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Unformatted text preview: 10.391J/1.818J/2.65J/3.564J/11.371J/22.811J/ESD166J SUSTAINABLE ENERGY IAP 2007 PROBLEM SET #2 Due January 19, 2007 Energy Conversion and Economic Analysis In class example problems: 1. Forest fires for electricity-- The United States has a lot of federally owned land. Unfortunately, and uncontrolled natural forest fires destroy large areas in the Western US every summer. Last year alone about 1,000,000 acres of standing timber in National forests were consumed. Some consideration is being given to improved management practices that could produce electric power from residual forest thinnings. Estimate the lost energy content of burned US forests during 2002. Assuming the US average electricity demand load is about 300,000 MWe, how much forested land would be needed to produce all the countrys power? Is this a sustainable alternative? A few facts to consider: (i) the total forested area on US Federal lands in the lower 48 states is about 600 million acres with a standing stock density of about 100 dry metric tonnes of wood per acre (ii) woody plants and trees capture solar energy via photosynthesis at an average rate of about 0.8 W/m2 which corresponds to producing about 5 to 10 dry tons of biomass per acre annually with an average heating value of 8000 BTU/dry lb. Note that 1 acre = 43,560 ft 2 = 0.405 hectare = 4047 m 2 (iii) the average heat to work conversion efficiency of a biomass-fired electric power plant is about 35% 2. Batteries for families What weight of lead acid batteries are needed to power a family sized electric car with a range of 200 miles. You can assume that the power needed is 50 hp for speeds up to 60 mph with regenerative on board flywheel storage for additional acceleration when needed. 3. Hydrogen versus gasoline If the US converts to a hydrogen economy to replace its current energy system, how much natural gas would be needed per year to produce the hydrogen required for all our transportation fuels? Currently the US consumes about 45 quads/year in energy for transportation and the worldwide production rate of natural gas is 90 trillion SCF per year. 4. Economic discounting of human life A Performance Assessment (actually a probabilistic risk assessment) for a high-level waste (HLW) repository estimates that the mean radioactive dose rate to a member of the public living in the vicinity (i.e. within 50 miles) of the repository is negligible for <5000 years and then equal to 5 mRem|year...
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