The Dyson Sphere

How It Works: each satellite in the Swarm absorbs or reflects the star’s sunlight and beams it to where it is needed—such as to an inhabited planet or orbital space stations.
Uses: the captured energy could power an entire civilization, propel massive spaceships using photon sails, or run planetary-scale supercomputers and artificial intelligence networks.
Materials: constructing a comprehensive Swarm requires a staggering amount of raw materials. Theorists suggest that disassembling an entire rocky planet, like Mercury, could provide enough mass to build the initial stages of a Swarm.
Gradual Build: our Civilization wouldn't build a full Swarm all at once. We would likely start with a "proto-swarm" consisting of space-based solar arrays, expanding it over thousands of years.