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How to cut the cost of cooking

12 October 2006

Energy-saving cooking equipment has tended to be a contradiction in terms. But as Bruce Whitehall discovers, manufacturers are curbing excessive consumption with the help of load-matched control systems and more direct heating technology.

Most chefs will admit to firing up ranges first thing in the morning and leaving them on for hours, no matter how much is being cooked, resulting in burning up twice the amount of energy needed to cook the food. But beyond strict scheduling of equipment usage precisely matched to cooking activity, such practices are hard to avoid. Chefs cannot, for example, afford to wait half-an-hour or more for range-ovens to get up to temperature.

Range-tops offer more scope, although mechanical sensing arms which automatically cause gas rings to switch down to standby when pans are removed have so far proved too vulnerable to damage and tampering. Manufacturers such as Lincat can now equip hotplates with thermal cut-outs which switch down the energy if a pan is removed. Greener still is the ceramic-topped induction hob, which has become more affordable as well as more durable in heavy-duty catering applications.

Induction's transference of electrical energy directly into appropriate cooking pans not only enables them to act as an automatic on-off switching mechanism for the energy - which has ancillary benefits in keeping the kitchen environment cooler - but also achieves a more rapid heating effect. A simple comparison provided by Signature FSE, supplier of the Adventys series of induction hobs, highlights the relative speed of heating up two litres of water from 20°C to 95°C: 4.46 minutes on a 2.8kW induction compared with 8.18 minutes on a 2.8kW gas burner and 9.5 minutes on a 2.8kW electric ring.

Inevitably, not all chefs like cooking on a flat glass plate, but concerns about induction's robustness and flexibility are steadily being answered. Some manufacturers can now build induction sections into heavy-duty ranges and the "cold heat" concept is also spreading to other appliances. With the Garland Induction Griddle from Enodis UK Food Service Group, a full-size metal plate heats up responsively, with recovery speeds up to four times greater than a traditional griddle claimed for the direct energy connection.

Gas burner efficiency

Another major influence on energy efficiency is the way gas is burned in the enclosed chambers which heat ovens and other appliances such as fryers. Precise mixing of gas and air can have a big impact, according to Falcon Foodservice Equipment, which claims a gas burner efficiency of 83% on its Infinity series of fryers where the pre-mix chamber is claimed to ensure an optimum amount of air-to-gas ratio. The company's range of Eloma combi-steamers employ similar pre-mix systems.

Potential for reduced-life costs can also stem from detail changes to key components. Hobart's Convection Steamer has a heat-reflective, double-glazed insulated door which stays cool to the touch and is claimed to be 40% more energy-conserving than those of most competitors' combi-ovens.

Combi curbing

Combi-steamers have revolutionised cooking operations for many UK kitchens, and in certain key respects they have contributed to energy efficiency, most notably through fast heat-up and by enabling a number of different tasks to be carried out by one appliance, ensuring optimum utilisation.

Latest Rational SelfCooking Center combis benefit from new load-matched control technology and shorter pre-heat times, with only the exact amount of energy needed by the food. Comparative data suggests that two SCC10 combis used to serve 200 meals per day can get by with 2,500kWh per month compared with 6,300kWh when conventional cooking equipment is used.

Even so, combi-ovens are substantial users of water, which needs to be heated to produce steam. A 10-grid combi with a separate steam-generating boiler can, for example, use more than 25 litres of water per hour and a lot more when mainly steaming is required.

Boilerless combis, which generate steam by spraying water on to the heat exchanger which produces convection heat, can make a difference, with average water usage on a 10-grid oven dropping to about 12 litres an hour. Nick Bates, research and development chef at Angelo Po, which produces an extensive range of boilerless models, believes this design is inherently more energy-efficient in that it uses water only as and when it's needed.

Specialised appliances like the US-made Accutemp Steam ‘n' Hold oven, which is designed to steam-cook up to six pans of food at a time using patented vacuum technology, can offer an energy-conserving alternative. UK importer MCS Technical Products claims it can get by with only 20-25 litres of water a day.

Another answer to appliances which are profligate energy-users when left on for long periods - like atmospheric steaming cabinets and pasta boilers - is a specialised unit like the Round Up Variety steamer, which produces super-heated dry steam on demand - for example, to cook a portion of pasta - and therefore uses energy only when needed.

Logo power

Some idea of the importance now attached to energy efficiency in the kitchen by cooking equipment makers can be gauged from the Enodis UK Foodservice Group's introduction last month of an "Enerlogic" logo, a cross-brand initiative which relates to specific models in five cooking equipment series (Convotherm, Frymaster, Dean, Cleveland and Garland). The logo highlights models that meet Energy Star and CEE (Consortium for Energy Efficiency) standards as laid down by the internationally recognised body ASTM.

