Did they say how much energy it takes to produce Hydrogen, compared to how much you get out?
How much energy does it take to mine the raw materials, produce the metals, manufacture, transport, and construct a wind generator, compared to the power output over it's expected life span?
How much energy does it take to manufacture a solar cell, and the batteries needed to make it usable? How much energy is wasted in charging the batteries, and rectifying the current to have a usable 120 volt AC current?
When these scientists answer these questions I will take their "Conclusions" seriously. Until then this appears to be just more "agenda driven" research.
More to the point, regarding "clean" solar: how much pollution is involved in the MANUFACTORING of the hundreds of square miles of solar cells that it would take to make a dent in our energy consumption?