School catering operations both consume and waste large amounts of energy. In some kitchens, as little as 40% of the energy consumed is used for the preparation and storage of food; much of the wasted energy is dispersed into the kitchen as heat. Effective energy management in catering can provide substantial savings, as well as improving working conditions in the kitchen.
It is common in school kitchens for all equipment to be switched on at the beginning of a shift and left running throughout the day. Not only is this extremely wasteful, but equipment left on unnecessarily generates heat, making a kitchen unpleasantly hot and uncomfortable to work in. All catering establishments can save energy by implementing a simple switch-off policy and providing staff with information about preheat times, control settings and good practice.
School kitchens use a variety of highly energy intensive equipment to provide food for pupils. The energy consumed by this equipment varies considerably, according to how it is used, how regularly it is maintained and how it is set up within the kitchen environment. Selecting the most energy efficient equipment for the job can yield major cost savings.
Aim of the investigation
During the energy audit, you will look for opportunities to reduce the amount of energy used in the school kitchens without negatively affecting the output (the food provided!). When you have completed your audit you should be able to identify priorities for improvement in the kitchen, which you can present to the school catering and management teams.
Design a spreadsheet or handwritten results table to record kitchen appliances, their energy consumption, and usage patterns. Equipment to include: Ovens, hobs, grills, fryers, serving hot plates or trolleys, fridges, freezers, dishwashers, microwaves, extractor fans, electric mixers or food processors, anything else you spot in your school kitchen which uses gas or electricity.
- Use the Energy Sparks charts to check whether your school has separate meters for gas and electricity for the school kitchen? Can you find out how much energy your school kitchen uses each day in term time, split into gas and electricity? Can you find out how much energy the kitchen uses over the weekend and in the school holidays from appliances left running constantly, such as fridges and freezers?
- Go around the school kitchens recording the number of different types of appliances. Try to find out how much energy each electrical appliance uses when in use. Most appliances will have a label on them telling you their energy consumption in watts (W) or kilowatts (kW). Record their energy use in your results table.
- Interview kitchen staff to understand:
- Approximately how long do they use each appliance each day?
- When do they switch on ovens and hobs?
- Do they ever use ovens or hobs to heat the kitchen?
- Do they switch off ovens, grills, fryers and hobs immediately after use?
- Do they use lids on saucepans?
- Do they always close fridge and freezer doors?
- How often are freezers defrosted?
- Do they switch off other kitchen equipment, lights and extraction fans when they are not being used?
- Do they use the most efficient cycle on the dishwasher?
- Do they use sterilisers?
Data Analysis and Presentation
- Calculate how much electricity you think the school kitchen is using on an average day in kWh. You can do this by multiplying the power consumption of each electrical appliance, by the number of hours it runs each day. How does this compare with the data shown in the Energy Sparks electricity charts?
- If your audit and the Energy Sparks data give significantly different results, can you identify what you might have missed.
- Can you identify the top 5 electrical appliances in the school kitchen for energy consumption?
- Can you identify where you think energy is being wasted in the school kitchen considering both gas and electricity? Use the Next Steps below to help you.
- How would you recommend that kitchen staff change their behaviour to save more energy? Again, use the Next Steps below.
- Can you devise a way to share your top energy saving recommendations with the catering and school management teams and your fellow pupils?
From your audit of kitchen appliances and your interview results, can you identify how energy efficient you think the school kitchens are? Give your evidence for your conclusion. How can you use the information you have learnt to create an action plan to save energy in the school kitchens?
Next Steps to save energy
- Find out cooking equipment preheat times and display these next to the appliance.
- Move fridges and freezers so they are away from heat sources such as cookers.
- Check the door seals on fridges and freezers are intact so cold air is not escaping.
- Ventilation units and extractor hood grease filters should be cleaned at regular intervals. Regular cleaning of ventilation systems can increase efficiency by as much as 50% compared with systems that are not maintained.
- Ask your school management team to consider heat recovery from the kitchen. Large volumes of warm air are expelled from catering facilities through the ventilation system. Over 50% of this ‘waste’ heat can be recovered using heat recovery devices which can significantly reduce energy costs. An air-to-water recovery device is often the most effective method of recovering heat because it can then pre-heat hot water, providing a year-round use.
Create an energy saving checklist for the school kitchens, which could be displayed in a prominent position. Consider including:
- Use the correct equipment for the job – utensils, pots and pans must be of appropriate size for the heating ring or oven.
- Avoid over-filling saucepans and kettles and use lids and covers to retain heat, steam and fumes.
- Switch off grills, fryers and hobs immediately after use.
- Keep hot storage of cooked food to a minimum, both to reduce energy use and to retain the quality of the food.
- Switch on equipment only when necessary.
- When pans come to the boil, turn hobs down to the minimum to simmer (boiling does not speed up the cooking process).
- Use microwave ovens to reheat relatively small amounts of food.
- Switch off extraction fans when they are not being used.
- Set fridge thermostats at the right level for the contents.
- Always close the door to the fridge or freezer immediately after use.
- Defrost freezers regularly.
- Turn off fridges and freezers during holiday periods, where appropriate. If it is not possible to switch off all appliances, consolidate the contents so that some can be turned off.
Evaluate how you carried out the audit and what could be improved.
Carry out the same audit in the Food Technology department.