Solar Energy
The sun, one of a billion stars, is the energy source of all known living creatures on Earth. Reaching solar energy to earth in 40 minutes would cover the perennial human need.
Natural fuel such as coal and oil, continue to operate at the same rate as now exhausted in the next century. Nuclear power plants, which seemed to be a good alternative is quite risky, as shown in the Chernobyl disaster (Ukraine) in 1986 from all sources of energy, solar energy is the safest.