Time flies, twelve months have passed, and now is time for a one-year review of the Princess Margaret Cancer Centre (PMH) deep lake water cooling (DLWC) project.

My former co-worker Chad explained a similar system at Toronto General Hospital here.  Lisa wrote a blog Deeply Cool on how it works.  It’s a natural and sustainable way to provide cooling and a great gift from Mother Nature.  There is no need to run chillers, which require electricity and are expensive to maintain.  

The chillers use refrigerants that can cause global warming issues.  Actually, one of the refrigerants used is R-134a, thousands of pounds of it.  Its global warming potential (GWP) is 1,430 times that of CO2!  Now, because of DLWC, those chillers seldom run and the chances of an expensive refrigerant leak are much lower.  As you can imagine, there are huge savings on energy alone – This Picture’s Worth 3.3 Million Kilowatt-Hours! – according to monitoring by Ed Rubinstein.  His latest chart shows in the 2020-2021 fiscal year, we saved 5.1 million kWh of electricity.   The project is eligible for $1.06M incentive from the SaveOnEnergy program. 

Other than that, we also saved about 33,458,000 L of water for cooling tower makeup in the first year. Since cooling towers evaporate water to derive cooling, not using them means not evaporating all that water. The incentive from City of Toronto’s Capacity Buyback Program is about $27,500.  Even with relatively clean electrical grid in Ontario, associated greenhouse gas reduction with those is enormous. 

There’s also a health and safety reason to love this project. Open loop cooling towers are notorious for Legionella bacteria.   Now we can provide cooling without running the cooling towers.  This eliminates droplets that may spread the bacteria.   Each cooling tower dumps lots of heat removed by chillers plus energy used to remove the heat to the atmosphere by spreading and evaporating those tiny water droplets.   It’s one of the reasons why there is heat island effect in downtown Toronto and many large urban centres.   Mother Nature is smarter than us in every way and what we need to do is to listen to her hints.

Toronto heat island effect.  Source: Perez C., 2008

So how did the new deep lake cooling perform in the past year?  As part of this project, we placed flow meters and temperature sensors everywhere.  Those allow us to monitor the system and trouble-shoot possible issues.  All those data points are trended continuously.  I am happy to report that our records show that the system is working as expected.  During hottest days in 2020, chilled water temperatures for 610 University cooling loop and process cooling loop are well maintained and our facilities management team is very impressed.  It is true green technology that can reduce energy consumption by up to 90 percent in contrast to conventional air conditioning.