Clean energy, for the next 50 years, will be limited in its usefulness.
Solar and wind have been proposed. What is involved? The following are my assessment of current solar possibilities, with aid from "How Stuff Works."
SOLAR-
Solar energy technology could be sufficient to service homes in much of the world. This may be done individually, or collectively by a commercial or cooperative company.
Individual- how many people can afford to make the installation necessary?
The average house requires c. 14000 watt hours/day. This requires 285 square feet of solar panels.
Because of cloudy days, a battery bank, inverter, etc. are needed in the installation.
Solar panels- $16,000
Battery bank, etc. Another $16,000.
Could be required for new homes, but for most people in older homes, retrofitting
appliances, roof, adding labor costs, control room, etc. would require a mortgage addition. Cost prohibitive for most.
In the U. S. and Canada, state and provincial rights prevent nationwide regulation.

Retrofitting apartment towers and comdominia is doubtfully economic.

The alternative, large commercial solar panel fields with transmission lines to towns have many drawbacks- from withdrawing large parcels of land from agricultural, livestock, recreational, wildlife and other uses. Costs of auxilliary equipment high.

For northern sites- settlements in northern Europe, Asia and North America- solar power must be supplemented as it is not feasible for exclusive use.

Local zoning and preferences. No overall plan is possible. The federal government cannot override state laws, and the people and their communities vote their preferences.

Solar power for industrial purposes- Impossible!

To power industry, only fossil fuels and nuclear technology available with present technology. How long to develop otrher technology? At least 50 years if large budget allowances made.

Similar problems exist for wind power proposals.