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Waste Not, Want Not

by David Pescovitz
UC Berkeley, Lab Notes - December 2003

In the near future, the heat that warms your apartment in the winter may be piped in from the dry cleaner next door. According to UC Berkeley researchers, harnessing the "waste" heat that's currently vented out the back of turbines and generators could help ease our energy bill woes by doubling the effective efficiency of fossil fuel combustion in a wide range of power plants.

This alternative to gas or electric heaters is part of an energy technology called "combined heat and power" (CHP), where both the waste heat as well as the electricity is captured from the combustion of fuel. The CHP effort is being driven by a growing interest in distributed power generation, the integration of small power plants into buildings, so individuals and businesses can produce their own electricity instead of buying it from centralized power plants.

"Building a market for waste heat improves the economics of distributed power generation," says Daniel Kammen, professor in the Department of Nuclear Engineering, the Energy and Resources Group (ERG), and the Goldman School of Public Policy.

In the United States, more than 60 gigawatts of power are generated via CHP, with a Department of Energy (DOE) goal of 92 gigawatts by 2010. After all, CHP makes perfect economic sense. For example, a gas turbine requires approximately 1000 megawatts of input fuel to make 333 megawatts of electricity. That means the turbine's fuel efficiency -- the ratio of the useful energy obtained to the fuel it burns -- is just 33 percent. Capturing the heat that's generated during the combustion process ups the unit's efficiency to nearly 70 percent in some cases.

With some shifts in policy and the design of infrastructure to transfer waste heat, Kammen is convinced the U.S. building industry could put CHP and distributed power generation to more widespread use here as well. For example, take a mini-mall where a dry cleaner and restaurant both produce a great deal of heat.

"All of that heat currently vents out the windows or the backs of turbines and generators," Kammen says. "If the mini-mall could sell the heat to an apartment complex next door, it improves the mall's economics and decreases our overall need for fossil fuels to make heat."

In that scenario, Kammen envisions public utilities acting as the middleman, connecting heatsellers with buyers. It's a model that's already been proven to work by the Danish National Power Utilities, among others. Indeed, heating homes with the waste heat from large and small CHP power plants, like those at industrial facilities, is already commonplace in many European towns, Kammen says.

"The utility can even work the deal so that their income is a percentage of their customers' savings over a period," Kammen says. "This kind of performance-based contract gives the utility a revenue stream, an incentive to do a good job, and provides a way for customers to participate in CHP programs without much up-front cost." While there are plenty of lessons to be learned from European CHP efforts, importing their approach isn't so easy, Kammen says. For instance, some regions in Europe take CHP opportunities into account during urban planning. Physically connecting heat sellers and buyers in this country's urban sprawl environments is much more difficult.

The aim of a new DOE-funded partnership between UC Berkeley, the California Energy Commission, UC Irvine, and San Diego State University, is to get a handle on the viability of widespread CHP in this country. Under the direction of Dr. Timothy Lipman, executive director of Berkeley's Center for Interdisciplinary Distributed Energy Research (CIDER) and an ERG research associate, the Southwest CHP Regional Application Center (SWAC) is charged with studying and promoting CHP in the southwestern United States.

The multidisciplinary SWAC effort spans engineering, economics, and public policy. For example, students in Kammen's Renewable and Appropriate Energy Laboratory are developing novel technologies for heat conduction along with new power generators -- from fuel cells to "greener" external combustion engines. Meanwhile though, the DOE grant calls for the researchers to act as "a conduit of information to the private sector," Kammen says.

To that end, Kammen, Lipman and their colleagues are assessing the feasibility of CHP systems for several large industrial facilities, examining regulatory policy, and beginning outreach to the private sector to encourage a shift in the "energy economy."

"Hopefully once we get the story out, building and industry will see the opportunities," Kammen says. "Combined heat and power is good economics and contributes to energy independence."

David Pescovitz
Waste Not, Want Not
UC Berkeley, College of Engineering, Lab Notes, December 2003

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