Wonder if raising voltages would not be an alternative as well. Power lines dissipate heat as R*I², so higher tensions help transmit more power with less current, and less dissipation as well. It would be great if this allowed us to totally replace scarce copper with more abundant aluminium or at least use thinner wires that demand less raw materials, given scarce metals like copper are a bottleneck in energy transition.
Besides the safety issues others have brought up, you'd also have to replace the substations on both sides of the lines to support raising and lower at 2x the voltage. Most likely that would require roughly a 2x size in transformer and copper.
A better idea in the short term is using temperature sensors along the wire. In the winter, we should be able to push more current without risking burning out the wires if we can effectively monitor the temps in real time.
They are significantly more likely to arc bigger distances. A 200kv line will arc twice the distance a 100kv line will. You'd need bigger separation between the different phases on a tower, you'd need longer insulators, you'd need new towers.
For transmission of electrical energy, this is the way. Voltages should be as high as equipment, costs, and safety practices allow.
Let me opine how expensive it was to refit my 80's van electrical system which has its 12v battery in the front to bring enough current to the starter 4 meters away. (Battery relocation isn't an option.) It originally had a piss-poor 14 ga / 1.6 mm wire to feed the starter and the charge battery, and the losses were awful. What it needed was a single 000 ga / 10.4 mm wire for the positive lead, which requires special cutters and special crimpers to create a usable wire. (The body of the vehicle is used for the negative/neutral lead.)
If a higher voltage were implemented, most/all of the switchgear and power lines would be retrofitted per engineering specifications.
Design values change, but not as much as you think. 1 cm for every 10 kV is reasonable between parallel plates. The dielectric strength of air is roughly 3 kV/mm.
Perhaps there's room for improvement in the last mile. Copper is expensive, insulation is cheap. Wonder how much higher the tensions in electric outlets could be made while still keeping overall safety of the system.
For transmission lines, AAAC, AAC, and AACSR exist.
For residential grid hookup, aluminum has been an option for a long time.
While aluminum residential wiring has historical baggage of risky and bad practices, the problem with it is inherent fatigue failure. Copper should be required for residential structural high voltage wiring.
Locating, mining, and recycling more copper is necessary because demand is far exceeding supply. Perhaps at some point in the future, we may need to mine disused 20th-century waste dumps for metals and rare earths we just threw away and failed to recycle.
if there were pylons already going to where the solar and wind farms are built then yes, this 'rarely used technique' of adding larger capacity wires to existing pylons would be the obvious answer, but the problem is these uninhabitably hot sunny deserts and windy plains ideal for new solar and wind energy do not have grid connections because people don't live there.
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