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2015|16 Annual Report Fraunhofer IGB

128 1 STORAGE OF RENEWABLE ENERGY IN CHEMICAL ENERGY MEDIA Fabian Steffler, Lenard-Istvan Csepei, Tobias Gärtner, Volker Sieber The challenge for renewable energy The energy supply system in Germany is facing a huge chal- lenge in converting to renewable forms of energy for electric- ity, heating, transportation, and industrial feed stocks in the long term. This conversion requires expanding the utilization of renewable energy sources on the one hand, and on the other accelerating the expansion of the power grid and set- ting up integrated high-capacity energy storage to level out energy fluctuations particularly from solar and wind sources Linking the energy economy with manufacturing processes is critically important for this balance. The e trema resulting from both the e pansion of fluctuating renewable electrical energy sources and discontinuation of further conventional demand-follow power station operations could lead to reduced energy reliability and are already in evidence today. According to the “Agorameter” of the Agora Energy Transition initiative, power generation in Germany from renewable sources reached a temporary peak proportion of 75 percent of actual electricity consumption on May 11, 2014. In contrast, there was a minimum of only 12 percent on February 11, 2015 [1]. These extrema may bring increas- ing challenges, since they might encroach on the stability of a future power grid laid out based on distributed power generation. Chemical energy storage Chemical storage has the potential of usefully coupling the areas of electricity, heating, chemical production, and transportation. The development and implementation of new concepts and innovations are being promoted in all areas of technology with the goal of increasing storage efficiency, reducing costs, and making available suitable storage for each of these areas. Besides the principal approaches already available, such as power-to-gas for example [2], Fraunhofer IGB is involved with systematic development of the necessary storage technologies through its Center for Energy Storage set up in 2012. We develop implementations of applied tech- nologies in the areas of biotechnological, chemical, and bio- electrocatalytic processes in order to store renewable energy in chemical energy media. Fermentation processes As biotechnological processes, fermentative synthesis pathways were investigated that facilitate the utilization of C1 compounds like CO2, methane, and methanol using microorganisms. This involved applying a broad strain screen- ing procedure to select suitable microorganisms capable of absorbing and utilizing these C1 compounds in their natural metabolisms. In a further step, the cultivation of the microor- ganisms and the formation of chemical energy storage com- pounds as reaction products, such as branched long-chain terpenes for example, were established, and optimization of the microorganisms with regard to substrate adsorption and product formation begun. Chemical processes The activities in the area of chemical processes have concen- trated on topics including development of catalysts for metha- nol synthesis and development of new manufacturing pro- cesses. Various doped Cu/ZnO/Al2O3 catalysts were produced for manufacturing methanol that subsequently demonstrated excellent volumes in synthesizing methanol from CO2 and H2 in the gas phase reaction. Besides already familiar catalysts, 2 ENERGY