The fundamental imbalance of supply

The fundamental imbalance of supply and demand represents
the ultimate limit for system penetration of variable renewables in
the electric power grids. The concentration of solar PV output
during the day can produce unusable excess electricity, increasing
costs and requiring non-optimized installed capacity, thus preventing
the ability to achieve very high PV generation share. As a
result, if solar PV is to provide a large fraction of a system's electricity,
some valuable use must be found for its excess output.
Electric mobility offers an opportunity to use that excess electricity.
However, the fact that most of the solar excess electricity will
naturally be generated during daytime, the coupling of solar
photovoltaic and electric vehicles will require that most of the
electric vehicle charging will have to take place during working
hours, which will have significant impact on social habits and infrastructures,
namely the existence of charging spots for
commuting vehicles at or near the work facilities.
This long term scenario with electric mobility and large penetration
of photovoltaics was explored for the particular case study
of Portugal in 2050. Model results show that the introduction of EV
demand on the network leads to a reduction of excess production of
electricity in the system but does not imply major changes on the
average load diagram. In other words, the majority of the extra
electricity demand from the EV can be fulfilled with the otherwise
excess electricity.
Two EV charging patterns were tested: a night charging profile,
corresponding to the night period when overall electric demand is
lower and there is typically stronger wind potential, and a day
charging profile, corresponding approximately to the average PV