@jhm, I think you’re really onto something with the link between the physical scale of these two technologies and the speed at which they change. After mulling it over, I have these thoughts.
In biology, there is a strong correlation between physical size and generation time. For example, in the time it takes for a single generation of elephants to be born, reproduce, and die, a population of bacteria associated with those same elephants will go through hundreds of thousands of generations. At each generation, all the variants composing the population will experience selection and other evolutionary forces - some variants will die, some may reproduce more quickly than others - and the next generation will have a different pool of variation than the last, perhaps better adapted to prevailing conditions. This means that organisms with short generation times can evolve much more quickly than organisms with long generation times: beneficial variation can spread very quickly while harmful variation can be purged very quickly. Kind of a similar idea to the Silicon Valley ethos of “Move fast and break things”.
I think a good analog of “generation time” for solar pv and wind might be the duration of individual project timelines for each technology. I did a cursory search and found some evidence that seems to confirm our suspicion that wind takes longer to get up and running than solar. I imagine there’s a ton of variation based on project size/specific technology deployed, but
this source suggests wind project timelines on the order of a year or several years, and this
CleanTechnica article cites NREL data for solar pv showing a median of 53 days (with a lot of variation). If that’s even close to accurate, I’ll channel Elon by observing that there’s a gap of at least one order of magnitude (and perhaps two) between the project timelines for these two technologies. I’d bet solar’s faster descent of the cost curve than wind can be partly explained by that difference in project timeline length. With shorter project timelines, new innovations in pv technology can be introduced and evaluated by the market more quickly. With the market imposing such strong selection for the lowest possible $/kwh lessons learned from each project can spread very rapidly.
More individual solar projects than wind projects?
I couldn’t find data on this in a quick search - most of the information about both solar and wind capacity is reported in terms of total installed GW installed - but I would bet that there are more individual solar projects installed each year than individual wind projects, and I would bet it’s also linked to the physical scale of each technology.
If that’s true, it may also help explain the faster learning rate in solar relative to wind. As the data
@winfield100 presents illustrates, wind may have deployed more GW of capacity, but from an evolutionary perspective, the number of independent projects for each technology may matter more than the total number of installed GW.
Selection is more efficient in larger population sizes than in smaller population sizes (well, technically effective population sizes, but I don’t think the distinction is critical for this analogy). The basic idea is that in small populations, evolutionary mechanisms
other than selection (such as migration, or random effects like a natural disaster) make a larger relative contribution in determining what traits are passed on to the next generation than they do in large populations. This means that small populations may respond to selection less strongly than expected or even evolve in the opposite direction of selection. Imagine two populations of birds, one with 10 individuals and one with 1,000. The individuals in each population are 50% blue and 50% red, and selection favors red birds (i.e. red birds have more offspring on average). Say a storm randomly kills half of each population. Color frequencies in the larger population will probably still be in the neighborhood of 50-50, but in the small population it’s not improbable that say, 4 red and 1 blue bird die, leaving you with 80% blue and 20% red. Similarly, if you introduce 5 blue migrants to each population, it won’t appreciably change the color frequencies in the larger population, and the addition will probably get drowned out by selection for red birds. But in the smaller population you end up with 2/3 blue and 1/3 red. In both cases, despite selection for red coloration, the smaller population evolves in the opposite direction towards a higher frequency of blue birds.
For solar and wind I can imagine a number of extrinsic factors that may run counter to selection imposed by the market for the lowest $/kwh. Corruption, natural disasters, unexpected tariffs, counter-productive policy decisions, etc. A larger “population size” of solar projects may minimize the impact of these factors, allowing selection solar pv down the cost curve faster than wind. Come to think of it, this line of reasoning may also help explain why technologies like nuclear generation seem to get more costly over time. Evolution produces sub-optimal outcomes pretty regularly, often related to the reasons discussed above.
Both of these attributes - shorter project timelines and larger number of individual projects - also introduce more opportunities for “mutations” to arise. Every time someone starts a project, they might try something new or do things a little differently, either intentionally or as the result of a mistake. The more independent projects in total, the more variation can arise. Very rarely these mistakes or little experiments might result in Eureka! moments that are analogous to a beneficial mutation in some biological population. I don’t have any specific examples for solar pv in mind, and perhaps that’s not how it really works with these projects, but it seems like reasonable speculation.
So, yeah, I agree that there are definitely some fundamental differences between these two technologies that end up really favoring photovoltaics over wind when it comes to how quickly each improves.
A tangentially related side-note to a discussion about wind vs. solar technology that I find interesting: I can think of a lot of indirect ways that organisms have evolved to harvest wind energy: birds gliding on air currents, dispersal of seeds and pollen, spiders catching wind-driven prey in their webs, etc., but I don’t think there’s a single example of an organism that has evolved a mechanism by which to directly convert wind energy into chemical energy. That’s in stark contrast to photosynthesis, which is obviously the foundation of (nearly) every food web on earth. Maybe there’s a lesson there.