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This discussion relates to Technology Review's article Efficient, Cheap Solar Cells.

Discussions: Business: Efficient, Cheap Solar Cells

dtutelman

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09/23/2008 09:09 AM
Global warming? Global cooling? Global climate difference?

I'm usually a numbers guy, but I admit I don't have a clue about the numbers here. I'm way out of my area of expertise, so this must be treated as non-quantitative speculation.

What are the prospects for global climate change if we adopt large-scale solar electric power? (Or, for that matter, wind power as has been suggested in this discussion.)

Consider: One fossil-fueled power plant would not make a measurable change in the climate. Nor would ten. But thousands do, especially if you add in our transport systems as well as electric power. Enough fossil fuel for the world's energy needs makes a very discernable impact.

So what about solar? Reading between the lines of the article, a 25% efficient solar cell would be competitive with other forms of generation. Let's use that number. At 25% efficiency, how much of the southwest desert would have to be coated with solar cells to supply the country's electric (and transportation, assuming a transition to hybrid/electric vehicles) needs? I'm assuming the southwest desert and electric transmission elsewhere, because that seems to be the highest-yield strategy for the continental US.

IF 0.1%, then I won't worry.

IF 50%, then I have to ask, "What does it do to the climate -- local and global -- if 1/8 of the sunlight on the desert (25% efficiency times 50% coverage) is neither reflected nor absorbed there and turned into heat? If, rather, it is transported elsewhere on the planet and converted to heat, light, or motion at the point of consumption?"

The same could be asked about wind farms, if there were enough of them to supply all our power.

Does anybody have the numbers on coverage? I'm sure nobody has the answers [yet] on climate effects, though I sure hope the question is asked before we actually get there.

DaveT
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- Urbanstatue
  
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  09/23/2008 11:57 AM
  Re: Global warming? Global cooling? Global climate difference?
  
  I don't think your heat-transfer concerns would be a big issue. Using any other form of energy is already releasing heat into areas where it wouldn't be otherwise, so the real issue would be a sudden cooling of the area it's being absorbed from.
  
  It's possible that the reflection of light from the desert is already cooling the area to the same degree that absorbing it into photovoltaics would be.
  
  And of course any resultant heating would be way less than the green-house effect from burning fossil fuels.
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- Andrew Leinonen
  
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  09/23/2008 12:10 PM
  Re: Global warming? Global cooling? Global climate difference?
  
  While I remember there was a Scientific American article about 6 months ago with the U.S. specific math, I've read that approximately 2% of the Sahara desert (9 million+ square km) would provide more than enough energy to supply the entire world. Now obviously that wouldn't work from a logistics point of view, but in terms of round numbers, that's what you're looking at.
  
  Who knows, solar farms might even provide beneficial microclimates, creating shade and enabling new ecosystems to thrive in the desert.
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- nilsdavis
  
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  09/23/2008 12:42 PM
  Re: Global warming? Global cooling? Global climate difference?
  
  DaveT - these are great questions. Luckily, a lot of people have considered them. One potential, very rough estimate, is covered in my blog post here, extrapolating based on the 550MW Topaz solar farm planned by PG&E in California. My conclusion was that we would need about 800 Topaz-sized plants, total cost about $1 trillion, to meet the U.S. electricity demand. And it would require about 8,000 square miles of sunny land.
  
  My goal with this estimate was to get something simple and easy to understand - there are many much more detailed analyses out there.
  
  Hope this helps.
  
  Nils
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- shomas
  
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  09/28/2008 11:52 PM
  Re: Global warming? Global cooling? Global climate difference?
  
  I'd like to make a disclaimer and state that this comment is based on all assumption. corrections are welcome and encouraged
  
  assumptions:
  1. 90% of solar light is absorbed by solar cell 10 % reflected back into space
  2. of that 90%, with these cells 20% is converted into electricity the remaining 80% becomes heat in the solar cell.
  3. 90% of the electricity ends up as heat. with a remaining 10% as electronic emissions or street light that makes it out to space
  4. sand may have a much higher reflectivity, maybe 70%
  
  The conclusion that can be reached if the assumptions are even close is that maybe 12% of light that hits a solar cell does not heat the earth in one form or another.
  it might be worth considering areas that have lower reflectivity to start with before transforming an area with solar cells.
  
