INTEGRATING MICROTURBINES IN THE ORGANIC RANKINE CYCLE
Capstone Turbine Corporation (Chatsworth, CA), a leading manufacturer of microturbines, has teamed up with TurboGenix, Inc. (Brookville, FL), a supplier of waste-heat recovery systems, to integrate microturbines in Organic Rankine Cycles (ORC). The TurboGenix product can recover heat from a variety of sources, such as engine and turbine exhaust, to produce power. Major market segments for the TurboGenix system include exhaust heat recovery from power generation systems at landfill gas plants, biogas plants, wastewater treatment plants, and combined heat and power plants.
A single TurboGenix ORC combined with four C65 Capstone microturbine systems can increase power output from 260 KW to 380 KW and boost electric efficiency from 30% to 44%. The TurboGenix ORC typically uses a waste-heat source in either gaseous or liquid state at 210°F or above. This heat converts the ORC refrigerant (245FA) to saturated vapor, which drives a turboexpander directly coupled to a rare-earth magnet generator. The generator spins at 30,000 rpm, uses magnetic bearings, and produces 125 KW of 480 V, three phase power. The vapor is condensed to liquid and recycled.
Individual exhausts from a gang of microturbines can be connected to a single stack in which a heat exchange coil carrying the refrigerant can be installed to act as a waste heat boiler, says Robert Miller, president of TurboGenix. The installed costs are typically $200,000, although the exact cost varies with the project. The cost of power produced is the maintenance cost of $0.0075/KWH, plus the cost of capital, adds Miller.
Copyright Turbomachinery International Jul/Aug 2007
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