Cumulative solar exergy allocation in heat and electricity cogeneration systems

Heat and electricity cogeneration is effective to improve energy efficiency but with no a unified allocation method. Both the emergy and cumulative exergy methods could evaluate the resources consumption, with the issues caused by total inheritance principle and inequivalence of primary exergy, respectively. This paper takes solar exergy as the basis for cumulative exergy, proposing a concept of cumulative solar exergy (CSE), which provides a new insight for allocation problems and sustainability evaluation. The CSE allocation is performed by taking the CSE transformities (TrCSE) in the stand-alone heat and electricity generation systems (alternative systems) as baselines. The CSE method is applied in the biomass and coal gasification cogeneration systems, with back pressure steam turbine (BPT), extraction condensing steam turbine (ECT) and gas-steam combined cycle (GSC) taken as power generation facilities. The results show that the TrCSE of biomass-based systems are lower than those of the coal-based systems. The resource utilization efficiencies can be improved by cogeneration according to the TrCSE of cogeneration and alternative systems. The allocation results of CSE and exergy methods are in the range of energy and enthalpy drop methods. The electricity coefficients of the CSE method are higher than those of the exergy method. (C) 2022 Elsevier Ltd. All rights reserved.

Automated summary

This paper proposes the concept of cumulative solar exergy (CSE) and improves resource utilization efficiency by allocating based on the transformities in independent power generation systems. The results show that biomass-based systems have higher resource utilization efficiency, and the CSE method has higher electricity coefficients.