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Energy Use - Guidelines

There are several energy labels in the world today and the best known one is probably “Energy Star”, an energy label designed and supervised by the EPA (Environmental Protection Agency) in America and the U.S. Ministry of Energy. As can be expected most energy labels concern electrical appliances. In general it can be said that only a small part of the energy that enters Earth’s atmosphere is being used to satisfy the needs of mankind and that therefore there is no energy crisis. However the problem is that we have not yet learned how to harness the energy in an ecological and efficient manner. Therefore we are still using fossil fuels and coal for electricity production, space heating and transport.

Fortunately, Icelanders have not been forced to use fossil fuels for space heating or electrical production except in a very few cases. Nevertheless the release of greenhouse gasses is similar in Iceland as in other European countries, and energy use per capita is one of the highest in Europe. This situation is mainly caused by a large fishing fleet and energy-intensive industry. Even though electricity in Iceland comes mainly from hydropower, this fact does not mean that we can just use energy as we please. In the first place energy is expensive and in the second place hydropower has a certain negative environmental impact. In fact if Icelanders were to save energy and use existing hydropower more effectively they could export more than they do. All energy-intensive industry is an indirect export of electricity and electricity is a local resource that can replace fossil fuels such as gasoline and oil. If I Icelanders were to reduce their energy use then it would be possible to use what was saved for hydrogen production which hopefully would replace gasoline and oil for transport within a few years. This is only a simple example showing that everything is connected; energy saving in the home or in the workplace saves not only money but also can benefit the environment.

Energy Use

The simplest way to buy the most efficient appliances is to check their energy use. Energy use is usually measured in watts, (W), kilowatts (kW), kilowatt-hours (kWst) or amount of fuel used.

The relation between W, kW and kWst

The energy use of electric appliances is usually measured in W, for instance a 60 watt light bulb. One kilowatt is 1000 W. It is therefore possible to write 60 W also as 0,06 kW. One kWhour corresponds to one kW used or produced in one hour. A 60W lightbulb shining for 16 hours and 40 minutes uses one kWhour of electricity.

Energy Efficiency

Energy efficiency very rarely reaches 100%. Most of the energy in a 60W lightbulb is used to generate heat instead of light. It is possible to obtain a similar amount of lighting from an energy saving lightbulb which is only about 11W. A Kilowatthour (kWh) is the same as  watts x  the number of hours /1000. The  number of hours in one year is 8760 (36524). A 40 watt lightbulb which glows for one year, therefore, requires about 350 kWh  and costs about 3000 IKR. To have several lightbulbs glowing for no reason can be costly.

Energy Use

Energy use can be described and represented in several different ways. For electric appliances and lightbulbs it is most usual to describe energy use in watts.  For cars,   energy use is usually described as fuel use, that is, fuel use per 100 km. With the arrival of new fuels it is also possible to represent fuel use indirectly by listing the amount of carbon dioxide released per driven km. A car using 10 litres per 100 km for instance releases 230 gr. of carbon dioxide per driven km. When considering various electrical or fuel driven appliances the energy use is described in watts (W) or fuel use per hour.   
Energy losses of some construction materials, like windowpanes, are measured with a heat release constant, sometimes called the cooling constant. The cooling constant is measured as watts per square meter (W/m2°C) and is used to measure the energy  emitted through each square meter of windowpane. The lower the cooling constant,  the lower the energy release is through the window in question or  insulated  material. In Iceland all residential housing or other housing where people dwell shall for instance have  insulation glass with a cooling constant lower than 2,0  W/m2.

Grafik: A symbol exclusively used for energy use at nature.is ©Nature.is.

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