Abstract
The compressed air energy storage (CAES) system, considered as one method for peaking shaving and load-levelling of the electricity system, has excellent characteristics of energy storage and utilization. However, due to the waste heat existing in compressed air during the charge stage and exhaust gas during the discharge stage, the efficient operation of the conventional CAES system has been greatly restricted. The Kalina cycle (KC) and organic Rankine cycle (ORC) have been proven to be two worthwhile technologies to fulfill the different residual heat recovery for energy systems. To capture and reuse the waste heat from the CAES system, two systems (the CAES system combined with KC and ORC, respectively) are proposed in this paper. The sensitivity analysis shows the effect of the compression ratio and the temperature of the exhaust on the system performance: the KC-CAES system can achieve more efficient operation than the ORC-CAES system under the same temperature of exhaust gas; meanwhile, the larger compression ratio can lead to the higher efficiency for the KC-CAES system than that of ORC-CAES with the constant temperature of the exhaust gas. In addition, the evolutionary multi-objective algorithm is conducted between the thermodynamic and economic performances to find the optimal parameters of the two systems. The optimum results indicate that the solutions with an exergy efficiency of around 59.74% and 53.56% are promising for KC-CAES and ORC-CAES system practical designs, respectively.
Highlights
Due to the increasing depletion of fossil fuels and the deterioration of global environmental pollution, integrating renewable energy sources into the power system has developed rapidly during the last few decades
The round-trip efficiency η of the system is the ratio of the total energy generated ∑ W out and the total energy consumed by the system
The compression ratio and temperature of the exhaust gas (Teg ) are the key parameters to find the different requirements for the two proposed systems to recover the heat efficiently
Summary
Due to the increasing depletion of fossil fuels and the deterioration of global environmental pollution, integrating renewable energy sources into the power system has developed rapidly during the last few decades. Because of the advantages of the gas engine in the small-scale industrial system, integrating the gas engine with CAES could boost the system output power, and improve the efficiency of energy utilization and operation flexibility in the system [5]. Zhao et al [8] proposed an integrated energy system based on CAES and the Kalina cycle, which can recover the waste heat of exhaust from a low pressure turbine during the discharge process. We consider the possibility of recovering heat from the exhaust gas of the compressor and the gas engine by means of KC and ORC in this paper to improve the operating efficiency of the system greatly and expand the scope of application of the energy storage system. The working process of the system can be divided into two periods: charge period and discharge
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