While the concept of zero-point energy is generally accepted, the idea that this energy can be harnessed as a power source is highly controversial. The theory is that a device could capture the zero-point energy, which is commonly considered to be infinite. This idea is, at its root, in conflict with the current understanding of the zero-point, according to physics.
The problem, it turns out, is that the zero-point is a level which a thermodynamic system can never dip below. This means that if energy could be pulled from a system at its zero-point, that point would lower instead of yielding infinite energy. Thus, a "perpetual-motion machine" based on zero-point energy would be chasing a goal it could never -- thanks to quantum mechanics’ reach.