Energy Conversion and Management, Vol.173, 271-282, 2018
Ability of adjusting heating/power for combined cooling heating and power system using alternative gas turbine operation strategies in combined cycle units
Gas turbine combined cycle (GTCC) based combined cooling, heating and power (CCHP) or combined heating and power (CHP) system driven by natural gas is encouraged to set up for district heating/cooling demand in China due to the clean and efficient energy conversion. This paper presents a GTCC based CCHP system, which consists of a heavy-duty gas turbine, triple-pressure heat recovery steam generator (HRSG), steam turbines, heat exchanger and absorption chiller. Turbine inlet temperature (TIT) strategy and inlet guide vanes (IGV) strategy for the gas turbine are adopted to access the part load performance. The energy distribution and exergy destruction of the CCHP system are investigated under different gas turbine loads. The primary energy saving rate (PESR) and carbon dioxide emission rate (CDER) are set up to evaluate the system at various gas turbine loads and steam extraction ratios. The ability of shaving peak power for the system is investigated. The results show that IGV plays a role in increasing the steam turbine power output and reducing the exhaust heat in HRSG but causes more exergy destruction in the steam turbine expansion process. The PESR and CDER have been enhanced as the steam extraction ratio increases for the same gas turbine load. The IGV strategy reinforces the part-load performance of the CCHP system. For instances, the PESR has been enhanced from 0.2409 to 0.3108, and CDER has been strengthened from 0.8274 to 0.8465 by the IGV strategy at half of gas turbine load and without steam extraction. For the same heating load, both PESR and CDER are enhanced by the IGV strategy. The ability of supplying heating is deteriorating as the decrease in TIT. The ability of shaving peaking power is going to be deteriorated as heating load increases. For the small heating load, like 50 MW, the advantage of the IGV strategy is prominent, the PESR and CDER is advanced 5.81% and 1.48% respectively by the IGV strategy.