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Biodiesel Backup


Beaver Creek, Minn. — Wind power is getting a boost from soybean power.

AURI is pairing two renewable energy sources — wind and biodiesel — to produce electricity even when the wind isn’t blowing. The demonstration project links seven Buffalo Ridge wind turbines with a 2,800-horsepower diesel engine and generator fueled by 100 percent biodiesel. When the wind stops or drops, the biodiesel generator takes over. The goal is to guarantee two megawatts of dependable, renewable electricity.

The tandem system compensates for wind energy’s main disadvantage: its variability. Having a continuous supply of wind power available during peak demand times could make the renewable more attractive to utilities — and more profitable for small producers, says Dennis Timmerman, AURI project director. Cogeneration would also provide soybean growers with another market for biodiesel, while helping Minnesota meet its renewable energy objectives.

This is the first time that a utility-scale wind power system has been supplemented by biodiesel power. It’s also the first test of pure biodiesel, or B100, in a large diesel engine. “It’s an intriguing idea,” says Michelle Swanson, policy analysis manager at Xcel Energy, which is buying the hybrid power. “A renewable backed up by a renewable.”

The demonstration is supported by a $760,000 research grant from the Xcel Energy Renewable Development Fund, which encourages commercialization of green-energy technology. The Fund has also supported research on wind-speed forecasting, wind-power storage and wind-tower assembly methods.

Providing firm power

The hybrid system is being tested at an 11.55 megawatt wind farm operated by Minwind Energy, LLC. The company has built 11 wind turbines in southwest Minnesota and sells power to Alliant Energy and Xcel Energy.

“We’re interested in firming up wind power when wind speeds are low,” says Mark Willers, Minwind CEO. “And being in an agricultural area, we are also interested in another market for biodiesel.”

In May, AURI installed a leased Caterpillar V-16 diesel engine and two-megawatt generator at Minwind’s Beaver Creak wind farm. The generator is connected to existing transmission lines. Minwind is operating the biodiesel system from June through September — the period when wind speeds are lowest and demand for electricity is highest. The biodiesel generator runs from 1 p.m. to 9 p.m. daily, augmenting the output from Minwind’s seven 1.65 megawatt turbines. This enables Minwind to sell a guaranteed amount of continuous — or firm — power during peak-use hours.

The 120-day field trial is collecting data on power output and efficiency, equipment and software performance, biofuel handling, consumption and emissions, and costs. Afterwards, Willers says, “we’ll be able to say, here’s what works, here’s what needs improving, here’s what we wouldn’t do again.”

B100 performance test

One question researchers hope to answer is how B100 functions in a large, stationary diesel engine, says Kelly Strebig of the University of Minnesota Center for Diesel Research, which is overseeing fuel analysis and emissions monitoring.

Biodiesel fuel, which can be made from vegetable oils or animal fat, is fast gaining acceptance. B2 — a mixture of two percent biodiesel and 98 percent petroleum diesel — can be used safely in any diesel engine. B5 and B20 blends are increasingly being used in farm machinery and transit bus fleets. And B30 has been approved for some engines by Caterpillar and other manufacturers, Strebig says.

But so far, no diesel engine makers have okayed the use of greater concentrations of the renewable fuel. So this research is of great interest in Minnesota and other states that have renewable energy objectives, Strebig says.

After the demonstration, the leased dieselgenerator will be returned to Caterpillar, which will take apart the engine and look for B100-related damage. “We don’t anticipate any big problems,” Strebig says, “but we want to find out for sure.”

Favorable results from this and other B100 tests could open up huge new markets for the ag-based fuel, he says. Stationary diesel generators are widely used — by industry, hospitals, small municipal power plants and others — for standby or emergency electricity. Large utilities also use diesel and natural gas to meet peak demands for electricity. In the Twin Cities, for example, power companies contract for over 300 megawatts of diesel-generated peak power, Strebig says. Those contracts could represent millions of gallons of biodiesel fuel, he says.

Does it make financial sense?

The Minwind demonstration will also provide the first hard numbers on the actual cost of generating electricity from a hybrid wind-biodiesel system.

