Danfoss Energy Transfer Stations Help Sheridan College’s District Energy System Make the Grade

Creating a sustainable energy system to heat, cool and power an entire college campus is no easy feat. In 2013, when Sheridan College launched its Energy and Climate Master Plan, with the goal of lowering campus energy and greenhouse gas emissions by half, they realized that they would need to transform their heating and cooling system. They looked to the Trias Energetica model, first developed in 1979, as a guide to developing a sustainable energy system, integrating heating and cooling functions and recovering energy that might otherwise be wasted.

“We wanted to position Sheridan as a role model on sustainability and follow best practices. This ties into our educational mission as well,” said Herbert Sinnock, Sheridan’s director of sustainability. After an evaluation of the HVAC infrastructure in existing campus buildings, the college realized that the most effective way to make its heating and cooling operations more efficient was to install an entirely new system, using a district energy model, starting at its Trafalgar Campus in Oakville, Ontario.

Sheridan began constructing its third-generation district energy system in the summer of 2016, burying 3.5 km of pre-insulated pipes that carry pressurized hot water across the campus from a central plant to every building. Sinnock notes that the pipe network is not installed very deep in the ground, which made it quick and easy to install. Modern pre-insulated pipe systems integrate leak detection, helping operations teams quickly identify any problems to ensure that the system will continue to operate at peak efficiency.

Reciprocating heat and power engines, installed in 2017 and 2018, generate baseload heating for the system along with a modest amount of electricity. Supplemental boilers provide additional temperature lift on very cold days. Centralized delivery uses less energy than a distributed system with separate boilers in each building. 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 (ETS). The ETS is 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. 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. The ETS is a key component of the district energy system because it contains automated controls which provide continuous digital metering and can monitor and adjust to the demands of the building, controlling critical temperatures and working to maximize the combined efficiency of the primary loop and the buildings.

“We wanted to acquire the product from a company with an established track record of installing these devices. We were aware that Danfoss had a rich history of selling ETS outside of North America,” said Sinnock. “We liked that the stations could be factory built, customized and programmed to match our facility, then delivered fully-assembled and ready to operate on Day One.”

In 2019, Sheridan began a three-year project to decommission a nearly 50-year-old steam plant serving six of its Oakville buildings, 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. That means that the campus buildings would potentially be without heat during the installation period. Sinnock noted that while it was a challenge to coordinate both contractor schedules and the school’s academic calendar, the installation went smoothly.

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’ ability to customize the pipe network on each ETS to facilitate connection to the unique conditions in each mechanical room minimized delays in connecting the new equipment. It also enabled quick movement of complete energy transfer stations into the tight spaces of the existing system.

“It only took a couple of hours per unit to start up the system,” said Sinnock. “The pre-programming and pre-testing helped make the transition seamless.”