The largest new sector of the renewable energy industry, wind power is also one of the most interesting for cable makers; it is predicted to account, along with biomass, for 80% of the increase in renewable energy installations between now and 2030. Wind power systems have developed in recent years from small multi-kilowatt turbines, such as those now used for individual household or small business supply, up to today’s more common grid connected 2-3 MW designs, with 5 MW systems being developed and in the early stages of commercial exploitation, especially in offshore installations.
Obviously there are two main types of wind farm installations, onshore and offshore, and whilst the designs for the turbines themselves are basically similar, the implications for cable usage are significantly different in respect of the grid connections.
There are of course numerous applications where cables are required in wind farms such as:
Cables within the turbine and tower are often required to be of the low smoke, zero halogen type in order to protect both workers and sensitive equipment within the installation in case of fire. Similarly, vertical cables connecting the rotating nacelle, which can oscillate by more than 1 full turn either clockwise or anti-clockwise, need to exhibit excellent flexibility to withstand the constant torque changes imparted by this movement.
The development of wind farms has introduced a new market for existing wire & cable product ranges as listed above, but the emergence of offshore wind farms has probably given the industry the biggest boost in the renewables field, that of sub-sea power cables in the form of single and multi-core XLPE and, for high capacity transmission, mass impregnated HVDC cables. Offshore, wind turbines are typically spaced at least 500m apart and with arrays of up to several hundred turbines in planned large wind farms, the opportunity for MV interconnecting cables is considerable. Similarly, though current farms are usually sited a few tens of km offshore, but future “over the horizon” large arrays are being considered up to 200km offshore, greatly increasing the requirement for the so called “export cable” that transmits the power to the onshore grid.