Increase of thermal efficiency of cogeneration plant by waste heat utilisation with absorption heat pump

Abstract

The very rapid growth of share of electricity generation from renewable sources is observed recent years. However, even if that share reaches about 50% in 2050, almost 50% of electricity will still be generated based on fossil fuels combustion rather than on nuclear energy. That means, energy generated from coal will still be important for the next decades. The largest sources of energy loses within the steam power plant is the steam cooling system. The energy dissipated to the atmosphere in that system is very difficult to be utilized mainly due to the relatively low temperature, and its direct utilization without additional equipment is rather impossible. The large amount of energy lost to the environment leads to low overall thermal efficiency of the plant, therefore, utilization of this energy should be of primary importance. The paper shows concept of increasing efficiency of cogeneration plant thermal cycle by utilisation of waste heat from flue gas with absorption heat pump, for the purpose of system heat generation. Calculations of combined system of power plant fuelled with biomass fuel with implemented waste heat utilisation system were performed for one heating season and different moisture content in the fuel. Results show, that owing to waste heat utilization instead of conventional heat exchanger, additional electricity generation during the heating season at even 46864 MWh may be achieved which is over 18% more for the moisture content in the biomass fuel at 0.5 kg/kg, the same ambient conditions and heat generation.