The relevance of energy storages for an autarky of electricity supply ...

3 Electricity Grid
The electricity grid is divided into four different voltage levels. The high voltage grid
with 220 kV and 380 kV is used to transport electricity within the country as well as
within the European interconnection of electricity produced in large power plants. In
switchyards, the high voltage mentioned is reduced to 110 kV, which is transported
to large industrial enterprises as well as other switchyards, where voltage again is
reduced to 20 kV or 10 kV. Through the medium-voltage power grid electricity is
then transported through cities, villages and other industrial enterprises. With another
reduction to 400/230 V electricity can finally be transported through a low-voltage
power grid to households and smaller enterprises. (Neupert, 2009)
3.1 Balanced Management of Renewable Energy
In general, energy consumption and production, primarily from PV and wind, in
Central European countries does not progress linearly, as the highest energy
consumption occurs during winter months when PV contributes less to the electricity
production. Furthermore, a higher amount of REN leads to a stronger delocalized
production over the territory. Therefore, the grid has to be well-balanced. To
overcome these problems one strategy would be load shifting, i.e. energy needs are
shifted from times when overall demand is large to periods in which other needs are
reduced. Smart Grids, in this context, will be of high importance in the future. Load
management, in contrast, means to constantly adjust the combination of actual
energy production and stored energy to current energy and power requirements. In
general, no more than 20 % of intermittent energy can be connected to the grid
without disturbing the grid operability. As the electricity grid does not have any
storage capacity, the consequence of an increased share of REN is the need to
balance electricity production and demand with the help of storage technologies to
avoid any interference, which can occur on the demand side (e.g. less demand during
night or on weekends) as well as on the supply side (e.g. wind conditions for wind
energy, breakdown of plants). Generally the electricity system should be well
designed, as on one hand the storage of energy is accompanied with high investment
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