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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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  • 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?
  • 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
  • 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@xmsn[ ]nl ['et.' in gap]> 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%.
  • Re:Cost is the issue (Score:2, Interesting)

    by mrbluze ( 1034940 ) on Wednesday December 06, 2006 @04:39AM (#17125986) Journal
    A viable business model for the solar energy solution might be for new houses to be built with high efficiency solar arrays on rooves, using the energy for household purposes and selling excess energy. Therefore a return on investment could be expected. Excess daytime energy can be stored for night-time use, though this is fairly inefficient (the most efficient method is pumping water uphill to a dam). In places like Australia this is quite achievable, as governments have been fairly forthcoming at times with giving grants and subsidies to people taking up environmental initiatives, and on the other hand issuing strict regulations for energy saving methods of house design. With the prices of electricity which exist in Australia, for example, it's actually a very achievable aim - with a $10,000AUD outlay for a regular household solar array, recouping the investment occurs in about 10 years. I don't think having solar farms is the only solution - only the big business solution.
  • Re:where the facts? (Score:2, Interesting)

    by YourMoneyOrYourDuck ( 1033800 ) on Wednesday December 06, 2006 @04:56AM (#17126078)
    Can't you use a prism to split out photons of different energies and direct them at the appropriate receptor?
  • Re:Cost is the issue (Score:2, Interesting)

    by glittalogik ( 837604 ) on Wednesday December 06, 2006 @05:01AM (#17126100)
    They're only related if the more efficient panel isn't significantly more expensive to produce. That is, of course, largely a matter of demand; the more of something you want/make/buy/sell, the more refined the production process becomes and the cheaper the individual units become - in this case, solar panels and therefore kilowatt hours.

    Frankly I'm in favour of biting the bullet and making this a personal routlay, and am looking forward to doing so when I have a property to do it to. If someone can afford to buy a house, they can afford to put some bloody photovoltaics on the roof and if that adds an extra 6 months to their mortgage then so be it. For once it'd be nice to see economics take a back seat to environmental responsibility.
  • Re:Here's an Idea (Score:5, Interesting)

    by MichaelSmith ( 789609 ) on Wednesday December 06, 2006 @05:04AM (#17126116) Homepage Journal
    How about we build a ring or spherical grid of energy-collecting satellites around the Earth?

    Its not exactly a new idea. []

  • 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.
  • Re:where the facts? (Score:2, Interesting)

    by frostband ( 970712 ) on Wednesday December 06, 2006 @06:33AM (#17126556) Homepage

    I was really hoping they would (but knew they wouldn't) link to a specific journal article about the devices being used. If anyone knows if this group has produced a scientific article (IEEE, AIP, etc...), I would appreciate a link. I did a quick IEEE search on multi-junction solar cells and didn't find anything about the device mentioned in TFA.

  • Bright Future (Score:2, Interesting)

    by sam0vi ( 985269 ) on Wednesday December 06, 2006 @06:39AM (#17126588)
    I see a bright future for Middle East countries. If i were them i'd be investing now on solar cells before they run out of oil. Imagine the whole arabic peninsule covered by 40 or 50 percent eficient solar cells. I only wish i had a billian euros to invest
  • Re:transport losses? (Score:5, Interesting)

    by Eivind ( 15695 ) <> on Wednesday December 06, 2006 @06:44AM (#17126614) Homepage
    True, if you had enough solar-power to cover the entire grid, and surplus in addition to that, then producing hydrogen for vehicles would be fine.

    Aslong as you're doing less than covering grid-use though, you're better of with a storage-mechanism that wastes less, such as pumping water to a magazine higher up.

    You can store substantial amounts of power. If your magazine is 400 meter higher than the powerplant, then each additional cubic-meter of water up there contains 1Kwh. Thus, for example, the Veltdalslake (western Norway) with a size of about 12km^2 and 25 meters of regulation, at 1100m can store on the order of 900 million Kwh -- which counts as a substantial battery in my book. :-)

  • Re:transport losses? (Score:3, Interesting)

    by fbjon ( 692006 ) on Wednesday December 06, 2006 @07:45AM (#17126968) Homepage Journal
    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:transport losses? (Score:2, Interesting)

