Well, that very nearly is the method of power generation. It would presumably be paired with some sort of Dyson sphere around the white dwarf. (Remember that a "Dyson sphere" isn't necessarily a solid shell, but just some configuration of matter where no matter which direction the energy goes it is intercepted by something.) You may also enjoy: ▶ this video which is a minutephysics on black hole power using much the same principles but attaining yet higher efficiencies.
in “We've spotted a planet surviving its dying star” · View on HN