Combined heat and power with fuel cells or internal combustion engines using nearly green hydrogen for decarbonisation

The carbon footprint of fuel-cells and internal combustion engines for cogeneration with green hydrogen are compared. A new definition based on the exergy destructions by the renewable energy systems is introduced for the green hydrogen concept. With six rating and evaluation metrics, 11 major emission-responsible points were identified in comparing fuel cell and internal combustion engine type of combined heat and power. Flat-plate solar panels, and geothermal energy are considered for temperature peaking to replace heat pumps. Results show that they cannot meet the emission minimisation objective. Case studies provide ways and for minimum carbon dioxide emissions responsibility.