Sainsbury's has installed LED lighting systems in 15,000 freezer display cases throughout its UK store portfolio. Sainsbury's claims an energy saving of 75% per freezer.
Tesco, not be outdone, has signed a contract to install LED in freezers in Ireland. Tesco UK has as yet made no announcement, but is known to be installing LED in freezers.
In the USA, Wal-Mart has been using LED freezer lighting for some time. What makes LED freezer lighting so attractive to major retailers?
LED solves many of the problems previously associated with lighting in freezer cabinets. Fluorescent tubes are still to be found in most freezers, but they have never really been satisfactory for this purpose.
Firstly, fluorescents, although much more efficient than the old incandescent bulbs, still put too much of their energy input into heat rather than light. This energy is wasted. But also, heat generated in a freezer means the refrigeration has to work that much harder to keep the temperature at the required level, using even more unnecessary energy. By contrast, LEDs produce very little heat, so they use less energy to provide equal or better illumination and they put no significant additional strain on the refrigeration.
Secondly, fluorescents don't actually work very well at low temperatures. In particular, they often won't start at all at freezer temperatures. This means leaving the freezer display lighting switched on during the closing hours of the store, using up still more energy and making the refrigeration work away at night to keep up with the heat generated by the lighting. By contrast, LED freezer lighting can be turned off at night or whenever desired. Wal-Mart even controls some of its LED freezer lighting with occupancy sensors: the freezer lighting only comes on when a customer approaches the display.
LED has other advantages. Fluorescents have a relatively short life, whereas LEDs will often outlast the life of the freezer. With fluorescents, there is the occasional nightmare of a broken tube, distributing glass fragments and poisonous mercury among the product. LEDs by contrast are comparatively robust. And LEDs, being individually very small, can be individually focused, putting the light just where it's needed in the cabinet and thus producing much better general levels of illumination for the same or less actual light output.
Admittedly, LEDs require some upfront investment. In a retrofit situation, where the existing lighting does not otherwise need to be replaced, the extra investment may seem hard to justify. But Tesco claims that a €1.3m retrofit investment will save them €250,000 a year, paying for itself in energy-savings alone in just over five years. If reduced maintenance costs are also allowed for, the payback period comes down to three years. For a new freezer case, the energy saving over the fluorescent alternative would pay for the extra cost of LED lighting more quickly.
Governments are likely to encourage the changeover. In a report prepared last year for the US Department of Energy, it was estimated that if 100% of US retailers switched to LED systems for refrigerated display cases "there is a potential to save 25.4 TWh of electricity. This corresponds to a primary energy savings of 273.8 TBTu, equivalent to the annual consumption of four large coal power stations or the annual electricity consumption of over two million households".
It seems likely that fluorescents will now gradually disappear from freezer cases and maybe reach-in chillers with doors – more common in the USA than they are (so far) in the UK and Ireland. But what about open chillers? Although similar energy savings can be expected, major retailers so far appear more difficult to convince. This will probably change, because in fresh food chillers, LEDs have another advantage. The US Department of Energy report points out that fluorescents actually radiate heat on fresh foods: "Surveys of typical retail outlets show that typical meat surface temperatures are 4˚C higher than the refrigerator temperature...LEDs are ideal for meat display applications because they provide similar levels of illumination while radiating less heat than fluorescents, which slows the growth of bacteria and increases the meat products' shelf life."
Shoppers judge meat by colour; so sales are lost even if there is no deterioration in flavour. And heat from fluorescent lighting can also partially dehydrate meat, causing weight loss. And what applies to meat, applies also in varying degrees to fish and deli items.
Liam Kelly, CEO of specialist LED manufacturer Nualight, believes that retailers will increasingly appreciate the superior lighting performance rather than simply the energy-saving advantages of LED: "The emphasis so far has been on the hard factors such as energy and maintenance, which are very easy to demonstrate and audit and show the difference afterwards. I think the next phase is going to be performance-based."
Nualight has been awarded the €1m contract to retrofit the freezers in Tesco Ireland.