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Mechanical power generation based on solar Thermodynamic Engines

Final Report Summary - POWERSOL (Mechanical power generation based on solar Thermodynamic Engines)

The POWERSOL project aimed to develop an environmentally friendly shaft power generation technology of improved cost, which would be optimised for addressing basic needs of rural or small communities. The proposal was based on solar thermal energy and included a solar-heated thermodynamic cycle for mechanical power generation, electricity generation or brackish water and seawater desalination.

The optimisation of the thermodynamic cycle was performed by extensive experimental tests with selected working fluids using three solar collector prototypes. The output was coupled to a high-pressure pump connected to a conventional reverse osmosis system. The acquired power generation was in the range of 50 kW to about 500 kW. Apart from being technically developed and evaluated, the POWERSOL technology was economically assessed, while potential social and development impacts were investigated.

The most suitable boundary conditions and working fluids for the thermodynamic cycle were selected for three different top temperature ranges. The examined solar collector prototypes operated in the same temperature range and consisted of a stationary flat plate collector, a stationary compound parabolic concentrator and a single axis sun- tracking. The results were promising, providing the potential for patenting technologies and allowing for numerous applications.

The produced equipment was validated through the design and construction of an experimental power plant, including hot and cold circuits to power and refrigerate the thermodynamic cycle. It was, however, difficult to obtain stationary conditions for the proper unit assessment. Nevertheless, components with unsatisfactory performance were identified and were planned to be replaced during additional experimental campaigns. An electricity generation system was also simulated based on POWERSOL technology. Simulations were performed for different sizes of the thermal storage system and for two irradiation scenarios for heat losses over night.

The use of solar organic Rankine cycle (ORC) for freshwater production was highlighted, after comparison to other conventional and solar-driven methods, as being the most suitable application for Mediterranean regions. The proposal was beneficial in terms of the required solar field size, the capital cost, the minimal conventional energy consumption and the potential for creating standalone systems, which was a major advantage compared to existing alternatives. Software developing continued after the project completion, in order to compare the POWERSOL system for fresh water production with existing desalination technologies at an industrial scale.