By Lee Consavage

I apologize for my tardiness in posting this blog but fortunately I can blame it on renewable energy (and the IRS - I just completed and submitted our company’s tax forms which were due March 15th). Due to the recent increase in energy costs, I’ve been fielding a lot of questions about renewable energy alternatives. I now have lots of interesting projects I’m working on, but not much time to write about them. So I’ll update you on my most interesting project, which is a tri-generation project. Tri-generation is also known as Combined Cooling, Heat and Power or CCHP. 

In a previous blog I described a co-generation system being considered for the new Cross Roads House facility to be built in Portsmouth (refer to my blog on January 12th, 2008). Again to briefly summarize, a co-generation unit, such as a Capstone microturbine (, creates both electricity and heat. The co-generation unit is typically located inside the building that is using both the electricity and heat. So essentially the building has its own power plant to meet some or all of its electricity and heating needs. Heat is actually the by-product of creating the electricity, so the facility pays to create the electricity but then gets free heat. The microturbine uses natural gas, propane or landfill gas to create the electricity.

Getting free heat is great during these long, cold New England winters. But what about the summer months when air conditioning is needed. Won’t all that excess heat being generated by the microturbine result in higher air conditioning costs? The answer is “yes” if the heat cannot be used and needs to be exhausted from the building. So wouldn’t it be great if your co-generation system could somehow use all that heat for cooling purposes. Well it can! Absorption Chillers, such as the ones made by Yazaki ( are made exactly for that purpose. It uses heat to provide cooling. Sounds unbelievable doesn’t it, but it really does work. Absorption chillers use hot water (190 degrees F) to provide chilled water to cool the building. Absorption chillers are only available for large buildings, but residential sized units are currently being developed. When an absorption chiller is used in conjunction with a microturbine, the system is referred to as tri-generation.

I recently visited the home of a very, very, very wealthy family in western Massachusetts who are interested in a tri-generation system being installed on their property to provide electricity, heating and cooling to their home and other buildings on their 100+ acres. Due to the enormous amount of electricity and heat produced by a microturbine, it is highly unusual for a tri-generation system to be installed at a private residence. I applaud this family for taking the time to learn about the tri-generation technology and its huge positive environmental benefits. The current plans are to install four Capstone C65 (65 kilowatt) microturbines and two Yazaki 20-ton absorption chillers.

The greenhouse gas reduction attributable to using this tri-generation system is approximately 1,400 tons of carbon dioxide. This reduction is equal to removing the carbon that would be absorbed by 400 acres of forest! Wow! So why is the greenhouse gas reduction so great? It’s because the tri-generation system uses a relatively low emissions fuel (natural gas, propane or landfill gas) and has an efficiently rating greater than 80%. A typical power plant is 25% efficient since none of the heat by-product is captured and used. And then there are the transmission losses of 5% or more.

I know you’re thinking that similar environmental benefits could be realized if this family were to just purchase their electricity from a renewable energy source, such as wind or solar. Then they could avoid the high cost of installing the tri-generation system. You’re right to a certain extent. But they would still need to transport the wind or solar energy to their home, resulting in transmission losses. Also the heat generated by the wind turbine and/or the solar electric panels is wasted. And the family still needs to heat and cool their home. So taking the heating, cooling and electricity production into consideration, the environmental benefits from a tri-generation system have a greater impact than just using wind or solar. More to come………


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