It looks like the number of workers in the solar industry has surpassed those working in the coal industry. Based on local activity this growth continues unabated. The company that installed our system had 4 full time worker when they installed it a bit over 2 years ago. They now have 35 employees and are booked solid.
http://www.businessinsider.com/us-has-more-solar-workers-than-coal-miners-2014-7
Wind workers passed coal miners a few years ago. Solar is rapidly catching up to wind in terms of scale, with a higher growth rate and ultimate potential.
The growth of solar electricity has been a very smooth
exponential function for more than a decade, and its recently been doubling every 2 years or so (globally). In contrast, agencies like EIA have been doing linear projections on the future growth of solar for more than a decade now, and revising them dramatically upward every year without comment.
A back of the envelope calculation: Since solar PV currently provides ~0.25% of worldwide
energy (not just electricity), we would need only 8 doublings to get to 100%, this is only
16 years or ~2030.
Of course, nothing is ever that simple, if it were, around 2100 the earth would be a ball of solar panels expanding into space at the speed of light.
The question is, where does the exponential growth stop?
1) If growth is fueled by public subsidies, these can run out, or be capped (leading to linear growth). Example: Italy has more PV than the US, but growth is currently flatlined.
I claim that we are hitting the point where PV growth does not rely on subsidies. The European case pays folks $$ per year for years after installation, which creates an entrenched constituency that defends the subsidy, and makes the future budget look terrible and politically untenable.
I think the current growth of PV in the US and China are organic, and would continue w/o subsidies.
2) We can run out raw materials....fortunately silicon and aluminum are 27% and 7% of the earths crust, so no worries there.
3) We can run out of space. Nope. There is plenty of unused open space to install enough PV to run 100% of human needs.
4) We can run out of money.....world GDP is $71T/year. The last year of our 'growth to 100% and then stop scenario': we would need to add ~50% of world energy production (15 TW) in the form of PV during the last year. Assuming 25% capacity factor for PV, comes in as 30 TW(rating) of PV panels around year 2030. If we think installed PV prices settle down to $0.50/W by then, that would be $15T or 25% of world GDP.
Realistically, we would switch to linear growth for the last few years to avoid overbuilding factories and training too many workers (almost all of which would be obsolete when 100% was reached). In this scenario ~5% of world GDP for 5 years could finish the job, say, around 2035. Note that this 5% would be scored as 'growth' in the economy in the late 2020s, not a tax or cost.
5) Some folks claim we don't have enough energy to build out PV, reducing Al and Si from their oxide form is very energy intensive....Energy payback on solar PV is ~1 year at favorable sites. So making the panels in those last five years (enough to yield 50% of world energy) would require 10% of world energy for the final 5 years. Doesn't seem impossible at all (given that PV would already be providing >50% of world energy at that point).
So there you have it, solar PV can produce enough energy to power essentially 100% of the global economy, using a much smaller fraction of the earths surface than agriculture does currently, and can be built out via something called free enterprise using existing, familiar PV tech, by about 2035.
Of course, many holes can be poked in the above. But the point is that if/when solar PV gets cheaper than fossil fuels (currently true in nearly all markets when external costs are factored, many markets even when they are not) then free enterprise will drive solar growth that leads lead to jobs and economic activity and growth. Realizing this transition will require new utility business models, new grid infrastructure, new long-range grid transmission, heat pumps for home heat and DHW, cheap electric storage, electrified rail for cargo and EVs for residential use. But all the necessary tech exists and is currently under intensive development, mostly by industry leaders that see the future coming.
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For the record, 20-30 year energy use projections by the EIA and the oil majors assume a nearly linear growth model for solar. Or an exponential growth followed by a flatline at a penetration level they simply make up. Our current politicians are happily battling over setting CO2 thresholds to meet in 2030 or 2050 without reference to the emerging solar reality being created by private enterprise. Mostly they will just need to get out of the way.