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Power The Military Technology

Towards a 50% Efficient Solar Cell 129

Posted by timothy
from the bounty-from-the-roof dept.
necro81 writes "IEEE Spectrum magazine has a feature article describing DARPA-funded work towards developing a solar cell that's 50% efficient, for a finished module that's 40% efficient — suitable for charging a soldier's gadgets in the field. Conventional silicon and thin-film PV tech can hit cell efficiencies of upwards of 20%, with finished modules hovering in the teens. Triple-junction cells can top 40%, but are expensive to produce and not practical in most applications. Current work by the Very High Efficiency Solar Cell program uses optics (dichroic films) to concentrate incoming sunlight by 20-200x, and split it into constituent spectra, which fall on many small solar cells of different chemistries, each tuned to maximize the conversion of different wavelengths."
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Towards a 50% Efficient Solar Cell

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  • by Dyinobal (1427207)
    Republicans would have no issue with this. It's military spending and that is fine, but if we ever want to invest in solar in the USA for purely clean energy purposes they'd call it wasteful spending and all sorts of crap.
    • by Firehed (942385) on Friday September 14, 2012 @07:28PM (#41341663) Homepage

      Know your audience. As long as DARPA's research comes to the public eventually (we got the internet, after all) it's still beneficial. Quite possibly delayed and almost certainly more expensive than it should be, but slow and expensive progress is still progress.

      • As long as DARPA's research comes to the public eventually (we got the internet, after all) it's still beneficial. Quite possibly delayed and almost certainly more expensive than it should be, but slow and expensive progress is still progress.

        Unless, of course, it comes at the expense of the same result being achieved by someone else at a lower cost and/or in less time, or even other, completely unrelated, results which may be valued more highly. Whether it is beneficial for DARPA to do the research depends on the opportunity cost, even if the research ultimately produces usable results.

        Naturally, when your source of funding is taxes, the (externalized) opportunity costs are never given any serious consideration.

      • by galanom (1021665)

        No, slow progress is not that useful, if it is outpaced by others. Because with or without DARPA progress will be made and solar cell efficiency will continue to increase. That would be a chance to accelerate it.

        But I don't care that much. I've seen trillions of stories in Slashdot about huge capacity batteries of bizarre materials, huge capacity storage media for the masses, etc, etc, but never seen these discoveries to bear fruit.

    • Re: (Score:1, Troll)

      by Charliemopps (1157495)
      Governments do not "invest", Governments move money from one place to another... VERY inefficiently.
      How are Obama's solar investments doing? Oh, that's right, they taxed you... took your money, then gave it to some businessmen that promptly filed bankruptcy and drove off in their BMWs. Congrats.
      • And Bush Jr. delivered pallets of cash to Iran which 'got lost'.
      • Re: (Score:2, Informative)

        by Anonymous Coward
        Except in the case of Spacex, where that model is dandy and fine, right? Which side of the Space Nutter camp are you on??

        "As of May 2012, SpaceX has operated on total funding of approximately one billion dollars in its first ten years of operation. Of this, private equity has provided about $200M, with Musk investing approximately $100M and other investors having put in about $100M (Founders Fund, Draper Fisher Jurvetson, ...) [22]. The remainder has come from progress payments on long-term launch contract

        • by jamstar7 (694492)
          Read what you wrote. NASA paid the 400-500 mil for launch capabilities, i.e., delivered assembled vehicles to stand up on the pad, fuel, and go.
      • by hawguy (1600213) on Friday September 14, 2012 @08:41PM (#41342321)

        Governments do not "invest", Governments move money from one place to another... VERY inefficiently.
        How are Obama's solar investments doing? Oh, that's right, they taxed you... took your money, then gave it to some businessmen that promptly filed bankruptcy and drove off in their BMWs. Congrats.

        In this list of recipients of the DOE's 1705 Loan program, 5 of out 26 are listed as being in serious financial difficulty, the majority of the projects on the list are on-track.

        Direct costs of the war in Iraq were $800B, by the time all direct and indirect costs are accounted for (interest, injured and wounded, veteran care and pay), it could hit $4T. The Loan Program cost $34B (and that's only if all $34B loans are defaulted on).

        So, for somewhere between 5% and 0.8% of the cost of war that we shouldn't have started, the US Government can help to move us toward alternative energy sources, and off of foreign oil (I know we have domestic sources for much of the oil we use, but since it's a global commodity, any oil we consume means more that volatile middle eastern states will sell)

        I'm not sure that the vetting process for all companies is fair and balanced, but I do think it's a useful program.

