Renewable and Nonrenewable Resources; Global Energy Consumption：练习题

A community is considering replacing a 600 MW coal-fired power plant with a utility-scale wind farm. The coal plant operates with a capacity factor of 0.85, while the proposed wind turbines have a capacity factor of 0.35. Each wind turbine has a rated capacity of 4.0 MW. Calculate the minimum number of wind turbines required to match the annual energy output of the coal plant.

A coal-fired power plant has an efficiency of 35% and produces 800 MW of electricity. If the energy density of the coal used is \(24 \text{ MJ/kg}\), calculate the approximate mass of coal consumed by the plant in one hour of operation.

Consider the use of hydrogen fuel cells in transportation. Which of the following represents a significant thermodynamic challenge that limits the overall 'well-to-wheels' efficiency of a hydrogen economy compared to direct battery electric vehicles?

Calculate the Net Energy Yield (in Joules) for a wind turbine system over its 20-year lifespan. The turbine produces an average of \( 2.5 \text{ MW} \) of power with a capacity factor of \( 0.30 \). The total energy required for manufacturing, installation, and decommissioning is \( 4.0 \times 10^{13} \text{ J} \). (Note: \( 1 \text{ year} = 3.15 \times 10^7 \text{ seconds} \)).

A natural gas power plant has an efficiency of 45%. If the total energy input is \(2.0 \times 10^{9}\) Joules, calculate the amount of waste heat released into the environment and discuss one mitigation strategy for thermal pollution.

A parabolic trough solar power plant operates with an overall efficiency of \( 15\% \). If the solar intensity is \( 900 \text{ W/m}^2 \) and the total collector area is \( 200,000 \text{ m}^2 \), calculate the net electrical power output in Megawatts (MW) and identify one environmental disadvantage of using utility-scale solar farms in desert ecosystems.

A regional power grid is transitioning from a reliance on traditional coal-fired power plants to a diversified portfolio including concentrated solar power (CSP) and photovoltaic (PV) systems.

(a) A specific CSP plant uses a field of heliostats to focus sunlight onto a central receiver. The system has a solar-to-thermal conversion efficiency of \( 40\% \) and a thermal-to-electric conversion efficiency of \( 35\% \). Calculate the overall system efficiency of the CSP plant.
(b) The plant is located in a desert with an average solar insolation of \( 8 \text{ kWh/m}^2/\text{day} \). If the plant must produce a constant net output of \( 100 \text{ MW} \) for \( 12 \text{ hours} \) each day, calculate the minimum required area of the mirror field in square meters (\( \text{m}^2 \)). (Note: \( 1 \text{ MW} = 1,000 \text{ kW} \)).
(c) Explain why CSP systems often include molten salt storage, and describe how this technology addresses the issue of intermittency differently than lead-acid battery banks used in PV systems.
(d) Describe one thermodynamic disadvantage of using PV cells compared to CSP in high-temperature desert environments regarding the movement of electrons and semi-conductor efficiency.

Unit 6: Energy Resources and Consumption
A small town is evaluating the transition from a coal-fired power plant to a combination of natural gas and wind energy.
(a) Calculate the total amount of energy (in BTUs) produced by the coal plant in one year if it has a capacity of \( 500 \text{ MW} \) and operates at a \( 70\% \) capacity factor. (Note: \( 1 \text{ kWh} = 3,412 \text{ BTU} \); \( 1 \text{ MW} = 1,000 \text{ kW} \)).
(b) If natural gas releases \( 117 \text{ lbs of CO}_2 \) per million BTU and coal releases \( 210 \text{ lbs of CO}_2 \) per million BTU, calculate the reduction in \( \text{CO}_2 \) emissions if the town switches completely to natural gas for the same energy output.
(c) Identify one economic advantage and one environmental disadvantage of hydraulic fracturing (fracking) used to extract natural gas.
(d) Explain the concept of 'intermittency' in wind energy and suggest one technological solution to address this issue. <\/p>