Investigation of multi-effect mechanical vapor compression desalination system powered by photovoltaic/thermal, photovoltaic-evacuated tubes, and photovoltaic solar collectors: Techno-economic study

Abstract

Energy and potable water are two serious necessities for human life all over the world. Solar energy can be used to produce potable water at low cost. Multi-effect mechanical vapor compression desalination system powered by solar energy technology could be a solution of the production of freshwater with high performance and low cost. Techno-economic performance of forward-feed multi-effect mechanical vapor compression desalination system powered by photovoltaic/thermal collectors is investigated. The feasibility of using the electrical and thermal energy of photovoltaic/thermal collectors to directly power the multi-effect mechanical vapor compression system is studied. Performance of the desalination system with photovoltaic/thermal collectors as a power source is assessed and compared to another two systems powered by photovoltaics with evacuated tubes and photovoltaics only. The three proposed systems’ mathematical models are built and solved using MATLAB. The impact of changing effects number, compression ratio, and last effect temperature on systems’ performance is investigated. Results showed that the external preheater enhances the system performance as high-grade electricity is replaced by low-grade heat when increasing the number of effects. Multi-effect mechanical vapor compression could be powered by photovoltaic/thermal collectors at a wide range of compression ratios and number of effects but with a limited range of last effect temperature. Coupling photovoltaic/thermal collectors to multi-effect mechanical vapor compression greatly reduces the required collectors’ surface area in comparison to photovoltaics with evacuated tubes and photovoltaics only with specific collectors’ surface areas of 7.36, 10.65, and 11.98 m2/(m3/day), respectively. The highest performance ratios recorded are 28.42 for photovoltaic/thermal collectors, 16.5 for photovoltaics with evacuated tubes, and 12.96 for photovoltaics only. The lowest unit water costs are 4.15 $/m3 for photovoltaics with evacuated tubes, 4.22 $/m3 for photovoltaic/thermal collectors, and 4.31 $/m3 for photovoltaics. Furthermore, replacing electricity with heat reduces energy storage shares of capital cost from 63% to 48%.