As an example, we briefly described a possible way to store access energy. Please note that this is just a short example to give a direction of a possible solution. This however has not to be the final solution.
We have an access of energy produced via solar panels. We want to store this energy in a chemical form. Methanol is a good option since it is liquid and a simple molecule that can be combusted.
There is a way to produce methanol out of CO2 and H2, the direct hydrogenation of CO2:
With the excess energy of the solar panels, we can produce H2 via electrolysis of water.
By using a CO2 capture unit, for example, we can take CO2 out of the air and use it for the reaction.
This means we theoretically have a green way to produce methanol with our access energy.
This reaction takes place over an copper-catalyst and has a high selectivity to methanol.
Further research would be needed to determine the exact/best reaction conditions, but this is not done for this short example.