Combined heat & power (CHP) or cogeneration, is really not an energy source itself, but rather more of an energy multiplier, squeezing more usable energy out of each unit of fuel most everywhere it is applied.
According to the EPA, CHP is not a single technology, but rather, an integrated energy system that provides electricity and heat, usually in the form of hot water or steam. Heat is an inevitable byproduct of any power produced by gas or steam turbines, which would include all gas, coal, oil or nuclear power plants in use today. In these turbines, pressurized hot gas or steam is expanded across a turbine, which spins the blades that ultimately drive the generator. The hot gas needs to be cooled immediately after leaving the turbine for the system to work. This was traditionally done with a condenser or cooling tower, but using the heat to keep a building comfortable or drive a production process, with steam or hot water, will also do the job with little loss in efficiency. However, in order for the heating application to replace conventional cooling systems, the demand for heat must be continuous. Typical CHP system will reclaim upwards of 80 percent of the heat that would otherwise be wasted.
A conventional fossil fuel plant achieves a thermal efficiency of approximately 33 percent.
When integrated into a CHP system, the same power plant can achieve efficiencies between 60 and 80 percent. It is estimated that CHP systems can reduce carbon emissions by up to 30 percent.
Without CHP, fuel is used to provide electricity and then additional fuel is used for heat, which in many cases is a missed opportunity.
Cogeneration systems are generally installed on-site for large facilities, such as factories, institutions, commercial buildings, multi-unit residential buildings and district energy systems. It is particularly attractive for facilities with a high heating demand. These facilities then have their own source of electricity as well as a source of heated water or steam. The CHP needs to be located close to where the heat will be used so it won’t cool down. It is therefore an inherently distributed energy source. CHP is seen to be cost-effective in areas where the cost of electricity is seven cents per kWh or higher.
CHP is generally based on fossil fuel technology, though some companies are now marketing solar cogeneration products: Naked Energy in the UK, and Cogenra in the US.
The number of building with CHP potential in this country has been estimated at well over a million, with energy usage close to 80,000MW. Cutting that by 30 percent would be equivalent to shutting down twelve 1000MW coal plants.
The systems can be installed by any of a number of contractors, many of whom are members of the EPA’s CHP Partnership.
RP Siegel, PE, is the President of Rain Mountain LLC. He is also the co-author of the eco-thriller Vapor Trails, the first in a series covering the human side of various sustainability issues including energy, food, and water in an exciting and entertaining format. Now available on Kindle.
Follow RP Siegel on Twitter.
RP Siegel (1952-2021), was an author and inventor who shined a powerful light on numerous environmental and technological topics. His work appeared in TriplePundit, GreenBiz, Justmeans, CSRWire, Sustainable Brands, Grist, Strategy+Business, Mechanical Engineering, Design News, PolicyInnovations, Social Earth, Environmental Science, 3BL Media, ThomasNet, Huffington Post, Eniday, and engineering.com among others . He was the co-author, with Roger Saillant, of Vapor Trails, an adventure novel that shows climate change from a human perspective. RP was a professional engineer - a prolific inventor with 53 patents and President of Rain Mountain LLC a an independent product development group. RP was the winner of the 2015 Abu Dhabi Sustainability Week blogging competition. RP passed away on September 30, 2021. We here at TriplePundit will always be grateful for his insight, wit and hard work.