Now that we are groggily emerging from our hibernation of sitting on the couch in a Snuggie and binge TV watching while eating cookie dough ice cream, it’s time to think about spring cleaning. On second thought, sweeping the garage, sorting old junk, and throwing mittens in a drawer sounds awful – let’s talk about spring greening instead! Here are a few tips for an energy efficient spring and summer: Continue reading
My previous blog described a unique energy conservation project at UHN’s Princess Margaret Cancer Research Tower (PMCRT). With innovative contaminant sensing technology, we were able to convert our research lab exhaust system from constant flow to variable flow, which significantly decreased loading on the exhaust fan motors. As described in the blog, this change produced a reduction in electricity peak demand (kW) of 38.5% and reduction in overall annual electricity consumption (kWh) of 42.7%.
We thought this was a Continue reading
Next in our list of exciting energy endeavors, this blog will discuss huge savings realized by a retrofit to the laboratory exhaust system at the Princess Margaret Cancer Research Tower (PMCRT). The lab exhaust system has been converted from constant speed to demand controlled to ensure more efficient operation. I’ll get into all the super interesting details below, but the best part is the savings so I’ll start off with that. Continue reading
With the last moments of warm weather dwindling and Halloween fast approaching, let’s take a look at the Continue reading
Grizzlies, mountains, and sustainability! Earlier this week, I had the opportunity to attend the Canadian Healthcare Engineering Society (CHES) annual conference, hosted in beautiful Vancouver. The theme of this years conference was sustainability in healthcare. This theme refers to both systemic sustainability and environmental sustainability, with the goal to preserve health care services as well as the natural environment so that you’ll be able to get a timely appointment for your tennis elbow injury suffered during a round of frisbee golf and so that grizzlies can continue to survive in their natural habitat.
UHN had great Continue reading
In my last cold beverage related… ehh… I mean refrigeration related blog, we learned about complicated stuff like how the refrigeration cycle works and how water savings can be achieved by retrofitting old systems. Since we’re all experts already, I’ll skip all the boring techno-babble and get straight to the good stuff.
Our old refrigeration system at Toronto Rehab’s Bickle Centre used domestic water to cool the refrigeration condensers, meaning that to keep our fridges cold we were continuously pouring water down the drain. How much water? I’m glad you asked because we set up an ultrasonic flow meter on the discharge line to measure just how much water (and $$$) we were sending down the drain.
Until this summer, the chiller plant at Lyndhurst was the same one that had been chugging away since the original construction of the building in 1974. The old cooling plant at Lyndhurst included an oversized centrifugal chiller, constant speed chilled water and condenser water pumps, and a constant speed cooling tower with two fans. Older chillers such as this one tend to operate very inefficiently at low loads, which is usually the case with this system because the plant was originally designed to accommodate a third floor expansion to the building (which never occurred). For lots more info on how building cooling works, take a look at Chad’s Blog here.
To assess the performance of the existing chiller, logs were reviewed and electrical metering conducted.
Chiller performance is often measured based on the unit kW/ton, meaning the amount of electrical power required in kW to generate each ton of cooling. The chart below shows the performance of the old chiller, broken down based on cooling demand. Spot metering was also conducted on the pumps and cooling tower to determine their base case performance, however the chiller is the largest electricity consumer.
As you can see, the old chiller’s performance drops off as the cooling demand decreases. Newer chiller technology can easily perform at 0.6kW/ton at full load and is actually more efficient at part loading with variable speed chillers going down to 0.3kW/ton. The calculated annual consumption of the existing systems is 704,249kWh, with a peak demand of 291kW.
New Chiller Plant
The new plant design includes a variable speed chiller with very high part load efficiency. This chiller uses magnetically levitated bearings to eliminate friction in the compressor and eliminate the need for lubricating oil in the system. The plant also replaced the single chilled water and condenser water pumps with dual pumps for added reliability. The new pumps are variable speed to allow the system to adjust more efficiently to the cooling demand of the building. Here are some fun pictures of the chiller being craned into the mechanical penthouse:
Another unique feature of the new plant is the cooling tower. The new tower is made of a reinforced fiberglass material that does not corrode and has a much longer expected lifespan than a standard metal tower. The cooling tower fans are variable speed and the water nozzles are variable flow, allowing the tower to ramp up and down efficiently according to demand. Another key health care friendly feature unique to this tower is that the water is not exposed to sunlight, meaning it is much more difficult for algae and other harmful biological growth to occur.
As part of the project, we have installed flow meters and electric meters to monitor the performance of the system. Initial results suggest the entire plant (chiller, pumps, cooling tower) is operating at an efficiency of between 0.5 and 0.6 kW/ton, about half of the original chiller alone! We are still in the final stages of commissioning and optimizing the sequence of operations for energy efficiency, so hopefully we can squeeze a little more savings out of the new system. I’ll be writing a follow up blog after all of our monitoring is complete at the end of summer. In the meantime, enjoy the heat outside and the super efficient cooling inside Lyndhurst!