vinc -

And exactly how much energy do these cryocoolers consume per hour? If your power plant is using NG to generate your electricity, then you're still on a depletion curve. If NG becomes difficult to get hold of, then you're looking at another problem, but that one too, is related to resource depletion.

One of the points made is that the inputs for many of our materials are fossil energy - steel alloys, stainless, magnets, ceramics, silicon...  The question posed is: Can these materials be manufactured without NG. I think it is a very valid question. Heating with electricity has typically consumed more energy than heating with NG in manufacturing.

Replacing NG with electricity actually consumes more NG at the electricity generating end, and throws a very large load on the grid - that's why manufacturers have a special electric meter (called a demand meter) when they use large amounts of electricity. You get billed at the highest rate of consumption - if it's 10kw an hour for 2 minutes, then you get billed as if you are drawing 10kw an hour for everything you use. It definitely affects the bottom line, and it's there to discourage pulling a lot of juice.

These are the things a lot of us are thinking about and discussing - energy inputs and how to offset them or find alternative sources that are workable. The fossil fuel train is slowing down - we have to get off if we are to continue our journey forward.

An important property of a superconductor is its critical current density (i.e. the maximum current density it can carry while still remaining a superconductor). This is a particular problem for superconducting magnets since the critical current density decreases in the presence of a magnetic field. While high temperature superconductors exist (~110K) they don't have the critical current densities needed for magnets producing 13 Tesla fields where as for low temperature metal superconductors (e.g. Nb3Sn) it is just about possible. People are talking about using high temperature superconductors in Maglev trains some time in the future but the field strengths would be a lot lower than a tokamak. It should also be noted that because of all this the generally held notion that if we could get a viable fusion reactor working it would be perfectly safe is probably wrong. A full scale tokamak that produced useful amounts of energy would be huge (football stadium size) and hense the associated magnetic field would not only have a very large field strength but would encompass a massive volume. Playing around with the equation E = B^2.V/(2mu) you should be able to convince yourself that the energy stored in the field would be enormous and therefore a magnet coolant failure could be catastrophic.