Making a difference

When your family need to buy a new piece of electrical equipment you will see Energy Labels stuck on the display models. Equipment is also given a 'rating' ('A' is the most efficient). Look out for the labels and ratings when you are next passing a shop selling fridges or washing machines. The information is provided so that you, as consumers (buyers), can make informed decisions.

The labelling scheme is based on an energy efficiency index generated by comparing the individual fridge with an average European model. The energy rating is found by dividing the annual energy consumption (kilowatts of energy used) of a piece of equipment by the space within it (its volume). This allows us to compare appliances, even if they are different sizes, with different proportions of cool or frozen spaces.

Now find more examples of energy efficiency measurements using these web sites:

Total Equivalent Warming Impact (TEWI)

For a complicated industrial system it is harder to compare efficiency and environmental effect. A measure which takes into account all aspects of the system's effect on the environment has been devised called TEWI. In a refrigerating system it takes into account the following properties:

The TEWI of a system is never exact because there are so many uncertainties being measured, but it does provide a useful comparison.

What do you think the advantages and disadvantages of using Energy Efficiency measurements are? Do you think they are having any impact on the environment?

Now try our role-play exercise in your class.