Experts disagree on how many turbines will blanket the landscape if 25 by 25 amendment passes
Michigan's open spaces could be dotted with turbines nearly 500 feet tall — the same height as the 40-story Guardian Building in downtown Detroit — if voters pass Proposal 3 in November.
The proposal, which would mandate that 25 percent of Michigan's energy come from renewable sources such as wind by 2025, would require a huge increase in the number of turbines across the state.
The newest turbines have rotor blades that are longer than a football field. Experts are split about how many of the mammoth structures would be needed to generate as much as 20 percent of the state's energy from wind. Most experts think 20 percent of the 25-percent proposed standard would have to come from wind.
However, advocates and opponents of the 25-percent mandate disagree over how many turbines will be needed. Michigan currently has 292 wind turbines in operation with another 240 expected to be online by 2014.
To meet the 25-percent mandate, estimates range from 2,300 to 3,790 more turbines will be needed. Both sides do agree that the newer 2.4 megawatt (MW) capacity turbines will be used.
At issue is how efficient the turbines will be once they are installed. Wind turbines are measured by capacity factor, which tracks the percentage of the maximum energy turbines are capable of producing. Wind turbines aren't always online because wind can be unpredictable. The capacity factor can range from 15 percent to 45 percent in most cases.
The Michigan Environment Council is in favor of the 25-percent mandate and estimates another 2,300 wind turbines will be needed, said MEC Spokesman Hugh McDiarmid.
The MEC is basing its estimate on a 35-percent capacity factor, while Detroit Edison says it uses 30 percent, according to Matthew Wagner, manager of wind development for the company. By comparison, the U.S. Energy Information Administration makes its projections using a 30-percent capacity factor.
Thomas Hewson, principal of Energy Ventures Analysis Inc. in Virginia, said Michigan's existing turbines operate at a 25 percent capacity factor. Hewson said he made that calculation based on data provided by Michigan wind farms to the Energy Information Administration.
Using a 25-percent capacity factor, Hewson estimates a total of 4,082 turbines would be needed, including the 292 turbines already in existence.
Kevon Martis, of the Interstate Informed Citizens Coalition, is against the 25 percent mandate. He estimates at a 30 percent capacity factor, a total of 3,536 turbines would be needed, including the existing 292 turbines.
"The experience of several existing Michigan wind farms suggests a 25 percent to 30 percent capacity factor is more likely for Michigan," said Jack McHugh, senior legislative analyst at the Mackinac Center for Public Policy. "Higher figures are mere speculation at this time."