Case study

It's easy to see that there must be a substantial energy input in the prime cooking element of a catering facility. But is this energy input always provided in the most efficient way?

At first glance one could be excused for believing the only option is to pass the problem back to the equipment manufacturers to improve the efficiency of their equipment - the equipment used within the industry in a large number of cases is only 50% efficient, while the domestic market has to achieve 86% - but while this option is actively being pursued by the manufacturing fraternity, it's not the only way forward.

A typical kitchen required to feed 200 people over a two-hour service period for each meal is likely to have the following prime cooking equipment:

  • One gas bratt pan.
  • Two gas deep-fat fryers.
  • One electric filter unit.
  • One gas salamander.
  • One electric six-grid combi-oven.
  • One electric 10-grid combi-oven.
  • One gas open-top range.
  • One gas solid-top range.
  • One electric pressure steamer.
  • One electric tilting kettle.

The energy required to power this equipment is 69kW of electricity and 173kW of natural gas, and on average it will have an hourly usage of 43kW of electricity and 108kW of gas, giving a daily usage for electricity of 339kW and 858kW of gas.

In addition to the energy used for cooking, we need to extract 3.72m/sec of air and bring in 3.16m/sec of supply air. This will require 19kW of power every day to power the fans and on average 143kW of heat generated from natural gas to power the heater battery to temper the incoming air (this will be much higher in winter and very much lower in summer).

This means that in total the cooking operation is consuming 358kW of electricity and 1,001kW of natural gas per day at an energy cost of between £51.93 and £42.30 per day, depending on the energy supplier used and the tariffs offered.

By reviewing the requirements it's possible to provide a facility that has a different look to the original line-up with a reduced equipment content and a revised gas-to-electric ratio. This will provide energy savings and reduced carbon emissions:

  • One gas bratt pan.
  • Two new high-efficiency gas fryers.
  • Two new-generation gas combi-ovens (six-grid).
  • Two new-generation gas combi-ovens (10-grid).
  • One gas open-top boiling table.
  • One gas tilting kettle.

The energy required to power the equipment is 2.57kW of electricity and 182.3kW of natural gas and on average it will have an hourly usage of 1.59kW of electricity and 113.03kW of gas, giving a daily usage for electricity of 12.72kW and 904.24kW of gas.

In addition to the energy used for cooking, we need to extract 2.84m/sec of air and bring in 2.41m/sec of supply air. This will require 15.92kW of power every day to power the fans and on average 136kW of heat generated from natural gas to power the heater battery to temper the incoming air (this will be much higher in winter and very much lower in summer).

This means that in total the cooking operation is consuming 28.64kW of electricity and 1,040.55kW of natural gas per day, a saving of 21.3% in energy and 40.6% in carbon emissions.

The energy cost to run this operation is between £31.43 and £25.75 per day, depending on the energy supplier used and the tariffs offered, a saving of between £20.50 and £16.55 per day, or 39.1%.

Because of the new type and style of equipment, when compared with the original, there would be an increase in capital cost to provide this revised option which would be in the region of £1,302.50, which represents 2.5%.

However, even using the lower saving of £16.55 per day, the payback period could be as little as 79 working days.

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

• Angelo Po 0870 460 6750

• Enodis UK Food Service Group 0845 370 4888

• Falcon Foodservice Equipment 01786 455200

• Hobart UK 0700 2101101

• Lincat 01522 875500

• MCS Technical Products 01793 538308

• Meyer Commercialware O151-482 8282

• Rational 01582 480388

• Round-Up (Equip Line) 01895 272236

• Signature FSE 01908 235660

More contacts

The Carbon Trust
For help with energy audits and reducing carbon emissions.
0800 085 2005
www.carbontrust.co.uk

Hospitable Climates
Energy advisory programme managed by the HCIMA on behalf of the Hospitable Climates network.
020 8661 4916
www.hospitableclimates.co.uk

Energy Institute
Leading professional body for the energy industries.
020 7467 7100
www.energyinst.org.uk

Energy Saving Trust
Non-profit organisation set up to cut carbon emissions and achieve sustainable use of energy.
0845 120 7799
www.est.org.uk

ECA
Energy cost advisers for large and small companies
0870 264 6400
www.eca-group.co.uk

EMS
Independent consultancy helping industrial, commercial and public sector organisations to reduce energy usage.
01462 434522
www.ems.org.uk

Lighting Industry Federation
For information on energy-efficient lighting.
info@lif.co.uk
www.lif.co.uk

Pinniger and Partners
Lighting design consultant.
01883 744377
www.pinniger.co.uk

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