By Ken Silverstein Director, Energy Industry Analysis

Wasted energy is an awful use of resources. That's the message from those who espouse reusable energy as a way to limit the need to build power plants and to reduce the level of pollutants released into the atmosphere.

“Reusable energy” refers to the re-use of waste heat generated from the combustion of fossil fuels. It's an area full of possibility. Consider that for every BTU of coal or natural gas burned in a combustion turbine only 35 percent is converted into useful power. The other 65 percent is lost forever in the form of waste heat that is discharged into the environment. Interestingly, the technology exists to convert that waste heat into power or other useful forms such as steam. But the incentives that would compel industry to make the needed investments is lacking. Those in the reusable energy sector want to see federal legislation similar to what is given to the renewable sector—legislation that they say would improve the efficiency of power plants by 30-50 percent.

“We use trillions of BTUs every hour of every day,” says Daniel Stinger, CEO of WOW Energies. “That's a lot of energy that could be recaptured and reused but instead it is going up smoke stacks and into the atmosphere.”

That air is going out the stack at between 300 degrees Fahrenheit and 800 degrees Fahrenheit. It's all available to reuse and to convert to mechanical power, says Stinger. Combined cycle and co-generation power plants do just that but they perform best when the steam coming out the other end is 800 degrees Fahrenheit or more. So, there's a huge window of opportunity to capture energy in those refineries and industries where the wasted heat is released at 300-700 degrees Fahrenheit.

Put simply, it is like boiling water and then using the steam to power other things in the house. But for all practical purposes, the steam is just released and lost forever. Moreover, it takes a lot of energy to create that steam. So, the idea is to not just recapture and reuse the steam but to use less energy to produce it. In the case of WOW Energies, it vaporizes propane in multiple heat exchangers, which are similar to steam boilers. It then expands that vapor across multiple steam turbines to generate power. It is then condensed into a liquid and pumped backed into the system. The propane is not consumed; rather, it is used to convert thermal energy to mechanical energy.

“We take the throwaway heat and use it to drive another expander,” says Stinger. “If there were a heat source that was being thrown up the stack, the technology could improve efficiency by 30-50 percent.” The process works and is already being applied worldwide by many industrials, he adds. California-based Mafi Trench Corp., for example, manufacturers such “expander generators.” Its clients include Magma Electric Co. in Holtville, Calif., Mobil Chemical Co. in Beaumont, Texas and Amoco Production Co. in Wyoming.

Two Paths

Reusing energy in the form of waste heat recovery has been popular in Europe for years. Much of it comes in the form of combined heat and power systems. In the United States, where energy has been inexpensive and readily available, waste heat recovery has rarely been a priority. With high natural gas prices and involvement from some key states such as California, the combined heat and power systems are expanding. Those systems, however, are often restricted to the recovery of low temperature waste heat—releases of less than 200 degrees Fahrenheit—and then used for cooling and heating buildings and hot water.

The major thrust for waste heat recovery in the United States began in the early 1980s when Congress forced utilities to purchase excess power generated by such companies as Dow and DuPont. These companies wanted to re-use the steam in their plants but at the time, most were not allowed to sell the excess power produced by their facilities to their utilities or in some cases they wouldn't receive a high enough price for the surplus to make those projects viable. Their ingenuity and the subsequent congressional action taken ultimately spawned the creation of independent power producers that used high efficiency technologies such as combined cycle and co-generation power systems. Federal and state government participation is necessary if the concept is to be taken to the next level, advocates say.

“There are only two paths toward achieving big reductions in greenhouse gas emissions,” says Paula Dobriansky, U.S. undersecretary of state for global affairs, in an interview with the Financial Times. “One is to use existing technologies at the expense of economic growth. The other is to use breakthrough technologies that transform how we produce and consume energy and allow us to reduce emissions, while continuing to grow and to improve the world's living standards. The second course is the only acceptable, cost-effective option.”

WOW Energies, for example, has approached BP about implementing the idea. Its emphasis is on reducing pollution and not on power generation. The pitch: The waste heat is released at 600 degrees Fahrenheit. But, turning the thermal energy into electrical output can reduce the heat intensity. The vaporized propane that spins the turbine can bring the heat down to 100 degrees Fahrenheit. By cutting that heat to near ambient temperatures, the level of pollutants drops dramatically. Greenhouse gases are naturally reduced because the reliance on fossil fuels is diminished.

Energy is wasted daily. And a marketplace void now exists to recapture waste heat and to apply it to create electricity. Proponents of the concept say that the technology is available today to do just that but that the costs are a deterrent. If the government gets more involved, then they say that fewer power plants will ultimately be necessary and that the air will be much cleaner.

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