        • Re: (Score:2, Interesting)

          by JesseMcDonald (536341)

          So, for somewhere between 5% and 0.8% of the cost of war that we shouldn't have started, the US Government can help to move us toward alternative energy sources, and off of foreign oil...

          This may become a reasonable argument when you find a way to ensure that spending on alternative energy sources (and other projects) comes instead of, rather than in addition to, the money wasted on war. The "balanced budget amendment" proposal would be a reasonable place to start. Until then, massive overspending in one area cannot possibly justify spending other areas, no matter how small the latter might be by comparison. Quite the opposite, really; when you're that far over budget to begin with, any add

        • Re: (Score:3, Insightful)

          by ShanghaiBill (739463)

          Direct costs of the war in Iraq were $800B, by the time all direct and indirect costs are accounted for (interest, injured and wounded, veteran care and pay), it could hit $4T. The Loan Program cost $34B.

          This is a logical fallacy. You can't prove that something makes sense just by pointing out that something else is even stupider.

          • by RobbieCrash (834439) * on Saturday September 15, 2012 @01:22AM (#41343915)

            Are you suggesting that we shouldn't be looking into alternative energy sources?

            Private industry hasn't exactly done a whole lot to do anything other than prolong our dependence on fossil fuels. The oil, and oil related, industries are bigger than ever, more money than ever is spent on refining more and more difficult sources of crude. Oil sources that 15 years ago were thought would never be cost effective are now major suppliers in the whole chain.

            Solar power has made slight inroads, but only on a personal level. There's no significant widespread power generation through solar. We're NIMBYing wind turbines. Everyone is reluctant to invest in tidal power.

            Everyone just keeps pouring more and more money into oil. Spending money thinking about how to stop doing that is sensible, even if 90% of it goes nowhere. Only spending money on things that are proven to work is what got us here, if private companies aren't willing to risk failing, then fucking A rights the government should help out.

            • Are you suggesting that we shouldn't be looking into alternative energy sources?

              Not at all. But investments in alternative energy should be judged on their merits. The fact that the Iraq War was a colossal fiasco is completely irrelevant.

              • by hawguy (1600213)

                Are you suggesting that we shouldn't be looking into alternative energy sources?

                Not at all. But investments in alternative energy should be judged on their merits. The fact that the Iraq War was a colossal fiasco is completely irrelevant.

                It's only irrelevant if you look at each expenditure independently.. if you look at government spending as a whole, then you wonder why the same congress that supported getting into the Iraq war for no reason at all and ended up costing us trillions of dollars is suddenly worried because we're spending $34B to help USA industry compete on the world market. I guess we may as well keep buying our Solar cells from the Chinese - what possible harm could there be in sending more of our money to China?

        • by jcr (53032)

          >In this list of recipients of the DOE's 1705 Loan program, 5 of out 26 are listed as being in serious financial difficulty,

          Does that seem like a low level to you? I can tell you that any private lender looking at that many of his loans going bad would be in deep shit.

          -jcr

          • by ajaxlex (658555)

            I don't think that a Lender is the right analogy. Rather, the Govt is an investor, where the benefits are measured in repaid loans PLUS jobs created PLUS new technologies developed PLUS strategic resource concerns alleviated. Investing in startups means taking different kinds of risks than traditional lenders do - higher risk of default, but bigger payouts when things succeed.

            • by jcr (53032)

              > the Govt is an investor,

              No, the governent has nothing to invest. What it is, is an incompetent and utterly irresponsible gambler, wasting money earned by the people who perform productive work.

              -jcr

          • by hawguy (1600213)

            >In this list of recipients of the DOE's 1705 Loan program, 5 of out 26 are listed as being in serious financial difficulty,

            Does that seem like a low level to you? I can tell you that any private lender looking at that many of his loans going bad would be in deep shit.

            -jcr

            Of course they are risky investments, if their business plan was so sound that they were able to get traditional loans, they'd just get traditional loans.

            The government is acting more like a VC firm for these companies, and the average silicon valley VC firm has around a 50% success rate.

            • by DamonHD (794830)

              My expectation of VC success rate is ~20%, having several times been in receipt of VC money (and arguably succeeded once!)...

              Rgds

              Damon

        • There's a reason these companies came to the government: they could not get private sector financing. Why not? Most likely, because they have no convincing business case. However, they have good contacts in the government, so they get to waste your tax dollars.

