12 ms·

World record solar cell with 44.7% efficiency

177 points by X4 13y ago

TheLegace 13y ago
"These solar cells are used in concentrator photovoltaics (CPV), a technology which achieves more than twice the efficiency of conventional PV power plants in sun-rich locations. The terrestrial use of so-called III-V multi-junction solar cells, which originally came from space technology, has prevailed to realize highest efficiencies for the conversion of sunlight to electricity. In this multi-junction solar cell, several cells made out of different III-V semiconductor materials are stacked on top of each other. The single subcells absorb different wavelength ranges of the solar spectrum." If that isn't a reason to be investing in Space, I don't know what is. "This world record increasing our efficiency level by more than 1 point in less than 4 months..." I think we may start to see Moore's Law starting to be applied to Solar Cells. Which actually reminds of a chart on the waves of innovation[1] on the Stanford Tech Entrepreneurship course where we are now seeing the tail of IT and computing and beginning of renewable technologies. The same thing can be said about energy density of batteries(According to Tesla batteries). [1] Page 5 https://d2d6mu5qcvgbk5.cloudfront.net/documents/original/69bd3725d86ab970f2d9509424bb67ae4c832faa.pdf?1377910658 https://d2d6mu5qcvgbk5.cloudfront.net/documents/original/69b...
- killerswan 13y ago
  It is indeed interesting, but IIRC most of the funding for satellite launches (R&D for III-V semiconductors) came from intelligence, not NASA. So, um, thank you, NSA! :P
  - hrkristian 13y ago
    What with their love for predictability, it's no wonder they're strong supporters of the sun.
  - hxc 13y ago
    I would rather dump trillions of dollars into NASA and their tech :D.
  - D9u 13y ago
    I thought it was the NRO? http://www.nro.gov/about/ http://www.nro.gov/about/
- wyager 13y ago
  >I think we may start to see Moore's Law starting to be applied to Solar Cells. It would have to be a kind of inverse Moore's law, given that you can't double beyond 100%.
  - TheLegace 13y ago
    I guess what I really mean was exponential increase in gains.
    - markfx 13y ago
      Moore's law describes a polynomial increase, not exponential.
      - ScottBurson 13y ago
        I'm afraid you're mistaken. Doubling every 18 months is an exponential progression.
  - gilgoomesh 13y ago
    It's worse than that. There's no room for a single doubling of 44% efficiency. The theoretical maximum for multi-junction concentrator cells is about 86%: https://en.wikipedia.org/wiki/Shockley–Queisser_limit https://en.wikipedia.org/wiki/Shockley–Queisser_limit For single junction cells it's a mere 33%.
    - MikeCapone 13y ago
      Efficiency matters, but price/watt matters more and there's still room for a kind of moore's law there.
      - jnw2 13y ago
        Which of efficiency or price/watt matters more depends on the application. For example, I believe something like 4 m^2, 40% efficient, 8 hours of charging is enough to get electricity to drive a Tesla something like 30-40 miles. (In practice, I assume you'd cover all of the outside of the car with 40% efficient solar panels to make this work (or maybe even 80% if you can figure out how to build them), and then 4 m^2 approximates the effective useful area after you take into account suboptimal sun angle, the side of the car facing away from the sun, etc.) The number of people whose commutes could be entirely covered by 40% efficient solar panels built into the car being used to recharge the battery is a lot more than the number of people whose commutes could be covered entirely by 12-15% efficient solar panels. Current mass produced technology doesn't make any variation on this cost effective today, but it seems clear that in the future, a 12% efficient panel array built into a Tesla is never going to be all that attractive for this application no matter how cheap it might become. I suspect that high rise apartment buildings can cover a much larger percentage of their energy consumption from solar panels mounted on their sides and roof if those solar panels are 40-80% efficient instead of 12-15% efficient. If localized solar right next to the consumer of the power becomes cheaper than paying for electric grid transmission, this may become very relevant in 10 or 20 years. Even for residential suburban solar installation, where finding adequate space for an adequate quantity 12% efficient solar panels is generally not a problem, the really important thing is not the price per watt of the panels themselves, but the price per watt of the system as a whole. The mechanical support of the panels is a part of the system cost, and the cost of that portion will shrink with more efficient solar panels, though of course there is an open question as to whether that will end up lowering the total system cost or not in the long run.
