  The use of wind and solar generation is fundamental to the decarbonisation of
the United Kingdom electricity system. However, the optimal level of renewable
energy as a proportion of total demand is still being debated. In this paper,
several models, whose aims are to predict the efficiency of future system
configurations, are explained. The models use historic records from the
Gridwatch website for the year 2017, which are then scaled accordingly. The
model predictions are first demonstrated for the 2035 Scenario as proposed by
the National Grid in FES 2022. The analysis reveals that at least one third of
the available wind and solar generation will exceed the ability of the
electricity system to use it and will have to be shed. By defining an
efficiency measure, the Marginal Decarbonisation Efficiency, which quantifies
the incremental extent to which wind generation can decarbonise the electricity
system, it is shown that the 2035 Scenario will have a low efficiency.
Moreover, it will require the use of combined cycle gas turbines, which is at
variants with the predictions of the National Grid steady state model. The
paper also describes the derivation of a Generic Model, which allows the level
of wind energy and dispatchable generation for all system configurations likely
to be encountered in future decades, to be calculated without the use of
computer models.
