A superconducting hydrogen-electricity grid

When is there ever a need to transmit 5 GW from one particular point of an electricity grid to another – remote – discrete point? And how shall this boost the use of hybrid vehicles? How much energy is needed for liquefying the hydrogen? What happens when the use of hydrogen stalls at the end of this miracle cable? The cable will gradually warm up and finally burst. In order to avoid this, safety valves will have to open and probably burn the expensive but momentarily superfluous hydrogen. So this system requires a more or less stable flow of hydrogen through the cable – independently of the electrical load! I see no opportunity for a shift in the electricity / hydrogen blend because the need for cooling is constant.

Surely it is possible to build such cable and use it in a grid infrastructure that produces and transmits a part of its energy as electricity and the other part as hydrogen. Sure it may boost the electrical energy efficiency from 99% to 100% thanks to the use of a superconductor – if you ignore the cooling energy demand. But the hydrogen part of this system will operate at an overall efficiency of less than 50%. Is this more efficient than a plain expansion of the existing electrical system?

Surely the HV and EHV grids need expansion, but the point is not enhancing the power rating of the individual line but making the mesh denser! We need more lines, not stronger lines. And if we do, mind that doubling the use of copper in a DC line at a given voltage halves the losses, so there is a theoretically endless scope for loss reduction, should future energy prices justify this.

Where should the dramatic reduction of fuel costs for a future transport sector based on electric- and hydrogen-powered hybrid vehicles arise from? Suitable batteries for electric cars are still lacking, and the efficiencies of hydrogen engines perform poorer than diesels, adding to the poor conversion efficiency of electricity into hydrogen compared to refining mineral oil into petrol and diesel fuel.

There are several splendid applications for superconductors:

• Short-circuit current limiters,
• Magnetic energy storage (to mitigate voltage dips substantially),
• extremely strong magnets used in medical diagnosis and particle accelerators.

These applications are unique to superconductors because they are impossible to implement with any other conductor. Another sector, where the superconductor is not really indispensable but useful, is propulsion motors and alternators on ships, where they can save substantial amounts of volume and weight. A special advantage of the specific system is that in case the superconductivity quenches on account of a fault, the copper hull takes the electric current over and enables the ship to still operate at 10% of its rated power.