What's the point? You still have to have an energy source. What does the spring do that would be better than using the energy source to turn the generator directly?

Well this only a novel concept to highlight that energy can becranked up manually. It may be of only academic interest andnot commercially viable. Akin to a perpetual motion machine - itcould be only a educative tool.

I suppose it might be possible to use it as energy storage. For example, you could use it to store solar energy to use at night. It might be a possible low cost alternative to batteries or flywheels. It wouldn't need to be miles long though. You could probably make a household unit that fits in a box only modestly larger than the batteries it replaces. It's probably not a good choice for large scale storage. Pumped storage hydroelectricity would be cheaper.

The bigger it is, the more energy would get lost in the mass of the machine.

IMHO, it would only be practical alternative to batteries, where it could be human charged, and is for the freeplay radios, or as an engine starter

As an energy storage system I could see it working. It could be would up by wind action or wave action driving a ratcheted arm. When you need electricity, the brake on the spring is eased to allow it to drive a speed limited turbine (a flywheel would help here…, and voila, power on demand where it's required.

It is a workable idea - I always had the old punka (a kind of ceiling fan)in mind - a British invention of the Raj. It is possibleto harness the wind energy to wind a huge coil and use it when you need. The beauty of this idea is that the cam based punka is thatthe shaft can be brought out of the building and coupled to a wind mill quite easily.