Experimental study of a micro combined heat and power system with a solar parabolic trough collector coupled to a steam Rankine cycle expander

Micro Combined Heat and Power (micro-CHP) devices are seen as promising solutions for the reduction of fossil fuel consumption and CO2 emissions in the building sector. A micro-CHP system composed of a solar parabolic trough collector in direct steam generation coupled to a steam Rankine cycle expander has been developed and studied. The presented results show the feasibility of coupling a solar collector in direct steam generation to an expander for micro-CHP purposes. However, the dynamic tests point out important fluctuations of the expander inlet conditions due to the relatively high volume of the solar collector with respect to the flow rate. In order to limit these fluctuations, a PI controller has been implemented to control the expander inlet pressure. Two steady state points have been obtained. The reached electrical power output is relatively low (around 1.3 kW) and leads to a solar-to-electricity efficiency close to 3%. The solar-to-thermal efficiency is close to 38% for a thermal power output of 19 kW. These limited values are due to the low operating pressure (maximum 26.3 bar), to the high heat losses and to the efficiency of the solar collector. The temperature of the building supply water was measured around 60 degrees C and values above 80 degrees C can be reached, which is sufficient for hot water production or heating. (c) 2016 Elsevier Ltd. All rights reserved.