    by Calinous ( 985536 ) on Wednesday December 06, 2006 @07:51AM (#17127002)
    Yes, you will need to put plenty of cable to transport energy half a world away (like from USA to Australia). While Australia doesn't use much electricity, USA does. In 2003, the consumption was 3,660,000,000,000 kWh. This is 10,000,000,000 kWh a day, or some 400,000,000 kW. How could you transport these? Well, 400,000 MW could go on a line at 1000 kV, for 400,000 Amperes average (as electricity is not used at the same rate, let's say max would be double - for hours at a time). Now, for power transmission you could use a 0000 AWG line. This gives: OOOOAWG 0.46 inch diameter 0.16072 resistance (ohm/km) 302 A current max How much energy could you transmit over this? 302A, you lose 50V per kilometer - half a world away, at 20,000km - 1000kV losses. On a line of 1000kV, all the energy you can pump goes as losses. How much copper such a line would have? At 100mm^2 sectional area (10^-4 m^2), the wire volume is 2000 cubic meters (or a cube at 12.5 yards across, for each of the wires How many wires will you need on the US end? Some 2,000 (to support double the average current) - for a 36 millions tons of copper. World copper production is in the 10 millions ton area, so you would need some three years of world production to build such line.
  • by Anonymous Coward on Wednesday December 06, 2006 @09:51AM (#17128130)
    Link to Boeing implies that the cells are GaAs-based. On the figures given above (ie a square solar cell 265 miles on edge) and assuming the following:

    GaAs thickness on cell = 100 microns
    Density of GaAs=5.32 tons per m3
    %Ga in GaAs=48%

    a quick back of the envelope calculation indicates that you might need

    46445387.5 tons of gallium to generate all the world's power

    USGA figures give world 1996 production as 70 tons, and suggest world reserves of 1 million tons at grades of 50ppm in bauxite, although Ga in zinc deposits may also be potentially useful. However, this looks some way short of the 46 million tons required.

    Gallium is actually pretty common - average crustal rock has 19ppm Ga, much more than so called "common elements" like lead or copper. Unfortunately we never get large rich deposits of it concentrated in one place, so extraction cost, in terms of money and energy is too big.

    Back to the drawing board (at least for global energy supplies..)

    Of course, there might be a mistake in my sums...

  • by maggard ( 5579 ) <> on Wednesday December 06, 2006 @10:07AM (#17128354) Homepage Journal

    Actually, my Grandfather was a buggy whip salesmen.

    After returning from The Great War, WWI, he was disabled (indeed he'd been declared dead & in the morgue at one point - mustard gas.) The job he could get was selling buggy whips, and his territory was the US Midwest & Canada. He was away from home for long stretches of time, and as you can imagine had some pretty amazing tales to tell of traveling to remote ccommunities back when travel was HARD.

    However he saw the car taking over and once he'd saved up enough money he did the smart thing: Opened a service station.

    Later it went bust in the Great Depression. He then started again, in putting in power lines, then power plants, and eventually became VP of a a large construction firm and responsible for many of the major structures still standing in Kansas City including the Liberty Memorial [], Nelson Gallery [], and the Starlight Theatre [].

    The point is, he really was in the buggy whip business and when the new technologies came in he adapted and took advantage of them. Then when the bust came he reinvented himself again and took his skills and when into an entirely new career. Not a new high-tech story, rather from a fella raised in a sod hut in the Oklahoma Territory where buffalo were a constant threat.

  • Re:transport losses? (Score:3, Interesting)

    by hcdejong ( 561314 ) <hobbes@xmsn[ ]nl ['et.' in gap]> on Wednesday December 06, 2006 @10:52AM (#17129180)
    On second thought, I don't think the fuel burn rate matters all that much. The operating cost of a nuke plant is determined mostly by other factors (cost of building it, personnel etc., EOL disposal of the reactor). Running a nuclear power station strictly as a backup means you won't sell many kWh which means your cost/kWh goes through the roof.

    It's not a coincidence nuclear power stations are often run as a base load, running at 100% of capacity basically full time.
  • Re:transport losses? (Score:5, Interesting)

    by QuantumPion ( 805098 ) on Wednesday December 06, 2006 @10:56AM (#17129284)
    Not quite true. Lifetime on fuel rods is dependent on the number of fissions, not the time spent in the reactor. Control rods mediate the reaction or can shut it down nearly entirely. I have looked with "no joy" (unsuccessfully) for info on minimum power levels at nuke plants, my guess would be 5%-ish of maximum power just to keep the turbine spinning. There would also be some interconnect time if they're off-grid.

    The minimum power a nuclear plant can produce electricity at is around 20%, but this is due to non-nuclear issues (turbine vibrations, steam quality, etc). As far as the reactor is concerned, you could theoretically run at 5% power indefinitely, however there are issues associated with running at less then 100% power for extended periods of time. What happens is that in order to run at low power, you have to use the control rods to control power level, but if you deplete the core with control rods in you create axial asymmetries.

