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Storing the Sun in a tank

Among the several hurdles in making renewable energy a cost effective, reliable and diffuse reality is the storage of energy between the time it is captured and the one it is used. 
This goes for tides, for wind and for solar. They are all important sources of energy that can be harvested only in certain window and most of the times these windows don’t match with the usage needs.
There are several ways of storing energy but again the problem is finding something that is both cheap (affordable) and easy to use. Techniques include heating various chemicals, like sodium, pressurising air, spinning big wheels, moving water to high reservoirs…
Now researchers at Stanford are proposing to use energy harvested from the Sun (turned into electricity) to separate hydrogen in the H2O molecule (water) and storing it into a tank. The advantage of this method lies in the very high energy density of hydrogen. In a relatively small tank you can store plenty of energy. Once you need it you just add air (and in particular oxygen) and you get water back and along with it plenty of energy ready to use.
The problem with this approach is that the electrolytical process (electrolyses) used to split the water molecule in hydrogen and oxygen results in the production of protons, that is hydrogen atoms that miss the electron. In order to have the proton capturing an electron and therefore becoming a stable hydrogen atom you need to keep it "quiet" for a little while and that requires a catalyst. The ideal one is platinum, but platinum is not cheap! What researchers at Stanford have been able to do is to use a much cheaper element, molybdenum, to do the same thing.
They got the inspiration from looking at petroleum refineries where the molybdenum sulfide is being used. It does not work well for what they needed but a variation of it does, almost as well as platinum: molybdenum phosphosulfide.
So now we have a way to place Sun energy in a bottle, literally!

About Roberto Saracco

Roberto Saracco fell in love with technology and its implications long time ago. His background is in math and computer science. Until April 2017 he led the EIT Digital Italian Node and then was head of the Industrial Doctoral School of EIT Digital up to September 2018. Previously, up to December 2011 he was the Director of the Telecom Italia Future Centre in Venice, looking at the interplay of technology evolution, economics and society. At the turn of the century he led a World Bank-Infodev project to stimulate entrepreneurship in Latin America. He is a senior member of IEEE where he leads the New Initiative Committee and co-chairs the Digital Reality Initiative. He is a member of the IEEE in 2050 Ad Hoc Committee. He teaches a Master course on Technology Forecasting and Market impact at the University of Trento. He has published over 100 papers in journals and magazines and 14 books.