Design of a small-scale organic Rankine cycle engine used in a solar power plant

Under the economic and political pressure due to the depletion of fossil fuels and global warming concerns, it is necessary to develop more sustainable techniques to provide electrical power. In this context, the present study aims at designing, building and testing a small-scale organic Rankine cycle (ORC) solar power plant (similar to 3 kWe) in order to define and optimize control strategies that could be applied to larger systems. This paper presents a first step of the design of the solar power plant and focuses more specifically on the ORC engine. This design is defined on the basis of simulation models of the ORC engine and takes into account some technical limitations such as the allowed operating ranges and the technical maturity of the components. The final configuration includes a diaphragm pump, two plate heat exchangers for the regenerator and the evaporator, an air-cooled condenser, two hermetic scroll expanders in series and R245fa as the working fluid. Simulations indicate that an efficiency close to 12% for the ORC engine can be reached for evaporating and condensing temperatures of 140 and 35 degrees C, respectively.