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Power Science

Solar Cell Achieves 40% Efficiency 632

Fysiks Wurks found on the U.S. Department of Energy website news of a breakthrough in solar energy efficiency. From the article: "...with DOE funding, a concentrator solar cell produced by Boeing-Spectrolab has recently achieved a world-record conversion efficiency of 40.7 percent, establishing a new milestone in sunlight-to-electricity performance." A page linked from Wikipedia's article on solar energy calculates the land area that would need to be covered by solar collectors at 8% efficiency to meet the world's energy needs (using 2003 figures). At 40% efficiency, it looks like a square 265 miles on a side in the American southwest would do it.
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Solar Cell Achieves 40% Efficiency

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  • transport losses? (Score:5, Insightful)

    by toQDuj ( 806112 ) on Wednesday December 06, 2006 @03:42AM (#17125638) Homepage Journal
    yes, a few hundred miles in the american southwest would do it (anyone objecting to using Texas?), but only if the entire world lived in the american southwest. As it is, energy losses due to transportation are quite significant and hinder an all-out world power source plan.

    • Re: (Score:3, Insightful)

      When you say energy losses due to transportation, are you just talking about transmission over wires?

      How about conversion to something like hydrogen?

      There are lots of desert areas that I'm sure could be used for energy generation, at least it would be better than polluting our way to global death....
      • by jtorkbob ( 885054 ) on Wednesday December 06, 2006 @04:14AM (#17125852) Homepage
        Hydrogen conversion has its own inefficiency, so that's out.

        That statistic is simply an illustration in any case. Obviously there are some other places in the world where such installations could be put; perhaps some less sunny ones would require more space to reach equivalent capacity.

        In any case, I think that a 100% solar earth is unlikely:

        * Much of the time it is night, and storing that much juice in batteries is impractical. Things like hydroelectric storage and thermal solar plants could help with this problem, but its a whole different research issue.
        * In the event of, say, a major volcanic eruption or meteor impact, world power production would plummet. That could be the least of our worries.

        Solar and wind are like the icing on the clean power cake. They are great for the role they serve, but you can't have them for dinner without getting a stomach ache.
        • Re: (Score:3, Insightful)

          by poopdeville ( 841677 )
          I think the best use for this technology would be to put it on every roof in in America (and Europe and eventually the world), and use nuclear power as a method to buffer against periods of low sunlight.

          While the major volcano/meteor event you mentioned could deplete the nuclear buffer, it would do that (and worse) now.

          At the very least, considering the effects on the economy that nearly free energy would have, we could build enough nuclear power plants to completely handle our energy needs in case such an
          • by Anonymous Coward on Wednesday December 06, 2006 @04:55AM (#17126072)
            Mod parent up. He clearly knows how to achieve the technological utopia we all long for.
          • by jtorkbob ( 885054 ) on Wednesday December 06, 2006 @05:36AM (#17126276) Homepage
            I think the best use for this technology would be to put it on every roof in in America (and Europe and eventually the world), and use nuclear power as a method to buffer against periods of low sunlight.

            I agree that local micro power is another good peice of the puzzle. My number one goal in life is to eventually live in a home with a net energy surplus. Of course, my penchant for running Linux on old hardware might turn into a barrier to this.

            While the major volcano/meteor event you mentioned could deplete the nuclear buffer, it would do that (and worse) now.

            Well, given a 'minor' event like Mt. Saint Helens, light blocking would only be a minor concern to the overall energy supply as we have it now. Obviously ash and debris in equipment, supply chain interruption and so on would be another issue entirely.

            Hell, we could sell of the surplus nuclear energy to subsidize projects like the complete mechanization of food production, -- obviously using our nearly free energy. Or just lower taxes (though I would prefer the former)

            Well, that's a different question, one I hadn't considered too deeply. Still, until we develop a 'perfect' single energy source a la Mr. Fusion, there will have to be a wide variety of energy sources in order to have a stable energy system. Nuclear/fossil systems require finite and largely imported fuel. Wind, solar and geothermal require specific geography. Hydroelectric fsks up the ecosystem. Each has its place in the ideal system, however limited.
          • Re:transport losses? (Score:5, Informative)

            by hcdejong ( 561314 ) <hobbes&xmsnet,nl> on Wednesday December 06, 2006 @07:44AM (#17126960)
            Nuclear power is an inefficient method to create a buffer. You'll need to run the reactor at a significant power level to keep the steam circuit hot enough that you can start generating immediately. Starting up a cold reactor takes hours, so you're better off not shutting it down at all.
            And even at low power levels, your fuel will keep fissioning merrily along, so in essence you're throwing away a finite resource. Also, your buffer will be significantly more expensive than the solar energy you're using as primary.

