Ed_nickname has missed the point, I think by misreading para2. Naturally the system can only make hydrogen when the sun shines. The issue with solar is one of producing power continuously (ie baseload power). This is one of the main arguments why solar power can't provide for a standard electricity grid, hence the political significance of the 24h power generation. I think he/she has misread the intent of the sentence. What it is trying to say is that PVs can be combined with this catalytic process to make a SYSTEM that generates electricity 24h/day. It isn't trying to say that PVs store chemical energy.
The second paragraph is completely wrong. It works as follows PV cells make electricity, electricity and catalyst make hydrogen, store hydrogen somehow, fuelcell and hydrogen make electricity, use electricity do to something useful like run your clothes dryer. Primary energy production only takes place when the sun is shining. Secondary conversion of stored hydrogen to electricity can take place at any time, even if the sun is not shining.
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