Energy Storage Technologies:
1. Due to the absence of adequate market structures for energy storage, an efficient introduction of such a market is recommended. The socalled energy storage market has to bring forward especially the energy storage technologies that are needed by an energy supply system based on wind and photovoltaics. Incentives must be offered to increase investment in energy storage technologies. With first economical applications, necessary cost reductions can be achieved due to learning curves regarding production, operation and maintenance.
The energy storage market structure is indispensable to make the volatile renewable energies dispatchable. Therefore, several options for the introduction of a market exist:
a. Subsidies for energy storage solutions may be financed by fossil power plant operators through paying a penalty for power generation based on fossil fuels.
b. Every power plant operator must offer storage capacities depending on its ratio of renewable to fossil energies.
c. When constructing new fossil power plants, that are not able to handle quick load changes, energy storage plants must be built extra by the same operator with a corresponding capacity.
d. Necessary energy storage plants will be announced by the German grid agency (Bundesnetzagentur). Funding is covered with the contribution of all power plant operators depending on their size and fossil to renewable ratio.
e. Promotion of the build-up of storage plants by a Renewable Energy Storage Technology Act (as claimed in point 6d in the “Legal framework conditions” chapter).
f. Operators of renewable energy power plants can be obliged to provide energy storage capacities for their fluctuating plant capacity.
2. In particular fast-reacting storage technologies are necessary to provide grid system ancillary services in combination with photovoltaics. In addition, large scale energy storage capacities are required to compensate daily, weekly as well as even seasonal fluctuations and calms of renewable energies.
3. The installation of decentralized, (virtual) independent power plant systems is highly recommended. Thereby volatile renewable energies can be combined with energy storage (such as battery systems, hydrogen or synthetic natural gas systems, pumped hydro storage and compressed air energy storage) as well as with flexible geothermal, biomass and waste power plants to provide a controllable system.
4. Decoupling of thermal energy and electricity production in combined heat and power plants has to be constantly increased by using cheap, thermal energy storages such as e.g. hot water storages.
5. Large scale energy storage is indispensable for a 100 % renewable energy supply system. Synthetic natural gas (SNG) and hydrogen are recommended because of their large energy density. Additionally they can be used as fuels as well as for heating processes.
6. The development of a national subterraneous storage field book, as it is currently developed by the Federal Institute for Geosciences and Natural Resources (BGR), has to be published. The usage of the limited belowground capacities should be regulated, with a priority for large scale energy storage (SNG and H2) or a strategic European reserve, respectively. Carbon Capture and Storage (CCS) should in consequence have less priority.