Granite Power is a geothermal company that has developed GRANEX®, a patented direct supercritical fluid heat transfer technology for the efficient, economic, and zero carbon emission generation of electricity from low grade geothermal sources using the Organic Rankine Cycle (ORC). This technology is typically used with recovered waste heat (RWH), solar-thermal sources, conventional geothermal sources, and engineered geothermal systems to generate electricity.
The construction of a pilot plant to demonstrate the use of the GRANEX technology with a solar parabolic trough linear concentrated receiver system was partially funded through a grant from the Australian Renewable Energy Agency (ARENA. Rated at 150 kW thermal, the receiver system consists of six 1,800 mm by 35 m parabolic concentrating troughs. The GRANEX fluid is heated by pumping it directly through the troughs, and without changing states is passed to a turbo generator. Designed in conjunction with the University of Newcastle, this generator spins at speeds of up to 70,000 RPM to produce 30 kW of electrical power for the power grid.
Waste heat is passed through a heat exchanger to heat the water for a local swimming pool, allowing it to stay open for more of the year. During peak solar periods, energy can also be transferred to an insulated oil-filled thermal storage vessel. The energy stored there is sufficient to keep generating power for up to 90 minutes during periods of no sun or after sunset.