From Wikipedia -
A Dyson sphere is a hypothetical that completely encompasses a star and captures a large percentage of its power output. The concept is a thought experiment that attempts to explain how a spacefaring civilization would meet its energy requirements once those requirements exceed what can be generated from the home planet’s resources alone. Only a tiny fraction of a star’s energy emissions reaches the surface of any orbiting planet. Building structures encircling a star would enable a civilization to harvest far more energy."
I know it would be way overly audacious to require teams to construct a Dyson Sphere (at least in this century). However, there are other ideas for useful mega-structures in space, like swarms with hundreds-of-thousands of satellites that can together harvest large amounts of solar radiation.
The feasibility of such a project has been evaluated in a scientific paper published in PNAS in 2006, with the author claiming that this kind of a system could be developed and deployed by 2030 or so. See -
What do you think?
And thank you, @crointel, for mentioning the concept of Dyson Spheres in this forum!