this post was submitted on 13 Jul 2023
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But why are you surprised? What's driving your intuition to expect it to be higher?
I'm surprised because I would have assumed that they would be at least 50% efficient given how long they have existed and how ubiquitous they are. I'm sure many billions have been put into research and development of solar power and for 30% to be a noteworthy achievement after decades is surprising to me
But where is this 50% efficiency number coming from? Are you familiar with the Shockley–Queisser limit on PV efficiency?
I mean I could "expect" internal combustion engines to be at 75% efficiency by now given the billions of dollars of R&D spending over a century and a half of time, but that would be ignoring things like the Carnot cycle.
Besides, the most important metric for solar power is typically cost, not efficiency. We do have multi junction solar cells with efficiencies approaching 50%, but they're not widely used because they're incredibly expensive. It's a much better deal to use solar modules that are half as efficient, but 1/10th the cost.
The final point I want to make is that a single percentage point gain in absolute efficiency is huge when the overall efficiency is low. A single percentage point gain in absolute efficiency is small when overall efficiency is high. For example, if you increase a 5% efficiency solar module to 6% then you've actually increased energy output by 20%. That's a big improvement. But if your base rate efficiency is already 50% then going to 51% represents only a 2% increase in energy output. Not really a big deal. This is why improving a 20% efficiency module to 25% is a big deal. It's a 25% increase in energy output for the same cost. For energy economics that's insane, even though it's "only" a 5% increase in absolute efficiency.
By far the biggest story in solar energy over the past few decades has been the collapse in costs to the point that large scale solar projects are selling electricity at ~3¢/kwh. This means that in many locations it's now cheaper to build brand new solar generation than to operate old, fully capitalized coal power plants. The other big point is that given the scalable nature of solar PV, new projects can be up and running within a year of breaking ground. Now obviously intermittent energy sources like PV without storage are not the same as a baseload coal plant, but this crude cost comparison represents an ongoing seismic shift in energy markets.