Numerical investigation of the smart energy management of modular latent heat thermal storage on the performance of a micro-solar power plant

Solar energy is widely considered as one of the most attractive renewable energy source to curb CO2 emissions at residential level where micro-cogeneration has a very interesting potential. One promising application of solar energy is in combination with Organic Rankine Cycle (ORC) plants due to the ability to utilize low-medium temperature heat sources. However, because of the intermittent availability of solar energy, thermal energy storage (TES) systems are required to improve the performance of such systems and assure their prolonged operation. At medium temperatures, latent heat thermal energy storage (LHTES) systems allow to effectively store and release the collected thermal energy from the solar field. However, room for improvements exists to increase their efficiency when in operation. For this reason, in this work the authors have numerically investigated the performance of a 2 kWe micro-solar ORC plant coupled with an innovative LHTES system that is going to be built and tested under the EU funded project Innova MicroSolar. The novel LHTES, developed and designed by some partners of the Consortium, is subdivided into six modules and consists of 3.8 tons of high-temperature phase change material. In this study the effect of the storage volume partialization on the performance of the integrated plant is evaluated using a fuzzy logic approach. Main aim of the storage management is to achieve a reduction of the thermal losses and improve the plant overall efficiency. Annual dynamic simulations are performed in order to determine the optimal storage volume needed in different operating conditions. Results clearly show a remarkable annual increase in electric and thermal energy production of 8 % and 6 % respectively, in comparison with the configuration without fuzzy logic control: this achievement was obtained decreasing the working LHTES modules in winter and conversely increasing them in summer.