The typical solar panel is maybe 25% efficient or less. The typical steam engine is maybe 50% efficient. Once things are in the form of electricity, we have a large variety of options for efficient transport and storage.
But sometimes electricity isn't useful. Li-Ion will never be light enough for a serious airplane for example, while hydrogen _IS_ light enough for an airplane. (But maybe too volumetric, as every practical H2 airplane engine relies upon high-pressure storage or even cryogenics to keep H2 at a small enough volume).
EDIT: If we think of it as chemistry... perhaps we can make liquid fuels out of H2 like coal liquefaction turns one fuel source into another. After all, classical fuels are nothing more than carbon + hydrogen + energy... and H2 is a very efficient form of storing energy for that reaction. Or maybe we learn to just use H2 directly? There are fuel cells and engines running on H2 today, but I'm always worried about the volume of H2 (requiring either compression or cyrogenics before you reach practicality).