Analysis of multi-cascade CCHP system with gas turbine bypass extraction air energy storage

The operational load of gas turbine can be regulated by using compressor bypass extraction. In this paper, a combined cooling, heating and power (CCHP) system integrating gas turbine cycle (GTC), compressed air energy storage (CAES), supercritical CO2 Brayton recompression cycle (SCRC), organic Rankine cycle (ORC) and ab-sorption refrigeration cycle (ARC) is proposed. The use of CAES not only enables flexible recovery of waste heat and load demand regulation, but also enables effective storage and secondary use of bypass extracted air from the compressor. The temperature of the graded expanded air is reduced and returned to the gas turbine unit, improving its thermal performance. The exergy and economic analyses show that the GTC has the largest per-centage of both exergy destruction and investment cost rates, over 60%. Under the proposed operation model, the payback period of a single gas turbine is 4.12 years, and the payback period of the proposed CCHP system is 2.44 years. Thermodynamic, economic and environmental evaluation models are established to analyze the system performance at different loads. At the lowest load operation, the energy efficiency of the CCHP system can reach 75.99%, the exergy efficiency is 45.89%, the unit energy cost is 0.032 $/kWh, and the greenhouse gas equivalent emission is 0.313 kgCO2e/kWh. Compared with the other four cascade waste heat recovery systems, the proposed CCHP system greatly improves the thermodynamic performance and reduces the unit energy cost rate and greenhouse gas equivalent emissions, especially under low load operation conditions.