Minneapolis, Minn. — They’re out there. Waiting in hospitals and schools. Biding their time, ready to spring into action and devour … biodiesel?
They are backup generators, installed to provide power when the lights go out. The Minnesota Pollution Control Agency estimates there are enough generators in the 7-county Twin Cities area to produce 300 megawatts of power. A typical generator runs less than 150 hours a year to alleviate peak energy demands.
Still, Ken Bickel, research fellow for the Center for Diesel Research, estimates those generators could consume more than three million gallons of fuel a year. Some are fueled by natural gas; most run on petro-based fuels, including diesel. Bickel is researching a promising fuel for those generators: soy-based biodiesel.
Pollute where they stand
Generators are often in confined areas, including high-rise office buildings, hospitals and universities. “These may be stand-by or peak-shaving generators that produce power to meet demand or that have been contracted to produce power,” Bickel says. “Most just provide power for where they are located.”
It is estimated that if all Minnesota generator sets were running at the same time, they would emit more pollutants than a large coal-fired power plant, Bickel says. There is a “large concern with emissions, especially in the immediate area.”
“A large percentage of the smog effect in metropolitan areas comes from standby generators,” adds Max Norris, AURI scientist. “If we can reduce those emissions, it will open up another huge market for biodiesel.”
Last year, as part of a project supported by AURI, the Minnesota Soybean Growers, the Minnesota Department of Commerce, and the Legislative Commission on Minnesota Resources, Bickel began evaluating air quality results for generator sets run on biodiesel.
Although biodiesel emissions have been tested previously with vehicle engines, the research doesn’t transfer to generators, Bickel says. “Peak-shaving generators run at one speed with high loads, compared to a vehicle that runs at variable speeds.”
Lab tests evaluated different biodiesel blends, additives, and adding a charged air cooling system. Gases and particulates were sampled to determine the best options.
The lab tests gave the nod to a 20-percent biodiesel blend with charge air cooling. Researchers found that pumping cooled air through the generators reduces nitrogen oxide emissions.
Comparing biodiesel-run generators to regular diesel, “we did see some reduced emissions, including carbon monoxide, particulates and hydrocarbons, in the lab tests. There’s no reason to believe we won’t see the same thing in field tests.”
Into the field
Field emission tests are scheduled for this spring, with the project completed by June. Energy Alternatives, part of Dakota Electric, is the industry partner for the field tests.
“The state has goals for producing up to 10 percent of our energy by 2015 from renewables,” Bickel says. “And power companies are always interested in alternatives that are better.”