[GeeTwo]

Using a refrigerator, even an Einstein refrigerator (which is only really distinctive in that it has no moving solid parts) to drive this is unlikely to be useful due to the inefficiencies. If you coupled this with a ratchet, you could probably use this in areas with many freeze-thaw cycles during the winter to lift heavy loads a relatively short distance. Switching the "hot/cold" as described in the video is essentially making this into a StirlingRankine engine, with the working phase change being the freezing and thawing of ice. There are a number of gas/liquid Rankine model engines that can work MUCH more quickly (e.g. the steam turbine).

The big advantage of this system is the very large pressure that can be generated. This pressure is NOT going to be efficiently utilized in a plastic tube, but in a thick-walled steel or even harder metal piston. Further, the high pressure comes at a price - the high heat of latent fusion at the water/ice state change. As I recall from my undergraduate physics, this is about 80 cal/g at standard pressure (1 atmosphere). (Confirmed online - ~ 336 J, which is 80.3 cal). That is, the amount of energy it takes to freeze one thimbleful of water is equal to the amount of energy required to lift 34 kg (about 75#) by 1 meter (39"). I strongly suspect that at the pressures cited in the video, there is a significantly higher latent heat of fusion.

Don't misunderstand me - I'm not saying that there is no point in pursuing this technology, merely that it is not going to be a magic bullet that will solve the world's energy problems with a few dozen hours of work. There probably are a few high-force niches where it can be a game-changer.