            If you have an abundant source of renewable energy, you're better off using some of that to drive a buffer. Hydro buffer plants such as Dinorwig (see elsewhere in this discussion) have been shown to work well.
            • Re: (Score:3, Insightful)

              by Dr. Spork ( 142693 )
              Realistically, I don't think that any nuclear station would need to have down-time. If the public grid was producing enough of its own power, the nuclear plant's energy would go to hydrogen electrolysis. After all, even in an energy utopia, we'll need energy in some sort of a transportable form - say for cars and rockets.
            • Re: (Score:3, Insightful)

              by QuantumPion ( 805098 )
              This isn't quite correct. First, nuclear fuel doesn't get used up if it is not at power. The neutron flux at shutdown, compared to full power, is many orders of magnitude lower. The amount fuel is depleted is called the burnup, and is measured in gigawatt-days per metric ton uranium. Typical fuel is designed to last 40-60 gwd/mtu. If the reactor is at low power, the fuel will not be depleted at a significant rate. However, there are issues with running at low power for extended periods of time, this is beca
            • No, dummy! (Score:3, Funny)

              by Trails ( 629752 )
              The solution is easy! We use cold fusion to buffer. Since there's no steam circuit to heat up, we can have it going very quickly.

              And to those who complai about the weather, once we build the space elevator, we can put solar collector in orbit and beam power down to earth!

              With all that power, we can finaly build robots to clean our homes, cook our food, even "companion" models!

              Cold fusion, solar energy, space elevators, and robo wives! I think I just messed my mylar pants!
          • Re: (Score:3, Interesting)

            by fbjon ( 692006 )
            I can't remember what it's called, but Sanyo had some interesting futuristic plans for solar panels installed in the world's deserts (or similar places). Having them spread around the world would mean that power is available around the clock, with some converstion to other forms of energy of course.
        • Re: (Score:3, Funny)

          by Basehart ( 633304 )
          "Much of the time it is night, and storing that much juice in batteries is impractical."

          Doesn't it say in the bible somewhere that it's a sin to stay up after the sun goes down? Regardless, maybe we could get back to a more wholesome existence and put a stop to all that late night fun I hear people having outside while I'm stuck here coding until I go crosseyed.
      • Re:transport losses? (Score:5, Informative)

        by dbIII ( 701233 ) on Wednesday December 06, 2006 @05:19AM (#17126190)
        The big point with photovoltaics is you can stick a little panel just about anywhere and not worry about line losses or being on the grid at all - plus the lead time to set something up is very low - buy a panel and get an electrician to wire it up. The big problem with photovoltatics is it doesn't scale up - so for a really big facility you are better off with something that does like a thermal solution or very large water turbines if you are lucky enough to have somewhere to put them. Having a lot of cheap mirrors putting heat on some expensive photovoltaics gets halfway there.

        If you are just going to put bare panels somewhere it makes more sense to stick them on the top of existing poles instead of in some big facility since they act as discrete units anyway. Once they get rolled out there really isn't much that has to be done with them - the photovoltaics that existed when Einstein was young probably still work.

        Personally I think we are already seeing the start of one of the major potential uses for photovoltaics - appliances that don't have to be plugged into the grid. If the prices come right down things like solar mobile phone chargers may well become mainstream.

    • Yes, so they could use a much smaller area for just the US instead, and have the cells a bit better distributed. I don't see how that would be a bad thing though. Sure, perhaps for underdeveloped countries (who're going to spend all the money to build for them?), but not really elsewhere. 40% efficiency would have enormous benefits, let's hope we get their in production cells soon enough.
      • by Shados ( 741919 )
        Just having it as standard on the roof of 80% of the houses of the metropolitan areas of the world probably would cover a large chunk of the energy requirements. Then build a couple of "solar plants" here and there over the world to sell it like we do with hydro-electric dens right now. Then finish it all up with a few hydrogen or whatever "factories" that use this as power, and you should cover 95%+ of energy needs of the world. Because no solution fits everything, cover the last 5% with the good old fash
    • Nobody said that the area couldn't be split up and put in different places, but you make a good point anyway.

