Alphabet's Google said on Monday it has struck a deal to buy power from a project in Virginia fueled by fusion, the reaction that powers the sun and the stars but is not yet commercial on Earth.

The deal comes even though Commonwealth Fusion Systems has yet to demonstrate that its future power plant can generate power reliably or economically.

Google is making a big bet on a power source that hasn’t yet been used successfully anywhere in the world: nuclear fusion. The tech company said on Monday that it will buy power from a planned nuclear fusion plant in Virginia developed by Commonwealth Fusion Systems,