[tbknnbkz] Ice energy

Water curiously expands when it freezes into ice.  Can we extract energy from this effect?  I'm imagining a piston driving a linear generator.

How much energy can be extracted?  Is it more than the heat of fusion?

If so, we can sort of create a perpetual motion machine by recycling some of the energy to melt the ice.  I think it is not actually perpetual motion because it will stop when the cold reservoir is exhausted.

If not, we get a weird high pressure ice with the same density as water.  Or perhaps the water refuses to freeze.