      Also (not contrary to anything you were saying), I did not read the article, but the summary said 265 miles on a side, which turns out to be 70,225 square miles. Texas is 268,581 square miles []. A solar array that large would take up a little over 26% of Texas. When put in that perspective, that's a huge mass of land. Using "265 on a side" just doesn't do the size justice.
      • Re: (Score:3, Funny)

        by Anonymous Coward
        Great. You've been so brainwashed by the media measuring in Libraries of Congress or Size of Texas that now you are forced to convert into those units to understand a size.
    • Re: (Score:2, Insightful)

      by nicholas. ( 98928 )
      And yet somehow we have no problems tranporting oil to non-oil producing regions. A huge solar farm could produce massive amounts of hydrogen. And hydrogen transports just as easily as oil via the same infrastruture. Cheap, unlimited, nearly clean energy and all we have to do is build it. I bet (no figures nor money to back me up) that we could have built several solar farms for the cost of one war in Iraq --not that I'm getting the two issues confused ; )
      • Re:transport losses? (Score:5, Informative)

        by Anonymous Coward on Wednesday December 06, 2006 @04:18AM (#17125884)
        And hydrogen transports just as easily as oil via the same infrastruture.

        Bzzt! Wrong answer. Hydrogen requires a completely different infrastructure that has never been massively developed. Transporting hydrogen trapped in a hydrocarbon is feasible and could use the same infrastructure, but hydrogen itself is a much more complicated issue. You either need to cryogenic cooling or you need to build infrastructure that has low hydrogen diffusion and low hydrogen embrittlement (and probably very high pressure to move a significant energy density of hydrogen around if you go the gaseous path). People who want hydrogen for various industries tend to steam reform it from hydrocarbons instead of using this oil infrastructure you think can transport hydrogen.
      • by SnowZero ( 92219 )
        At $50 a square foot (the current cost of a 25%-efficient cell), a 265-mile square of solar panels would cost $98 trillion dollars. That's quite a bit more than fighting even an expensive war. We will still need a few more breakthroughs for solar to be practical. With a 5x reduction in price, for example, you'd probably start to see it on a lot of buildings.

        • Re: (Score:3, Insightful)

          by JohnFluxx ( 413620 )
          As opposed to the cost of electricity for the whole world over then next 30 or so years?

          How much is the total electric bill for the world?
    • by kiddailey ( 165202 ) on Wednesday December 06, 2006 @05:54AM (#17126374) Homepage
      Why not just start making it mandatory for every high-rise and large-roof building structure to be covered with a certain percentage of solar cells that power part of the building during the day and feed the rest back into the grid? After all, the concrete and steel aren't doing anything with the sun.

      It seems to me that if we had started doing this years ago it may have a) reversed some of our energy problems and b) potentially made solar panels more affordable so I could cover my home's roof with them.
    • by Eivind ( 15695 ) <> on Wednesday December 06, 2006 @06:17AM (#17126464) Homepage
      Sure. That's actually another *advantage* of solar.

      It's a lot more practical to scatter a large numer of smaller solar-plants around than it is to do the same with nuclear, oil or coal-powered plants.

      If you do this, for example, by installing them on the roofs of homes you get 2 extra benefits:

      • It makes the house less hot. If 40% of the sun is converted to electricity, then that's 40% which is *not* converted to heat. Decreases the demand for AC.
      • It produces the most power precisely on the days when the demands on the grid is at its peak. (assuming warm/sunny areas) Which, is optimal if your goal is reducing the strain on the grid.
    • Re: (Score:3, Funny)

      by plopez ( 54068 )
      I would reccomend Nevada as there are HUGE military reservations there. The only problem being is that the giant mutant ants love silicone panels. But I'm sure we could figure sometning out. :)
  • by nullchar ( 446050 ) on Wednesday December 06, 2006 @03:44AM (#17125652)
    A large solar collector would also shade the ground and absorb the heat (energy) that the surrounding ground and air would normally receive. I guess, taking extra heat (energy) from one place, and adding it to lots of others may not be bad...

