>, but foundries and aluminium smelting plants have commonly been sited near generators in Britain.

IDK about Britain, especially historically when you would have been building aluminum smelters. It's not normal in the US more or less since the advent of the grid. I'm sure people will be along shortly to construe exceptions or special cases where the fossil fuels were extra cheap as the norm or heat was what they also needed and it was cheaper to capture that locally and make some electricity too.

>Every DC I've visited - probably ten - has on-site generators, for redundancy. To a certain type of mind, that's capital going to waste. I can imagine a bean-counter desire to sweat that plant.

But they don't use those for any semblance of "normal" load. Those are strictly for redundancy not "ah it's 3pm, power's getting expensive better fire up the genset for 4hr". At least that's normally how it is. It's not normal for it to be possible to out compete the utility even after fixed costs are amortized in. Bigger generation is more efficient, if you're buying fossil fuels then buying them in bulk is more efficient. Etc. etc. It should be cheaper to have the people who benefit from all that string you a wire.

In most places aluminum smelters have been located near power plants, because aluminum smelters have large electricity demand and transporting large amounts of electricity over large distances is expensive (high capacity power lines are expensive).

Electricity costs are between 40% - 50% of costs of the finished aluminum.

Also, reliability.

"Due to the nature of the process, power outages have the potential to cause damage to production cells as the molten liquids could solidify in absence of adequate current. For this reason, production facilities need to be near secure and reliable sources of energy."

https://arcticecon.wordpress.com/2012/02/15/aluminium-smelti...