          Note these tidbits from a report written for the House Oversight Committee: [house.gov]

          - "The Government Accountability Office (GAO) found that the DOE loan guarantee program was riddled with program inefficiencies"

          - "the absence of government intervention the pr

          • There's a reason these companies came to the government: they could not get private sector financing. Why not? Most likely, because they have no convincing business case.

            That's because in this day and age, a "convincing business case" isn't "Give me funding for R&D and I can probably exceed your wildest expectations eventually", it's "We'll give you a guaranteed 6 billion dollar payback next quarter". Corporations have all but abandoned long-term thinking and speculative research in pursuit of the largest profit in the shortest interval.

            Governments, for all their faults, are not expected to show a profit (and, in fact, if they do, it probably means there's something ami

        • by galanom (1021665)

          Direct costs of the war in Iraq were $800B, by the time all direct and indirect costs are accounted for (interest, injured and wounded, veteran care and pay), it could hit $4T.

          They say that was is business, but I fail to see what kind of businessman would invest $4tn in a high risk bid to control some oil, a control that IF it is gained, may be lost in a regime change, something that seems to get frequent in Middle East.

  • by Anonymous Coward on Friday September 14, 2012 @07:33PM (#41341689)

    There's basically two ways to get power in space. One involves plutonium, the other high efficiency solar cells.
    Since launch costs are related to weight, anything that increases panel efficiency, even if expensive, is great
    for solar applications.

    • Re: (Score:2, Informative)

      by Anonymous Coward

      The solar (photovoltaic) panels used in space are already very efficient and use some of the most expensive materials such as being made out of Gallium Arsenide (GaAs) with multiple doped layers to collect at different valence levels. Panels used in space also receive sunlight that doesn't pass through the atmosphere allowing for higher power gains.

      The problem has always been with getting high efficiency rates on earth without the high cost.

  • by deatypoo (1837038) on Friday September 14, 2012 @07:36PM (#41341725)
    When the US starts paying what other countries pay for fossil fuel (as any European could say), then maybe solar power research will skyrocket. Until then, as it's not even currently appealing profit-wise, it's quite sad to say but only military applications and some rare initiatives (often subsidized) remain and that's just because soldiers can't be carrying their weight in oil to fuel the devices they use and batteries are still inconvenient. Let's give it a few more years, but recent events in the middle east should help a few make up their minds.
    • by SeaFox (739806)

      When the US starts paying what other countries pay for fossil fuel (as any European could say), then maybe solar power research will skyrocket.

      So why isn't this research a hot field in Europe?

      • by manu0601 (2221348)

        So why isn't this research a hot field in Europe?

        Because the hot field can be another research. France is a top player at nuclear energy, for instance.

      • by DamonHD (794830)

        Germany (and others) for example already *has* a lot of *installed* solar PV.

        But yes, research is going on in the EU too.

        Rgds

        Damon

      • Because several european countries are past the research phase and buying 100% of the output of the last breakthru solar (for another year or so too) and installing it in industrial scale solar power plants.

    • by gewalker (57809)

      The US generally pays the same for fossil fuels as any other country in the world -- O you mean the US should raise taxes on fossil fuels to the levels seen in Europe, etc. so that the end-user has to pay a painfully high price. There are a number of different possible ways to reduce your carbon footprint if that is the goal. Tax policy is usually best left to the locals -- taxation without representation seems to be a bit of a sticking point here in the US.

      I believe we should be reduce our carbon footprint

      • Just raise them high enough to pay for the unfunded wars which we are only in because of energy dependency. Oops then we would be paying what they pay in Europe I guess. Our 2 parties seem to give of only 2 choices Tax and spend Democrats and No Tax Just Spend Republicans.
        • Re: (Score:2, Interesting)

          by hairyfeet (841228)

          The simple fact is, whether anybody likes it or not, is that we simply haven't found ANY tech that can replace oil when it comes to the amount of energy per unit. Last I checked oil gives you a return of something like 30 to 1, most of the other techs are around 3-5 to 1. that isn't even close folks.

          Then there is the problem of the NIMBYs, that frankly have a living shitfit if you do ANYTHING anywhere near them. Look at China, they are gonna have a good 25 nuclear reactors online in the time it takes the US

    • When the US starts paying what other countries pay for fossil fuel (as any European could say), then maybe solar power research will skyrocket.

      Just because Europeans let their governments gouge them on fuel taxes, you think that everyone else should, too? The price of oil is the same in Europe and the U.S. The price difference between what an American and a European pay at the pump is primarily due to the taxes that European citizens let their governments add.

