HVDC systems are preferred for transmitting electricity over vast distances due to their lower energy losses compared to alternating current (AC) systems.

The limitations, resistance loss of the HVDC means substations.

These substations would supplement for loss if the main power plant supplying the entire Earth electrical requirement was from a single location.

As the cable link is likely offshore, one or more substations could be wind, wave energy.

Likely, the solar power plants would be in several locations around the globe. Perhaps 5 and each accounting for 20% of the Earth's electrical requirement.

The substations are caused by the limitation of HVDC transmission technology, and any improvements would result in decommission of the substations.