Ironically for the parent's thesis (cheap energy replacing human slave labor), one of the major objects of modern slavery is... the manufacturing of solar panels,

https://www.nytimes.com/2023/08/01/business/economy/solar-xi... ("Solar Supply Chain Grows More Opaque Amid Human Rights Concerns / The global industry is cutting some ties to China, but its exposure to forced labor remains high and companies are less transparent, a new report found")

https://www.csis.org/analysis/dark-spot-solar-energy-industr... ("A Dark Spot for the Solar Energy Industry: Forced Labor in Xinjiang")

(Maybe there's some kind of evil Jevons Paradox for slavery, where the automation of human labor counterintuitively increases total slavery; i.e. the technologically-augmented effectiveness of slave labor increases the value of slaves).