by Alistair Bell, Danfoss
Over the last few years, supermarkets have made great advances in energy efficiency, reducing both business overheads and their environmental impact. Reducing energy use, while maintaining optimal performance, is valuable and always will be.
Worldwide, there’s a growing need to manage fluctuations in energy generation, caused by the unpredictable nature of renewable energy, and times of peak demand.
As a result, utility companies and grid operators are increasingly offering incentives to energy users who can help them balance this equation. This gives supermarkets the potential to take advantage of low off-peak energy prices, or to avoid short-term spikes in energy use that increase the cost for the rest of the year. But for the sake of food safety, retailers have largely avoided making changes to refrigeration and limited themselves to managing air conditioning and lighting. Unfortunately, this dramatically reduces their ability to make any meaningful difference to peak energy use.
Now, Danfoss is working with supermarkets globally, to help them access bigger savings by shifting refrigeration patterns—whilst providing ideal conditions for their produce.
Peak demand has a disproportionate impact on energy cost
In many countries, reducing peak electricity demand is now the fastest way to significantly reduce a supermarket’s energy bill. With ever increasing energy shutdowns and power load shedding, power grids experience moments of peak demand which threaten safety and reliability. At other times there’s excess supply.
For a large energy user like a supermarket chain, this has several key impacts. Often, the price per unit a store pays will be influenced by its highest energy demand, even if this was only for a few minutes. Retailers which manage this one moment better can achieve a significant, year-round saving. Reducing the peak demand level can also bring savings into a store’s own energy infrastructure.
For example, downsizing the transformer will have a noticeable impact on initial installation costs. As grids use more renewable energy, their need to balance excess demand and supply grows.
Food retailers, especially those which run their own renewable energy or have a chain of stores, are well placed to make significant tariff savings, over and above the strong business case for renewable generation itself. But to maximise this, they need to make changes to their refrigeration arrangements.
Electric vehicles will make managing demand more challenging
Every supermarket’s technical team needs a plan to cope with the future demand of electric vehicle (EV) charging; if your store does not already provide this, it will soon need to. Wherever you are, most cars will soon be electric-powered.
Bloomberg predicts 57% of all new cars worldwide will be electric by 2040. Soon supermarket chains will allocate parking bays and offer customers free EV charging to gain a competitive edge. This is a commercial opportunity, but for a chain’s energy manager, it poses a problem.
Depending on the type of vehicle and charging station, too many EVs charging at once could temporarily double the store’s energy use—setting an artificially high peak and inflating its energy price.
Cooling capacity: the supermarket’s built-in “battery”
Thankfully, supermarkets are especially well-placed to reduce peak loads and respond to demand events, and energy managers have several good options. A growing number are generating their own renewable energy by using battery banks to store excess energy for when it can be used most profitably.
Until recently, however, supermarkets struggled to dynamically optimise their own energy consumption patterns. Up to 60% of a store’s energy is used on refrigeration, so if this cannot be changed, only minor savings can be made. And efficient technology like LEDs—while saving power—also mean there’s less opportunity to use lighting systems to influence demand.
Danfoss has a long history in food refrigeration, which means it could never compromise food quality. And several ways have been found to adjust when a refrigeration system uses energy while always keeping the temperature well within safe limits.
The simplest way to optimise energy consumption is to ensure that any energy-intensive maintenance, like defrosting and rail heating, is carried out away from peak energy times. This gives an immediate, but relatively small improvement. For larger results, one can also use the system like a battery, effectively storing or borrowing cooling capacity.
For instance, a supermarket expecting a peak in energy demand can lower its freezer temperature while energy is cheap, then temporarily switch off the compressors until the peak has passed. This is also a good way to prepare in advance for a demand response event.
Conversely, it’s possible to reduce refrigeration compressor power by as much 30% for a short time when there’s peak demand. The system must then be run more intensively to compensate and ensure the temperature remains within safe limits. These approaches may seem counter-intuitive, because running the refrigeration system this way will use more energy overall; it’s called the “rebound effect”. But used properly, the unit price savings often far outweigh the increase in use – and balancing demand is an essential part of low-carbon power generation, so the method is also environmentally sound.
Supermarkets will lead the energy revolution
Renewable energy sources are increasingly important, but they can be unpredictable. Tomorrow’s energy market will therefore need more than just energy efficiency; it will need far more flexibility to match changing supply and demand. Supermarkets are ideally placed to benefit from this.
Between them, food retail chains consume a great deal of energy, so they can take a prominent role in the community and ensure flexibility within the local grid. This is especially true with renewable energy generation: large roof spaces create opportunities for solar photovoltaic panels—while a supermarket’s energy demand profile neatly matches the times when solar generation is most productive.
Depending on the weather, the store often generates more electricity than it needs. It can then sell some energy back to the grid, or reduce the temperature of the supermarket’s chilled counters, ready to offset demand when the weather changes. The system’s own algorithm calculates which approach is most profitable at any given time. The whole process can be managed remotely, because the system manager is connected to the internet.
The Danfoss Enterprise Service dashboard allows them to see and optimise the store’s many energy features, not just refrigeration, but solar, wind, EV charger, and battery status too.
What’s more, should the store use CO2 refrigerant, the system’s heat is reclaimed and reused. The need for low-carbon energy means that one day, this kind of energy arbitrage will be completely normal—everywhere, not just in food retail. Until then, cost pressures mean supermarkets will maximise every opportunity to save energy costs. And that means energy managers in food retail will continue to lead the way for the rest of us to follow.
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