A study of the thermodynamic performance and CO2 emissions of a vapour compression bio-trigeneration system

A trigeneration system (simultaneous production of heating, cooling and electricity) using a heat engine and a vapour compression chiller, running on biofuel, is studied. A system configuration, capable of meeting the three energy demands in a realistic situation, was devised. It consisted of a compression ignition internal combustion engine driving an electric generator, an electrically driven vapour compression heat pump and a peak boiler. Part of the heating demand was met by recovering waste heat from the engine and the heat pump condenser, thus reducing the overall fuel consumption. New criteria parameters, based on the relative magnitudes of the three energy demands, were defined to evaluate thermal performance and CO2 emissions. A comparative analysis between the biofuel trigeneration and conventional fossil fuel with no waste heat recovery was carried out, showing that, depending on the relative values of energy demands and on component characteristics, significant reduction on primary energy consumption (up to 50%) and on CO2 emissions (up to 5% of the original emissions) can be attained with the biofuel-trigeneration combination.