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Exhaust power provides new resource for Basin Electric

A new source of "green" power with a potential of hundreds of megawatts is just waiting to be tapped, and Basin Electric Power Cooperative is getting in on the ground floor.

The North Dakota-based co-op has signed a power purchase agreement with Ormat Technologies, Inc. for 22 megawatts from four new plants “powered” by hot exhaust. Ormat is building three powerplants in South Dakota and one in North Dakota that will generate electricity using the hot exhaust from compressor plants along the Northern Border Pipeline.

"The hot exhaust would otherwise be released into the atmosphere, so the plants actually reduce the environmental impact of existing operations," explained Ron Rebenitsch, Basin Electric Member Services Manager. "That makes the power even greener than wind or biomass."

New application captures waste heat

The power might be more accurately described as recovered energy generation rather than renewable energy. The generating technology is not new, "But the application is unique to Ormat," said Tom Buchanan, the company's heat recovery systems manager. "The Ormat Energy Converter is an air-cooled, heat-recovery system based on the Organic Rankine Cycle."

Many powerplants use the Rankine Cycle, in which superheated steam drives turbines to generate electricity. Typically, water is the working fluid in the process. In the Ormat unit, the Organic Rankine Cycle uses pentane, a non-freezing, ozone-benign organic fluid.

The Northern Border Pipeline, a 1,249-mile system that carries natural gas from the U.S.-Canadian border to the upper Midwest, is particularly well-suited to this application. The gas-turbine-powered compressor stations exhaust 900-degree gas which will vaporize pentane. The pentane vapor, in turn, drives the turbines connected to electricity generators. The process is a closed system and produces virtually no emissions and uses no real fuel or water. The only energy input required is the waste heat in the exhaust gases.

The technology turns what is now a waste product into a steady, long-term revenue stream for pipelines and other locations where waste heat is available. Given the large number of pipelines and compressor stations in the United States, the potential for energy recovery is vast.

Member co-ops, Western support project

Construction on the four powerplants is underway, and they are expected to be operational by summer 2006. "Part of the appeal of the project was that it could be up and running in one year to 18 months," Rebenitsch acknowledged.

Basin Electric members East River Electric Power Cooperative and Mor-Gran-Sou Electric Cooperative agreed to build about 15 miles of transmission lines and substation interconnections to distribute the power. "Their cooperation was essential in making the project happen," said Rebenitsch.

The two co-ops will own the lines that will feed the power directly into their systems.

Western, too, worked with Basin Electric on the logistics of the purchase, he added. "The Upper Great Plains staff really helped on the transmission studies," Rebenitsch said. "Their expertise was valuable for identifying some of the issues that are specific to a behind-the-meter project like this."

Benefits will create demand

The 20-year purchase agreement with Basin Electric represents Ormat's first sale of power from a recovered energy plant. If the demonstration succeeds as expected, there is plenty of opportunity for other utilities to follow in Basin Electric's footsteps. Buchanan estimates that hundreds of sites in the United States are suited to the application.

Rebenitsch believes that the demand for the resource will be there. "It's long-term, base load power; it can be developed fairly quickly and the cost is competitive with coal generation," he pointed out. "Best of all, it is environmentally benign."

So far, no renewable portfolio standard recognizes recovered power as green energy, something Rebenitsch hopes will change. "We are exploring ways to get it accepted as a renewable resource," he said.

The first utility in the country to buy recovered power is likely to have some influence on that discussion. In the pioneer spirit, Basin Electric is ready to meet that challenge.