Waste not, want not. Waste heat from the production of blast furnace coke at this Indiana steel plant generates as much electricity as all the world's grid-connected solar panels, without using any additional fossil fuel.

Thomas Casten, Recycled Energy Development

Harvesting Heat for Power

SAN DIEGO—Banks of solar panels gleaming on rooftops. Fields of windmills turning gracefully offshore. Such images adorn one hopeful report after another on the potential of clean energy. But an even more potent image might be a massive industrial plant—albeit one that's fitted with special equipment to harvest energy from its own wasted heat. What's more, such energy recycling can bring down power costs, saving companies and society serious money.

That was the take-home message from yesterday's panel on energy recycling at the annual meeting of the American Association for the Advancement of Science (which publishes ScienceNOW). At the session, economist Lester Lave of Carnegie Mellon University in Pennsylvania framed the issue by presenting recent results from a National Academy of Sciences panel he chaired on America's energy future, which provided some of the first hard numbers on the potential of ramping up energy efficiency.

"For decades, the United States has been trying solve the energy crisis by producing a lot more energy," Lave said. But energy efficiency could reduce total U.S. energy use in 2030 by 28% to levels last seen in the 1980s, the panel found. What's more, by improving the energy efficiency of buildings, the nation could offset all projected growth in electricity demand until 2030. "The source of energy that's cheapest, has the least CO2 and pollutant emissions, is the most sustainable and has the greatest benefit to national security is efficiency," Lave said.

Recycling waste heat to generate electricity is one of the most efficient ways to improve energy efficiency, said Thomas Casten, chairman of Recycled Energy Development, LLC, a Westmont, Illinois-firm that installs industrial-scale energy recycling systems.

Casten described a project he led at Cokenergy Mittal Steel, an Indiana steel plant, which he said illustrated the method's potential. Steel plants bake coal into blast furnace coke, which is used to melt and meld steel. Cokenergy Mittal Steel added equipment that trapped the heat from the baking process, producing steam that drives a turbine that produces 95 megawatts of electricity—as much electricity as all the world's grid-connected solar collectors produced in 2004, Casten said. Similarly, heat from burning fossil fuel at a power plant can be recycled, doubling the efficiency of electricity production and thereby halving CO2 emissions.

Unlike some other clean energy options, waste energy recycling actually makes reducing CO2 emissions profitable, Casten said. "It's profit for the company, profit for investors, and profit for society," he said.