Although we all should cheer the fact that energy derived from solar power increased dramatically in 2011, champions of alternative energy aren’t quick to boast about the total power it supplied. That’s because it didn’t supply very much.
Solar power capacity (not delivery) increased from 18 gigawatts to 24 gigawatts between 2010 and 2011. The world’s energy consumption was 15 terawatts.
So one burning question about solar is will growth be arithmetic or logarythmic. If the pace is 1, 2, 3, 4, we’ll need to get our coal-digging shovels out. If on the other hand it’s 1, 2, 4, 8 then the magic of compound growth will have solar providing significant energy.
Since all the figures for solar are always given in watts capacity, let’s stay with that measurement instead of my preferred quad.
If energy consumption does double by 2075, we’ll need about 30 terawatts. A bit more than 1,000 times growth. (Oh, don’t gulp yet… it’s undignified. Whimper, moan and beg for mercy…)
If the past–since 1978–is any indication, we’ll actually get there. Solar has increased in capacity by an average of 36% annually–and we only need an increase of 11.6% every year to get there.
Here’s historical performance, courtesy of Professor Emanuel Sachs at MIT:
Now, nobody should think that innovation and penetration can improve at an incredibly high rate forever. Moore’s Law doesn’t cover every industry, and the logistical chain for microprocessors is infinitely more complex (and therefore amenable to continuous improvement) than the chain for solar power.
But it doesn’t have to improve forever–if it improves for four more years it’ll be cheaper than electricity provided by coal in most places and it’ll be off to the races. Increased installations of solar will cease to be driven by improvements and begin to be driven by comparative advantage.
We won’t mind.
3000 Quads 
I assume commercial size solar installations are being sited in areas which have been shown to have less than average cloud cover over the course of the year. I also imagine there are marginal differences in cloud cover whether over land or sea, and whether day or night. If I recall correctly the overall average global cloud cover is in the neighborhood of 70%.
It seems to me the ideal locations to place large scale systems sunlight-wise will be exhausted fairly quickly and many lower quality sites will have to be used. This leaves me to believe whatever figures arrived at by use of nameplate ratings must be a severe underestimate of what would be required. This is due to 70% of the installed systems(both ideal and poor) always having some degradation simultaneously.
It would be nice to have long term output figures from one of the currently installed systems to use as a baseline reference for real-world annual output. Do you have any such figures?
I really think solar will always be a boutique product and need backup by a more reliable generating source. You never know when or how cloudy it will be.
Hi Bob
I don’t think solar will dominate energy sources any time soon, unless we figure out the storage issue. And both siting and orientation of arrays are important, and I hope we do better with that than the wind farm industry.
But there is plenty of unused land that gets more than enough sun. That’s really not an issue and won’t be any time soon.
So just what are your thoughts on the environmental issues vast tracks of land that solar panels will cover? What about the same issues from wind generators, your thoughts? How come these so called sources of green energy do not get the same environmental reviews as oil and gas? Where is the hue and cry from greenies about the hundreds of thousands of birds and bats killed by wind generates? But have a fraction of that number die in a oil sands settling pound and one would think the third world war had broken out.
Hi NC,
Well, I don’t think that solar is going to cover vast tracts of land. Wind turbines take quite a bit of space, it’s true. But I think they have plans to grow pot underneath them, don’t they? Just kidding–but I think that you could put solar panels underneath wind turbines. I honestly think we’re so far from that being an issue that it’s not really a priority right now. As for bird losses, they’re real and regrettable, but I think they amount to about 1% of the birds killed by domestic cats, so again, let’s wait and see on that, okay?
Remember that I want to see solar panels on rooftops, not in huge arrays on solar farms.
I’m wondering if the graph above includes subsidies and if it is based on nameplate capacity or real-world production? I am amazed that solar is already competitive with natural gas. Given that gas can run 24/7 solar must already be three times more efficient than gas.
I found a list of large solar stations which indicates most stations have a less than 20% capacity factor. Not very good at all.
http://en.wikipedia.org/wiki/List_of_photovoltaic_power_stations
I assume small scale individual solar installations would not be significantly different to start with, but suspect most people will soon forgo proper maintenance and end up with even lower capacity. Human nature being what it is, constant forays onto the roof to clean various forms of detritus from the panels will, after awhile, become be a pain in the neck for most people.
So to be green it is okay to kill birds, including rare raptors. Considering all the materials, manufacturing, installation, roads, transmission system I fail to see the green. Oh right, green as in money.
I would check your units for the second paragraph. Consumption is usually in units like TWh p.a. Almost nothing ever has logrithmic growth for very long. Computer chips processing power being the honourable exception.
And like Bob Koss, I believe the load factor and reliability are the critical parameters for a critical utility like electricity. Solar is ideal for remote or off grid sites, but the peaking nature of it means it will never play a major part of the grid based systems. The cost of storage and backup needs to be factored into any price analysis.
One thing that many don’t realise is grids need large spinning generators for the inertia to give frequency control (along with their governors’ droop characteristics) and for both the power factor correction and the sinewave characteristics. Frequency converters or inverters chopped waveforms and lack of frequency control give a lot of problems on many appliances and process plant. A simple example is the thousands of motor bearings trashed because of electrostatic discharge through the races. It is so bad with some VSDs that silicon carbide bearings need to be fitted.
Tom
Thought you would be interested in this article from the UK which puts the carbon indiuced madness of our policticians into sharp perspextive. Access to energy is one thing, but being able to afford it is another
http://www.independent.ie/opinion/columnists/kevin-myers/kevin-myers-energy-policy-based-on-renewables-will-win-hearts-but-wont-protect-their-owners-from-frostbite-and-death-due-to-exposure-3012098.html
tonyb
Hi Tony
It’s enough to make me feel schizophrenic. On the one hand, I’m incredibly optimistic about the future of renewable energy, especially solar. On the other hand, I find it nothing short of bizarre that some want to tear down our existing infrastructure before the future arrives. I think there are a lot of people who are mathematically challenged…