Energy and exergy analyses of an integrated CCHP system with biomass air gasification

• Propose a biomass-gasification CCHP system.
• A heat pipe heat exchanger is used to recover waste heat from product gas.
• Present the energy and exergy analyses of the biomass CCHP system.
• Analyze the annual off-design performances.

Biomass-fueled combined cooling, heating, and power (CCHP) system is a sustainable distributed energy system to reduce fossil energy consumption and carbon dioxide emission. This study proposes a biomass CCHP system that contains a biomass gasifier, a heat pipe heat exchanger for recovering waste heat from product gas, an internal combustion engine to produce electricity, an absorption chiller/heater for cooling and heating, and a heat exchanger to produce domestic hot water. Operational flows are presented in three work conditions: summer, winter, and the transitional seasons. Energy and exergy analyses are conducted for different operational flows. The case demonstrated that the energy efficiencies in the three work conditions are 50.00%, 37.77%, and 36.95%, whereas the exergy efficiencies are 6.23%, 12.51%, and 13.79%, respectively. Destruction analyses of energy and exergy indicate that the largest destruction occurs in the gasification system, which accounts for more than 70% of the total energy and exergy losses. Annual performance shows that the proposed biomass-fueled CCHP system reduces biomass consumption by 4% compared with the non-use of a heat recovery system for high-temperature product gas.