    What about the cost in sending that energy down the wire? Would it be best to build one big-ass solar array? Or would it be better to distribute smaller collectors over a large area, even if the sunlight is not optimal?
    • A large solar collector would also shade the ground and absorb the heat (energy) that the surrounding ground and air would normally receive. I guess, taking extra heat (energy) from one place, and adding it to lots of others may not be bad...

      PV cells have a lower albedo than the Earth as a whole, at least solid land, anyway. So over land they will result in more heat being transferred to the amosphere than the soil under them would have. Sea water has a pretty low albedo so I don't know if this applies ove

    • by AK Marc ( 707885 )
      Both. Build a big ass array in Arizona/Nevada to power the west coast. Then have smaller areas around the midwest and south for the rest. Also, having offshore platforms with panels on them to desalinate water and generate H2 would not be a bad idea.
    • How about we put them some place that is already covered. You know like above houses. Kind of like... say... a roof. I don't know how many square miles of the US is rooftops, but I bet if you added it up, you wouldn't need much in the way of non-building covering space for whatever extra power was needed to power the US.
  • Gee, that's about the size of Utah [].
  • where the facts? (Score:5, Informative)

    by Anonymous Coward on Wednesday December 06, 2006 @04:07AM (#17125808)
    So it's a bit unclear what the article means by 40% efficient as the article seems to confuse the concentrator part of the solar cell with the multi-junction part. The concentrator doesn't make the device more efficient at converting solar radiation into electrical power, it just concentrates the light so you don't have to use as large of a device. The idea being that the solar cell material is expensive but the optics are relatively cheap, so you might as well focus as much light on the device as it will absorb and still function.

    The multi-junction part comes from the idea that you can, using a solar cell, only extract as much energy from a photon as the size of something called the band gap of the material that the cell is made from. At the same time, a solar cell can only absorb photons with energies higher than the band gap. If the bandgap is small, as it is in silicon, then you can absorb most of the suns rays, but you can only get about 1 electronVolt of energy out of each one no matter how much energy the photon has. Since the bulk of photons emitted by the sun have more than 1 electronVolt of energy Si solar cells waste alot of the energy in sunlight as heat. If you make the solar cell out of a semiconductor with a larger bandgap then you absorb fewer photons (more of the solar spectrum lies below the critical energy for absorption) but you extract more energy from each photon. So, for a solar cell made from one material there is a sweet spot in terms of the bandgap that maximizes the energy extracted. Multi-junction cells try to overcome this by combining multiple devices with different bandgaps so that you can maximize both the total number of photons converted to electricity and the energy extracted from each photon.
    • by jannic ( 152373 ) on Wednesday December 06, 2006 @05:52AM (#17126360)
      What kind of facts do you expect from an article which contains units like kilowatt/hour, instead of kilowatt x hour? That really looks like the author was only interested in economics, not in scientific facts.
  • Downsides (Score:2, Insightful)

    by ChowRiit ( 939581 )
    I'm all in favour of clean energy, I think it's a laudable goal, but we shouldn't be patting eachother on our backs just yet.

    Firstly, these solar cells are no doubt incredibly expensive - any high efficiency ones are. Secondly, they're probably made using rare and/or exotic materiels, making manufacturing in bulk tricky, and thirdly there's likely to be a lot of pollution created in the manufacturing process for by-products et cetera (it's a problem with less efficient cells too, but the more efficient ones
    • Re: (Score:3, Insightful)

      Er, ever heard of batteries? It's perfectly possible to have capacatance stations built into the grid that serve as temporary UPS units for when the power slacks. Similarly, if you spread the generating stations out roughly evenly around the planet and build in enough extra capacity, (maybe 5%, I'm talking out of my ass here) the chances of cloud covering enough of that generator grid to cause a severe power loss are probably negligable.

      Presumably, you'd want the capacitance spread out across the grid- not
    • And That... (Score:4, Interesting)

      by Belial6 ( 794905 ) on Wednesday December 06, 2006 @04:25AM (#17125924)
      "Lastly, there's another issue. What happens when the sun goes behind a cloud? You need to be able to cover the entire slack in an instant, because you NEED a constant power output. That means you NEED enough GAS powerplants to power the whole world too, as they're the only type of power plant you can literally turn the dial and turn up the output."

