Energy and economic assessment of solar Organic Rankine Cycle for combined heat and power generation in residential applications

Abstract The installation of solar heating systems for new buildings is currently imposed by regulation in different European countries. An interesting option to improve the use of solar thermal systems is its integration with an Organic Rankine Cycle to generate electricity, what would potentially increment the utilization factor of existing solar installations. The objective of the paper is to evaluate technically and economically the integration of solar thermal and ORC to conform a residential microCHP system able to cover a significant amount of the energy requirements of a standard house. Moreover, several strategies are analyzed to incorporate energy storage within the microCHP system. Two operation modes of the system are evaluated, isolated and integrated within the grid network: i) Solar energy for producing domestic hot water and electric power production in the ORC auxiliary power system; ii) Reversible micro-scale ORC with a scroll compressor to run as a scroll expander. An economic analysis is done under different scenarios. Results show the appeal of the implementation of these systems at small scale for residential applications in locations with specific climate conditions. IRR values above 15% with short payback periods from 3.1 years and positive NPV are obtained.