Increasing use of combined heat and power (CHP) systems in commercial and institutional settings in the United States could improve grid efficiency but boost greenhouse gas emissions, according to a Carnegie Mellon University report in the journal Environmental Research Letters.
CHP already accounts for about 7% of U.S. electricity generation capacity, with schools, hospitals, prisons, swimming pools, nursing homes, and laundries most likely to tap the opportunity to meet their hot water needs using waste energy from power generation. The Carnegie Mellon study looked at what would happen if that output grew by 2% to 9% per year over the next decade.
“According to the model, as the number of CHP systems increases, energy system costs would decrease by around 7% compared to a scenario with no CHP, and network congestion would also decrease,” Environmental Research Web reports. “But at the same time, the researchers found that greater penetration of CHP was also likely to lead to an increase in carbon dioxide emissions, with a 5% penetration of small commercial CHP producing a 2% increase in carbon dioxide emissions.”
The added carbon was mainly linked to wasted energy, the research showed.
“In general, CHP is not designed to be turned off more than once a day,” and “the increase in emissions occurred because of a tendency to run CHP continuously, even when the extra heat wasn’t needed,” ERW notes.
“It was the buildings that had the greatest variation in heat demand, such as schools, offices and retail outlets, which produced the greatest increase in carbon dioxide emissions. Meanwhile, buildings with a more constant heat demand, such as hospitals, large hotels, and full service restaurants, were less likely to let their CHP energy go to waste.”