  • In order to do this, it relies on the sun being a nice bright disk.
    If you try to split the image of the sun on a prism, it works well.
    If you do the same with a cloudy sky, it totally fails,

    So, this technique will not wWork at all during light cloud.
    In many places, that more than halves the output.

    • by Anonymous Coward

      Too many people still believe (and want others to believe) that PV output drops to zero at the first sign of a cloud, but it simply isn't so.

      My array is something like 15% efficient, give-or-take a few percent. Even on cloudy days it manages to charge my battery banks and power my loads.

      Granted, the output decreases as the density of cloud increases, but, even on the most dismal and rainy days, there is still usable output from the array.

      It's true that some places aren't exactly ideal for PV. (Seattle?) How

    • No. (Score:4, Informative)

      by mosb1000 (710161) <mosb1000@mac.com> on Friday September 14, 2012 @09:08PM (#41342535)

      If that were true, this would only work if the sun were at a very specific angle. But that's not how it works. It concentrates light from the entire sky into a narrow beam which is then split into different wavelengths. It says that right in the summary.

      • It concentrates light from the entire sky into a narrow beam which is then split into different wavelengths. It says that right in the summary.

        No, it doesn't say that in the summary. It says (incorrectly) that dichroic films are used to concentrate sunlight 20-200X, but nothing accurate about how it achieves that concentration. TFA says that for the concentrators to work, they would have to be pointed at the sun.

        This is consistent with my personal experience. I've never seen a concentrator that can collect

        • FWIW once the light is truly diffuse, it cannot be concentrated. This is fundamental physics, closely related to the laws of thermodynamics.
    • by dbIII (701233)
      There are some photovoltaics that work well when it is cloudy.
      • by jamstar7 (694492)
        They work okay when it's cloudy. Hell, a Junior Scientist Kit solar cell will still put out some power in an indirectly lit room. It'll put out more in direct sunlight.
        • There are some photovoltaics that work better on wavelengths that are blocked less by clouds than the normal silicon cells. If you expect a lot of cloud cover then those are the ones you pick for that job. They cost more because they are not a byproduct of making microprocessors like the silicon cells, but they have been available for probably a longer time than the poster complaining above has been alive.
  • by Anonymous Coward
    but that still means it's 50% not efficient. I don't know, I'm just in a pessimistic mood tonight.
    • by icebike (68054) *

      Even a half glass of water gets a thirsty man's attention.

      50% efficiency as something approaching today's cost is probably enough of an improvement to start a world wide movement toward Solar.

  • by TrumpetPower! (190615) <ben@trumpetpower.com> on Friday September 14, 2012 @08:55PM (#41342439) Homepage

    Developments like this are awesome, because they open up the possibility of doing exactly what the summary describes -- using solar power to recharge things where size / weight / surface area is at a premium.

    But those sorts of scenarios are few and far between. Most of the time, cost is the limiting factor, and these high-efficiency designs are always costly.

    That's okay, though: PV panels are already plenty efficient for their desired function in most cases [ucsd.edu].

    A typical location within the U.S. gets an annual average of 5 full-sun-equivalent hours per day. This means that the 1000 W/m solar flux reaching the ground when the sun is straight overhead is effectively available for 5 hours each day. Each square meter of panel is therefore exposed to 5 kWh of solar energy per day. At 15% efficiency, our square meter captures and delivers 0.75 kWh of energy to the house. A typical American home uses 30 kWh of electricity per day, so we’d need 40 square meters of panels. This works out to 430 square feet, or about one sixth the typical American house’s roof (the roof area of a two-car garage). What’s the problem?

    Cheers,

    b&

    • by Anonymous Coward

      Price.

      • Re: (Score:2, Interesting)

        by TrumpetPower! (190615)

        Don't be a price snob, either.

        If we wanted to go 100% solar for electricity generation over the next 50 years, it'd only take about as much as we're currently spending on federal government pensions. No small chunk of change, to be sure, but peanuts compared to the other big projects our society doesn't even bat an eye on.

        (Assume $2 / watt installed, not much below the current bottom end but well above what such huge economies of scale would push it to. Assume 1 MWH per year per kW of panels, quite pessimis

        • by Anonymous Coward

          Assume $2 / watt installed

          That is rather low, rather 80% low.

          Including wiring and batteries, and battery housing, and battery maintenance, typically it costs around $10 per watt initially and an additional $2-5 per watt every five years thereafter just to replace the batteries. Did I mention batteries?

          The current cost of a complete solar solution is significantly higher than the cost of an average house and would take more time than an average person lives in any one house to recoup the cost.

