Energy recycling in Japan is getting a new spin as turbines can now be powered by low-temperature steam and hot springs, sources that were until now ignored as waste.
Known as "binary cycle" generators, these miniature power plants use lower-heat materials than conventional plants and companies see a financial incentive after feed-in tariff payments for renewable energy went into effect in July.
The binary cycle uses hot water or steam to vaporize hydrochlorofluorocarbons, more commonly known as HCFCs. These liquids have a low boiling point, and their gases can spin a turbine. Traditional thermal plants use steam to drive the turbines.
In autumn 2011, Kobe Steel Ltd. developed a Microbinary apparatus capable of generating up to 70 kilowatts from water heated to between 70 and 95 degrees. The device, a cube just over 2 meters per side, is the smallest in the industry. The manufacturer has received orders already from a hotel in Yufuin, and from a company that supplies hot water in the renowned Beppu hot springs district. Yufuin and Beppu are in Oita Prefecture. The orders should be completed this year.
The device sells for 25 million yen ($322,000). The feed-in tariff system guarantees 42 yen per kilowatt-hour for electricity generated by small geothermal facilities for 15 years. That means the initial investment can be recovered in the first five to six years.
Geothermal power usually requires the extraction of very hot, high-pressure steam from deep underground. Hot spring resorts shy away from it because of the large-scale engineering required; they also fear extraction might deplete their source of hot water. The binary cycle solves the problem, as a hot spring alone can drive a generator.
Kawasaki Heavy Industries Ltd. has developed what it calls a green binary turbine with an output of up to 250 kilowatts. Testing is now under way using the hot water and steam byproducts of conventional thermal power stations. The temperature of the byproducts ranges from 80 to 130 degrees. The trials are taking place at the Yamagawa geothermal power station in Kagoshima Prefecture, and at a garbage incinerator in Osaka's Taisho Ward.
"Inquiries are up 50 percent since a decision was made to introduce the feed-in tariff system," said a spokesman for Kawasaki Heavy Industries. The feed-in tariff for biomass power generation, which comprises the burning of material like garbage, offers payments of 14 to 41 yen (17 to 52 cents) over 20 years.
Hitachi Zosen Corp. is getting in on the act, too, with a power generation system producing up to 2,000 kilowatts from waste heat of at least 80 degrees. The company plans to test it next year at a factory in the Chubu region of central Japan. Hitachi Zosen envisages the system being tied to a geothermal source or waste heat from factory boilers.
Japan Environment Systems Co., an environmental consulting firm in Tokyo, says in 2020 trapping waste heat in urban areas across Japan could save energy roughly equal to the output of one nuclear reactor.
A financial incentive is what often drives change. Currently, the feed-in tariffs apply to the use of biomass and geothermal heat, but waste heat from factories is excluded, on the rationale that the original heat source is not renewable energy. Manufacturers developing binary cycle technology say tariffs should be expanded to spur take-up of this new technology.
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