Energy  
Energy Use
Energy Conversion
Energy Storage
Sustainability

Energy Storage
The future sustainable energy economy has to be based on closed cycles. The re-newable energy leads to heat and electricity. Therefore, the storage of large amounts of energy is a major challenge. Especially for mobile applications an en-ergy carrier with an energy density comparable to the energy density in fossil fuels (10 kWh/kg) is required. Worldwide the energy demand is 25 kWh/capita per day and in Switzerland 150 kWh/capita per day. EMPA Materials Sciences & Technology research topics for energy storage focuses on materials and systems, which have the potential to be competitive with the energy density of fossil fuels.

New batteries with liquid cathode and air electrode
The energy density of Li-ion batteries has doubled over the last 20 years and has reached almost 0.2 kWh/kg. The potential for further improvement is limited.  However, new batteries with a new concept and the direct oxidation of a light metal with oxygen from air are able to reach an energy density of 1 kWh/kg. Exchangeable electrodes require a liquid fuel, e.g. metal nano particles, liquid metals, liquid hydrides etc. Making use of air as oxidant requires an efficient air electrode adapted to the electrochemical reaction.

Hydrogen production by electrolysis and storage in solid and liquid hydrides
Hydrogen exhibits the greatest gravimetric energy density of all combustibles know today, i.e. three times the energy density of the fossil fuels. The efficient production of hydrogen from renewable electricity requires improved electrolysers using tailored materials for membranes and electrodes. The availability of a safe and effective way to store hydrogen reversibly is a second major issue for large scale use of hydrogen as an energy carrier. Hydrogen storage in solids offers a safe alternative to the technically established storage in compressed or liquid form.

Reaction of hydrogen with CO2 from the atmosphere to hydrocarbons
The storage of hydrogen in hydrocarbons is very convenient and if the CO2 is ab-sorbed from the atmosphere to react with hydrogen, the synthetic hydrocarbons are CO2 neutral. Starting from findings by Sabatier in 1902,  it is known that CO2 can be reduced by H2 over a catalyst producing eventually (Fischer-Tropsch) hydrocarbons and water.  If the hydrogen is produced from renewable energy sources by electrolysis and the carbon dioxide is extracted from the atmosphere, the hydrocarbons from such a process represent a CO2 neutral synthetic fuel.

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