Rational Use of Energy

Rational Use of Energy

It is estimated that over 8% of the electricity consumed in standard European homes and businesses is lost due to the way the equipment has been designed and installed. Yet electricity is the most expensive energy available-about eight times the cost of coal and three times the cost of gas-all the more reason to use it efficiently and to engage in energy consumption control programs.
Power losses in electrical equipment are due to electrical resistance in conductors and losses in the magnetic material which occur primarily in motors, transformers and in all cabling. Copper is one of the key materials to be considered when work is being done to improve the energy efficiency of electrical equipment. High conductivity is one of its most important properties and 60% of copper currently produced is used in electrical applications. Copper magnetic wire is widely used in the motor industry, while electronics is successfully developing copper-based semi-conductors.

Identifying opportunities

The identification of energy saving opportunities must be carried out in a systematic manner so that it can be shown that the initiatives proposed are those which will yield the greatest benefits.
Major opportunities will arise during the planning of new buildings, where the incremental cost of high efficiency equipment will be easy to determine, the lifetime will be longest and there will be no, or little, difference in installation costs.

Motors

Since its invention in the 1880s, the electric motor has had a long history of development, with early efforts aimed at improving power and torque and reducing cost. It is only more recently (1970s according to the CDA UK) that the need for higher efficiency became apparent.
Most motors operate at less than their design loading. It is important that high-efficiency motors retain their energy efficiency at these loads. The justification for the initial premium is simple: an electric motor can consume electricity to the equivalent of its capital cost within the first 500 hours of operation-a mere three weeks of continuous use. The lifetime cost of losses is several times the purchase price of the motor.
Clearly the lowest overall cost will not be achieved unless both capital and running costs are considered together.

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Power Cables

While the installation and use of improved energy-efficient equipment is underway, the energy losses in undersized power cables are frequently ignored. High conductivity copper is usually efficient enough to significantly reduce losses, however attention must be paid to the cables’ function and purpose. If cables are installed with a conductor size that is the minimum permissible to avoid overheating, energy losses can be very significant.
In a medium voltage power cable, the cost of losses over the lifetime of the equipment can be 10 times higher than the initial purchase cost, including installation.
If the energy demand of a system subsequently increases to a level above the safe cable rating, the installation of extra power cables can be a significant expense. The initial specification of cables that are an optimum economic size is therefore a recommended practice, notably encouraged by an IEC Standard.

Transformers

Transformers are among the most efficient machines ever designed by mankind, and are usually built of copper or aluminum. As copper has a conductivity almost twice that of aluminum, it is often preferred in transformer construction. The largest power transformers have efficiencies at full load of 99.75%. Distribution copper-based transformers are smaller, less efficient and more lightly loaded. Transformers in urban distribution (typically 250-1,000kVa) may lose 1-2% of energy transformed as heat. For smaller transformers in rural areas (50-100kVa), efficiency in operation can be as low as 95%.
In a constantly developing environment, energy consumption is an issue to be urgently dealt with. In EU, over 4 million distribution transformers have been installed, i.e. 1 unit for every 80 citizens. It takes 7-8 of the largest nuclear power stations to compensate the energy losses in these transformers. All the wind-turbine capacity that has been installed in the year 2000 covers only 10% of these losses in distribution transformers.
Clearly, energy efficiency in distribution transformers is a key factor in sustainable electrification.

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