        • by Anonymous Coward

          The return on investment for PV just doesn't make sense. It is non-existant. You could spend a fraction of the cost of PV insulating everyone's attic, replacing windows, buying tubes of caulking, or changing furnace filters and save tons of energy. The program would actually payback!

          PV is a marketing statement more than a practical energy saving strategy.

          • Does insulation, double glazed windows, caulking and new furnace filters make hippie chicks puddle?

            There goes that idea. I bet you don't even own a hybrid.

    • by Anonymous Coward

      $6 per watt average installed cost = no payback. And you still need a grid connection.

    • by nocain (2730619)
      So I am missing something because this does not add up, 40 meters squared is nowhere near 430 sq feet, unless my drunken math is that bad or I am missing something entirely, hoping since its from UCSD and titled do-the-math.... I get 1 meter about 3.3 foot so 40x3.3=132feet so 132ft x 132ft area... thats a lot bigger than my 2 car garage, maybe they meant 2 airplane garage?
      • by Anonymous Coward

        Yes, you are missing an education. Assume 1m=3ft, then 1msq=9ftsq so 40msq=360ftsq. Right in the ballpark.

    • by pev (2186)

      A typical location within the U.S. gets an annual average of 5 full-sun-equivalent hours per day.

      You do realise that there is a whole world outside of the US that does not have the same weather as the US? It is conceivable that the rest of us in the world (including us UK folks with, er, not as sunny weather) are interested in more efficient solar panels too.

      As a second point, no improvements in science (or manufacturing tech) ever got made by people saying "Oh, the stuff we've got now works alright so let

  • by evilviper (135110) on Friday September 14, 2012 @09:41PM (#41342749) Journal

    Why would the military focus so heavily on solar power? I mean, the research is a very good thing, and will be a huge boon for satellites, and maybe electric vehicles as well, but for soldiers, they have a lot more options available.

    The main thing which comes to mind is the backpack which converts motion into electricity, which happens to have a side-effect of altering one's stride into a more efficient motion as well:

    http://www.msnbc.msn.com/id/9245155/ns/technology_and_science-science/t/backpack-generates-its-own-electricity/ [msn.com]

    This could be supplemented by a set of foot-pedals, so if the soldiers are stationary, they could assign one guy to generate the power they need... If they're stationary and not marching, I'd suppose the workout might even be welcome.

    These options have the added advantage of working just as well in high latitudes, bad weather, and during sandstorms, and not requiring soldiers with other concerns to deal with panels hanging off their pack, and needing to be oriented to catch the sun.

    • by Squirmy McPhee (856939) on Saturday September 15, 2012 @07:04AM (#41345121)

      Why would the military focus so heavily on solar power?

      It's not just solar, they are also very interested in wind, geothermal/ground source, and biofuels. But they think solar and wind have the most potential for their purposes (it's mostly only the Air Force interested in biofuels, for fueling their planes).

      As for why, well, 80% of the convoys run in Iraq and Afghanistan are fuel convoys. On average, a soldier died or was wounded in one of every 46 of those convoys in 2010. And by the time you take into account the cost of the fuel and the expense of moving it, the military is paying something like 5-10 times the price you pay at the pump when you fill your gas tank.

      What is this fuel used for? Some of it is used to power vehicles, of course, but the vast majority of it is used to provide electricity at remote and forward bases. They dump it in a generator, burn it, and wait for another convoy. On the other hand, the sun and the wind come to many of their locations without the need for a convoy.

      The upshot of all of this is that with sufficient energy densities, the military could spend a whole lot more on solar panels and wind turbines that would seem justifiable to the average homeowner and still have it be economical -- I mean, just think of the money and lives that could be saved if a base could reduce the number of convoys it needs by 80%.

      For all of that, you probably don't need cells with 50% efficiency, and I guess that's why TFA focuses on soldiers' gear instead of base power.

      Your concern about a soldier contending with solar panels hanging off his back is a bit misplaced, I think. TFA says that at 50% efficiency, a 10-cm square panel is all that would be needed. That is already smaller than a single standard silicon cell in production today (standard is 15-cm square). And if you're worried about bad weather, sandstorms, and distractions then I would think that the last thing you want is a mechanical device with moving parts like foot pedals.

  • by Shavano (2541114) on Friday September 14, 2012 @09:59PM (#41342877)

    And this is going to be cheaper than triple-junction cells? And DARPA is going to be in charge of making it cheap?

    I'm not holding my breath.

  • 100% more expensive, brok brok brok.

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