The Carnot Limit

The thermodynamic ceiling on any heat engine — and why direct conversion is attractive.

The Carnot limit caps how efficiently any heat engine turns heat into work, based on its temperatures. Because the burner converts charged-particle energy directly at about 0.70, it sidesteps the Carnot ceiling that bounds the breeder's thermal cycle.

The Carnot limit is why every thermal power plant, fusion included, tops out well short of unity: efficiency is bounded by the ratio of its temperatures. Direct energy conversion is attractive precisely because it never turns the energy into heat, recovering charged-particle energy at about 0.70 and sidestepping the ceiling.