Energy and Exergy Analysis of a Hybrid Solar System in Terms of Thermal Energy Production and Cooling

Abstract

In this study a hybrid solar system, already available in the Laboratory of Applied Thermodynamics at NTUA is examined in terms of thermal energy and cooling power production. The system is installed in Athens, Greece and it comprises of two types of solar collectors, namely one series of CPC-PVT (Compound Parabolic Concentrator-Photovoltaic Thermal) collectors and one series of ETC (Evacuated Tube Collector), one indirect water buffer with an intermediate heat exchanger and a commercial zeolite adsorption chiller (LTC vario, Invensor). Simulations are carried out in order to estimate the energy and exergy efficiency of the system, the produced cooling capacity as well as the thermal energy stored in the buffer. Moreover, the performance of the chiller is evaluated for various months by determining the Cooling Capacity and COP, both solar and thermal. In order to determine, if the proposed solar cooling system performs better than a conventional that covers the same load, the primary energy savings and the reduction of CO2 emissions are calculated. The operating cost savings are also estimated. The simulation results show that the under study systems can indeed work sufficiently when the specific types and surface of collectors are considered. In specific, the system exhibits an average COP of 0.5 for the under study period while its solar exergy efficiency (nearly 2.5%) leads to the conclusion that the system, especially the collectors, can undergo an optimization process.