Copper, helping to power the winds of change

The rapid growth of renewable energy sources, such as solar, wind, tidal, hydro, biomass, and geothermal, in recent years has been as a response to the increasing costs of fossil fuels as well as their negative environmental impacts.

The global wind industry has grown enormously, as the fundamental drivers for wind power development still hold: there is a need around the world for new power generation, which is clean, affordable, indigenous, reliable and quick to install. In 2012, the global wind power market grew by more than ten percent compared to 2011, and the nearly 45GW of new wind power brought on line represents investments of about Euro 56 billion. The new global total at the end of 2012 was 282.5GW, representing cumulative market growth of more than 19 percent, an excellent industry growth rate given the economic climate, even though it is lower than the annual average growth rate over the last ten years of about 22 percent.

Africa is beginning to exploit its enormous wind power potential, particularly around its northern coasts and in the eastern highlands, with several countries announcing long-term plans for installing large quantities of commercial scale wind power. This includes South Africa, Ethiopia, Morocco, and Kenya, among others, explains Copper Development Association Africa’s (CDAA) centre director, Evert Swanepoel.

Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity. The basic components of a wind power system consist of a tower with rotating blades containing an electricity generator and a transformer to step up voltage for electricity transmission to a substation on the grid.

Copper is primarily used in coil windings in the generators, which convert mechanical energy into electrical energy, as well as in low voltage cable conductors, the coils of transformers and gearboxes. Copper may also be used in the housing of the wind turbine that rests on the tower containing all the main components, in the auxiliary motors that are used to rotate the housing as well as control the angle of the rotor blades, in the cooling circuits and in the power electronics.

The largest amount of copper used in wind power is in the generator, and varies according to the type of generator, its power rating, and its configuration, with the weight of copper used having an almost linear relationship to the power rating of the generator. After the generator, cabling is the second largest copper-containing component. A wind tower system with the transformer next to the generator will have medium-voltage (MV) power cables running from the top to the bottom of the tower, then to a collection point for a number of wind towers and on to the grid substation. The tower assembly will incorporate wire harnesses and control/signal cables, while low-voltage (LV) power cables are required to power the working parts throughout the system. Copper is also the dominant material in all underground cabling.

Given their height, turbine masts attract lightning strikes, so they require lightning protection systems; and copper is vital to the electrical grounding system. When lightning strikes a turbine blade, current passes along the blade, through the blade hub in the housing and down the mast to a grounding system. The blade incorporates a large cross-section copper conductor that runs along its length and allows current to pass along the blade without damaging heating effects. The housing itself is often also protected by a copper lightning conductor; and the grounding system, at the base of the mast, is also comprised of copper.

“Traditionally, wind power has been generated on land, but higher wind speeds are available offshore. Technologies are being improved to also exploit the potential of offshore wind power. The harsh environment means that the individual components need to be more rugged and corrosion protected than their onshore counterparts. Increasingly, long connections to shore with subsea MV and HV cables are required, and the need for corrosion protection favours copper nickel cladding as the preferred alloy for the towers.

“As we can see, copper is an important component in wind power generation, with wind farms containing up to several hundred-thousand feet of copper,” concludes Swanepoel.