- MysticFear 13y ago
  There are many reasons to be investing in NASA. They actually have subdomain devoted to highlighting their spinoff technologies. http://spinoff.nasa.gov/ http://spinoff.nasa.gov/
- dpatru 13y ago
  > If that isn't a reason to be investing in Space, I don't know what is. To justify government research, the results need to be compared to the alternative. Had NASA scientists not been working for the government, they would have been working for private companies engaged doing useful work. The Soviet Union had similar resources to the US, yet their research budget was spent wholly by government, whereas a large portion of the US research during that time was directed by private companies. If you want to restrict the comparison just to the US, ask yourself what would the massive wealth that was dedicated to NASA had produced had it been directed by private interests? What would NASA engineers have produced had they been employed by in Y-Combinator-style startups? (or even big private companies like Google, Apple, Facebook, Amazon, etc.)
  - eru 13y ago
    > (or even big private companies like Google, Apple, Facebook, Amazon, etc.) Or IBM, or everyone's favourite, Tesla. A similar argument always crops up with people always looking at how much technology came out of war-time efforts. The opportunity costs are huge.
  - nitrogen 13y ago
    While you're considering alternatives, what would the massive wealth dedicated to the DOD have done in the hands of NASA and private non-military researchers?
  - scarmig 13y ago
    A couple points: 1) It's not like the Soviet Union was a terrible hellhole for research. It had impressive research output for decades. 2) That's almost beside the point, however. Let's take it as a given that more good research, whatever that is, is a worthy goal for a society, and that the market under-invests in it in favor of short term profits. It's obviously not a binary of either 100% government funding or 100% private; it's not even really a one-dimensional continuum, because for the large capital expenditures typically involved in research, the government always has a heavy involvement, either in tax breaks or grants or collaboration. The question is, how do we allocate money to produce the best research? It's undoubtedly at some value that's somewhere between 0% and 100%. 3) There's a whole lot of money floating around now that makes endeavors like SpaceX practicable. That wasn't the case in, say, the Sixties. Even if the arguments for government spending on research were weak now, they'd be stronger in the 1960's, particularly for things like space exploration that required substantial concentrations of capital.
tomasien 13y ago
I'm going to turn to Hacker News, as I always do, for context: what would 50% efficiency mean?
- brownBananas 13y ago
  Probably just a benchmark. Goal # 1: "At least get half the way there".
- ChuckMcM 13y ago
  Short answer is that more of the solar insolation that hits Earth gets converted into electricity. So on the equator its about 1kW per square meter, in North America closer to 700W sq Meter, and converted at 50% you would start at 350W per sq meter, which after rectification might be 300W per square meter.
- regularfry 13y ago
  Where nowadays you might put a 2kW installation on your roof (using 14%-ish efficient cells as are currently available), you'd be able to fit a 7kW installation in the same space, start putting 2kW installations on houses with much smaller available roof area, or start using solar effectively in much more overcast areas. 2kW is a usable approximation for the total power usage of an "average" house.
brownBananas 13y ago
Is the composition of this one solar cell from 4 subcells of any significance? Is it just 4 for a reason?
- chmod775 13y ago
  "The single subcells absorb different wavelength ranges of the solar spectrum."
- ars 13y ago
  The way a solar cell works is it absorbs only at one single frequency. Photons below that frequency are lost and not used at all. If the photon is above the frequency then the energy up to that cutoff is used and the rest is wasted (either emitted as a new photon or as heat). Meaning if you set the target frequency at infrared then you loose all the additional energy UV has over infrared. By making multiple layers (junctions) you waste less energy, the more the better (in theory anyway).