      And that is what fuel cells are really for. Forget having hydrogen delivered to your home so that you can use a fuel cell as a generator. No, you use photovolic at the home to generate a tank of Hydrogen so that you can convert it back to electricity when you need it. The real promise of fuel cells is for use as a very clean battery.
    • Re:Downsides (Score:5, Interesting)

      by hcdejong ( 561314 ) <hobbes&xmsnet,nl> on Wednesday December 06, 2006 @04:35AM (#17125966)
      That means you NEED enough GAS powerplants to power the whole world too, as they're the only type of power plant you can literally turn the dial and turn up the output.

      No, they're not. Hydro plants can do this as well. The UK uses several hydro plants like Dinorwig [] to cover peak loads. Dinorwig can go from 0 to 1320 MW in 12 seconds, and has a peak output of about 1800 MW. It is built as an accumulator system, pumping water up the mountain at night (using excess capacity from nuclear and fossil fuel plants) so it doesn't depend on a huge water supply (river). Efficiency (W generated vs. W needed to pump the water up the mountain) is about 70%.
  • Panels On The Roof (Score:3, Interesting)

    by DaftShadow ( 548731 ) on Wednesday December 06, 2006 @04:13AM (#17125844)
    I've been recently wrestling with the idea of putting solar panels up myself, but the truth of the matter is that I cannot afford the current RoR's length of time (approx 13-18years), nor can I get enough panels onto the limited rooftop I plan to use to cause a very big dent. A huge increase in efficiency of space, as well as cost/watt, changes these numbers *dramatically.* This is awesome.

    - DaftShadow
    • by Nasarius ( 593729 ) on Wednesday December 06, 2006 @04:47AM (#17126032)
      Contact your local power company. Many (such as LIPA) will pay for a large percentage of your costs.
    • Re: (Score:3, Funny)

      by jez9999 ( 618189 )
      What I do, in SimCity 2000, is build a few hills. Then, I apply 'water' to each tile of the hill, and build a hydroelectric damn on each one. Best form of power by far; no explosions, breakdowns, and lots of power per square.

      Hmm. Wonder how realistic this is. :-P
  • by WindBourne ( 631190 ) on Wednesday December 06, 2006 @04:16AM (#17125864) Journal
    The issue is not one of generation. There is actually plenty of energy production (and more is coming on line with new wind and geo-thermal). Our problem is one of energy production when it is needed. Since solar (and most alternatives) will NEVER be able to produce 24x7 or even 8x7, then you need a way to save the energy. As it is, USA feds has been trying to force more research down the path of hydrogen. But the earliest will be around 2025 ,and that depends on having some MAJOR advancements in cost economics that make this solar cell efficiency games look like child's play. IOW, this route will not be happening.

    Do not get me wrong. These solar cells are most likely a good thing. Of course, it depends on how the true cost relative to other methods. But this country needs to quit subsidizing oil and coal as well as have a multi-prong research in energy storage to really make the alternatives happen.
    • Re: (Score:3, Insightful)

      by magman ( 1036252 )
      You've got it completely wrong... One of the main benefits of the solar production is that it's distributed and produces during peak hours. In other words, the power is generated when it's needed and you don't have to transport it to the areas where it's being used. Think air conditioning In Japan it's already cost effective to install solar panels without subsidies, in other parts of the world you generally need subsidies to get it working economically. But this business is growing at a rate of 40% each y
  • "At 40% efficiency, it looks like a square 265 miles on a side in the American southwest would do it."


  • by Anonymous Coward on Wednesday December 06, 2006 @04:23AM (#17125910)
    1. Deserts are not empty. They have an ecosystem.

    2. There is no reason at all to fill a desert with solar cells, and then transport the energy across to the other side of the planet. Solar cells are installed locally, like on your roof, or in your back yard, on every roof across the planet. Most of the electricity consumed would be as Direct Current right from your rooftop, with an inverter converting for those appliances you still insist on retaining that us AC.

    3. For dense city sitatuions with high rises who's energy needs can not be met by rooftops, etc., electricity can be sent via conventional AC lines across the conventional power grid from say no more than 50 miles away. Not the other side of the world.

