Technical, economic and environmental optimization of combined heat and power systems based on solid oxide fuel cell for a greenhouse case study

摘要

The aim of this paper is to investigate the application of solid oxide fuel cell (SOFC) as the prime mover of a combined heat and power (CHP) system. In this paper, four hybrid systems are proposed to improve the performance of CHP and compare with baseline condition. Capacity design and operation strategy of hybrid systems are applied to a case study of a greenhouse located in Mahabad, Iran and optimized by using technical, economic and environmental objective functions. Levelized cost of energy (LCOE) and CO2 emission rate are considered as the objective functions. For LCOE optimization, three scenarios are considered to evaluate the impacts of future energy prices and CO2 tax. In scenario i (Regional energy prices in Iran without CO2 tax), none of the proposed hybrid systems are competitive with the baseline case and the difference between LCOEs of the best hybrid system and baseline is 2.8 (sic)/kWh. In scenario ii (Regional energy prices in Iran with CO2 tax), although the difference between LCOEs decreases to 1.8 (sic)/kWh, none of the proposed hybrid systems are beneficial in comparison with the baseline. In Scenario iii (world average energy prices with CO2 tax), in contrast with previous scenarios, optimized LCOEs of two hybrid systems (11.15 and 11.4 6/kWh) are lower than baseline LCOE (17.56 (sic)/kWh). From CO2 emission point of view, all of the proposed optimized hybrid systems have lower CO2 emission than baseline. Finally, a multi-objective optimization is done to consider both techno-economic and environmental objective functions simultaneously and provide a powerful decision support tool. The results show that yearly CO2 emission of SOFC base CHP hybrid systems are averagely 62% lower than conventional systems. Moreover, they would be economically beneficial in the case of increasing energy prices and environmental limitations.