keywords: wind power, wind turbines, corn ethanol, ERoEI
If a farmer has 1,000 acres of land, and he/she planted it with corn for making ethanol and erected wind turbines for generating electricity, how much energy will the farmer produce and what are the economics?
A typical wind farm will have about 15 wind turbines per 1,00o acres. Each wind turbine will generate about 500 kW of power (assuming 33% capacity factor). Electricity retails at about 12¢ per kW hour. So 1,000 acres will produce 15 x 500 x .12 = $900 of electricity per hour, which equates to about $8,000,000 per year, representing about 224 trillion BTUs of energy.
Corn Ethanol Power
A typical 1,000 acre corn farm will produce about 7,500 pounds of corn, yielding about 340,000 gallons of ethanol. Ethanol retails at about $1.80 per gallon. So 1,000 acres will produce 340,000 x 1.8 = $612,000 per year, representing about 26 billion BTUs of energy.
Energy Returned on Energy Invested
It takes energy to produce energy. The Energy Returned on Energy Invested (ERoEI) for wind turbines is an impressive, state of the art wind turbines are providing ERoEI of over 50:1.
It takes a lot of energy to produce corn ethanol, which yields a far lower ERoEI of between .8 and 1.65 (see Ethanol’s Energy Return on Investment: A Survey of the Literature 1990-Present by Roel Hammerschlag).
Side-effects of Wind Power and Corn Ethanol Production
Wind turbines are often perceived as an eyesore, marring the land with imposing manmade structures. Flying creatures such as hawks and bats are often killed as they pass through the turbine blades. Wind turbines are noisy, and are best located in rural areas, or at sea. Wind power needs to be located near power transmission resources, it that infrastructure will need to be built.
Corn ethanol yields just a bit more energy than it takes to produce it. It takes about 1,700 gallons of water to produce each gallon of corn ethanol. Corn used for ethanol production is corn not used for food production. As food corn supply is reduced, corn-based food prices rise.
Given 1,000 acres of land, planted with corn and a typical density of wind turbines, the table below summarizes the annual economic and energy value of corn ethanol fuel and wind turbine electricity.
|Wind Power||Corn Ethanol|
|Energy Yield||224 trillion BTUs||26 billion BTUs|