Power delivered by the hot water heater at a flow of 3 gal/min:

(130-50)deltaF; shv_water; 3 gal/min ? kilowatt = 35.2195 kilowatt

On page 36 of the September 93 issue of Popular Science there is an article titled "Green turbines" in which it is stated that a 30 megawatt wood burning electrical generation plant requires about 27000 acres of forest, but could run indefinitely by selective logging. Lets consider this statistic in other terms for comparison:

First of all, how big is a 27000 acre forest?

sqrt(27000 acre) ? miles = 6.49519 miles (as a square area)At a conversion efficiency of 40%, how much wood would be required on a daily basis? (Calchemy knows that the heat of combustion for wood by mass is approximately 8750 btu/lbm, pretty much independent of the type of wood)

30 megawatt / (hcm_wood * 40%) ? tons/day = 350.962 tons/dayWhat's that in tons per acre per year?

30 megawatt ; hcm_wood * 40% ; 27000 acre? ton / acre / year = 4.74448 ton / acre / yearOr in cords of pine per year

(350 tons / day) / dens_pine ? cords / year = 58135.1 cords / yearHow many trees is that? Guess that a tree ready for harvest is about 25 ft tall and about 1 foot in diameter at its base shaped as a "right circular cone" (V = 1/3 pi r^2 h).

(58135.1 cords / year) / ((1/3) pi (.5 ft)^2 * 25 ft/tree) ? trees/day = 3114.92 trees / dayAbout How many trees are in a 27000 acre forest? (Guess that the trees are about 10 feet apart on a more or less square grid.)

27000 acre / ((10 ft * 10 ft) / tree) ? trees = 1.17612E+07 treesAbout 11 million trees, so what percentage is harvested in a year?

11 million trees ; 3114.92 trees / day ? % / year = 10.3359 % / year Harvesting about 10 percent per year, each tree would have about 10 years to grow.Assuming an average power from the sun of about 200 watts / square meter, what is the overall solar efficiency of the system?

30 megawatt / (27000 acres * (200 watt/square meter)) ? % = 0.137281 %The entire facility operates at a solar to electrical conversion efficiency of about 0.14 percent!

How many "AA" Alkaline batteries does it take to heat a cup of coffee?

Assume 1 cup coffee = 6 oz, starts at 50 degF, ends at 212.

"E_alkaline_AA" is energy in this type of battery
(fuels database in Windows version)

For Reference E_alkaline_AA = 3.21 watt hours

shv_water; 6 floz; (212-50) deltaF ? E_alkaline_AA = 5.78591 E_alkaline_AA

Calchemy Software Inc.

Fort Collins, CO

Last Updated 6/21/2009

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