According to REN21’s 2025 review, global renewable power capacity increased 18%, adding a record-breaking 741 GW in 2024. Solar PV was the primary driver, contributing 602 GW and accounting for 81% of the total capacity increase, taking PV to 2,247GW in total.
Solar does look likely to be a winner in many parts of the world, along with wind. But in an ecumenical mood, as maybe befits the season of good will, what about nuclear? Some see it if not booming, then having a niche role in some locations. For example, on the basis of some conceptual modelling of a hybrid solar photovoltaics/Small Modular Reactors micro grid system, with hydrogen and Lithium-ion battery storage, some Chinese researchers have claimed that the system achieved an average operational cost reduction of approximately 18.7%, while reducing carbon emission intensity by nearly 37.1%, compared to a conventional fossil-dominated microgrid.
That’s not stunning, but it is quite good. But the report also says that resilience indicators, such as critical load supply reliability, are also enhanced to above 98% across all uncertainty scenarios, ‘underscoring the framework’s capacity to maintain secure operation during both regular and extreme conditions.’ Though note that it was for relatively small project. The modelling simulated a 100 MW hybrid microgrid that served an industrial load with an average demand of 85 MW, exhibiting daily peak demand fluctuations of up to 25%, and a residential demand component with an average load of 15 MW and a peak-to-average ratio of 1.6. The system assumed an installed PV capacity of 40 MW, with solar irradiance data obtained from historical weather records over a one-year period. The 50 MW SMR was assumed to have a minimum stable output of 10 MW and a ramp rate limit of 5 MW per hour.
Well at that rate it would take 8 hours to ramp up from 10MW to full power, but assuming high irradiance in Chinese desert areas, plus storage, it may not have to do that often. And the paper says ‘the PV–SMR configuration integrates dispatchable nuclear output with intermittent solar generation, thereby reducing storage oversizing requirements and providing a firmer, more resilient low-carbon backbone’. While that may be true, there are cost and inflexibility issues with SMRs. And also safety/security/risk issues- do we really want to rely on system using and generating radioactive materials?
The paper claims that cost would be lower than for a fossil fuelled system. If it was just a solar based system that would not be not too surprising, but you might expect that to change with nuclear added. Certainly the capital cost quoted in the paper for the nuclear SMR unit is very high compared to the PV costs. Moreover, that is presumably for fairly a straight forward mini pressurised water reactor, the most common sort of SMR currently under development. More advanced SMR/AMR designs are being considered. For example Terrapower’s 345MW US sodium cooled fast reactor concept includes a molten salt energy storage system to give it enhanced output flexibility. But that still some way off and it’s possible that it will be expensive. However, that’s not certain and, in some cases, capital costs may be offset by their operational flexibility.
Flexibility may be the key issue. Though we will have to wait to see. The paper says, ‘nuclear reactor ramping constraints and thermal inertia limit the extent to which Small Modular Reactors can provide fast-response power balancing’. But evidently, it sees their SMR as able to ramp up to full power reasonably quickly, and that is a good, optimistic, selling point.
However, fully flexible SMRs may still some way off, and it’s unclear if more complex and possibly more costly and risky flexible systems would make sense in the hybrid SMR-PV context. Especially since PV costs look likely to continue to fall and performance improve as the global PV market builds and as the technology develops. For example, there is a new ‘photon multiplier’ technology offering 15% higher energy output. Battery and other types of storage are also improving and costs falling as new technology like green hydrogen conversion and storage get developed.
So although the hybrid SMR-PV option may have some attractions in some locations, even being optimistic, it is still a way off, and PV plus storage may in fact win out longer term. Overall then, it looks like PV is safe for a while and maybe for longer. Including in sunny areas, like deserts, where solar with night storage ought to do very well. See the Ember chart and study.
And that could also be the case in the often cloudy, mostly densely populated UK, with floating solar also picking up (in China too), and with cheaper storage also developing too.
Nuclear/PV hybrid mini grids? A good try, but arguably not just yet. And although I may be wrong (there is a lot of PR at the moment for widespread SMR use, maybe in clusters), personally I suspect that individual local SMRs may be more viable and acceptable in fairly remote areas – even perhaps only as per the original idea, as power sources for the likes of bases in the Arctic and Antarctic. Where PV isn’t much of an option!
Though I’m sure the nuclear lobby will see it all differently. And even be keen on more big nuclear plants. For example, the chair of EDF UK claimed that ‘we’ve transformed the way we’re building the station, with prefabrication in civil construction now approaching 60% - effectively making Hinkley Point C a Large Modular Reactor.’ Well, it’s been the most expensive energy project ever. Good luck with getting the cost for the next one (Sizewell C) down. But I think this upbeat presentation on solar’s falling costs and its other attractions from Jonathon Porritt is bit a more convincing.
After my next short post, I will be having an Xmas/New Year break. Seasonal greetings to you all!
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