Okay, so let's build a petawatt-scale fusion power plant. I can actually think of practical ways to build one if it can be that large.
But that's not going to happen. A petawatt-scale fusion power plant is not going to be economically or politically feasible this century, no matter what progress we make on plasma physics and no matter how cheap it would be per watt.
Every power source has a preferred scale. A fuel cell can be the size of a mitochondrion, but a combustion engine, in order to be efficient, really wants to be at least big enough for a lawnmower, and an efficient fission reactor wants to be at least a good few megawatts.
My conjecture is that a fusion reactor wants to be at least a petawatt, and even if we solve the plasma physics problems, a gigawatt fusion reactor will cost more per watt than the equivalent in solar plus appropriate attached storage - which makes it pointless to work on fusion at this time.
There is no such thing as an 'efficient' combustion engine. There are only combustion engines that are more efficient than other combustion engines but all of them are inefficient compared to other types of engines.
Fair enough, I guess I just question your two premises. Can you link me to anything that would support the Petawatt number? If China can make use of a 20 GW plant (the Three Gorges Dam) and the Congo can make use of a 40 GW plant (the proposed Grand Inga Dam) at locations determined by nature, don't you think that many countries on earth could make use of 100-1,000 GW plants with significantly more freedom for location?
I don't know whether the limit for economical fusion power is 1GW or 1TW or 1PW either. But if it turns out to be the higher side of that, then I'd be leaning against it. Sure, we could use the power, but right now, our power needs are low enough that we might build only one or two of them to run whole countries or even continents off of. I don't really like the idea of having One Huge Power Plant for most of a continent Seems too vulnerable to all sorts of failure modes to me. Imagine if some important part deep in the machine breaks because of some mistake somewhere, or even sabotage. The whole continent's power could be down, and it might take weeks or months or longer to make a new widget and get it installed, given that there's so little demand for them with only a couple of plants.
I'm afraid I can't; it's my personal guess, and with an admittedly large margin of error. You make a fair point that if it turned out to be more like a terawatt, that might not be out of the question.
But that's not going to happen. A petawatt-scale fusion power plant is not going to be economically or politically feasible this century, no matter what progress we make on plasma physics and no matter how cheap it would be per watt.
Every power source has a preferred scale. A fuel cell can be the size of a mitochondrion, but a combustion engine, in order to be efficient, really wants to be at least big enough for a lawnmower, and an efficient fission reactor wants to be at least a good few megawatts.
My conjecture is that a fusion reactor wants to be at least a petawatt, and even if we solve the plasma physics problems, a gigawatt fusion reactor will cost more per watt than the equivalent in solar plus appropriate attached storage - which makes it pointless to work on fusion at this time.