Direct Conversion and Cogeneration

[nakile]

I remember reading from a sankey diagram on the old site that for 5 MWh of electrical output there would be 8.4 MWh of thermal output. That’s a 38% electrical efficiency (is this ratio linear across all loads?).

To me, that’s low enough that it would be (borderline) worth putting the waste heat to work instead of tossing it. I know that a steam or gas turbine is mostly pointless because of the cost and direct conversions main purpose it to avoid the complexity of them all together, but what about cogeneration? Is there also no economic case for building a pipe network to put the heat to work directly? You could easily get the overall system efficiency into the 80%+ range by doing nothing new or amazing. It could even be cheaper for heating purposes than even electricity from a FF unit, which would already be really low.

I suppose the major factor is how much quicker direct conversion technology can reach higher efficiencies. If it has the potential to reach into the 50%+ range in a decade or two then a cogeneration network most likely could never get amortized in that time. Or is starting out at 38% optimistic? Will the final reactor be more in the lower 30s upper 20s range? If so cogeneration would be a no brainer, I think. Especially if these units are most likely to be built close to the point of use.

[zapkitty]

Actually, industrial process heat will be a great driver of FF sales. A great deal of current industrial energy use is simply to generate heat in the first place.

With a 5 MW FF unit supplying 5 MW electric and 8.4 MW thermal an industrial site has a win/win/win situation… the site gets electrical power, process heat and its overall thermal footprint actually goes *down*

For a residential area the unit can supply residential heating in winter and the heat can even power residential absorption chillers in the summer.

Oh yeah, there’s going to be use for an FF units’ “waste” heat… a *lot* of use.

And where heat is not needed, just the power, the FF unit can be air cooled and distributed widely so as to have minimum impact on its surroundings as well as a much lower overall thermal footprint than fossil fuels.

[nakile]

As much as I agree, economics has its way of making the best idea not happen all the time…

To narrow down and rephrase my original post, is there a good economic case for putting the waste heat to work with residential and commercial applications? Will it be worth building a hydronic pipe network along side a new electric grid (we’re due for a new one soon no matter what) or will economics favor just building a beefy power grid that can do everything with electricity for these customers and the reactor waste heat simply gets thrown out?

Again, if the reactor will be hitting higher efficiencies in decades time, I think the answer is most likely no. Even 38% is borderline. In both scenarios I’m imagining a decentralized municipal level system, that’s how these units would work best. But how will the infrastructure itself come together? I guess the major factor/question here is what is the theoretical maximum direct conversion efficiency and how likely is it to be reached?

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