Worldwide power grid with glass insulated HVDC cables

Concept and potential benefits

• Proposal: worldwide HVDC grid using aluminum conductors inside thick fused‑silica (glass) tubes at ~14 MV, laid continuously from a ship with onboard glass/aluminum furnaces.
• Supporters like it as a thought experiment: materials bill looks surprisingly cheap per 10 GW ocean‑spanning link, and a global HVDC mesh could dramatically improve renewable utilization across time zones.

Mechanical and materials challenges

• Major skepticism around bending: a meter‑scale glass tube has a huge minimum bend radius; accommodating seafloor contours without cracking may require trenching, careful span limits, or buoy support.
• Big concern over thermal expansion mismatch between aluminum and silica; some argue cooling will create gaps that relieve stress, others think repeated temperature cycles and Z‑pinch–like forces risk delamination and fracture.
• Debate over whether pre‑stressed glass (Prince Rupert’s drop–style) helps or just makes catastrophic crack propagation more likely.
• Foam flotation for neutral buoyancy is questioned because many foams collapse at deep‑ocean pressures.

Electrical limits and HV engineering

• Present HVDC projects top out around 1.1 MV; jumping to 14 MV is viewed as orders‑of‑magnitude harder, not a linear extrapolation.
• Dielectric strength numbers are disputed: unit confusion (MV/m vs MV/mm) and claims that realistic, derated strengths for fused silica (~tens of MV/m) would drastically reduce feasible voltage.
• Designing breakers, converters, and transformers at 14 MV is seen as near‑fantasy; even existing multi‑hundred‑kV equipment is enormous and complex.
• Some argue you’d avoid ultra‑high‑voltage switchgear entirely and treat the cable as a sacrificial “fuse,” though others question the economics and safety of that.

Manufacturing and deployment practicality

• Onboard continuous glass‑coating and quenching is criticized: rapid cooling induces large internal stresses, and annealing in a moving ship environment may be unrealistic.
• Questions about extrusion rate, cable weight versus ship capacity, and whether simply using much thicker plastic insulation and bigger cable‑laying ships is cheaper and more robust.

Repairability, security, and reliability

• Subsea cables already fail regularly from anchors and fishing; a brittle, unpatchable glass dielectric at planetary scale is seen as extremely fragile and attractive for sabotage.
• Some repair schemes (pre‑weakened sections, spare cable loops, epoxy joints) are floated but judged comparable in cost to just laying redundant conventional cables.

Use cases, economics, and alternatives

• Disagreement on “need”: some claim only a few geographies (e.g. large east‑west imbalances) justify extreme long‑distance transmission; others say the US and Europe already underbuild transmission.
• Advocates see cheap HVDC plus renewables and storage as potentially undercutting nuclear; others argue nuclear and more localized grids are more realistic.
• Political feasibility and international cooperation are viewed as at least as hard as the engineering.