Refrigeration under control

Unlike most other kitchen equipment, refrigeration uses electricity day and night for 365 days a year. Now more precise matching of energy to cabinet usage is becoming a key environmental issue alongside the established issues of ozone-depleting refrigerants. Bruce Whitehall reports on progress

The thrust of refrigeration development is increasingly on control systems which precisely match cabinet operation to the actual storage need rather than simply keeping a fixed amount of air cold on a continuous basis. "All the new systems revolve around finding ways to tune the refrigeration circuit to the real refrigeration needs, environment and conditions," observes John Logher, managing director of Caravell UK.

Thus Caravell's Intelligent range of catering cabinets is programmed to space out defrost cycles dependent on levels of usage. The same control system can also spot drops in condenser performance due to a build-up of dust and grease and alert the user to carry out cleaning routines if necessary.

Williams Refrigeration's CoolSmart intelligent controllers, launched this year, are likewise designed to cut energy consumption - by up to 15% - by detecting changing situations and getting the refrigeration system to respond accordingly. Thus the system differentiates between "economy" periods such as overnight, and peak times, when warm products are loaded or doors are opened frequently. Other energy-saving functions include the elimination of unnecessary compressor start-ups, which also reduces equipment wear and tear.

Better energy usage

On-site adjustability of cabinet temperature to match food loads and product categories - including seasonally varying items - can also contribute to better energy usage, provided that management establishes clear parameters. For example, Hoshizaki refrigerators can be adjusted to work at any temperature from +12°C to -6°C, while freezer cabinets are similarly flexible within the -7°C to -25°C range.

One of the most critical areas of refrigeration energy loss stems from kitchen staff leaving drawers and doors open. Self-return door mechanisms are now a standard feature on some upright refrigerators, along with automatic fan cut-out when doors are open.

However, designers of upright refrigerators can do little to prevent cold air spilling out whenever the door is opened. Jeremy Hall, managing director of new British manufacturer Precision Refrigeration, believes that caterers should give more consideration to drawer-style cabinets for their energy-saving potential. His company is promoting a wide range of cabinets with drawers, from counter and under-counter fridges and freezers to full-size uprights with half-door above and drawers below. There are also choices in energy-saving half-door models. Hall concedes that, volume for volume, drawer cabinets have slightly reduced internal storage space and higher price tags than ordinary door models but he forecasts that, as energy prices increase, they will become a more economic solution.

Adande, which stirred up the commercial refrigeration business with its Varicool concept of multi-temperature cabinets, claims its insulated drawer design needs 40-57% less energy than a comparably sized drawer cabinet of conventional design. Varicool contents are held in removable plastic insulated boxes which drop into the drawers, to which seals are fitted. Even if the drawer is accidentally left open, cold air is retained at a stable temperature rather than simply "dropping out".

Curtains for coldrooms

The problem of cold air escaping and being replaced by warm air is amplified on coldrooms, especially where large numbers of staff need to access stock every day. Germany's Viessmann claims that latest air curtain systems available to supplement the doors on its modular coldrooms can gain energy savings up to 90% per year, as well as lowering risks of stored goods warming up or suffering condensation.

The system, available with blowing heights of 2.5 or 3m, has infinitely adjustable airflow between the areas of different temperature by means of adjustable louvres and double radial fans. The curtains are available on all common single and double-hinged Viessmann coldroom doors with special designs for sliding doors available on request.

Refrigerants

From an environmental standpoint, the choice of gas circulating inside refrigeration systems has been a critical environmental issue because of CFCs. New cabinets now use gases with low ODP (ozone depletion potential) but hydrocarbons (HCs), rated by organisations such as Greenpeace as the greenest option, are still more typically found on domestic fridges and freezers. As well as being better for the ozone layer, HCs also achieve up to 15% better energy utilisation than other gases, thanks to smaller molecular structure.

"It works under lower pressures and therefore, in simple terms, you don't need as much energy to pump it around the system," says John Savage, foodservice director at Foster Refrigerator, which now uses HCs on 80% of its refrigeration cabinets, typically R290 on fridges and K30 on freezers. They have not yet proved suitable for coldrooms.

Refrigeration has been an important element in the ECA (Enhanced Capital Allowance) scheme administered by the Carbon Trust, in which manufacturers submit their products for testing in order to prove conformity to various requirements on energy efficiency, performance and capacity. Glenn Roberts, sales and marketing director of Gram UK, reckons customers switching old cabinets to new-generation products which conform to the scheme can save the equivalent of up to 75% of their running costs. Gram has nine products listed as eligible, including models from its Plus 600 range and Midi 425 and 625.

Choosing Energy-Efficient refrigeration Equipment: tips from gram

Glenn Roberts, sales and marketing director, Gram UK, writes…

Simply buying an energy-saving product just because you want to be an environmentally friendly business or you want to make cost savings can be a false economy unless you follow a few basic rules. To maximise the energy efficiency of your kitchen equipment, I recommend the following:

• Think carefully about how and where you will site the product within the premises. It should be positioned with adequate space all around the appliance, and within a well-ventilated area away from direct heat sources. Try to cut down the length of time the door is open. Using the Gram door alarm system will help you do this.

