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millijuna t1_j04gwfm wrote

Reply to comment by Robo-Connery in National Ignition Facility (NIF) announces net positive energy fusion experiment by Robo-Connery

For reference, most commercial scale power plants, regardless of energy source, use about 5-10% of their output to operate the plant itself. In Nuclear plants, this includes the energy required to operate the cooling and safety systems. This also includes the excitation energy required to operate the generators. I work with a small hydroelectric power plant (about 250kVA), and the exciter uses about 15kVA to make it operate when at full power.

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yellekc t1_j05v02w wrote

So I got a few questions. kVA is not real power, so depending on your PF it might not be consuming much. But the real question I have is about the plant capacity. 250 kVA is peanuts, the transformer at a small pump station I visited today was twice that. How does that work economically? I assume it is mostly unmanned cause it would barely generate enough revenue to cover the cost of an employee and maintenance.

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millijuna t1_j06x965 wrote

The power factor is relatively close to unity for the exciter. The actual excitation current is around 90A DC at 50V or so, though it varies.

Anyhow, the plant itself powers a remote wilderness community that's a good 50km from the nearest power pole. It's maintained largely by volunteers, and is a replacement for diesel power. The landed cost for diesel power right now would be on the order of $2.50/L for the fuel, nevermind the environmental costs. The feedwater for the hydro plant is run of the river type system, taken from a small creek that flows over a large waterfall (meaning no fish concerns).

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