Batteries are increasingly installed at buildings with photovoltaic systems in order to match the volatile solar power generation with the respective load profiles. However, solar batteries with pure local operating specifications do not fully exploit their potential. Free battery capacities are often available that could be used for service provision to the power grid on a demand basis. In this regard, the provision of primary control power in combination with a local increase in the degree of self-sufficiency is of particular interest. The basic idea is to reserve a portion of the technically available storage capacity for different grid services, while the other portion is used for optimizing local energy flows.
To ensure a successful energy transformation, the new stakeholders and systems in the electric energy system must not only deliver energy, but also assume responsibilities for providing system services (e.g. Control reserve power and provision of reactive power) of conventional energy power generators in order to
- Omit conventional power generators in times of sufficient generation from renewable energies,
- Ensure grid stability in the case of volatile solar power generation, and
- Exploit additional sources of income for renewable generators in addition to active power provision.
Thus, the approach of a power plant of decentralized PV battery systems with co-generation plants was developed in the “Net-PV” project. It will be tested in 2016 in a field test in the grid operated by the municipal utilities Stadtwerke Schwäbisch Hall. The provision of primary control power in combination with a local increase of the degree of self-sufficiency and a load reduction with respect to the next higher-order grid was identified as economically and technically particularly interesting option.
The simulations and investigations so far highlight that solar storage units can provide additional benefits, locally as well as for the energy and distribution systems, beyond the current purpose to increase the energy consumption of locally generated PV electricity. This is not only desirable from an overall system point of view, but also shortens the amortization times of the relatively high investments required for storage systems. Due to the developed algorithms, the provision of different services is actually symbiotic.