The history of solar energy is full of predictions that were not realized and appear in retrospect to have been too-wishful. Here's an example from 1978:
"No one's crystal ball works very well in examining energy futures, but based on available information and recognizing the uncertainties we view the following goals as optimistic but achievable if we commit the necessary resources to them:
...solar energy technology could meet a quarter of our energy needs by the year 2000.
...It is now possible to speak realistically of the United States becoming a solar society. A goal of providing significantly more than one-half our energy from solar sources by the year 2020 should be achievable if our commitment to that goal and to conservation is strong."
See also: Solar Futures: The View from 1973