Thermodynamic Analysis And Economic Assessment Of Biomass-fired Organic Rankine Cycle Combined Cooling Heat And Power System Integrated With Carbon Dioxide Capture

Efficient and low-cost utilization of renewable energy with ultra-low emissions is the focus of current energy transformation.Biomass-fired system based on Organic Rankine cycle with carbon capture(BE-ORC-CCS)can improve energy efficiency substantially,which is also the promising technology to control global temperature rise at low level.In this paper,the ORC model is first developed considering the cooling water loop,in which the effect of initial temperature of cooling water,water pump head and ambient temperature is studied,as well as the optimization of evaporation temperature and condensation temperature.Moreover,the model of single-effect lithium bromide absorption refrigeration cycle is established,in which thermodynamic properties of state points are calculated through regression equations of Li Br-H₂O.Limiting heat source temperatures are determined through the thermodynamic-iteration calculation and crystallization temperature of Li Br-H₂O solution,while economic heat source temperatures are achieved by experienced ranges of lithium bromide.Based on the principle of energy cascade utilization for the whole system,biomass-fired systems based on ORC combined heat and power or combined cooling,heat and power system have been developed.The pressurized hot water produced in the biomass boiler drives the ORC system to generate electricity,then supplying heating for users or driving the single-effect lithium bromide absorption refrigeration cycle to yield cooling.Meanwhile,the condensation heat can be utilized to supply domestic hot water.The exhaust gas is integrated with monoethanolamine-based CO₂ capture to achieve carbon dioxide emissions negative.As for thermo-economic models,it consists of the carbon-based fuel model for the original input,as well as comprising MEA-based CO₂ capture model at the end of exhaust gas.The analytical method of pinch point temperature difference is used to match heat source temperature and evaporation temperature,as well as cold source temperature and condensation temperature.Key operating parameters of biomass-fired ORC systems are optimized through thermodynamic analysis and economic assessment,as well as screening working fluids.The prospective BE-ORC-CCS technology is evaluated comprehensively in terms of efficient energy conversion and carbon dioxide emission reduction.In the CHP model,the power efficiency,exergy efficiency and primary energy saving ratio of biomass-fired ORC-CHP system would be improved with increasing evaporation temperature,while the heat source temperature can be optimized with total system investment,dynamic payback period or profit ratio of investment,screening HFE7000 as the best working fluid.As for the winter model,the biomass-fired ORC-CHP system achieves higher supplying heating ratio,exergy efficiency and thermal efficiency with higher temperature of supplying heat hot water,while presenting lower power efficiency,primary energy saving ratio and system total investment,in which the optimized evaporation temperature with dynamic payback period and profit ratio of investment is lower than the counterpart achieved by net present value.The biomass-fired ORC-CHP system(supply heating)achieves the best thermo-economic performance with R141b.In the CCHP model,biomass-fired ORC-CCHP system achieves lower supplying cooling ratio,primary energy saving ratio and system total investment as the input temperature of heat source for single-effect lithium bromide absorption refrigeration cycle,namely t_h1,decreases.The cooling efficiency and net present value are decoupled as subobjective functions.Then,the comprehensive objective function is achieved through the grey correlation method to optimize evaporation temperature T_eva and heat source temperature t_h1,with which the system presents better thermodynamic and economic performance simultaneously.The biomass-fired ORC-CCHP system achieves the best thermo-economic performance with Cyclopentane.The optimum condensation temperature is directly linked to domestic hot water standard temperature,while the earning of domestic hot water is the main annual income.The costs of MEA-based CO₂ capture system account for the largest investment in the whole system.The expenditure of biomass fuel contributes to the main annual spending,followed by the heating costs of stripper.The thermo-economic performance of biomass-fired ORC-CHP systems or ORC-CCHP system is declined when integrating with MEA-based CO₂ capture.However,the bioenergy system with optimized parameters is still thermodynamically feasible and economically attractive,eco-friendly with negative carbon dioxide emissions thanks to the CO₂capture.