The challenge of achieving aggressive decarbonization goals can be daunting for any university, let alone a growing one. With an expanding campus and student population come expanding requirements for heating and cooling. Coupled with the need to keep operating costs under control and tuition affordable, many universities struggle to find actionable, enduring solutions.
At the University of British Columbia Okanagan (UBCO) campus in Kelowna, part of the challenge lies in decarbonizing their existing thermal energy networks, which include a medium-temperature district energy system (MDES) connecting older buildings and an ambient low-temperature district energy system (LDES) connecting newer buildings.
District heating and cooling is nothing new, of course. In North America, the first networks for sharing thermal energy were created more than a century ago. With each new generation, thermal energy networks have become more flexible, reliable, and efficient.
Even so, many modern district energy systems still rely on gas boilers for significant portions of their annual heating loads, which means they're producing large quantities of greenhouse gas emissions every year—a big problem when you're trying to decarbonize.
For UBCO, the solution starts with deploying a Vitalis Coolshift™ centralized air-source heat pump (ASHP). It utilizes R744 (CO2), an A1 natural refrigerant with ultra-low global warming potential (GWP) and no PFAS toxicity.
The Existing System: Over 14,000 GJ of Heating to Decarbonize
Before getting to the R744 ASHP, it's important to understand the existing setup.
Unlike the MDES which supplies water at 80°C, the LDES at UBCO supplies ambient-temperature water between 8°C and 25°C. The water is distributed via underground, uninsulated PVC piping to individual hydronic heat pumps in each connected building, which either absorb heat from the LDES loop for heating or reject heat to the loop for cooling.
Infrequently, during shoulder seasons, these heat pumps can maintain the LDES loop temperature thanks to a balanced load (i.e., some buildings require heating while others require cooling). But most of the time, when the thermal load is unbalanced because of extra demand for either heating or cooling, the LDES taps into centralized systems that include natural gas boilers, a connection to the MDES, open-loop geothermal, and fluid coolers.
The total annual heating demand of the LDES loop is 14,267 GJ. Nearly 70 percent of that demand occurs with outdoor temperatures between -5°C and 5°C.
Natural gas boilers provide the vast majority of heating to the loop, followed by the connection to the MDES, which is also served by gas boilers. The open-loop geothermal system supplies the rest of the heat, though in smaller amounts.
For summer cooling, fluid coolers (i.e., wet cooling towers utilizing evaporative cooling) are the primary source of heat rejection from the LDES loop. They are highly efficient and augmented by occasional heat rejection into the geothermal system.
Like most district energy systems, the LDES has several advantages. For this thermal network, UBCO has cited benefits such as:
Minimal heat losses due to the ambient low-temperature distribution
Energy sharing between buildings for higher efficiency
The ability to provide both heating and cooling
Compatibility with diverse thermal energy resources
Centralized maintenance with reduced space requirements for mechanical equipment
The Challenge: Displace Gas Boilers With a Future-Proof Solution
As part of its climate action plan for campus operations, UBCO is targeting a 65-percent reduction of greenhouse gas (GHG) emissions from 2013 levels by 2030. This goal is extra challenging in light of plans to expand the campus.
Since natural gas boilers represent the largest source of GHG emissions for the LDES, UBCO knew that decarbonizing the thermal network would require replacing them—as much as possible—with technologies that don't burn fossil fuels.
Beyond GHG emission reductions, any decarbonization strategy must also include considerations for issues like capital and operating costs, scalability, and resiliency to known and potential regulatory changes.
That led UBCO to explore various potential solutions before arriving at centralized air-source heat pumps as the most appropriate technology for this particular application.
Heat pumps are popular solutions for high-efficiency electrification of heating and cooling loads. However, all heat pumps are not created equal. The type of refrigerant in a heat pump plays a crucial role, not just for performance, but also for sustainability.
Hydrofluorocarbons (HFCs), synthetic chemicals, are the dominant refrigerants used today. But they are being phased down due to their high global warming potential (GWP), which can be hundreds or thousands of times greater than the GWP of carbon dioxide. That makes HFCs not just bad for our climate, but also increasingly expensive and harder to obtain.
So for UBCO, the challenge was to source economically viable, low-GWP ASHP technology that aligns with their decarbonization strategy.
The Solution: A 1.5 MW R744 Air-Source Heat Pump From Vitalis
For this type of application, at this scale, "off-the-shelf" solutions either don't exist or carry unwanted drawbacks. The solution had to be customized, which provided the opportunity to design a system with the best possible performance for the specific operating conditions.
Carbon dioxide (aka R744 when used as a refrigerant) offers several advantages over other refrigerants. For example, CO2:
Has a GWP of 1 (compared to 20-year GWP values up to 12,400 for HFCs)
Is an A1 refrigerant with no toxicity, no flammability, and no corrosiveness
Has zero ozone depletion potential
Is widely available and up to 12-20 times less expensive than synthetic refrigerants
Carries no risk of regulatory bans as a natural refrigerant
Does not contribute to environmental PFAS contamination, unlike hydrofluoroolefins (HFOs) and many HFCs
R744 is also well-suited to ambient low-temperature district energy applications. In heating mode—under subcritical operation—the performance of an R744 heat pump for an LDES like UBCO’s can't be surpassed. No other refrigerant can match the efficiency.
That's the key. In the subcritical thermodynamic cycle, carbon dioxide remains below its critical threshold of 31°C and 1,073 psi. It doesn't reach the higher pressures and temperatures required of a transcritical cycle, in which the refrigerant moves between the subcritical phase and the supercritical phase (i.e., above the critical threshold).
Today, most R744 systems operate in a transcritical thermodynamic cycle. But for UBCO's LDES, the Vitalis Coolshift heat pump will be able to operate subcritically most of the year.
The reversible air-source heat pump has a nominal capacity of 1.5 MW at -10°C and is designed to operate with outdoor temperatures between -20°C and 40°C.
It will become the primary source of heat for the LDES, making the network much less reliant on natural gas.
During summer, the heat pump will operate in a transcritical cycle, acting as an auxiliary source of cooling with the high-efficiency fluid coolers remaining as the primary source.
Anticipated Outcomes
The 1.5 MW Vitalis Coolshift R744 ASHP project includes an upgrade path for scalability capable of providing 2.5 MW of capacity.
Based on an energy analysis by Vitalis, installing this ASHP is anticipated to result in:
815 tonnes of GHG emission reductions
The displacement of 430,000 cubic meters of natural gas
The delivery of 14,000 GJ of heating—98.4% of the LDES' total heating demand
The delivery of 99.9% of the required auxiliary cooling demand
An annual coefficient of performance (COP) for heating of 3.5
An annual COP for cooling of 3.6
With UBCO looking to economically decarbonize their LDES in pursuit of achieving their 2030 climate targets, this R744 heat pump project will go a long way toward helping them do just that.