Waste Heat: More than Just Hot Air

In producing electricity, heat makes things work. Any power plant that uses steam to spin turbines and generate an electric current which includes nuclear, coal, and natural gas-fired power plants needs heat to keep things moving.

The heat created by burning fossil fuels or through a nuclear reaction isn't any different than that used in factories to produce glass, paper, aluminum, steel, chemicals, bricks, and other materials. Unfortunately, a lot of the heat used in manufacturing processes goes straight up the smokestack. It stands to reason that some of that waste heat could also be used to generate electricity.

A lot of waste heat is located at rural sites served by electric co-ops, explains Ed Torrero, executive director of the Cooperative Research Network (CRN), the research arm of the Arlington, Va.-based National Rural Electric Cooperative Association. This presents co-ops with an attractive but challenging opportunity to access local generation with almost no emissions at low or no incremental cost. Under many states renewable portfolio standards laws, this type of energy qualifies as a green resource.

In the late 1970s researchers began focusing on harvesting the potential of waste heat for generating electricity, a process also known as cogeneration or combined heat and power. The U.S. Department of Energy's Lawrence Berkeley National Laboratory puts the electricity-making potential of using industrial waste heat at 96,000 MW, equivalent to 10 percent of existing installed generating capacity in the country. A new study by CRN estimates that roughly 30,000 MW could be generated by waste heat within a decade.

The CRN report explores the sources of all this heat, many of which are located in rural sites served by electric co-ops. Along with the factories already mentioned, natural gas pipelines, ethanol refineries, landfills, and water treatment plants produce large volumes of waste heat.

Ethanol plants are singled out by the CRN report as an ideal [co-op] target for examining possible waste heat to power projects because of the amount of electricity and steam consumed. Torrero, though, points to natural gas pipelines as the source being tapped most effectively by electric co-ops.

Basin Electric Power Cooperative, a generation and transmission co-op based in Bismarck, N.D., generates 33 MW of renewable base-load power from waste heat recovery stations located at six compressor sites along the Northern Border Pipeline, which

carries natural gas from Canada to Chicago. Basin Electric Power obtains about 5.5 MW from waste heat off one compressor alone, or enough to serve the electrical needs of about 5,000 average residential homes. Compressors are spaced 70 miles apart, and the pipelines run thousands of miles, allowing ample room for growth.

These projects are excellent first steps, but to really take advantage of waste heat on a larger scale, some technical hurdles must be cleared, a new crop of technologies in development must be commercially proven, and a more compelling business case for all parties must emerge, emphasizes Bob Gibson, senior program manager at CRN. The potential is there.

Researchers at the U.S. Department of Energy's Idaho National Laboratory (INL) are also looking into innovative ways to put waste heat to work, but they're thinking small: A team has developed intricate materials that use millions of microscopic antennas to collect heat energy from the sun and industrial sources.

Every process in our industrial world creates waste heat, says Steven Novack, an INL physicist who leads the research team. Its energy that we just throw away!

Basin Electric Power, a generation and transmission cooperative based in Bismarck, N.D., generates 33 megawatts of renewable base-load power from waste heat.