  Several research studies have shown that future sustainable electricity
systems, mostly based on renewable generation and storage, are feasible with
current technologies and costs. However, recent episodes of extreme weather
conditions, probably associated with climate change, cast shades of doubt on
whether the resulting generation portfolios are sufficiently robust to assure,
at all times, a suitable balance between generation and demand, when adverse
conditions are faced. To address this issue, this work elaborates a methodology
intended to determine a sustainable electricity system that can endure extreme
weather conditions, which are likely to occur. First, using hourly production
and demand data from the last decade, along with estimates of new uses of
electricity, a worst-case scenario is constructed, including the storage
capacity and additional photovoltaic power which are needed to serve the demand
on an hourly basis. Next, several key parameters which may have a significant
influence on the LCOE are considered, and a sensitivity analysis is carried out
to determine their real impact, significance and potential trends. The proposed
methodology is then applied to the Spanish system. The results show that, under
the hypotheses and conditions considered in this paper, it is possible to
design a decarbonized electricity system that, taking advantage of existing
sustainable assets, satisfies the long-term needs by providing a reliable
supply at an average cost significantly lower than current market prices.
