A comprehensive performance analysis is presented of various cogeneration systems for buildings, using energy and exergy analyses. Various cogeneration plants are considered, including steam-turbine, gas-turbine, diesel-engine, and geothermal. Here, cogeneration refers to the simultaneous generation of electrical power and heating for buildings (especially for space heating and hot water). Selected actual operating data are employed. The same amount of electrical and thermal product outputs are considered for all systems, except the diesel, to facilitate comparisons. The diesel-engine and geothermal systems are thermodynamically more attractive in that they have higher exergy efficiencies than steam-turbine and gas-turbine systems. The results demonstrate that exergy analysis is a useful tool in performance assessments of cogeneration systems and permits meaningful comparisons of different cogeneration systems. Such results can allow the efficiency of cogeneration systems to be increased, and the applications of cogeneration in larger energy systems to be configured more beneficially, leading to reductions in fuel use and environmental emissions.

Units: SI