Comprehensive 4E analysis of a biomass-fired CCHP system integrating a high-efficiency absorption chiller and a supercritical CO2 Brayton cycle

This paper presents a comprehensive 4E (Energy, Exergy, Economic, and Environmental) analysis of a biomass-fired Combined Cooling, Heating, and Power (CCHP) system integrated with a High-Efficiency Absorption Chiller (HEAC) enhanced by a Hot Box. The system includes three components: an open Brayton cycle, a supercritical CO 2 Brayton cycle (s-CO 2 ), and an absorption chiller (AC). Compared to existing studies, the proposed configuration demonstrates superior fuel savings with improved energy and exergy efficiencies. A key innovation is the design of a HEAC achieving a COP exceeding 82% by incorporating a Hot Box and advanced heat recovery methods. Base case results indicate energy efficiency of 83.65%, exergy efficiency of 47.78%, total exergy destruction of 4366 kW, total cost rate of 4.526 $/h, overall unit cost of product (OUCP) of 36.54 $/GJ, and Modified Ecological Coefficient of Performance (MECP) of 2.17 kW/kW. Thermodynamic analyses show that at a Hot Box outlet temperature of 160°C, energy- and exergy-based COPs of the AC are 82.21% and 32.33%, respectively. Key operating parameters, including preheated air temperature before the gas turbine (GT), CO 2 turbine inlet temperature, and Hot Box outlet temperature, were optimized. With GT inlet at 750°C, CO 2 turbine inlet at 700°C, and Hot Box outlet at 170°C, maximum thermal energy recovery is achieved. Correspondingly, exergy efficiencies of the primary CCHP components reach 51%, 54%, and 53%. The system attains an MECP of 2.62 and OUCP of 47.83 $/GJ, reflecting a 12.1% reduction in OUCP versus the base case.