Dimensioning of Decentralized Photovoltaic Storages with Limited Feed-in Power and their Impact on the Distribution Grid

Abstract

The growth of photovoltaic (PV) in Germany frequently reaches its limit due to constraints in the distribution grid. In addition, we soon face an excess of renewable energy at certain day times. For both, distributed storages are a good solution.Here, at first limitations in the distribution grid are analyzed in typical residential areas, which are rural region, suburbs, town center and multistory building areas. As limiting parameters the rated power of the transformer and cables as well as voltage limits are considered. The possible feed-in power is related to the potential of PV in the corresponding area. As a result in suburb and rural areas only a fraction of the PV potential can be used. The same analysis was also performed assuming PV storages and a feed-in power limitation of 30% of the related PV peak power. A significant improvement of the use of the PV potential results.Next, the consequences of a feed-in power limitation are investigated. Depending on the limit height, without storage a certain amount of energy is lost. With 30% peak power limit, 2/3 of the PV energy is fed in, while with a “large” storage, more than 90% is fed-in (orange). The variation of the storage size reveals a reasonable size of 4 kWh, scaled to a PV system of 1 kWpk.Another criterion for the storage size is the optimization of self-consumption. A full autarky needs a very large storage covering seasonal storage. A plateau is visible for 2 kWh, scaled to a self-consumption of 1000 kWh/a, which relates to a daily storage and is independent of the PV size.