With recent string of extremely high temperatures, it’s the perfect time to talk about how Bickle’s new chiller plant is saving us energy and improving reliability. For those less interested in the story and pictures, here are the cold, hard results:
- Annual Electricity consumption savings: 647,000 kWh (equivalent to about 65 houses in Ontario)
- Electricity demand savings: 188kW (equivalent to about 2,350 flat screen TVs running simultaneously)
- Huge electricity consumption savings of 78% over the old chiller system!
Keep reading for more details and photos.
Old Chiller Plant
Similarly to the project at UHN’s Lyndhurst Center, Bickle still had the original chiller plant that was installed when the building was constructed in the 1970s. This plant was in poor condition, with the chillers typically requiring costly repairs at the beginning of every cooling season. The system was unreliable, inefficient, and ran so loudly that it disrupted the staff on the floor above. Here are a few photos:
In order to measure the performance of the older system, an energy meter was installed on each of the old chillers for a period of one month during cooling season to generate a part load performance profile. Spot measurements were done on constant speed equipment, including chilled water pumps and cooling tower fans. These meter readings were combined to produce an average power consumption of the plant for various outside air temperature (OAT) ranges.
New Chiller Plant
Key technologies employed in the new chilled water plant included chillers with magnetically levitated bearings, variable speed pumps and cooling tower fan motors, and new control sequences. Pumps and fans were also downsized where appropriate.
The new chillers installed use compressors that have magnetically levitated bearings. A major efficiency gain is achieved because the system is frictionless (picture a hover board instead of a skateboard). Unlike Bickle’s new chillers, chillers with standard bearings need to be lubricated, which can eventually lead to oil migration into the refrigerant stream and fouling of the condenser/evaporator tubes. The new chillers also employ variable frequency drives meaning that the compressor motor can run slower, using much less electricity, at part loading.
The old cooling plant had one chilled water pump, one condenser water pump, and one standby pump with a convoluted valving setup to allow the standby pump to operate as a backup for either pump. To accommodate this, the original chilled water pump appeared to have been oversized, wasting energy. The new plant employs three smaller chilled water pumps (one per chiller plus one standby) and two smaller condenser water pumps. Even if a chilled water and condenser water pump failed, we would still be able to operate both chillers. The project also added a separate connection that could be used to to connect an external source of chilled water if power was lost for an extended period. In addition to these resiliency improvements, we added variable frequency drives (VFDs) on all the pumps so that they can ramp down at lower periods, saving significant energy.
Photos of the new pumps (left) and VFDs (right)
The new cooling tower is made of fiberglass instead of the standard galvanized steel. Fiberglass does not corrode and should provide a longer life expectancy than a standard tower. The tower has 6 smaller fans replacing the 4 large fans of the old tower. The 6 fans are controlled by a VFD to maintain condenser water temperature. The new control sequence resets the condenser water temperature lower when outdoor conditions allow to take advantage of higher chiller efficiency at lower condenser water temperatures.
As mentioned at the beginning of the article, the new plant runs using almost 80% less electricity to provide the same amount of cooling as the old plant. It is much easier to track the performance of the new plant over time because the chillers and pump/fan VFDs directly report power consumption back to our building automation system. The new part load performance is shown below (compared to the old plant):
As you can see, performance is especially strong during lower demand times when outdoor air temperatures (OAT) are mild. This is important because most hours of the cooling season tend to be at milder temperatures between 10-25C. We are also saving over 60% on power consumption during peak times. Power consumption is so low during the 10-15C bin because we are now automatically shutting down the plant at these temperatures, whereas the old plant did not have this control capability and was often left running over night or over the weekend “just in case” of high temperatures.
Note: The “Peak” kW is lower than the highest temperature range because it uses a Toronto Hydro formula that averages the peak over longer time windows that include lower temperature periods.
Thanks to the following people who made this project possible: Val Cadar, Angelo Suntres, Jana Jedlovska, Eoin Kane, Joe Angione, and Allan Wu!