- mchannon 13y ago
  Imagine you have commissioned 100 different manufacturers to make you 100 different arbitrary Lego knockoffs; each manufacturer picks a color, thickness, and a peg pitch (spacing between the pegs). Each manufacturer only makes exactly one kind. Some manufacturers' legos will fit together, and some won't. Some manufacturers make theirs very cheaply and in mass quantities, and some will take years to deliver a very small number at very high prices. As a solar cell designer, you want to make a stack of these legos to form a rainbow. It has to go from blue on the top to red on the bottom, and it has to stack together without too much force. Think of a brand-X terrestrial Home Depot crystalline solar cell as just yellow lego bricks. They aren't the whole rainbow (and green would actually be a closer match to sunlight if you could only pick one color) but they're cheap. Gallium Arsenide legos are green, but they're really hard to make. Germanium legos are red, and it turns out that the green Gallium Arsenides fit on them really well. Yellow Silicon ones, on the other hand, don't fit well with either. So that brings us to two. Indium Phosphide legos are blue and so are Gallium Phosphide legos. But neither of those fit well on the green Gallium Arsenide; one's lego pins are too dense, the other too sparse. It took a long time for a manufacturer to come up with the right blend, thickness, and color, but they were able to come up with a lego that is blue, made from a mix called Indium Gallium Phosphide, and stacks nicely on top of the green Gallium Arsenide. So that's 3. The fourth layer might be Indium Gallium Arsenide Nitride (let's just call it orange), shoved between the existing layers; somehow making a mix of a good quality lego, but one that makes the right color, right thickness, and right pin pitch. Now to translate to real physics: The pin pitch is the lattice parameter of each of these crystals, or the distance between individual atoms. If you attempt to epitaxially grow (grow on top of in the same fashion) a different compound than what already exists there, it tends to work ok if the lattice parameters are close. If they're radically different, you can get growth but it's highly disordered and ends up making a lousy layer and a lousy solar cell.
greglindahl 13y ago
Odd that the figure says that the efficiency was 44.7% +/- 3.1% -- given the big error bar, how could they say they'd increased 1% in 4 months? Measure it again, who knows what you'll get!
- nazgulnarsil 13y ago
  ERROR BARS DO NOT WORK THAT WAY
  - asab 13y ago
    There aren't even error bars in the article's graphs
  - kyberias 13y ago
    Care to elaborate?
    - scythe 13y ago
      The +/- 3.1% is relative to the efficiency. The way to read it is: 0.447 +/- 3.1%, where now it's more obvious that it translates to more like 0.447 +/- 0.014.
      - greglindahl 13y ago
        Even if it really means 0.447 +/- 0.014, an increase of 0.01 is not very significant!
  - pkroll 13y ago
    +1 for the Futurama reference
sejje 13y ago
Maybe I missed it in the article, but what was considered a good efficiency prior to this?
- brownBananas 13y ago
  > Back in May 2013, the German-French team of Fraunhofer ISE, Soitec, CEA-Leti and the Helmholtz Center Berlin had already announced a solar cell with 43.6% efficiency. Read more at: http://phys.org/news/2013-09-world-solar-cell-efficiency.html#jCp http://phys.org/news/2013-09-world-solar-cell-efficiency.htm...
- diydsp 13y ago
  someone on wikipedia has been maintaining a beautiful image of the history of solar cell efficiency for various technologies.. let's see if this has been added yet. It looks 1. No, and 2. There was a recent discovery by Sharp of 44.4%. Main page: http://en.wikipedia.org/wiki/Solar_cell_efficiency http://en.wikipedia.org/wiki/Solar_cell_efficiency http://en.wikipedia.org/wiki/File:PVeff%28rev130923%29a.jpg http://en.wikipedia.org/wiki/File:PVeff%28rev130923%29a.jpg
  - contingencies 13y ago
    Image is credited to L.L. Kazmerski of the National Renewable Energy Laboratory (NREL), Golden, CO. Have a look at the types of markers shown on the image key again. While vast amounts of resources are being dumped on efficient electricity extraction through expensive, advanced manufacturing processes, some are looking at going back to organics, which NREL classes as 'emerging'. Apparently hybrid organic/electrical photovoltaics date back to 1958, and can produce 11.1% (roughly 1/3-1/2 of currently available manufactured products) efficiency while remaining cheap to produce at high volumes. Mitsubishi is one of the research leaders. More at https://en.wikipedia.org/wiki/Organic_solar_cell https://en.wikipedia.org/wiki/Organic_solar_cell
twelvechairs 13y ago
this is great but its worth noting that efficiency isn't really what's holding solar production back, its price. few peoples roofs are crammed with PV to the point where they can't fit more in.
- paul_f 13y ago
  This is the fundamental problem with PV. Compared to cheap natural gas, there just isn't much future in it
  - jussij 13y ago
    No Future? That might be true, except for that rather large elephant in the room call human-induced climate change.