    Big nuke power plants are designed to be base load generating plants, running at 100% all the time. They are sensitive to making power changes on the fly and if you shut down completely, you can't go back online for a couple days due to xenon. However, there is no reason why you couldn't design a smaller reactor designed for peak loads or emergency use. It would work just like a naval reactor: compact, high power, and using highly enriched uranium.
  • by uncledrax ( 112438 ) on Wednesday December 06, 2006 @11:08AM (#17129522) Homepage
    I pretty much just picked a comment here at semi-random to talk about.

    Keep in mind a few things when people are talking about 'solar paneling a roof'..

    - Here where I live, we have a ton of pine trees.. they dump a ton of pine needles on my roof. I'd say at peak, almost .25-.3 of my roof can be obscured. That == instant cut of service.. obviouslly, i'd have to clean my roof more often.. are solar cells safe to walk on and do they stand up to abrasive brooms without degrading the surface quality?
    Obviously the same would apply to Snow until it melts off (which takes how many hours during the day, of which you're getting far from peak efficiency from your panels with?
    When it hits the rainy season, you have similar issues since your typical week is overcast?

    - Reflecting the suns heat is desirable in the warm months, but not in the cold months. Currently I count on the sun during the day to help heat my house in the winter. If I panel my house with the same goal of attempting to collect/reflect all that sunlight during the summar to save/run my AC, I also have to run my heater more often because my house doesn't warm up?

    - what the TOC on solar panels anyhow? I fully realize that the cost of replacement will go down as demand and technology increase.
    I can get 10+ years from my current roof.. how often do solar panels need replacing? keep in mind they will be getting hit by (branchs | snow | heavy rain | leaves/pine needles | occasional base balls | people walking on them to clean them | cleaning chemicals | other forms of harsh weather such as hail and/or debris in hurricanes, etc..). Someone throw me some real-world numbers here?

    I'm not trying to be a neigh-sayer, just trying to keep people aware of the every-day issues associated with such things.. i'm far from an expert on solar paneling, but these are some things that 'average joe' will want to know. And lets face it.. if you want it to get wide-spread adaptation, you gotta get the 'average-joe' vote.

  • Re:transport losses? (Score:4, Interesting)

    by Rei ( 128717 ) on Wednesday December 06, 2006 @12:58PM (#17131732) Homepage
    "On every roof" isn't necessarily a good idea. Up here in Iowa, we don't get that much sunlight compared to all of those in the desert southwest. Not that this makes solar panels worthless; I have some to run my greenhouse's vent fans, since they come on when it's sunny (and thus, when the greenhouse will be heating up). But for general energy consumption, it would take a major cost reduction from the major cost reduction that would make energy in the southwest profitable. Which may well happen eventually, but not soon.

    As for the original poster's comment about a volcanic eruption distrupting energy supplies and using nuclear for backup, there are ways to deal with power loss: energy displacement. The cheaper electricity gets, the more the world will use electricity-intensive industrial processes -- for example, aluminum smelting (that is, to say, use of aluminum use would displace steel use). Such processes can scale output based on available power supply. If the price of energy leaps due to a shortage (say, from dust blocking out the sun), such industries will be economically forced to curtail their production until the dust clears, thus freeing up power for everyone else to use (aluminum prices would spike, and steel use would begin to take over). Long term light shortages would be more problematic, but short term wouldn't be. Not that I think the world ever would be completely solar powered, but I just felt I should point this out.

    As for hydrogen production, there's a much nearer-term option that I find really keen: Honda's "Home Energy Station" concept. Basically, almost every home in the US has natural gas lines running to it. Currently, natural gas is the cheapest way to produce hydrogen, so producing as much hydrogen as you need, straight from your natural gas line, seems a reasonable proposal. Of course, this raises the question, "Why not a natural gas-powered car? Why waste the energy converting it into hydrogen?" Well, apart from the very high energy efficiency of using hydrogen in fuel cells, with Honda's system, the energy released in converting natural gas to hydrogen isn't wasted. The waste heat from the process fires your water heater, so it's an almost lossless system unless you're consuming large amounts of hydrogen and using almost no hot water.
  • Re:transport losses? (Score:3, Interesting)

    by AmericanInKiev ( 453362 ) on Wednesday December 06, 2006 @04:05PM (#17135500) Homepage
    I don't see a loss of jobs related to the adoption of solar energy (in consumption country). The losses would occur in oil-fields ie Venezuela, Saudi, Dubai, etc...

    The new jobs created by the Solar energy (and Wind sector) thus far are on the whole very good jobs, and there would be more jobs in a renewable economy, look at the O&M component of these "Concentrator" systems. They have moving parts, they require education to install, and the jobs would be create in every state and county. Nuclear plants, by contrast create jobs with a high risk-premium, but they also create less jobs per kilowatt than any other electrical provider, as the plant size is bigger, and there are fewer of them generally.


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