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!