Alternative energy systems certainly are not new to The Hotchkiss School who installed a central biomass heating plant to serve the winter heating needs of their campus back in 2012. However, with limited summer heating loads, the school simply could not justify operating the central biomass plant outside of the main New England heating season. This forced a few buildings, including the Forest E. Mars Jr. Athletic Center, back to heating water with a HEWH-500-WS – High Efficiency Water Heater legacy oil boiler during the warmer months.

The oil boiler, originally sized with enough capacity for winter heating, before the biomass plant came online, was oversized for the smaller summer thermal loads which included pool heating and domestic hot water. This revealed the need for a much more efficient heating system during the milder parts of the year.

A Solution With Propane

Enter the Ilios HEWH-500-WS high efficiency water heater from Tecogen Inc. The HEWH-500-WS, applied as a dedicated heat recovery chiller, is a perfect fit for the 212,000-square foot Mars Center due to the Center’s simultaneous need for water heating and space cooling during the spring and summer months. By leveraging the advantages of combined heat and power, commonly referred to as “CHP”, the Ilios unit is able to efficiently and cost effectively drive a heat pump process with a gaseous fueled reciprocating engine.

Because the Hotchkiss School is off the natural gas grid, the engine is driven by clean burning propane. Tecogen’s patented Ultera emissions aftertreatment package, ensures near zero criteria pollutants—a major plus over the legacy oil boiler. Waste heat from the engine’s exhaust, block, and oil heat are recovered and added to the heat from the condenser of the heat pump cycle, increasing the source efficiency to levels much higher than that of an electric heat pump. This results in substantial lower greenhouse gas emissions, largely due to the lower carbon content of propane vs. heating oil.

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