> Time for napkin math. If we want to convert half of our 490 exajoules of global annual fossil fuel energy to offshore wind energy (let's say all offshore so we can use a generous 50% capacity factor). Then we need 5.22 million offshore wind turbines (3MW each), which will require 94 million tons of copper. That's 11% of all the copper we think exists on Earth. For one generation of wind turbines that will maybe last 25 years. Maybe. This is before we build ANY battery storage, which also needs large amounts of copper, not to mention lithium. It just doesn't make sense to me.

State of the art offshore turbines are 15MW each (so about 5-8MW net). There are commercial 3MW turbines which only have a relatively tiny amount of copper in the nacelle. 6t/MW is high for the turbines alone, but low if including substations and cabling, so I don't know where they drew the boundary. Worldnuclear uses 27t per MW net.

Here's a commercial wind turbine with no copper windings or permanent magnets https://electriccity2021.windeurope.org/sites/default/files/...

Bus and internal cabling is sometimes Al in smaller turbines as well.

Connecting cables and transformers can also be done with Aluminum. It doesn't happen very often yet because the wind industry lives in the real world where a $1/MWh O&M increase means something won't happen unless it has a commensurable reduction in capital. The second copper rises in price by 50% or so the industry will swap. Al coil substation transformers are already viable.

This cuts out about 80-90% of the copper in onshore wind and 50% or so in offshore (transmission is extremely copper intensive)

Subsea Al transmission cable exists in demo projects but has maintenance issues. It has been tried at scale but would increase costs substantially.

> Solar PV is even worse than wind for utility scale energy because of its abysmal capacity factor. The main drawback for PV will be the amount of storage or overcapacity needed. So unless we get a miracle breakthrough in energy storage soon, I don't see how wind/solar can scale to replace most of our fossil fuel energy

We've had the 'miracle' in the form of sodium ion batteries in about 2018 -- niche safety critical applications for aqueous chemistries are on the market and multi GWh/yr scale factories are presently being built. $60/kWh cell cost is a reasonable expectation (at which point 48hr storage is viable and all PV+battery production is cost competive with nuclear at ~45 degrees north). There are also various projects to radically reduce the cost of brine mining.

Fe-Air is highly promising for 100hr storage but still building out a demo project. AlS and molten salt NaS are undergoing initial commercialisation steps but there have been other technologies at this level that never materialised.

Re. The 480EJ of fossil fuels. There are only 800EJ (2400EJ thermal -- which has relevance for heating and hydrogen) of commercially viable Uranium ore for use in a PWR (even if all the lower efficiency ones are decommisioned immediately). BWRs are a little more efficient, as are Candus (which can use about 4kg of natural uranium where a PWR would use 1kg of enriched). Even in the existing FNR plants (which have resource constraints, cost, reliability, and safety issues to work through before they can be commercial), a closed fuel cycle has never been demonstrated. Reprocessing via MOX and existing designs only adds another 200EJ (600EJ thermal).

Sea mining might be possible, but a world where we can extract the 8kg of natural uranium for 1kg of fuel is a world where we get several thousand tonnes of copper from the same water.

The problem is immense, and the role nuclear energy can provide is only small. Reduction is the primary tool we have.