    4. Those who produce an excess of electricity beyond their need, sell it into the grid.
    • by X ( 1235 )
      1. Nobody is implying they don't have an ecosystem. If you consider the amount of damage being done to ecosystems to provide the world's current energy supplies, entirely destroying 265 square miles to provide the world's energy would be an improvement.
      2. I don't think anyone sane was suggesting all the world's energy actually be produced in one place. It just provides people with an idea of the minimum amount of land needed if the whole world used solar energy.
      3. You can do better than 50 miles (keep in mind that s
  • Solar cells cost a lot of energy to make, so what's the life span on these things? What's left if you subtract the manufactoring costs from the life-time energy generation of these things?
  • Figures a bit out (Score:4, Informative)

    by tttonyyy ( 726776 ) on Wednesday December 06, 2006 @05:18AM (#17126186) Homepage Journal
    According to this site [], estimated world demand was 13.9 trillion kilowatt-hours in 2001.

    13.9 trillion kW/h / 8776 (hours/year) = 1.58TW

    This figure is comparable to the statement in the wikipedia that 2001 average world consumption was 1.7TW in 2001 []. So our sources agree within a reasonable margin.

    According to the wikipedia, the energy density from solar energy reaching the surface as a global average is 170 W/m2 []. At 40.7% efficient, that's 69.2W/m2.

    Using the lower figure of 1.58TW calculated above, you'd need 22.8 x 10^9 square meters, or approximately 8800 square miles of solar cells to meet 2001 world demand. (Or "just" 1900 square miles to meet the peak US demand of ~3 trillion kWh in the late 90s). Of course, these areas halve if sited in an area of the US where the solar energy density is 375 W/m2 (4000 square miles for world demand, 860 square miles for US demand).

    Neither correspond to the whopping (265x265) 70000 square miles the article summary claims. Sorry kdawson, looks like you're a magnitude out!
  • Gallium Nitride (Score:5, Informative)

    by GanjaManja ( 946130 ) on Wednesday December 06, 2006 @05:54AM (#17126370)
    A student at The Univ. of California, Santa Barbara just presented research showing the use of multi-junction devices using Gallium Nitride. This is awesome because Nitride materials are very well suited for a HUGE amount of the sun's radiation, and since he managed to perfect a way of sticking several layers of differently absorbing Nitride Materials together in ONE device, we could theoretically see solar cells that absorb the Entire spectrum of the sun's rays in the near future!

    Here's some links:

    Indium-Gallium-Nitride can be made to absorb the entire spectrum of solar rays: ll-spectrum-solar-cell.html []

    Tunnel Junctions - this is how you stick together many different layers of material, each layer with their own optimal absorption range (in terms of wavelength, aka. color): /2005/11/28/review07.pdf []
    (sorry, this is the best I could do, there was no simple paper explaining a tunnel junction. "tunnel" is for electron tunneling...)

    In essence, you have different layers that absorb only one range of wavelengths (colors of light), and whatever isn't absorbed goes straight through, and the next layer absorbs another range, etc. etc.

    As an aside, did you ever wonder how blue LEDs & lasers finally managed to get working? Nitrides paved the way for emission (and absorption) in a range of visible wavelengths, including blue. This is also why they're great for this application.
  • No streaks? (Score:3, Funny)

    by maximthemagnificent ( 847709 ) on Wednesday December 06, 2006 @09:44AM (#17128032)
    >> At 40% efficiency, it looks like a square 265 miles on a side in the American southwest would do it.

    Buy windex stock now, that's all I'm saying.
  • by NatteringNabob ( 829042 ) on Wednesday December 06, 2006 @03:31PM (#17134926)
    once you count the infrastructure costs. I own an off-grid second home which is about 3000ft from the nearest power pole. The cost to extend the power to our house is estimated by PG&E at about $20/ft, so about $60,000 to get to our house, and that is *after* you have negotiated an easement over the neighboring properties. By contrasts, a complete off-grid systems run about $10000/KW, so you can have a nice 3KW system for about $30K, or 1/2 the price, and the 'generation' cost after that is the cost of replacing the lead/acid batteries, which, unfortunately, are still the best storage alternative. Yes, it only works in places where there is a lot of sunlight, and you still need a generator for night and winter months, and it helps a lot to have all florescent lights (which, fortunately has also improved dramatically). The fact of the matter is that once everything is factored in, solar already looks pretty good. If you factor in the cost of things like conquering oil producing states (as well as the cost of maintaining a military large enough to do so at any time), solar is an absolute bargain.

Q: How many IBM CPU's does it take to execute a job? A: Four; three to hold it down, and one to rip its head off.