Design of an ORC system operating with solar heat and producing sanitary hot water

Organic Rankine Cycle (ORC) is useful to generate electricity from low temperature sources such solar heat (<120 °C). An ORC system, working with R-245a, is presented and analyzed. The system provides the required electric power and the required hot sanitary water of a typical dwelling during one day (24 hours). The system operates between a cold source of 25 °C and a hot source: water at 120 °C in solar hours, when solar flux is available, and between a cold source of 15 °C and a hot source: water at 98 °C coming from the accumulation tank in no-solar hours (morning, evening, and night). The maximum generated electric power is 2000 W, and the used daily hot water is 200 l at 60 °C. The required surface of the solar heater is 100 m2 assuming 8 solar hours per day and a mean solar flux of 400 W/m2. The advantages of the ORC system are the electricity generation, the hot water production and the low cost compared to photovoltaic electric power generation.