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Sizing a Wind Energy System
Most small wind turbines have a rating or size based on the maximum electricity they can generate - such as 1.8 kilowatts or 5 kilowatts. But that is not a very useful number for most consumers. Rated output is the peak production at a specific (and usually high) wind speed, and different manufacturers use different wind speeds to determine rated output.
A more useful measure is to determine how much of your power a wind turbine can supply. Any reputable small wind turbine representative will supply you with a power curve, showing how much electricity the machine produces at a given wind speed. Use this to estimate how much electricity (in kilowatt hours) the turbine will produce each month or year at the average wind speed you expect or measure at your site.
Match this output with your annual energy consumption. To determine this number, check your monthly bills to come up with the annual total of kilowatt hours of electricity you use.
Once you have determined your annual electricity use, you can decide how much electricity you want to offset with a turbine, based on budget and other considerations. For example, if you want to offset nearly all your electricity use and have determined you have annual usage of 10,000 kilowatt hours, select a turbine that will produce that much power over the course of the year at your average wind speed.
A state law passed in 2008 requires all utilities to allow residential and commercial users up to a certain size to connect to the grid. The grid performs the same function as a battery storage system. Power generated in excess of daily consumption gets credited back to the consumer at a retail rate. This credit goes towards power consumed during calm periods, when electricity is not being generated. At the end of the year, any power that is generated in excess of consumption is generally bought by the utility at very low rates, so it does not make financial sense to oversize your system. Colorado’s law is designed for people to offset their own power use, not sell it back to make an overall profit. It allows residential turbines up to 10 kilowatts of rated production, and commercial turbines up to 25 kilowatts to connect to the grid through a net meter. Net metering is only allowed for systems sized up to 120% of the customer's annual average consumption.
For more information, see: Wind Energy for Colorado Homeowners, Farmers, and Small Businesses – CSU Extension
Updated Thursday, May 17, 2012