International Journal of Energy Research, Vol.42, No.15, 4817-4829, 2018
A hybrid PV/T and Kalina cycle for power generation
This work introduces a novel hybrid system which uses the cooling water of a concentrated PV/T as a preheated water for lithium bromide-water-based Kalina cycle. The PV/T is a combination between solar photovoltaic cells and solar thermal collector. The solar cells convert the sunlight into electricity, and the remaining heat gets absorbed by the collector for additional power generation. As well as, extracting the excess heat from PV cells enhances its electrical efficiency. The Kalina power cycle is mainly driven by concentrated solar parabolic collectors (CSP). The advantage of combining these 2 systems is to employ the heat rejected from the concentrated solar-based PV cells for further electricity generation, thus increasing the system overall efficiency. The system of concentrated solar collectors is divided into 2 parts to avoid getting very high temperature for the PV cells: concentrated solar collectors with PV cells and without PV cells. Due to the high temperature of water which returns from the Kalina cycle, a cooling tower is employed to cool the water before entering the concentrated PV/T system. The mathematical model of the proposed system has been presented and simulated to investigate the effect of the main controlling variables on the proposed system performance: generator temperature, solar radiation, wind speed, and the ambient temperature. The results show that the amount of solar radiation is the primary variable for the investigated system energy productivity, while the design temperature of generator is found to be the most parameter that affects the system overall efficiency. While the overall efficiency is around 18% to 23%, combining PV/T with the proposed solar Kalina cycle increases the system overall efficiency by 22% to 27%. The electrical conversion efficiency of the proposed system is 40% to 68% much more compared to PV/T alone system.