The LOW-BIN project intends to complement and advance geothermal binary plants technology by developing two binary units, the first one for power generation at lower temperatures (65-90 °C) and the second one for heat and power cogeneration at higher temperatures (120-150°) with drastically improved overall energy efficiency.
Excluding a few early experimental units constructed in Russia and China, the majority of the geothermal binary plants operate with supply temperature above 100 °C, with no units at commercial operation with geothermal source temperature below 86 °C.
The first LOW-BIN prototype
The first LOW-BIN prototype intends to widen the application of commercial binary power technology to geothermal fields of even lower temperature, without any significant impact to costs and conversion efficiency. Existing plants are designed for higher temperatures and include expensive corrosion and temperature resistant materials. In lower temperature applications, materials of less cost can be used in order to reduce capital costs. The first prototype that will be developed for the LOW-BIN project will be tailor-made for low temperature geothermal environment, which allows the selection of alternative low cost materials and hence considerable costs reduction. In addition, the whole machine will be reengineered in order to identify recoverable energy losses and improve overall conversion efficiency. Existing geothermal cogeneration of heat and power plants, although resulting in significant reduction in energy production costs and improving overall energy efficiency from 11-15% to 35-60%, still have large amounts of wasted energy released to the environment through the cooling fluid circuit.
The second LOW-BIN prototype
The second LOW-BIN prototype intends to tap this energy, by raising the temperature of the cooling water from 10-25°C to 60-80°C, which allows the heat content of the cooling water to supply a district heating system. The energy flows in the second LOW-BIN prototype, compared with existing geothermal cogeneration binary plants, are presented schematically below. In terms of geothermal energy utilization, this configuration allows drastic improvements in overall energy efficiency of geothermal cogeneration schemes, to approach 98-99%, with corresponding reduction in overall power generation costs, especially when the machine is integrated into an existing district heating scheme. In order to further reduce capital costs contribution to the life cycle costs of the machine, the machine will be able to operate in both CHP and only-electricity generation modes (for the time period of the year that the district heating system has low heating load).