  It is also noteworthy to state that heating the earth is not the same as keeping heat in.
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vanopelli

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09/23/2008 12:44 PM
Small scale individual solar

I'm no scientist, nor much of a business man. But I wonder why everyone seems to think only of large scale solar production. Is the model of central distribution so ingrained in us that the idea of individual energy self reliance has been washed out of our brains? Is the idea to keep energy in the hands of the greedy corporate world?
To me it seems the promise of such technologies are feasible on a much more personal scale and could get many people off the "grid". Especially in times when that grid seems so vulnerable to natural and man made disasters. Or don't we have the right cut that hallowed cord? Or build new communities without expensive power lines? Empower the people!

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- nilsdavis
  
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  09/23/2008 01:27 PM
  Re: Small scale individual solar
  
  Great question. I think the reality is that there will be a combination of utility-level and distributed energy, and of different types - solar PV, solar thermal (heat your own hot water for showers), wind, etc.
  
  There's a very interesting set of Department Of Energy reports, including one (PDF) on the market opportunities for grid-tied distributed solar PV. It figures out, state by state, how much roof surface is available, how attractive the incentives and infrastructure are (e.g., is there net metering?) and uses some simple algorithms to come up with an expected market penetration for solar PV on commercial and residential roofs. The resulting amount of electricity generated in this distributed fashion is amazingly high.
  
  The report uses very conservative numbers for solar PV cost improvements - a breakthough like the one mentioned in this article would make the market penetration even higher.
  
  I was shocked (and pleased) to find out that our government has done this kind of research - I hope "W" doesn't find out or he'll cut off their funds!
  
  I just discovered this report myself, and will be blogging about it this week, but I thought I'd pass it on since you asked...
  
  Nils
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  - javs
    
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    09/23/2008 02:58 PM
    Re: Small scale individual solar
    
    You posted while I was writing. I agree about the importance of the great question, because it helps to lead. The issue remaining is how the retail market gets widely open to business model innovations competition to replace the obsolete price controls business model. An EWPC EPAct is highly recommended to enable such business model competition.
    
    I suggest reading the EWPC article, Let’s Avoid Many Expensive Fiascos, whose summary states “There is no need to cite any [analytical] evidence ‘to enable a highly competitive, pro-consumer, complete and fully functional market architecture and design paradigm shift.’ What is needed is to have ‘the global power industry … get out of the wrong jungle to produce a EWPC based EPAct as soon as possible.’”
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- javs
  
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  09/23/2008 02:23 PM
  Re: Small scale individual solar
  
  Not everyone thinks of large scale solar production. My post above Is this a Disrupive Technology?, is precisely about how to integrate small scale distributed solar production for the benefit of people even the poor at the BoP.
  
  A selection of my posts on this website Who is Afraid?, Demand Side Barrier, Small is Beautiful, A Barrier to this Potential Breakthrough, Off-the Grid Developments are representative of all posts on the Electricity Without Price Controls (EWPC) market architecture and design paradigm, which is the emergent paradigm that makes “such technologies feasible,” but not off the “grid,” to actually fulfill the late Fred C. Schweppe vision, as post on Comment on November 2004 Issue - Write and Wrong.
  
  An excerpt of the post says: “Contrary to the belief that IEEE Spectrum was wrong, Professor Fred C. Schweppe, of MIT, brilliantly predicted a mayor tech breakthrough in electric power, when he said that ""There is a good chance that by the year 2000 the term blackout (societal definition) will be considered to be a term out of the Dark Ages." The chance has been there all along, except that a powerful lobby has prevented it, by keeping the natural monopoly of distribution related or integrated with non monopoly retail marketing.”
  
  What you are suggesting is commented on the post Everyone for Himself Solution, which I will repeat in full with a minor upgrade by adding a link to “javs”:
  
  Off-the-grid housing is an everyone for himself extreme alternative solution, that is fed with uncertain generation, with on-the-grid housing being the other extreme. The optimal energy policy is one that separates the grid from the commercial business transaction. The grid is develop as a controlled market to service the whole at least costs and to enable a vibrant open market.Today's utilities monopoly retail business model of winning rate cases to the regulator shift to innovative business models that are open to competition, in order to coordinate customers and generators investments and operation costs, resulting in large saving that result in maximum social welfare.
  
  For details, please hit the javs hyperlink to read about the EWPC market architecture and paradigm that makes the grid a two way street.
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- advill
  
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  09/29/2008 08:12 PM
  Re: Small scale individual solar
  
  The point is 100% true, electricity has been developed in a central, concentrated,controled net, as so many other things it is becoming personal size.
  Information, education, transportation,etc are becoming more and more "personal" and energy production will be too.
  There is no coincidence that there are only 2 major suppliers of purified silicon ( another 5 will come into the market soon).
  
  A day will arrive where you will be able to build your home away from electricity grids and have all what is needed from yourself.... without central companies charging you and this is something you will see starting in a few years
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