Nov
25
Anything Hot Equals Power
November 25, 2008 | 3 Comments
Low temperature heat, now claimed down to 65 degrees C is being used to generate electricity. That would scald you but isn’t hot in terms of being past the boiling point of water or oven cooking temperatures. It’s well within range of lots of geothermal. It’s easily under the waste heat temperature in most all industrial processes, coal, nuclear, natural gas electrical power generation stations, and well, anything big enough and this hot enough to be worthwhile.
The whole idea is to use a binary system in a Rankine Cycle, a cyclical sequence of heating for temperature and pressure to achieve stored energy, evaporation at a preset temperature controlled by the pressure, then delivering hot gas to an mechanical engine to get the energy into mechanical work, and then recondensing the gas to a fluid returning to step one – heating again. The binary part is the heat is used to heat another closed loop system running the power set.
What’s at stake, or more accurately what’s available is over 60% of the heat from the fuel used that is simply lost to the environment.
The technology going to so low a temperature is using an air or hydraulic motor design instead of a turbine. These motors are a bit more efficient than a turbine by about 10% and run at lower temperatures. Ener-G-Rotors in Schenectady New York is having some success in getting their designs installed and getting some technology press attention.
Ener-G-Rotors is saying their gear rotor, a wheel with teeth cut around the circumference running inside a ring with matching teeth cut on the inner surface circumference. With the axles offset for the gear and ring, the difference in size of the two sets up an opening and closing airspace. It’s just like a hydraulic gear pump except the gas goes in and propels the output rather than the power going in to pump a fluid or gas.
Ener-G-Rotors has designed a proprietary roller bearing to mount the rotor that they say nearly eliminates friction so it turn very easily. The ease of motion is said to reduce the force needed to rotate the unit thus needs lower pressures from the heat source. George Yarr, the company inventor says that the engine can start from one atmosphere of pressure, which is a small input.
The first Beta Unit, a small five-kilowatt system is going to Harbec Plastics. “If this works, it’s so huge,” says Bob Bechtold, president of Harbec Plasticss, one of Ener-G-Rotors’ potential customers. “I’ve been dreaming about the concept of using [low-temperature waste heat] ever since I first knew what it was about . . . It’s all about using what we have more completely.” It actually about getting more work for each fuel unit – more efficiency.
Power Plant Fuel Split Used and Lost. Click to Enlarge
Ener-G-Rotors is also installing betas at a steam plant for New York utility Consolidated Edison and at a landfill-gas-burning plant for the New York State Energy Research and Development Authority. ConEd says that Ener-G-Rotors’ system is more efficient than others reviewed. In a power plant that uses steam generators, it could have the added benefit of reducing the amount of water needed to cool the steam condensation and cutting additional sewage costs for getting rid of the extra water, he says. Mark Taylor, an analyst at research firm New Energy Finance says, (Low-temperature waste-heat technologies) “Really are where the industry is going. This potentially could be applied to every coal plant, every nuclear power, and every natural-gas plant. Steel, anything that makes heat–anything.”
If the betas work out, Ener-G-Rotors plans to expand to a 50-kilowatt demonstration unit, which is much smaller than the scale that most of its competitors are targeting. The company is hoping the smaller size will open up a market for smaller industrial waste-heat streams.
Meanwhile the competition is already out there. United Technologies has larger units out in geothermal just to start, with a lot of orders to fill at Razer Technologies. Electratherm (Post with coverage here.) is also installing units closer to Ener-G-Rotors size.
But Ener-G-Rotors President Michael Newell says, “Our technology is more efficient and simpler than anything else out there right now,” he says. “There aren’t many technologies that are going to work here. And we think we have the lowest cost of any of the technologies out there.”
Still, it might be a good idea to look into other air motor designs.
Reports from the company’s area news has them pricing at about $45,000 with an 18 month payback. This is attractive if the beta’s work out, an awful lot of burners could be putting power on the grid or simply cutting their draw from the grid, getting paid or not writing such large electricity service checks.
We’ve looked at compressed air drives in the past and suspect that systems using heat to drive a refrigerant based closed loop evaporative gas may well have a huge future. Better than 60, more like 70% of the energy used in the U.S is just venting off into the atmosphere now. Harvesting any percentage is free-fueled power, and the efficiency will go up as smart companies use their heat, and revenues come in to manufacturers that fund improving the technology.
One has to wonder, with now two companies shipping tested and known waste heat to electrical generation units when it will occur to utilities and other investors this is a slam-dunk investment.
One hopes the “credit crises” rights itself soon. Opportunity is a waitin’!
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