Combined Heat and Power May Conflict with Decarbonization Goals-Air Emissions of Natural Gas Combined Cycle Power versus Combined Heat and Power Systems for Commercial Buildings

This study compares the environmental impacts of a centralized natural gas combined cycle (NGCC) and a distributed natural gas-fired combined heat and power (CHP) energy system in the United States. We develop an energy-balance model in which each energy system supplies the electric, heating, and cooling demands of 16 commercial building types in 16 climate zones of the United States. We assume a best-case scenario where all the CHP's heat and power are allocated toward building demands to ensure robust results. We quantify the greenhouse gas (GHG) emissions, conventional air pollutants (CAPs), and natural gas (NG) consumption. In most cases, the decentralized CHP system increases GHG emissions, decreases CAP emissions, and decreases NG consumption relative to the centralized NGCC system. Only fuel-cell CHPs were able to simultaneously reduce GHG, CAP, and NG consumption relative to the NGCC-based system. The results suggest that despite their energy efficiency benefits, standard distributed CHP-based systems typically do not have enough benefits compared to an NGCC-based system to justify a reorganization of existing infrastructure systems. Because fuel-cell CHPs can also use hydrogen as a fuel source, they are compatible with decarbonized energy systems and may aid in the transition toward a cleaner energy economy.

Automated summary

This study compares the environmental impacts of a centralized natural gas combined cycle (NGCC) and a distributed natural gas-fired combined heat and power (CHP) energy system in the United States. The results show that decentralized CHP systems generally increase greenhouse gas emissions, decrease conventional air pollutants emissions, and decrease natural gas consumption, but only fuel-cell CHPs are able to simultaneously reduce emissions and consumption, and are compatible with decarbonized energy systems.