[Falcon9]

From what little I understand, a Dyson Sphere would require so much material in terms of heavy elements that you'd have a great deal of trouble building a significant number of them even if you were raiding the entire universe for these materials. But like I said, I understand very little (and would love clarification).

[danieltillett]

There are alternatives to a classical Dyson sphere (Dyson bubble is one) that can be constructed to capture all the energy released by a star and which do not require much material [1].

I actually think you would use a series of nested Dyson bubbles to capture the energy via a cascade much like the electron transport chain [2] uses a multi-protein redox cascade to capture the energy of metabolism.

1. https://en.wikipedia.org/wiki/Dyson_sphere

2. https://en.wikipedia.org/wiki/Electron_transport_chain