Reducing Freezer Glass Condensation

refrigerationUpdating the technology that is used in one of the most innocuous actions in everyday life – something to which most people don’t give a second thought – can save grocery and convenience store owners a lot of money.

Refrigerator display cases eat up a tremendous amount of energy. That is unavoidable. But there is a subtle step that can drastically cut expenditures: Eliminate the condensation that obstructs shoppers’ views into these display cases.

The more time a refrigerator door stays closed, the better it is for everybody. It’s more comfortable for shoppers who generally don’t like the blast of cold air that hits them when they open the freezer door or freezer aisles that are cold due to folks keeping the doors open for long periods. It also is better for the store owner, who pays for all of that cold air that is escaping the freezer as think about whether the kids want vanilla or chocolate ice cream this week.

A third reason that paying attention to condensation in refrigerator cases is important is that the U.S. Department of the Energy (DoE) is increasingly setting stricter energy limits on commercial refrigeration. Finding clever ways to reduce energy use at each stage of refrigeration can help meet these mandates.

The problem is that keeping the doors of the freezer fog-free is not easy. Call it the Fog of the Freezer. The challenge is acute when a person keeps the door open for a few minutes and a second shopper subsequently steps up. It is likely at that point condensation  — droplets of water that form on the glass when the cold air hits the humidity of the outside air – will make it impossible for the second shopper to see clearly. The shopper then must open the case to shop, which perpetuates the problem for the next shopper. This is a common occurrence, of course.

The current approach to battling condensation, according to Tom Bernard and Kevin Byrne, is simply to run a small “anti-sweat” heater that diminishes the condensation that creates the fog. Generating heat in a purposefully cold place in order to keep the windows clear is an impractical solution. Producing the heat costs money itself. It also raises the heat of the refrigerator cabinet and makes the refrigerated case work harder to maintain the sub-freezing temperature. That, too, costs money. Tom Bernard is a Professional Engineer and Kevin Byrne is a spokesperson for Clear Energy Engineering LLC, which is the preferred partner of Celanese for Clarifoil.

Clear Energy — and obviously Celanese — claim that they have a better idea. Clarifoil, which is a product of the Celanese Corp., is a cellulose acetate film that adheres to the back of the glass. The firm says that technology – which is used in other applications, such as motorcycle helmet visors and ski googles – features moisture vapor absorption and “hydrophilic surface action” that spreads condensate into transparent thin layers.

Byrne and Bernard say that the original equipment manufacturers (OEMs) are offering a coating approach. It is, they say, a flawed technique because the coating is ruined by even a single application of Windex. This, they feel, open an opportunity in the retrofit market. “We are focusing on the end user, the actual grocery store owner,” Bernard said.

It’s difficult to say precisely how much money such an approach will save. Clarifoil provided a three-year old assessment by PE&G of a earlier product. It was based on a five-door refrigerated display with a surface area of 66 feet. The installation cost was about $984. The researchers pegged electricity costs of $0.137 per kWh. The researchers found that the energy savings was about $428 per year and the return-on-investment period was about 2.3 years.

The challenge of fog is more extreme in humid climates. That, Bernard said, is where most of the company’s pilot projects are. He wouldn’t provide specifics, but said that projects are ongoing with four chains in New York, North Carolina, New Jersey and California.

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3 thoughts on “Reducing Freezer Glass Condensation

  1. As a followup to this story, I would recommend looking at the Airius destratification fan system. Many grocers have installed Airius fans specifically to help eliminate condensation. Some have been able to turn off the door heaters, saving energy costs.

  2. Refrigeration costs in a convenient store can be as high as 40%. If this film can solve the fog on the doors, it is worth testing it. It is also important to keep the humidity levels in the store low so that there is less amount of moisture available in the air for condensation.

  3. Maybe replacing the glazing with smaller doors in a shelf by shelf vertical extent, each with a flat screen monitor showing the details (contents) of each shelf as well as or better than would be seen by a shopper through the un-condensated glass door.
    This could be combined with a smart phone app that has been a long time coming – a store search engine for all 5,000+ products in the store, taking the shopper directly to the item of interest with just a few seconds of key stroke. For the smart phone challenged among us, throughout the store kiosks could have dedicated search stations.
    Max. insulation/min. open time for all refrigeration units should be the design mantra.

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