Thermodynamic and economic assessment of a novel CCHP integrated system taking biomass, natural gas and geothermal energy as co-feeds

Abstract

The combined cooling, heating and power (CCHP) system based on biomass, geothermal energy and fossil energy contributes to less fossil fuel-dependent, alleviate the climate change and improve the flexibility of integrated system. Therefore, this paper presents a novel combined cooling, heating and power (CCHP) system based on biomass, natural gas and geothermal energy. The CCHP system consists of an air-biomass gasification subsystem, steam turbine electricity generation subsystem, gas turbine electricity generation subsystem, waste heat utilization subsystem and ground source heat pump subsystem. The thermodynamic and economic analysis of proposed system are investigated, and the influences of some key operating parameters (gas mass ratio and flue gas split ratio) and economic factors (such as biomass and natural gas price, interest rate, operating time coefficient and service life) on integrated system performances are also carried out. The results indicate that the introduction of natural gas contributes to improve the overall energy efficiency of proposed CCHP system and reduce the levelized cost of energy significantly. In the case study (gas mass ratio: 0.5, flue gas split ratio: 0.5), the overall energy efficiency and electricity generation efficiency of CCHP system can be reached at about 97.05% and 30.89%, respectively; the levelized cost of energy is 0.0315 $/kWh. The proposed system provides a new way for utilization of renewable energy and fossil fuels based poly-generation system, which is a promising approach for the utilization of biomass, natural gas and geothermal energy in the rural of China.