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Co-Generation: Clean as Wind, Reliable as Coal By David McClellan We think we could make about 19 to 20 percent of U.S. electricity with heat that is currently thrown away by industry. Tom Casten, chairman, Recycled Energy Development There are different types of co-generation, but the concept is simply this: take energy that is being wasted on an industrial scale and find a way to put it to use. Do that, and co-generation could provide up to 20% of the nation's electrical generation, replacing a large number of our coal plants at a lower cost and with roughly the same reliability. Another name for co-generation is combined heat and power (CHP). We have enough potential CHP to replace 40% of coal-fired generation. Producing 20% of our electricity from CHP would put it on par with our fleet of nuclear reactors, which also produce about 20%. CHP is also as clean as wind power, reliable enough to use as base-load power and has the lowest construction cost of any power source. The DOE and EPA in 2001 put together a road map to double the amount of CHP. It said,
A typical coal plant has an efficiency in the low 30% range, meaning 65% or more of the energy is wasted. CHP can improve the plant efficiency to the 60%-80% range. Waste heat is commonplace in heavy industry too: for example a West Virginia Alloys silicon plant uses high heat to refine the metal. For now, when they're done refining metal, they just let the heat dissipate. Recycled Energy Development (RED) is developing the CHP needed to capture that heat and drive a steam turbine that will produce 40 to 44 Megawatts of electricity. No additional fuel is used - all the power that is generated comes from capturing the heat that would've been wasted. Since there's no extra fuel, there's no extra fuel expense and no extra CO2 generated, making this as clean as wind or solar power. How Big? CHP already makes a significant contribution, according to the United States Clean Heat and Power Association, producing 8% of US electricity. How does that compare to the rest of the world? I couldn't find a comprehensive list, but the consensus is that Denmark tops the list at 55%. It's not clear if that figure is the percent of electricity generated from waste heat or if that's the percent of power and industrial plants that use some form of CHP, but regardless, it shows there is opportunity to do a lot more. From the DOE/EPA road map again:
Estimates on the potential vary but are usually about an additional 100 GW nameplate capacity. This DOE study says there could be 88 GW in the industrial sector alone. Reliable and Cheap The reliability is high, comparable to coal plants or nuclear power plants, although again there is some variation. In a 2005 Lawrence Berkeley Laboratories study done for the DOE, they identified 19 different types of what they called Recycled Energy. Most of these qualify as CHP as well. The reliability, that is the percentage of time they would actually run, was between 62% and 98%. The building cost is a bargain too. Just as there is no extra cost for fuel, much of the equipment a power plant would need is already in place. Conceptually, you need only to build equipment to capture and process the waste heat, not create it. The same 2005 Lawrence Berkeley study says the construction cost ranges from less than $1,000/kilowatt (kW) to $2,000/kW. The New York Times recently reported that new conventional coal plants cost about $2,100/kW to build, but I've looked at a number of recent plant announcements and they were all higher: from $2,500/kW to as much as $3,330/kW for this plant in Arkansas. Compared to those, the West Virginia Alloys silicon plant CHP is a real bargain : close to $1,000/kW, less than half of the price for the new coal plants. Not only that, but RED has lined up a partner to provide $1.5 billion of financing for CHP projects, making it very easy for the silicon plant owner to sign up. Fact is, there isn't anything else that is close to this cheap. Flavors of CHP Any place energy is wasted, there's a chance to capture it and do useful work. The scale of waste heat in a steel mill, cement plant or silicon plant makes the potential obvious, but there are a few other types that take a sharper eye. The heat from a power plant, instead of being lost in a cooling tower or surrendered to the atmosphere, can be used for local heating via underground hot water or steam pipes to nearby businesses, homes or industry. There's a limit on how far the heat can travel, hence the name, district heating. Once more common, today in the US this is mostly limited to college campuses and a few old downtown neighborhoods. Anytime there is a pressure drop in a pipe, a backpressure turbine generator can capture the lost energy. For example, long distance natural gas pipelines operate at high pressure and when the pressure is reduced for local distribution, some of the significant energy originally used to pressurize the pipe can be recovered. This is sort of like regenerative braking for gas lines. An investment of $8 to $10 billion could capture 6.5 GW, another bargain at $1,250 to $1,500/kW. Steam pipelines are more numerous and have even more potential. The college campuses with district heating mentioned above could also be producing some fuel-free power where ever the steam pressure is reduced from transmission pressures to the pressure used in buildings. Many industrial processes have leftover gas or create some low quality gas that can be burned. Quite often, this is simply flared ( that is, burned ) at the top of a smokestack. I watched flaring gas coming off steel mill blast furnaces for years as a kid in Gary, Indiana without knowing what it was. In any event, I was awed by 15 foot high tongues of flame dancing on top of a 300 foot high stack. Other sources are oil refineries, auto painting plants, carbon black plants and ethanol refiners. One more advantage of CHP is that the electricity usually doesn't have to travel far and rarely requires new transmission lines. Unlike many large utility plants sited far away from population centers, most CHP installations are already where there are people and power demand. Barriers If this is such a great idea, and it is, why haven't we used more of this fuel-free, cheap-to-build and reliable power? The biggest barriers are legal. In part because many of our state and federal laws are out-of-date and in part because monopoly power companies have tilted regulations in their favor, it can be the hardest part of implementation. In the DOE/ EPA road map, the main issue wasn't financing, technology or finding good projects, it was legal barriers. This is what the report said about eliminating regulatory and institutional barriers:
In most of the country, it is illegal for anyone but the power company to sell you power, reducing the market of CHP electricity to what you can use in your own plant. In the entire country, it's illegal for anyone but the electric company to run a power line across a street, making it even harder. When a company does consider a co-generation project, the local electric company can discourage it with high fees for interconnections, backup power and other services that make it uneconomical. This is far thornier than it appears at first. Check out RED's excellent blog for a real power industry insider's view of this and other issues. If you've been worrying about meeting the Gore Challenge and you didn't know about CHP, you should feel like you just found a $1,000 bill laying on the sidewalk. Or, even better, 100 GW of high availability generation nearly ideal to provide 20% of our electrical generation and replace 40% of our coal plants. ---------- Copyright ©2008 SolveClimate
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