Improving Efficiency with a Tri-Generation System

Improving Efficiency with a Tri-Generation System

This past November, the Town of Scarborough, ME started up a new project that involves providing power to its Town Hall building in a whole new way. Last year, the building was changed over from a traditional electricity, heating, and cooling system to a combined heat and power system using what is called a tri-generation configuration. This new system is expected to help to manage costs, improve energy efficiency, increase energy infrastructure resiliency, and reduce carbon emissions. 

The decision to install this state-of-the art system came out of the cost reduction goal in Scarborough’s 2011 Comprehensive Energy Plan, which was developed by the town’s Energy Committee. This project was a key strategy in this plan, as the group had been working continuously to create a power generation capacity to reduce the town’s reliance on market sources while reducing overall energy costs. The Energy Committee and town leadership’s vision ultimately includes a much larger campus-wide on-site energy system that will provide very low-cost, green energy to the Town Hall, High School, Middle School, Intermediate School, Sports Fields, and Library.

A Tri-Generation, or combined cooling, heat, and power system, produces electricity, heat, and cooling in one process and is sized for the heating and cooling needs of the host facility. In most models, excess electricity is produced while meeting the thermal needs of the facility. For the Town Hall, the excess, low-cost, electricity produced from this model will be used community-wide at other municipal facilities where Tri-Generation isn’t practical. Other alternative energy technologies could also easily be integrated into the campus-wide infrastructure if the town chooses to do so in the future. 

Making the transition to this new system required installing a natural gas fired 150 kW Kraft Power Systems combined heat and power unit. At this size, the system will be capable of handling future expansions at the Town Hall building, including the addition of the town’s new public safety building that is to be constructed on adjacent property. The overall system, designed by Self-Gen, an integrated energy solutions and services company based in Scarborough, will include the Kraft CHP unit, an absorption chiller and cooling tower for cooling, hot and chilled water piping systems integrated into the existing building, and a control system linked to the building’s automation system.

A project like this has a variety of complex moving parts, but the expectations for the benefits to the town are high. Even though this technology and its applications have been proven and around for decades, it is new to municipal settings, and everyone undergoes a learning curve before having the comfort level to move forward. I give Tom Hall (the town manager), his staff, and the Energy Committee a great deal of credit on being trailblazers willing to implement a project like this. They saw that the long-term benefits with cost savings and greenhouse gas reductions ultimately surpassed any concerns or reservations while laying the groundwork for future expansions at the same time.

The tri-generation system is expected to provide 100% of the Town Hall’s electricity, 60% of its heating in the winter, and 80% of its cooling in the summer, adding up to an estimated $40,000 a year in energy cost savings. The excess electrical output will be used under a Net Metering agreement with Central Maine Power to reduce electrical consumption at other town facilities, as well. Using a tri-generation system is a large part of the town’s energy management strategy for municipal buildings, which will allow for more control over their long-term energy costs and reduce exposure to changes in energy prices.

The new system has been running since November, and though it’s still too early to benchmark its performance, using the metrics provided during the completion of a preliminary energy balance, the town estimates the project can achieve 50% overall energy savings for the Town Hall. The savings could be even greater depending on the costs, revenues, and tax credits realized by the project. This project, along with other strategies in the Comprehensive Energy Plan, is a good demonstration of the leadership the Town of Scarborough continues to display for embracing projects like this one for the benefit of the whole community and serves as an effective model for other municipalities interested in doing the same. For more information on whether a combined heat and power system might be for you, be sure to look at our whitepaper on the topic.

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