Copper also has a broad field of application in renewable energies. A decisive key to the energy transition is increasing the energy efficiency of renewable systems. This always involves the entire energy conversion chain – from highly efficient electricity generation to transport and distribution to efficient use. However, energy-saving technologies are currently not only more expensive, but also generally require more or better materials.
Therefore, the production of these materials can have a higher environmental impact than those used in “conventional” technology. This must be taken into account in the life cycle assessment, i.e. offset against the energy saved. In energy technology, copper serves as a functional material and is mainly used as an electrical conductor. In contrast to many components, where resource efficiency is equated with a reduction in the amount of material used – for example to save weight – the term efficiency looks quite different for copper. Because in electrical engineering, the efficiency, i.e. the effectiveness of copper, increases the more of it you use. Copper’s excellent thermal conductivity, together with its corrosion resistance, ease of processing, strength, durability and formability, offer unbeatable advantages in solar thermal applications. In wind energy, copper is used in wind turbines in the stator and rotor windings of the generator, the power cables, the transformers and the earthing system. Copper is also found in the components of the solar cell used in photovoltaics, such as the wiring, inverters and earthing.
Current wind turbines are the largest rotating machines ever built by man. Today, wind turbines have a rotor diameter of up to 180 metres – and the trend is still rising, because larger rotor diameters improve the economic efficiency of the turbine through optimised “harvesting” of the wind. Today, modern wind turbines, including infrastructure, require up to 30 tonnes of copper to function. In the ring generators of large wind turbines, windings of up to several hundred kilometres of copper flat and round wire ensure environmentally friendly electricity generation. The outstanding material properties of copper are particularly evident in the so-called cable loop. This ensures that the nacelle, including the rotor blades, can rotate into the optimum position depending on the wind direction, with strong forces acting on the cables. Special class 5 and 6 copper cables (fine-stranded and superfine-stranded conductors) are used for this purpose, which are equipped with a specific stranding of the individual strands. Copper is also used in the motors that turn the rotor blades along their longitudinal axis and thus regulate the power according to the wind speed. The winding of the transformer, which connects the wind turbine to the wind farm’s medium-voltage grid, also requires a relatively large amount of copper. In addition, there are the cables and lines for data transmission and communications technology for control and monitoring.
Copper is an extremely important material for enabling the further development of solar energy and the energy transition in a cost-efficient and sustainable way. Thanks to its natural properties such as high conductivity and durability, copper is essential for the collection, storage and distribution of solar energy. It connects PV modules to the electricity grid and, in some cases, drives the motors that tilt the solar panels towards the sun. Furthermore, the copper used in PV systems is not consumed because copper is 100% recyclable and can be used and reused after the life cycle of a PV system without losing its beneficial properties. The amount of copper typically used in a 1 MW PV system is 3.1 to 4.8 tonnes, depending on the choice of inverter feed cables. These values are likely to increase by another 0.4 tonnes when tracking systems are used. In the future, silver on the solar cell could also be largely substituted by copper. SolarPower Europe forecasts that newly installed PV capacity worldwide will reach around 622 GW for the period 2018-2022, representing an average growth of around 124 GW per year. Assuming an average copper consumption of 4 tonnes / MW, the estimated additional annual demand for copper in the PV market can be estimated at 496,000 tonnes per year.
Combined heat and power plants (cogeneration)
Combined heat and power (CHP) is the combined generation of heat and electricity. Its advantage is that it enables the heat released by electricity generation to be used. The best-known form of CHP is an electricity generator – driven by a heat engine – in which heat released by the engine is used to produce steam and / or hot water. However, in order to fully exploit the economic potential, not only the electricity but also the heat must be used optimally: that is, a simultaneous demand for heat as well as electricity must be ensured. Incidentally, combined heat and power units (CHP) work according to the principle of cogeneration: combustion engines convert mechanical energy into electrical energy via a generator, and the resulting exhaust and waste heat from the engine is used simultaneously for heating water and for heating. This makes CHP units particularly efficient. In principle, thermal energy can be converted directly into electrical energy (Peltier element). However, this only works on a very small scale. If you want to generate electricity on a significant scale, you have to take the diversions via heat and mechanical energy: Some form of a so-called “heat engine” (gas turbine, steam turbine, petrol engine, diesel engine) drives a generator, i.e. moves it. Chemical energy in the form of fuel is used on a large scale to generate the heat. Copper is a key material here in several places because it gets the silver medal of all materials in conductivity for both electric current and heat. Combining the two, first exploiting the high temperature to generate electricity and then using the waste heat (of “only” 100°C instead of about 1500°C) to heat the house, is what a combined heat and power unit (CHP) does: a relatively small combustion engine is run on natural gas or fuel oil and drives an electric generator. In order for the generator to produce as much electricity as possible, its copper windings must be wound with the thickest possible wire.
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