Evaluation of turbo compressor performance for a water based HTHP to be utilized in solar assisted heat supply

Heating systems in industrial processes, transport and buildings are extraordinarily carbon-intensive and highly polluting. Fossil fuels by far account for the largest share of the heat generation, covering 85% of the heat demand in 2017. Industrial energy consumption covers a significant fraction (about 30%) of the total energy demand in the world. Heating accounts for about 75% of this energy consumption, consequently much of fossil fuels consumption for heating is caused by industry. This context arises the heat supply for industry by utilizing solar assisted heating in combination with a HTHP system, supplying heat up to e.g. 200°C. Sensible heat supply by means of parabolic-trough collectors and linear-fresnel collectors may reach temperature of up to 160°C. With in this framework the application of water as working media is favourable. Thus, the focus of this work is aiming towards evaluation of water vapour compression performance at a suction temperature range of 120 °C to 150 °C, with suction pressures of 1 bara to 3 bara. For this purpose, a two-stage turbo-compression system was developed been able to overcome challenges related to elevated suction pressure, e.g. such as working media leaking through the shaft seal. Testes of the mass-produced automotive turbocharger technology were performed. The turbo-compressor of the first stage reached a pressure ratio of 2.3 and the second stage up to 2, respectively under ambient pressure suction conditions. Resulting in a total pressure ratio of 4.6. Mass flow rate measured reached up to 800 kg/h superheated steam delivered at a pressure of 4.2 bara, having a saturation temperature of 146°C. For the 1st stage compressor, the maximum isentropic efficiency was 65%. The second stage yielded 70%, resulting in a second law efficiency based on Carnot of 48 %.