Simon St Hill and the team at Green Thermal Energy Technologies (gTET) have developed and commercialised a high speed microturbine Organic Rankine Cycle (ORC) system for use in recovering low grade heat energy and converting it to electricity.
The units can be used to convert heat from any thermal source including thermal solar, biomass, or industrial waste heat, reducing carbon emissions by displacing that power. Because industrial waste heat sources are generally continuous, the system can function as a base load power source.
The business was established seven years ago by engineers in the automotive industry with strong thermodynamics skills, who were anticipating the demise of that industry and looking to use the skills they had developed.
An ORC system is basically the same as a normal Rankine power system (steam boiler/turbine), except that it uses an organic fluid such as a refrigerant like R245fa. This makes it a hybrid between an industrial refrigeration plant and a traditional power plant.
They chose to develop a 170 kW unit, which would suit waste heat streams of around 1 MW of low grade heat, with typical ancillary loads being under 20 kW giving 150 kW nett to the client.
The system has been exported to South Korea where it is using the steam exhaust from a back pressure turbine on a municipal incineration plant, extracting every last bit of energy from the burning waste. They are currently manufacturing a system for the Winton Shire Council geothermal power station, which will convert heat from their bore water into electricity supplementing the town.
They have calculated that, in an industrial situation, payback times of under three years can be achieved. They are finding that the system appeals not just to engineers and environmentalists, but accountants too.
[Simon St Hill. Photo: Green Thermal Energy]