It's estimated that one third of the "change oil" from cars in the U.S. gets dumped into storm sewers, how does that compare to the Exxon Valdez oil spill of 260 thousand barrels?

Exxon_spill = 260 thousand bbl (1/3) * 150 million cars * 10000 miles/car/year * 5 qt/3000 miles ? Exxon_spills/month = 1.58985 Exxon_spills/month

What is the value of an acre foot of Colorado river water to the Hoover Dam power company? (Head is 500 ft).

500 ft wc * 12 cent/kWh ? $ / acre ft = 61.4493 $ / acre ft

Suppose you wanted to estimate how much forest land would be required to generate 30 megawatts of electricity on a "renewable" bases by burning wood.

Assume:

- The forest is pine and can produce about 4 tons of biomass per acre annually.
- The heat of combustion of pine is 8750 btu per pound.
- The generating efficiency is 40%.

30 megawatt ; 4 ton/acre/year * 8750 btu/lb * 40% ? acre = 32025.3 acreSo how big is this forest? (as a square)

sqrt(32025.3 acre) ? km = 11.3843 km (on a side)How much wood is that? (Assume the density of pine is approximately 550 kg/m^3)

32025.3 acre * 4 ton/acre/year ; (550 kg/m^3 ? million board_feet/month = 7.46176 million board_feet/monthor, for a more tangible perspective...

7.46176 million board_feet/month ; 12 feet * pi * (6 inch)^2 / tree ? trees/day = 2169.09 trees/dayAssuming an average power from the sun of 200 watts per square meter, what is the overall solar efficiency of the "system" ?

30 megawatt / (32025.3 acre * (200 W/m^2)) ? % = 0.115739 %

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Fort Collins, CO

Last Updated 6/21/2009

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