High-temperature solar organic rankine cycle - annual simulation of various system designs

This paper deals with the simulation of high-temperature solar organic Rankine cycles. In contrast to previous simulations the diurnal variations and the effect of charging and discharging the thermal energy storage are taken into account. Furthermore, the presented simulations cover one full year. The simulations use discrete time steps with a constant operation over a period of one hour. Considering a full year, 8 760 connected simulations have been carried out to describe the full and part load operation of one plant. Annual simulations allow a detailed evaluation of a solar organic Rankine cycle. The work describes the effect of varying solar field area and thermal energy storage capacity with different design points. High values of irradiance result in small solar fields. These fields often cannot provide enough thermal energy to produce the nominal electrical power at time steps with low irradiance. Design points using a low value for irradiance allow full load operations during the winter season. On the other hand, they generate a large percentage of waste heat during summer, which cannot be used due to limited storage and power capacity. The presented annual simulations show that different design points for a solar organic Rankine cycle cause various results for the plant performance over a full year. A design point in December leads to a large solar field and a thermal energy storage with a high capacity. The annual simulations show the continuous operation over a full year and are used to evaluate the plant designs.