Large turbines running at close to rated power actually have pretty good efficiency. Turbines are bad at scaling down to smaller sizes due to e.g. boundary layer friction, and also part load efficiency is poor. Recuperators help somewhat, though still not nearly as good as a piston engine.
Did you factor in the increase in running time? If you can run at almost 90% of the time then you get a 4 fold increase in output as compared to the bigger turbines. So instead of 25 times as many, it's 5 times as many which isn't that bad.
That is going off the assumption that he'll get his optimal running time.
For every cycle and construction, there is theoretical efficiency limit inherent to it. Implementations will approach that, more or less asymptotically, but can't exceed.
A novel cycle and construction may leave more headroom for improvement, even if first implementation aren't particularly efficient.
IIRC turbines are usually highly efficient, but only in a narrow band, near maximum output; at low RPM they literally suck. Perhaps a novel construction could widen the gap considerably.
34% efficiency on their first tests? That would be a huge deal. Microturbines have similar benefits (few moving parts, long lifetime, etc), but they only realize 30% efficiency on the high end.
I'm not am expert on turbines, but generally the turbine efficiency is directly related to the temperature and pressure difference between the inlet and outlet. Hence bigger plants have typically higher efficiencies. Bigger turbines have also more stages, so not only they have to withstand higher pressure, but simply there are more parts.
AFAIK I think there is some difficulty in getting turbines to scale down efficiently with a need of a recouperator to maintain a higher core temperature for better efficiency. The recouperator is additionally expensive on top of the turbine cost.
Having a rotary with a turbo should be able to work better at a lower scale for a pretty cheap production cost.
which to be honest is less of a testament to increased efficiency and more of a mathematical effect of circle area growing to the square of the diameter.
The other main reason to get bigger that‘s not even discussed is increased capacity factor. That doesn‘t have to do with efficiency, but with effectiveness, as the turbine will simply run more days of the year.
They're efficient at higher power levels but really not at small-power-generator level. An 8kw jet powered generator I saw recently used 0.5kw-hr per kg, which is 5x more than an equivalent one based on a traditional diesel engine. Their main advantage is high power for low mass of generator, but consume massive amount of fuels.
I wonder if it might be possible to develop miniaturized low power turbines, say anything under a megawatt range? it's already icebox size, can we make a high efficiency 100kW (133HP) turbine the size of a briefcase? (of course we'll also need some fairly decent sized radiators too).
I don't see how reducing turbine size is a good thing. Power plants aren't just a source of power; they're a source of mechanical inertia for the grid.
I suppose you can compensate by incorporating energy storage, which also has the side benefit of allowing the plant to be self-sufficient for cold-start.
If you make it harder to cool the turbine by putting those neat the radiator, efficiency will go down; if you make it harder to keep the heater hot, by putting those near the fire, efficiency will go down.
As animats already said, turbine efficiency on power plants is very near the theoretical optimum. The only way left to improve it is by increasing the temperature.
So for small turbines and with safe speeds, I guess the efficiency is compromised.
Having said that, I have come across efficient micro-turbines.
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