Everywhere you look people are talking about hybrid cars, hybrid classrooms, hybrid diets and now a hybrid roof top unit or RTU. A company called Ice Energys have developed a hybrid cooling unit that works with a standard RTU. The RTU works as a standard cooling unit during non peak electrical periods of the day and the “Ice Bear” unit works with it during the peak electrical periods of the day. The RTU unit has an extra cooling coil added to it for the “Ice Bear”. At night the “Ice Bear” compressor starts and freezes the unit much like a giant ice cube tray. When the ice section is frozen solid, the compressor turns off. In the afternoon during peak electricity periods, a pump turns on inside the “Ice Bear” and the compressor in the RTU unit turns off. The pump moves cold refrigerant over to the extra cooling coil inside the RTU and provides cooling until the ice is completely depleted from the “Ice Bear”. At this point in time, the RTU compressor will start again if cooling is still required. Watch this YouTube video, Thermal energy storage to see the unit in operation.
While this isn’t a new idea, it certainly is a new product. I worked on a similar system on a high rise in downtown Calgary. The three chillers in the building would only run once the tanks of frozen ice had been depleted. At night, one or two chillers would run until the tanks were frozen and then shut off. In the morning the building automation system would have a cooling demand call and would start the building pumps. The pumps would circulate water through the tanks cooling the water off to be delivered to cooling fan coils. When a certain percentage of ice was depleted from the tanks, one of the chillers would start, when a second set percentage of ice was depleted a second chiller would start and the same for the third chiller.
This is a fantastic idea but is unlikely to gain any traction in Alberta unless energy companies start charging different electricity rates for different times of the day. If we switch to the way other provinces providers charge for Time-Of-Use, such as hydro one in Ontario currently does, this could be an affordable option.
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