| I think wind and solar are plan A at this point, if for no other reason than they're hard to beat on cost. Battery storage is still expensive, though. If fusion works out, it could be used to make up the difference when the sun isn't shining and the wind isn't blowing (though if we eventually get high-capacity transcontinental HVDC lines to buy and sell power from practically anywhere or batteries become really cheap, that becomes less of a concern). Fusion would also would require far less land, and some people object to having a landscape covered in windmills and solar panels. Fusion might be useful in places where renewables are less practical, like on ships. Naval vessels might conceivably replace fission reactors with fusion. If they're safe and relatively simple to run, you might even see them on civilian ships. Or you could have fusion reactors in remote places, like floating on a buoy in the middle of the ocean, to serve as a charging station for battery-powered ships. Fusion may be useful for establishing a human foothold outside of Earth. For instance, methane production on Mars (for rocket fuel) will require enormous amounts of energy, which could be supplied by a fusion reactor. (A fission reactor would perhaps work just as well, but there are legitimate reasons why people get nervous about launching hazardous materials into space on a rocket that might blow up before it achieves escape velocity.) We might also begin engaging in projects that require enormous amounts of energy. For instance, if certain CO2 absorption strategies are energy-intensive, and we can't practically generate that amount of energy from renewables. At this point, we really don't know if it'll work much less what the practical limitations will be, so perhaps the best we can do is say "if a fusion reactor can produce X amount of energy and weighs Y tons and requires such-and-such amount of cooling and requires an overhaul once every N months at a cost of D dollars, we might want to use it in these applications". |
Fusion would be horrible for ships. Ships are volume constrained, and fusion reactors are very large.
Land constraints are not globally significant at current energy demand. The world is constantly hit by 100,000 TW of sunlight; average global primary energy demand is about 18 TW.
In space, DT fusion reactors will be inferior to fission reactors, which will be much smaller and lighter for a given power output (and also much simpler).
It's very difficult now to make a case for fusion. In the past, the case was something like "fission will be a big winner, but then we'll have trouble with uranium availability and safety and waste, and fusion, while slightly more expensive than fission, will still be cheap and solve these problems." But that's not how it turned out -- fission failed because it was too expensive, and fusion being even more expensive than fission makes it a nonstarter.