Sir, – Prof Philip Walton (August 17th, September 3rd) correctly points out that wind, wave and tidal power are variable by nature, and will only satisfy part of our future energy needs, but unfortunately he repeats some common misconceptions about these renewable energy sources. Even with a large installed capacity of renewables, 100 per cent back-up is not necessary because back-up capacity must be considered for the system as a whole, and is influenced by several other factors. These factors include unforeseen variations in electricity demand, the spatial spread and mix of renewable generators, and the necessity to also cover for the unexpected failure of any conventional generators in the system. As it is extremely rare for a diverse array of geographically dispersed power plants to simultaneously produce zero power, it is safe to operate with much less than 100 per cent back-up capacity. This is the norm throughout the world. The variability of renewables is reasonably predictable in the short term, which allows for the scheduling and efficient operation of any back-up generation required.
Critics of wind energy often refer to the large areas that would have to be occupied by wind turbines in order to satisfy a significant proportion of electricity demand, but neglect to mention that only a very small proportion of the area of any wind farm is actually occupied by the turbines, the remainder being available for agricultural or other use. Most non-renewable generation requires a considerably larger footprint than that of the power station itself when fuel extraction, processing and disposal requirements are included. – Yours, etc,