  The decision by the United Kingdom (UK) government in 2007 that the country
should build a 33GW wind fleet, capable of generating 25 percent of the UK
electricity requirement, was controversial. Proponents argued that it was the
most attractive means of lowering the UK greenhouse gas emissions, whereas
opponents noted that it would result in an unnecessary and burdensome
additional expense to industry and households. Subsequently there have been
calls for the wind fleet target to be further increased to perhaps 50 percent
of demand. Although the National Grid has had little difficulty in
accommodating the current output of about 10 percent of the total demand on the
grid, this will not be the case for a substantially larger wind fleet. When the
wind blows strongly, turbines shed wind which is surplus to demand, leading to
significant reductions in generating efficiency. The purpose of the research
described in this paper has been to develop a method for investigating the
likely performance of future large wind fleets. The method relies on the use of
mathematical models based on National Grid records for 2013 to 2015, each year
being separately analysed. It was found that the incremental load factor of the
wind fleet will be reduced to 63 percent of its current level should the wind
fleet increase from its current size of 14GW to 35GW, assuming a base load of
15GW
