LED luminaires get warm welcome in supermarket freezers

Figure 1 One application in which the use of LED luminaires makes a lot of sense is the provision of illumination in the temperature-controlled retail cases used in stores for the display of perishable goods. This is a billion dollar market for lighting, and is currently being serviced primarily by the provision of fluorescent illumination.

Anyone going to a typical supermarket will be aware of the variety of display case which is being used. There are typically long aisles of open freezer cases, vertical walls of closed-door freezer and cooler cases, and aisles of open-shelved storage, as well as a variety of individual free-standing displays for branded product.

NuaLight’s CryoLED™ luminaires are especially designed for freezer installation, either during case manufacture or for retrofit (see Figures 1 & 2). LEDs come into their own in cold environments, with increased brightness, extended lifetime and no on-off difficulties.

Figure 2 In this article we look at LED luminaires from two important perspectives:

1. Energy usage: even with current efficiency levels in mass-produced white LEDs, it is possible to make significant energy savings in some applications.

2. Improved sales performance: when a typical wall of freezer doors (with fluorescent tubes spanning the range from dead through flickering, dim to fully functional) is replaced with bright and uniform LED luminaires, there is a substantial improvement in sales from those cases. We have measured this effect in-store.

Energy usage

In a recent trial, NuaLight’s CryoLED lighting system was found to be 29% more energy efficient than comparable fluorescent lighting in a single door freezer case. The test consisted of the comparison of a pair of new 36-watt, 4 ft fluorescent tubes, and a pair of 30-watt 4 ft CryoLEDs.

Table 1 Both the fluorescent and the more directionally efficient CryoLED systems produced the same illuminance of 1,240 lux at the centre of the back wall of the case. The same case was used to evaluate both sets of lighting.

Table 1 shows the data measured during the 168-hour trial. Because the freezer has to deal with waste heat from the lighting, the difference in overall consumption in the case is greater than the difference in consumption in the lighting.

The result of the test is a reduction of the incremental illumination case consumption from 164 watts to 117 watts – a reduction of 29% - by using CryoLED.

Sales increase

Figure 3 In order to determine the effect on sales of improved illumination, we retrofitted 2 x 65-inch CryoLED units in place of 1 x 48-inch 36W fluorescent tubes in each of 32 doors in a normally operating supermarket (see Figure 3). The merchandise sold from these cases was a mixture of frozen foods.

The sales data were recorded during a typical 5 week period and annualised. The results are compared in Table 2 with previous sales data from the same units. The results are striking, with an additional annual margin per door of over $1000, leading to a payback period on the additional capital investment of less than 3 months.

Table 2 Margin on the merchandise sold in freezer cases typically varies between about 10% and 16%, depending upon the pricing policy of the supermarket and upon the type of good being sold. Even in the case of low margin product, the payback period will still be substantially less than 12 months, making this illumination upgrade a very worthwhile investment.

Summary

Although fluorescent lighting is relatively cheap to buy and install, the overall cost of ownership ends up being quite high, due to ongoing maintenance requirements (bulb and ballast replacement) and unnecessarily high energy costs.

This is especially true for freezer lighting in the majority of stores which open for 12 hours per day, where freezer illumination is often left on 24 hours per day due to difficulties in restarting in cold environments.

When maintenance, energy and additional sales performance are taken into account, there is a substantial return on investment over the lifetime of a typical display case, and a payback period as short as 3 months.