An April, 2006 study by University of Minnesota economist Douglas Tiffany offers a detailed analysis of cogeneration economics. Tiffany’s study estimates capital costs, revenues and expenses, cost per kilowatt-hour and rate of return under a variety of scenarios. (To read the full report, go to

Tiffany’s analysis suggests that it could be profitable to supplement wind power with biodiesel: From 9 a.m. to 9 p.m., Monday through Friday, in June, July, August and September. These are the prime “on-peak” hours, when utilities have the greatest need for continuous, or firm, power.

At sites with enough wind to run turbines at 35 percent efficiency or greater.

Provided that federal tax credits keep the priceof biodiesel equal to petroleum diesel.

Diesel-generated electricity is about twice as expensive as traditional sources. So “the price of biodiesel is an important variable in the feasibility,” Tiffany says, “along with the number of hours that a diesel ‘genset’ would have to run.” As the hours of generator use increase, hybrid-power costs go up and the rate of return goes down, the report shows. The same would be true as the price of diesel fuel rises.

The wind at Minwind’s Beaver Creek farm blows with enough frequency and strength to produce 40 percent of the turbines’ annual rated, or maximum, capacity, Willers says. AURI is estimating that the biodiesel generator will need to run about 400 hours during the demonstration period in order to produce two megawatts of continuous on-peak power. Assuming a biodiesel fuel cost of $2.60 per gallon, the blended price of the hybrid power would be 4.9 cents per kilowatt-hour, according to Tiffany’s estimates.

Making wind more attractive?

Minnesota utilities pay 3 to 4.5 cents per kilowatt-hour for wind power. But hybrid wind-biodiesel power may qualify for higher prices, Timmerman says. For example, from June through September 2005, Xcel Energy offered to pay 9.87 cents per kilowatt-hour for firm, on-peak renewable electricity produced through cogeneration.

The higher rates are not offered for more than a year at a time, however, Tiffany says, and the lack of longer-term agreements “reduces enthusiasm for investments in hybrid systems.”

Still, Timmerman says, reliable wind-biodiesel power “might be more attractive to utilities.” Minnesota legislation requires power companies to invest more in wind, biomass and other renewables. Within a decade, the state hopes to get 20 percent of its electricity from renewable sources. “Minnesota has been a leader in developing renewable energy,” Willers says. “The wind-diesel project is one more piece of this evolution.”

Catch and hold

Minwind Energy keeps wind power profits at home

Minwind Energy does more than catch the wind — it also holds on to it.

The company operates 11 wind turbines in Rock County. Owned by 350 southwest Minnesota farmers and business people, this renewable energy company “keeps wind power revenues here at home,” says Mark Willers, Minwind CEO.

Minwind is an example of how rural Minnesota communities can develop their wind resources, generate new farm income and keep energy profits local, says Jack Keers of Pipestone, chair of the Rural Minnesota Energy Board. The consortium of 15 southern Minnesota counties has been a leading voice on wind-power policy issues.

Minwind Energy started with the belief that “rural Minnesota needs to develop not only renewable energy production, but also the capacity to own it,” Willers says. Keers seconds that: “If you go out on the Buffalo Ridge, who owns most of the wind turbines? Not Minnesotans.”

In 2002, Minwind’s 66 original investors — most of them farmers — built four 0.95-megawatt wind turbines near Luverne. Two years later, a larger group of farmers put up seven more turbines at another Rock County site near Beaver Creek. Each 70-foot tower generates up to 1.65 megawatts of power. This summer, Minwind is testing the use of biodiesel generation to supplement its turbines when the wind isn’t blowing.

Minwind’s two wind farms have the capacity to generate nearly 16 megawatts. One megawatt of electricity can power about 300 average homes, according to the American Wind Energy Association. Alliant Energy buys the output from Minwind’s first wind farm; Xcel Energy buys the power from the second facility.

Minwind’s 11 wind turbines represent a local capital investment of $16 million, Willers says. Many of Minwind Energy’s shareholders have also invested in biodiesel and ethanol plants. Like the state’s ethanol businesses, Keers says, community wind farms benefit rural Minnesota; they pay property taxes and create new jobs and economic activity. Utility companies also benefit from broad ownership of wind turbines “when it comes time to build new transmission lines,” Willers says.

Community wind power businesses can educate the public, too, Willers adds. Minwind encourages area high schools to use its wind farms as real-life labs to study mathematics, physics, business and other subjects. “We spend a lot of time getting kids involved so they can understand that it’s up to us to get wind power going here. We can do it.”