Use the cold to save on refrigeration
Spoiler alert: Using cold external air to supplement commercial refrigeration would save US colds cities over 100,000 MEGAWATT-HOURS of electricity per year, or right around $10.6 million in power bills.
The contraption pictured above is designed to help a restaurant, grocery, or convenience store trim their electric bill by taking advantage of cold external air. The device is a fan box which draws air in from the outside, through a filter, and pushes it into the cooler. As the pressure builds up, air can escape up through a small damper and to the outside world. The small fan would operate with a thermostat of its own, with a set point generally lower than the activation temperature of the refrigeration unit. Most refrigeration systems are required to cool to 40˚F. The external air circulator could be set to 32˚F.
How widely could a system like this actually be used? I found a list of large US cities that have over 100 days per year of temperatures below freezing. Next, I compiled statistics from city-data.com to find how many restaurants, groceries, and convenience stores each city had. I put them all into a chart and multiplied days below freezing by the estimated number of coolers and totaled the Refrigerator-Days/Year. (These are the days on which refrigerators could be essentially switched off because outside coldness is doing the work. )
I then found an average sized walk-in cooler (8ft by 8ft) and then found the average power usage for that refrigerator. After that I found an average cost for electricity in the US. Finally, I chose a reasonable squirrel cage blower fan from Grainger, which would run in place of the refrigerator on so-called refrigerator days.
- Average walk in cooler power consumption: 38.83 kwh/day
- 2016 average price of electricity: 10.37 cents/kwh
- Power usage of fan used in ext. air circulator: 70W or 2 kwh/day
Having all of this lets you calculate the totals listed at the beginning. Tallied over all of the cities listed, there would be an electrical power savings of 102,572 Mw per year. Multiplied by the average cost for electricity, and you get $10.6 million.
So? Is this worth doing with my refrigerator?
It depends. Here is one scenario with one walk-in cooler: Imagine you have an 8 x 8 cooler that uses 38.83 kwh/day. Also, imagine that you live in a place that has 100 days below freezing. If your external air circulator uses only 2 kwh/day, you are still saving 36.83 kwh/day for 100 days per year. This is a power savings of 3,683 kwh or around $380 per year.
The hardware is similar to that of an evaporative cooler, which costs about $300 bucks. So... it *might* be worth it if you are savvy, and looking for ways to save where you can. It may save you considerably more if you have larger or more refrigeration, or if you live in Minneapolis, Minnesota.