the cost of electricity.
In addition to these specific roles, the provincial government can also play a leading role in raising awareness of energy issues and in mobilizing resources to address them. By working with the national government, the private sector, and civil society, the provincial government can help to create a more sustainable and equitable energy future for Koshi Province.
Here are some specific examples of what the provincial government of Koshi Province can do to address the province's energy-related difficulties:
By taking these steps, the provincial government of Koshi Province can help to address the province's energy-related difficulties and create a more sustainable and equitable energy future for all of its residents.
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