Energy and Environment II

HW#10

Due Friday, March 15, 2002

1. A landfill on average (over the year) runs two 1 MW_electric engine/generators at rated power on landfill gas. The efficiency of the engine/generators is 38% (lower heating value basis). The lower heating value of methane is 50,000 kJ/kg. The biomass digested in the landfill has a composition of C₆H₉O₃.

Determine the tonnes of biomass digested per year and the amount of electricity generated over the year.

2. A wood-fired steam electric power plant is rated at 50 MW_electric. The efficiency of the power plant is 25% (higher heating value basis). Determine the tonnes of wood burned if the power plant runs at rated power 8000 hours per year. Suppose sustainable practices are used to supply the wood. That is, the amount of wood harvested per year is equal to the new growth of the forest. How big (km x km) is the forest that supplies the power plant?

3. Could you help a dairy farmer whom wishes to know how much electricity could be generated from the waste of 100 cows?