The German energy transition (“Energiewende”, the shift in German energy policy targeting a fundamental transformation of the fossil-based energy system towards a renewable-based and sustainable energy system) poses a major challenge to the adaptive capacity of the national energy system. By 2050 it is aimed to reduce greenhouse gas emissions by 80% to 95% compared to its 1990 level. The overall aim is to reduce primary energy consumption by 50% and gross power consumption by 25% compared with 2008. For the transport sector the target is a 40% reduction of final energy demand compared with 2005. A further objective is to cut primary energy demand in buildings by around 80%. These reductions are to go hand-in-hand with a significant increase in energy efficiency in all sectors. In addition to these reduction targets a long-term objective is to boost the integration of renewable energies to cover 60% of gross final energy consumption and at least 80% of gross electrical power consumption by 2050 . This significant integration of renewable energies will result in a far-reaching paradigm shift, requiring acceptance by society as a whole to tackle the challenges these changes pose. The prerequisite for the energy transition to succeed and, therefore, maintain our prosperity, is to retain our strong industrial base and its qualified labour force and to create new ones through innovations in new technological areas. In the power sector, renewable energies include not only base-loadable hydroelectric power and biogas, but also increasingly wind and solar energy. This type of power generation, however, is not demand-side oriented. This requires the future energy system to react both to potential supply shortfalls and excesses. The integration of the hitherto 25% share of power from renewable sources (already 30% in the first half of 2014) and considerably lower shares of renewable energies in the heat and fuel sectors has so far been achieved by making minor adjustments and using existing technologies. Nevertheless it is already evident that further measures to increase flexibility together with innovative storage options will be essential in the power sector if the share of intermittent and fluctuating electricity fed into the grid continues to rise. While the various energy grids deal with spatial imbalance between supply and demand, energy storage systems can address the temporal dimension. This function does not necessarily have to be fulfilled by the same form of energy or by just one technology element alone. The resulting advantage of deploying energy storage systems is twofold: increased flexibility, and moreover these technologies can also boost the integration of renewables into other energy sectors, such as heat supply, transport or energy-intensive industrial processes, thereby fully exploiting temporary surpluses. Power storage technologies are in different stages of technological maturity. Hence, R&D efforts will have to be stepped up if the aims of the energy transition are to be achieved without jeopardising consumer comfort and at an acceptable price for industry and the general public. Generally a significant increase in power storage capacities to harness temporary surpluses and stabilise the grids is desirable; however, this cannot be achieved without major investments. The obvious solution to the problem of adapting electricity generation to fluctuating power generation by wind and solar would be to increase the use of gas turbines which allow very flexible operation. This option is currently not viable for economic reasons: the market value of electricity is currently too low and the gas price incurred through generating electricity in gas turbines is too high. This option, however, should serve as a reference case for economic analyses of other power storage concepts. Whereas the issue of power supply and its storage already features prominently in the public debate, the emphasis is on security of supply. Hitherto, however, the other energy sectors, heat and transport, and their energy supply systems do not attract the same level of attention in the public debate. Chemical storage systems, in particular, facilitate extensive linkages between the different energy supply systems and application areas, while exploiting their specific individual advantages. The key factors determining the selection of technologies for the future are the investment costs of the required storage units and the variable costs associated with the procurement of fossil energy carriers and CO2 certificates. Further factors are public acceptance and market penetration of electric vehicles. The latter would open up new perspectives for managing an intermittent power supply. Ultimately, the political framework will be decisive. To limit one’s view to Germany would be counter-productive, since international interconnectivity, for instance through the European power grid or the international energy markets, is already a reality. In this context it should be borne in mind that the expansion targets for renewable energy integration envisaged by the German federal government differ from those of the European Union.
English Version: “Energy Storage as Part of a Secure Energy Supply”
[Ausfelder et al. “Energy Storage as Part of a Secure Energy Supply”; ChemBioEng Rev 2017, 4, No. 3, 144–210. DOI: 10.1002/cben.201700004]