Sheridan began by burying more than two miles of pre-insulated pipes that carry pressurized hot water from a central plant to every building on campus. Reciprocating heat and power engines were installed to generate baseload heating for the system, along with a modest amount of electricity. Supplemental boilers provide additional temperature lift on very cold days. In the summer, the engines’ heat can be sent to an absorption chiller that feeds the chilled water network to several campus buildings.

At each building, heat is transferred from the system’s primary loop to each building’s secondary heating system through a Danfoss Energy Transfer Station, or ETS — an interconnected system of heat exchangers, valves, pumps, programmable controller, metering, and piping that draws heat from the primary loop of pipes outside each building to control and feed the building’s secondary heat network. Its controls govern critical temperatures and maximize the combined efficiency of the primary loop and the buildings. A pressure-independent control valve on the primary side of the ETS ensures that the heat exchanger operates efficiently, using an outdoor temperature sensor to modulate the heat transfer process for each building while allowing each building’s heating system to operate independently.

Then, Sheridan began a three-year project to decommission a nearly 50-year-old steam plant, replacing it with the new hot water district heating system. A steam-to-hot-water conversion requires replacement of all steam-generating equipment with a completely new system.

Because each Danfoss ETS arrives ready for start-up with factory-configured and pre-tested controls, they are able to control the heat exchange between the primary loop and the building upon first start. This meant that the period when buildings would be without heat could be minimized and multiple buildings could make the transition to the new district energy system in quick succession.

Danfoss customized the pipe network on each ETS to fit the conditions in each mechanical room, minimizing delays in connecting the new equipment. It also enabled quick movement of complete energy transfer stations into the tight spaces of the existing system. Startup took only a couple of hours per unit.

Prior to the switch to district energy, the college’s steam plant was losing about 65% of the heat it generated. Following the conversion to the hot water system, natural gas consumption was reduced by 20%, which equates to an annual carbon reduction of 530 metric tons.

Looking ahead, Sheridan’s district heating system creates an energy network where heat could be recovered — for example, from a local ice rink or the college’s glass-blowing studio — and supplied to other buildings in the district.