Exam 2: Biofuels, Geothermal Energy, Wind Power & Hydropower

What is the power density for a 22 mile per hour (10 m/s) wind?

How much energy does it take to raise 1 gram of water to the top of the troposphere? (Hint: Assume troposphere top is 10,000 meters)

How much Btu could be generated in a year in the USA if all biomass waste were incinerated for heat energy. Assume that there is 1000 lbs of biomass waste per person per year and the energy content is 4300 Btu/lb of biomass waste. Approximately what percentage of the total energy consumption of the USA does this biomass waste heat generated represent?

Consider a 15m diameter wind turbine. How much power could be delivered by the turbine if you had a 10 m/s wind and you are operating at 40% efficiency? What is the maximum energy density possible from such a system?

What is the power density for a 44 mile per hour (20 m/s) wind?

Calculate the amount of thermal energy available by cooling 1 m³ of rock from 240^o C to 100^o C. Assume the rock specific heat is 2.4 J/cm^{3 o} C.

How much corn field area would be required if you were to replace all of the oil consumed in the USA with ethanol from corn? Use the following assumptions: a corn field is 1.5% efficient at converting radiant energy into stored chemical potential energy; conversion from corn to ethanol is 17% efficient; assume a 1.2:1 ratio for farm equipment to energy production; a 50% growing season; and, 200 W/ m² solar insolation. What would the length of each side of a square be to have such an area?

Imagine a steam turbine electric generator power plant that utilizes geothermal renewable energy. With a steam temperature of 210^o C and a heat reservoir at 25^o C; what is the maximum efficiency possible? Also, what percentage of the steam's energy will be dissipated as waste heat?

Consider the Grand Coulee Dam in the state of Washington on the Columbia River. Assuming a water "head" (height fill) of 110 meters, how much potential energy is available from each cubic meter of water? About how much power is available if the flow rate is 6,000 cubic meters per second?

If we assume that 1.6 x 10¹⁰ kg of water is evaporated per second by the radiant solar energy, how much potential energy is given to the water vapor? (Hint: Assume the water vapor rises to an average height of 2000 meters.)