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Comment by pfdietz | Hacker News Reader

Say you don't understand exponential growth without saying you don't understand exponential growth.

Isn't exponential growth where the growth rate becomes more rapid as the stock of the thing gets larger (and, more precisely, the growth rate is a function of the stock)? How is growth in solar capacity exponential? Wouldn't it actually be logarithmic, all other things equal?

The graph looks rather exponential (and decidedly _not_ logarithmic) to me.[0]

The story is actually "the growth rate becomes more rapid as you accumulate experience manufacturing, which also grows as a function of the stock." AKA Wright's Law.[1]

You may notice this is faster than your definition of exponential growth, because Wright's Law also counts the decommissioned panels too. The industry still got that manufacturing experience, even if the panels don't count as 'stock' today. So technically the growth rate scales with total all-time production, not current stockpile size.

[0] https://en.wikipedia.org/wiki/Growth_of_photovoltaics

[1] https://en.wikipedia.org/wiki/Experience_curve_effects

PV has been growing with a time constant short compared to the lifespan of PV modules, so most of the cumulative production is still in operation today.

This is also why PV recycling hasn't had a chance to really get going -- very limited potential input to the process yet.

Yes that's true. My point is simply that solar (in this early phase) does show exponential growth.

Spangry's "the growth rate becomes more rapid as the stock of the thing gets larger" was confused enough to made exponential growth sound vaguely absurd, but in fact it's perfectly expected (and indeed observed).

Because the more solar gets deployed, the less the costs are. So each increase in growth triggers a reduction in costs which then enables larger growth and so on.

The key point here is that the potential market has been increasing exponentially with reduction in price.

There's no way solar can grow geometrically for long. It consumes real estate like there's no tomorrow. Land is limited; sunlight is limited. It has a hard, hard limit.

Unlike many other kinds of power generation, which are land-frugal and work 24 hours a day.

So, let's rethink who doesn't understand growth.

> It consumes real estate like there's no tomorrow.

Now you're really showing you haven't bothered to do basic arithmetic. Land use is not any sort of real limit to PV solar, especially in the US.

I suggest you check your assertions for validity before you commit them to writing.

Looking it up solar/renewables take up surprisingly less space than expected

Area required for all renewables: https://landartgenerator.org/blagi/archives/77565

Area required for just solar: https://landartgenerator.org/blagi/archives/127

Luckily we'll have more than enough energy long, long before we run out of land or sunlight. We could satisfy a large part of our energy demand just by replacing energy crops by solar panels, with the added benefit of not needing fertilizer and pesticides.

California has a lot of desert. A lot a lot.

The single most fragile ecosystem in the world is a desert. The casual way folks here throw that line out, again and again - shows a profound lack of understanding about what an ecosystem is.

If you are concerned about solar's use of land then you must be positively apoplectic about using corn for ethanol. That uses more than 40% of US corn production, an amount of acreage so vast it's difficult to comprehend.

Using PV with BEVs instead of ethanol in ICEs would be something like 200x more land efficient.

~40 million acres.

https://pv-magazine-usa.com/2022/03/10/solarfood-in-ethanol-...

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