• Check seals on doors regularly. They should be clean and pliable in order to be completely airtight. At busy times, don't be tempted to take out all the shelves and fill the fridge-freezer from floor to ceiling with products. It's vitally important that air flows around the shelves and foodstuff in order to safely control temperature. Using the internal Gram loadline will help to ensure that the cabinet is not overloaded. Unfortunately, if the unique Gram air distribution system is interrupted, the equipment will have to work twice as hard to keep temperature and therefore consume more energy than necessary.

• Setting the fridge or freezer at the right temperature for the products stored is also vital. You will store foodstuffs at their optimum, and also save money.

• To obtain the full day-to-day benefit of the most energy-efficient products available, contact the Gram sales team for further advice.

Case Study

When looking at a kitchen's energy consumption and the CO2 emissions generated, refrigeration equipment needs careful consideration as the energy it uses is estimated to be 6% of the total energy used.

The upright reach-in cabinet is the most-used method of refrigerated storage and accounts for an estimated 17% of all the commercial refrigeration energy used. The last 10 years have seen major changes in the design of the reach-in cabinet, with the efficiency of the freezer cabinet increasing by up to 30%, and the refrigerated cabinet up to 35%. With good housekeeping, it's believed that a cabinet will consume on average 35-50% of its connected load over the working year.

A facility feeding up to 200 people and needing 6,000 litres of refrigerated storage will have 10 single-door cabinets or five double-door cabinets. If we assume we're replacing cabinets that have reached the end of their working life after 10 years using a fix-when-broken policy and the split to be 40% freezer and 60% refrigerated, the following will apply. Existing situation:

• Four single solid-door freezer cabinets present yearly usage 5,757kW x 4 = 23,028kW.
• Six single solid-door refrigeration cabinets present yearly usage 4,649 kW x 6 = 27,894kW.
• Total yearly energy usage 50,922kW.
• Total cost of energy 50,922 x 5.5p = £2,800.71 per year.
• Total emissions = 21,927 kgCO2 (5,986kg/carbon).

If you're replacing existing cabinets it's generally less costly to operate one larger unit than two smaller ones. If, however, the operation sees regular periods of low usage it may be more efficient to use two smaller cabinets, because during quiet periods individual cabinets can be switched off. If the existing cabinets, which are more than 10 years old, are exchanged for new double-door cabinets to the same specification as the single-door cabinets, installing them in the coolest part of the kitchen and introducing a system of planned preventative maintenance to maximise the cabinet's efficiency, the following will apply:

• Two double solid-door freezer cabinets yearly usage 4,533kW x 2 = 9.066kW.
• Three double solid-door refrigeration cabinets yearly usage 3,526kW x 3 = 10,578kW.
• Total yearly energy usage 19,644kW-8% = 18,072.
• Total cost of energy 18,072 x 5.5p = £993.96 per year.
• Total emissions = 7,771 kgCO2, equivalent to 2,121kg/carbon.
• Yearly saving £1,806.75 (64.5%), equivalent to environmental saving of 14,156 kgCO2 (64.6%).

Hydrocarbons (HCs) are now being introduced in commercial refrigeration as a commercially viable alternative to the hydrofluorocarbons (HFCs) currently widely used. While units running on HCs are generally 15% more energy-efficient than comparable units that run on HFCs, because of their flammable properties certain requirements exist that limit their use. If we exchange the existing cabinets for new double-door cabinets using HCs in place of conventional refrigerants while implementing planned preventative maintenance, the following can be achieved:

• Total yearly energy usage 18,072kW-15% = 15,361kW.
• Total cost of energy 15,361 x 5.5p = £844.86 per year.
• Total emissions = 6,605 kgCO2, equivalent to 1,803kg/carbon.
• Yearly saving £1,955.85 (69.8%), equivalent to environmental saving of 15,322 kgCO2 (69.9%).

The other route to explore is a glycol secondary refrigeration system, which comprises a pair of external chiller units circulating a mixture of chilled glycol and water around a ring main connected to the independently controlled equipment. The system is capable of running a large number of different appliances, chilled areas and coldrooms on one system. A typical Glycol system will reduce the primary refrigeration gas used within a commercial kitchen by up to 72% and will reduce the energy usage by up to 25%. If we exchange the existing cabinets for new double-door cabinets using a glycol secondary refrigeration system while implementing planned preventative maintenance the following applies:

• Total yearly energy usage 18,072kW-25% = 13,554kW.
• Total cost of energy 13,554 x 5.5p = £745.47 per year.
• Total emissions = 5,828 kgCO2, equivalent to 1,591kg/carbon.
• Yearly saving £2,055.24 (73.4%), equivalent to environmental saving of 16,099 kgCO2 (73.4%).

Source: David Clarke of the Catering for a Sustainable Future Group, made up of food service consultants and equipment manufacturers and distributors, and a member of the Foodservice Consultants Society International UK

Contacts

• Adande VariCool 01502 537135
• Caravell UK 01280 826600
• Carbon Trust 0800 085 2005
• Foster Refrigerator 01553 691122
• Gram UK 01322 616900
• Precision Refrigeration 01842 753994
• Valera 01708 869593
• Viessmann 01952 675060
• Williams Refrigeration 01553 817000