State of Art of Small Scale Solar Powered ORC Systems: A Review of the Different Typologies and Technology Perspectives

Solar thermoelectric, even for small sizes, is continuing to garner more attention, by virtue of maturation of small size organic Rankine cycle generators, and of small size absorption chiller even if cost and reliability are still not optimal. Indeed, solar thermal power technology improvement would consent to stimulate an ambit already present in Europe and Italy with a well-known tradition and established leadership and efforts focused on a single solar technology would bring to positive effects concerning controllable electric and thermal energy uses. In this context, the present work tries to summarize the possible cycles and fluids that can be applied in a small solar thermal power plant. Despite a plethora of simulated and experimental cycles and fluids, the simplest cycle using near isentropic fluids seems to be the best choice for a small ORC-based CHP system, even if particular attention has to be done to all the sizing parameters (electricity, heating and cooling demand; area and type of solar collector; flow and temperature of the thermal carrier; flow, temperature and pressure of the working fluid; storage volumes; etc.). Indeed, efficiency and reliability of the reported systems are very different, but, it seems that global efficiency of even more than 10% and global cost of even less than 10,000 €/kW can be obtained even at size of few kW if adequate systems are constructed and managed.