Low-carbon fuelled MGT-CHP system coupled with PEM electrolyser and fuel cell units: A fuel flexibility and performance study

Recently, micro gas turbine (MGT) systems for combined heat and power (CHP) plants have attracted much attention due to their high energy efficiency and low carbon emissions. Therefore, this work presents a 5.5 kW MGT-CHP system coupled with a proton exchange membrane (PEM) electrolysis cell and a fuel cell unit for domestic applications. The simulation study includes an MGT unit that produces both heat and electricity, a low-temperature PEM electrolysis of H_2 O to produce H_2 fuel for the combustor, and a PEM fuel cell to generate electricity during system initialisation. The MGT unit in this study uses H_2, hythane (20% H_2 and 80% CH_4), natural gas (NG) and methane (CH_4) fuels to investigate the thermal and electrical efficiency and CO_2 emission avoidance for each fuel utilisation. The result shows that the combustion of H_2 and hythane in the MGT combustor produces almost the same amount of nitrogen oxides (NOx) due to the lower reaction temperature of the combustor. 7% of CO_2 and CO emissions were avoided by replacing NG with hythane. CO_2 and CO emissions were avoided by burning H_2 instead of other fuels. Higher thermal efficiency was seen on the H_2-fuelled MGT system. However, higher end-use costs were observed for the MGT system running on both H_2 and hythane fuels due to the higher purchase price of both fuels. The addition of a recuperator promoted lean combustion, which improved the overall efficiency of the proposed system. The outcome of the studied work achieved an efficiency of 82% for PEM electrolysis of H_2 O and an MGT-CHP efficiency of 96%.