Thermo-Economic and Carbon-Intensity Co-Optimization of Decentralized Bio-Hydrogen Systems in Commercial Buildings

Abstract

Decentralized bio-hydrogen systems, integrating localized biomass gasification, hydrogen cogeneration, and HVAC absorption cooling, offer a viable pathway for decarbonizing commercial real estate. However, existing control strategies fail to co-optimize second-law thermodynamic exergy efficiency with dynamic grid carbon intensity and fluctuating carbon-tax pricing, a gap consistent with the broader finding that carbon-pricing frameworks only translate into emission reductions when paired with dispatchable technology able to respond to the price signal. This paper formulates a nonlinear thermo-economic optimization model for building-integrated bio-hydrogen systems operating under regional emission-trading schemes, together with an explicit capital-recovery-factor-based definition of the Levelized Cost of Building Energy (LCOBE) tying the dispatch objective to the building's actual 20-year capital and financing profile. Evaluated across three distinct climate zones (Cold, Mixed, Tropical), the proposed Carbon-Exergy Co-Optimization (CECO) algorithm increases annual exergy efficiency by an average of 21% relative to conventional heat-led operation, and reduces LCOBE by up to 21.4% under a strict $130/ton carbon-tax framework.