Modeling of a new absorption heat pump-transformer used to produce heat and power simultaneously

A new cycle combining a heat pump-transformer and a turbine is proposed to simultaneously produce electric power and useful heat. The system was modeled using the ammonia-lithium nitrate mixture. Plots of power, useful heat, energy and exergy efficiencies are shown against the main system operating temperatures. The heat supplied to the system at a relatively low temperature was upgraded by 40 K to a higher useful level, whilst the proposed cycle was able to produce up to 300 kW of electric power at the same time depending on the operating system temperatures. The modeling showed that the overall energy and exergy efficiencies can reach values of up to 61% and 92%, respectively. Comparing the proposed system with an organic Rankine power cycle and an absorption heat transformer operating separately under the same operating conditions reductions in energy use and irreversibilities of up to 32.3% and 21.6%, respectively, could be achieved. In addition, a case study of the integration of the proposed cycle into a cogeneration pulp and paper mill is presented and it is shown that up to 25% of the gas natural supplied to the boilers could be saved together with 210 kW electric power production.