Thermodynamic analysis of waste heat recovery from hybrid system of proton exchange membrane fuel cell and vapor compression refrigeration cycle by recuperative organic Rankine cycle

摘要

According to day-by-day consumption increase, energy high costs and nonrenewable energy destroying effects, clean technologies such as fuel cells lead a remarkable decline in consumption. In the present study, waste heat recovery from a hybrid system of an 1180kW low-temperature polymer electrolyte membrane fuel cell and a vapor compression refrigeration cycle is surveyed using a recuperative organic Rankine cycle. The fuel cell system is equipped with a metal hydride storage. The heat absorbed from stack is divided into two streams. One stream flows into the recuperative organic Rankine cycle to produce power, and the other goes for waste heat recovery of the refrigeration cycle condenser; then, it is utilized for other components of fuel cell system including metal hydride to release hydrogen and H-2 preheater to preheat the hydrogen to the stack temperature. Effects of operational parameters including fuel cell thermal efficiency, cooling load, pressure ratio, mass flow rate and working fluid of recuperative organic Rankine cycle were thermodynamically analyzed. Two working fluids were surveyed including R-245fa and R-134a. Results indicate that hybrid system thermal efficiency falls down by increase in turbine pressure ratio. The maximum system consumption power was dedicated in the case in which the fuel cell has its highest thermal efficiency in addition to minimum net produced power. Additionally, R-134a was determined as the best working fluid. Net output power and efficiency of the system with R-134a are about 1.2 and 20% more than R-245fa, respectively.