Cogeneration, a.k.a. Combined Heat and Power, May Be the Future of HVAC
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If you haven’t already heard of cogeneration, chances are that you’ll be hearing a lot more about it in the near future. That’s because it represents one of the most effective approaches for optimizing building energy use. It’s also because our current political and cultural trajectory strongly favors this type of technology. And HVAC is one of the major areas that can benefit from it.
COGENERATION: DEFINITION AND HISTORY
Cogeneration, which is also widely known as combined heat and power or CHP, is defined by the EPA as “the generation of electricity and the capture and use of otherwise wasted heat energy byproducts.” Wikipedia offers a slightly more detailed definition/description when it explains cogeneration as “the use of a heat engine or a power station to simultaneously generate both electricity and useful heat.”
In other words, cogeneration is the practice of generating electricity, which can of course then be used for any number of applications, and then capturing and making productive use of the heat that is a by-product of electricity generation, and that is customarily siphoned away into the environment. The process effectively eliminates one of the major waste factors from the production of electricity.
As various sources point out, cogeneration has been around at least since 1882, when Thomas Edison sold not only the electricity produced by America’s first power plant but also the waste heat produced as a byproduct. So it has long been known to and used by the industrial world. But today something different is happening.
In its “Best Practice Guide for Commercial Office Buildings,” the website Flex Your Power explains that the commercial applications of cogeneration are now coming to light as the process gains popularity:
Industrial facilities that require process heat or steam have long benefited from cogeneration systems that supply both electrical and thermal energy. More recently, owners and managers of commercial buildings have discovered that cogeneration can be a cost-effective source of reliable energy as well as heating and cooling — the single most expensive operating expense in typical buildings.
The same guide explains that cogeneration systems in commercial office buildings, consisting of an engine, turbine, or fuel cell that generates on-site electricity plus a heat recovery unit,
are usually connected to an absorption chiller that provides heating and cooling for the central heating, ventilation, and air conditioning (HVAC) system. The absorption chiller, which is powered by thermal energy, replaces a traditional chiller powered by electricity. Cogeneration systems can also heat domestic water for use in the building.
A TIMELY TECHNOLOGY
If you ask why such a surge in popularity for non-industrial uses of cogeneration should be happening now, you can turn to the California Energy Commission for an answer, which they provide in their 1999 Guidebook for Combined Heat & Power (pdf), wherein they present an entire section titled “Why the new interest in CHP?” They offer five reasons for its increasing popularity in the commercial sector, including improvements in CHP technologies and a recognition among policy makers that use of cogeneration enables the burning of less fossil fuel.
You can also turn to the U.S. Department of Energy’s March 2000 report, Combined Heat and Power: A Federal Manager’s Resource Guide (pdf), which points out that cogeneration
has existed for more than 100 years and is now achieving a greater level of acceptance due to increased reliability and overall cost efficiency. Capturing and using the thermal energy produced as a byproduct from fuel sources such as oil, coal, or natural gas, increases the power gained from the original fuel source. CHP technologies have the potential to reduce energy consumption — decreasing energy bills, as well as pollution.
And if you’re thinking that all of these listed benefits intersect mightily with so-called 21st century concerns, you’re entirely correct. The DOE estimates that integrated CHP systems can increase a building’s overall energy efficiency by 30 to 40 percent, and as we are now living on the leading edge of an era of increasingly constrained economic conditions and energy resources, the political and social will to embrace radical efficiency seems to have arrived at last. Cogeneration may just represent the future of commercial HVAC systems and energy production. Only time will tell, but the indications right now look positive.
Next Steps:
- For more information about cogeneration, see the U.S. DOE’s page of information resources about CHP applications.
- Subscribe to our blog to stay informed on the latest cogeneration news and insight.
Matt Cardin
Goodway Blogging Team
miggs
Wonderful post. I’m associated with Recycled Energy Development, a leading CHP company, and though I’m of course biased, I can affirm that there’s a massive opportunity here. Indeed, studies done for the EPA and DOE suggest CHP (and its sister technology, waste energy recovery) could slash U.S. greenhouse gas emissions by 20%. That’s as much as if we took every passenger vehicle off the road. The main obstacle is a set of regulations designed to protect utilities and which make it hard to get such projects off the ground. But the opportunity exists regardless, and we should be doing much more.
Rob Johnson
Given the poor efficiency of absorbers (a COP of around 1.25 compared to a COP of 7.0 for electric centrifugals) I believe that Co-Gen is really best suited for those applications requiring process heat: large domestic water heating, industrials, labs, etc. Sincerely would like to know if others have a different opinion.
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Evo Energy Technologies
Wow, you’ve covered such a broad topic in a single article. Yes, you are right cogeneration will be the future of HVAC as cogeneration plants have a conversion efficiency of 70% to 90% and is useful in heating buildings and industrial process. Looking forward for more useful information on energy generation, thanks for sharing!!