Have you ever gone food shopping on a lovely hot day only to be turned into an icicle walking past the supermarket's open chiller cabinets?Suddenly that shorts and T-shirt combo doesn't seem like such a smart idea as you dive in to grab your organic yoghurts.Well all that chilly discomfort could soon be history thanks to a gadget inspired by Formula 1 racing cars.The device is basically a thin strip of aluminium and plastic shaped like a wing that is attached to the front of the cabinet shelves. "The aerofoil acts like the rear wing of an F1 car and guides the air to create an air curtain," explains Craig Wilson, managing director of Williams Advanced Engineering (WAE)."It stops cold air spilling out into the stores."The strip, a result of a collaboration between WAE, the offshoot of the Williams F1 team, and Aerofoil Energy, may look simple, but it could save supermarkets millions in refrigeration costs.UK supermarket chain Sainsbury's is so impressed it has decided to fit the aerofoils in as many of its 1,400 supermarkets and convenience stores as it can."My wife used to moan at me incessantly about the cold when she went shopping at our local store," says Paul Crewe, Sainsbury's head of sustainability."But after we fitted the aerofoils she thought we'd turned the heating up." Of course, it's not just about customer comfort. The supermarket chain's annual electricity bill is "in the hundreds of millions of pounds", he says, and refrigeration accounts for about half of that.Fitting the aerofoils is reducing the chain's refrigeration costs by up to 15%, says Mr Crewe - a potential annual saving of nearly Â£10m."By looking outside of our industry, and borrowing technology from an industry that is renowned for its speed and efficiency, we are accelerating how we are reducing the impact on the environment, whilst making shopping in Sainsbury's stores a more comfortable experience," he says.But why do we have open chiller cabinets in the first place? Wouldn't cabinets with doors be much more efficient?"Consumers didn't like having to open and close doors on fridges, so we needed a new solution," argues Mr Crewe.But Myles McCarthy, director of implementation at the Carbon Trust, a sustainability consultancy that does a lot of work with supermarkets, suspects this has more to do with marketing."They think we'll buy less if there's a barrier between the products and the consumer," he says.While he welcomes the aerofoil innovation, he says: "This is just a stop-gap. The best way to reduce energy consumption is to put sliding or pull-out doors on all their fridges - this could cut electricity usage by 30%-40%."He thinks all the leading supermarkets should get together and all agree to put doors on their fridges by a certain date.This would "achieve their sustainability goals and save a lot of money," he argues, "and then they wouldn't lose competitive advantage."But in the fiercely competitive, price-driven world of supermarket retailing, it's hard to see such consensus breaking out any time soon. One of the problems with refrigeration - apart from the high electricity consumption - is that the traditional coolants used - hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) - are extremely polluting greenhouse gases that inevitably leak into the atmosphere, contributing to global warming.So there are moves within the industry to switch to natural refrigerants based, ironically, on carbon dioxide (CO2), another greenhouse gas.But these natural CO2 alternatives are a thousand times less polluting than HFCs and HCFCs.Earlier this year, German discount supermarket group Aldi announced that it was spending Â£20m on installing natural refrigerants across all of its UK stores to reduce its environmental impact.Tesco, the largest UK supermarket chain, says it has reduced its refrigerant emissions by 14% since 2015/16.Of course, this is a global issue.Last year in Rwanda, nearly 200 countries agreed to amend the Montreal Protocol on Substances that Deplete the Ozone Layer and begin phasing out HFCs.Supermarkets in general have been trying to reduce their energy consumption and carbon footprints in a number of ways to combat global warming.For example, Sainsbury's is switching 250,000 lights to lower-energy LED fittings in its larger stores, slashing lighting energy consumption by 58% and reducing greenhouse gas emissions by 3.4% annually, the company says.Others have been making greater use of natural light, fitting solar panels on to store roofs, and working with suppliers to reduce their energy consumption.Tesco has committed to running entirely on renewable energy in the UK and Ireland by the end of this year, and worldwide by 2030. "A food retail business could reduce its energy use by 20%-40% just by implementing a range of existing technologies," says Mr McCarthy. "These companies are committing to significant long-term decarbonisation of their businesses and to the use of renewables - which is very encouraging."