According to the Energy Trust of Oregon, 21% of the total energy consumption in a cold storage facility comes from defrosting. The energy savings potential thus is significant. Using FabricAir® Defrost Ducts™ the defrosting energy consumption may be reduced by 50 to 75% depending on the make and model of the air cooler unit.
Having an efficient defrosting cycle is imperative to reducing the energy consumption of the facility, as is reducing the number of necessary cycles per day.
Operating conditions and defrosting method are key factors in determining the energy consumption. During operation, ice builds up on the air cooler unit coils, resulting in a defrosting need that in turn requires significant energy consumption. One of the common defrosting methods is to apply electric heat to the coils. The heat is applied until all ice is melted, at which point the coils are typically 37-50°C [100-120°F].
In a typical medium sized freezerwithout a FabricAir® Defrost Duct™, an air cooler unit runs through four defrost cycles a day, each lasting between 30 to 45 minutes; hence, even a small reduction in defrosting time can have significant impact on the total energy consumption of the cold storage facility.
As an example, a typical medium sized commercial freezer uses around 10,950 watts of energy per day, equivalent of 46,000 BTU/h of cooling. The energy consumption is divided between cooling and defrosting.
During a defrosting cycle, the unit first consumes energy to melt the ice accumulated on the coils inside the unit. Once the ice has been melted, the unit consumes energy to cool the coil back to below freezing, as well as counter the heat that was introduced into the space during the defrosting cycle.
The latter is known as the recovery factor and comprises the energy used to cool the coil down below freezing and to make up for the escaping heat and the negative effect it had on the room temperature during the defrosting cycle.
Each of the typically four defrosting cycles has a duration of anywhere between 30 and 45 minutes, during which time, the unit is not cooling the room. Heat that is used to defrost the coil escapes into the room negatively affecting the room temperature. The escaping heat also means a less efficient defrosting cycle. In fact, without a FabricAir® Defrost Duct™ it may take twice as long to defrost, as it does when the duct is applied. Consequently, the unit must use extra energy to cool the room and unit back down.
Using FabricAir® Defrost Ducts™ reduces the needed number of defrost cycles per day, as proven by end-user feedback. Because the duct efficiently prevents heat from leaking into the room, the air cooler unit uses less energy to keep the room at the ideal temperature set point, thus will not ice-over as quickly. This in turn results in a significantly longer duration in between the defrost cycles when using FabricAir® Defrost Ducts™.
The savings potential is thus significant, compared to the low pressure drop added by using a FabricAir® Defrost Duct™. Depending on the model of the air cooler unit, defrostingenergy consumption is reduced by 50 to 75%.