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Heat dissipation from electrical devices

Electrical energy which is supplied to a device (whether a washing machine, desk lamp, mobile phone charger or television) is not lost but is instead converted by the device into another form of energy. In the case of a light bulb this is in (small) part actually light; otherwise it is almost exclusively heat. Only sometimes is this heat actually “used” (e.g. in the case of a water heater). Other than that, it is almost always only an unnecessary heat flow; in the summer it is a heat loss which may need to be removed by cooling, in winter it is uncontrolled and expensive (15-30 cents/kWh if not subsidized) additional heating. Devices that produce a lot of heat (and exactly that is not their main purpose) are basically just inefficient. First of all it is necessary to identify such energy consumers. There are three ways to do that:

  • Checking electricity consumption: inexpensive devices are available for measuring electricity consumption; they do not always have to be purchased: they can also be loaned from many energy consultants and some local electricity providers. More exact information on how such a measurement can be carried out is provided in this section.
  • Feeling with the hand: devices that become quite hot on large surfaces are electricity guzzlers and it is worth checking their electricity consumption. However, also devices that are warm to the touch draw quite a few watts of energy and when these are continuously in operation (5 W are around 44 kWh in a year or electricity costs of quite some $$) they incur costs and cause unnecessary environmental damage.
  • It is a lot of fun to search for heat leakage using an infrared thermographic camera: scanning of the room takes less than a minute and it is often surprising what one can 'detect' in this way.

When the sources of heat leakage have been identified, one can consider various options:

  • Power supply units are often a source of heat: they do not have to be in operation continuously, or if they are, then they can be replaced with a modern switching power supply unit. Sometimes it is also helpful to use a power socket with a timer - or one of the latest “smart sockets” with wireless control. These in turn sometimes have a not so small (largely unnecessary) consumption of their own.
  • Landline telephones often have high electricity consumptions, so it is worthwhile to buy a new one. Interestingly, wireless-based telephones overall are often more energy efficient as they had to be energy-optimised due to their otherwise large batteries.
  • For household appliances (also called “white goods”), there are several approaches which can be considered according to the specific type of appliance:
    1. When not in use, disconnect from the mains using a power strip with a switch1)
    2. Use the appliance at the energy-saving setting (e.g. for the refrigerator: adjust the temperature control to a higher value; for washing machines and dishwashers use the “Eco” programme2).
    3. Always use washing machines and dishwashers with a full load so they are operated less often.
    4. When buying an appliance for the first time, it is always best to ensure that it is really energy-efficient; the EU label is helpful in this respect. The differences in the electricity consumption of appliances on the market are still quite large even though most large appliances today already have a much lower consumption than old appliances of the same type3). In economic terms, it is almost always worthwhile, even if the more efficient appliance costs a little more than some cheap brand4).

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efficiency_now/building_service/heat_dissipation.txt · Last modified: 2022/10/26 16:12 by wfeist