I wasn't talking about the burning of hydrogen in the fuel cell. I was talking about the burning of other fuels necessary to separate the hydrogen so it can be used as fuel.When hydrogen is used in a fuel cell, or even burned, the result is water and very little else. Little or no CO2. It's about as clean as you could hope for.
Solar has it's appeal, but storage costs are excessive. Unless that drawback is addressed, it's use will be limited. And square miles of arrays, with different reflectivity than the land beneath, and the shading effect on that land, will definitely have environmental consequences. Nothing if free, nothing is pure.
No one thinks there are ZERO consequences to massive use of solar energy. The human population is so huge that nothing we do can be totally harmless. But solar power has far less of a negative impact on the environment than any other sufficient energy source. (Wind and geothermal are also very clean, but completely insufficient to handle the world's energy needs.)
Addressing the costs of storage of power generated by solar plants would be part of the big R&D activity I am advocating. If all the problems of solar power didn't exist, then we would all be using solar power today. We are not, because there are problems. I am saying that the problems solar has are far less difficult to solve, and have much bigger payoff, than for any other energy source.