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

4.1 Storage demand
Energy storage options are commonly split up into daily, weekly and annual
balancing. For each technology, different requirements have to be taken into account
(see also Table 4.1). Reserve power, for example, not only has to be accessible very
fast but also has to be able to deal with a high amount of storage cycles. Uninter-
ruptible power supply needs to have low losses. Daily, weekly and yearly storage
need to have high energy content – in regard to dimensioning this means, that as
longer the time frame, as higher the energy content has to be. In addition to a longer
timeframe, the self-discharging rate should to be lower. (Neupert, 2009)
Reserve
Power
Uninterruptible
Power
Daily Storage
Weekly
Storage
Yearly
Storage
Fast access time ++ ++ - - -
High energy
content
High energy
density
Low selfdischarge
rate
Long calendrical
life-time
- - + + ++
- - - - +
- + - + ++
- + + + +
Long lifecycle + - + + -
Typical
operating time
10 s 10 min 10 min – 1 day 1 – 7 days
++ very important + important - less important
Table 4.1: Requirements for electrical storage systems for different purposes (Neupert, 2009)
4.1.1 Long-Term or Seasonal Storage
1 week – 1
year
Seasonal Storage involves mainly large installations like reservoirs and dams that
accumulate water primarily during the rainy (or snowy) season. By passing water
through large turbines, electricity can be produced. (Huggins, 2010)
4.1.2 Daily and Weekly Storage
Energy from sources that produce on a daily cycle like solar, wind or tidal energy
needs to be temporarily stored when not needed to be available later. These sources
can be affected by changes in weather and therefore vary over the year. (Huggins,
2010)
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