    - diydsp 13y ago
      yes and PP presupposes "cheap natural gas." as witnessed by recent fracking-induced earthquakes [1] there may be very little cheap natural gas in the future. [1]http://www.sciencemag.org/content/341/6142/1225942 http://www.sciencemag.org/content/341/6142/1225942
    - tsotha 13y ago
      Pretty sure that was sarcasm.
  - fauigerzigerk 13y ago
    I don't understand what you see as a fundamental problem with PV. Prices for panels are dropping like a stone and efficiency is increasing. What's the fundamental problem?
  - frabcus 13y ago
    Price per watt of solar PV is on an exponentially improving trend line, since the late 1970s. http://cleantechnica.com/2013/05/24/solar-powers-massive-price-drop-graph/ http://cleantechnica.com/2013/05/24/solar-powers-massive-pri... Natural gas is, well, much less predictable. But hasn't gone below its 1990s price. http://www.tradingeconomics.com/commodity/natural-gas http://www.tradingeconomics.com/commodity/natural-gas
marcfawzi 13y ago
When will the world run out of the "III-V semiconductor materials" ? And which nation or corporation currently controls the largest deposits?
- diydsp 13y ago
  haha a legit question, but i guess you got downvoted because you could have researched it and shared it? dunno. anyway. not a chem dude at all, but it appears III-V semis are when you combine: "III-V compound semiconductors obtained by combining group III elements (essentially Al, Ga, In) with group V elements (essentially N, P , As, Sb). This gives us 12 possible combinations; the most important ones are probably GaAs, InP GaP and GaN." [1] In other words, the materials in general are: Nitrogen, Phosphorus, Antimony, Arsenic, Bismuth, Boron, Aluminum, Gallium, Indium and Thallium. I imagine nitrogen, phosphorus and aluminum are the easiest to find generally throughout the world. China appears to control 90% of antimony [2] and its price seems to have gone up 700% over the last decade. Arsenic seems to have major supply issues, one of the most critical in terms of scarcity according to [3] and [4]. Nevertheless, the price has gone down over the last 100 years significantly and according to this source is less scarce than it was a century ago: [5] Bismuth is "relatively rare" but doesn't appear to be scarce. it is found mostly in Peru Japan Mexico, Canada, Bolivia and not in the USA. [6] remaining elements are left as an exercise to the reader. [1] http://www.tf.uni-kiel.de/matwis/amat/semitech_en/kap_2/backbone/r2_3_1.html http://www.tf.uni-kiel.de/matwis/amat/semitech_en/kap_2/back... [2]http://www.tf.uni-kiel.de/matwis/amat/semitech_en/kap_2/backbone/r2_3_1.html http://www.tf.uni-kiel.de/matwis/amat/semitech_en/kap_2/back... [3]http://www.acs.org/content/acs/en/pressroom/presspacs/2012/acs-presspac-february-8-2012/arsenic-criticality-poses-concern-for-modern-technology.html http://www.acs.org/content/acs/en/pressroom/presspacs/2012/a... [4]http://environment.yale.edu/news/article/arsenic-supply-at-risk/ http://environment.yale.edu/news/article/arsenic-supply-at-r... [5]http://theunbrokenwindow.com/2010/03/08/running-out-of-resources-arsenic-edition/ http://theunbrokenwindow.com/2010/03/08/running-out-of-resou... [6]http://www.carondelet.pvt.k12.ca.us/Family/Science/Nitrogen/bismuth.html http://www.carondelet.pvt.k12.ca.us/Family/Science/Nitrogen/...
- cauthonLuck 13y ago
  That is the question. All of the materials are expensive themselves (gallium, indium) or expensive to process ( silicon) - which means these cells will never scale and replace oil. Which is why dye-sensitized solar cells are such a promising alternative, despite their lower single module efficiencies of ~15% (20-30% for the expensive semiconductors discussed in OP). http://en.wikipedia.org/wiki/Dye-sensitized_solar_cell http://en.wikipedia.org/wiki/Dye-sensitized_solar_cell
SamuelKillin 13y ago
Good on them. In reality, however, fuel from the sun is free and we have unlimited land. Getting the cost down and economies of scale are what everyone is really focussed on.
- idProQuo 13y ago
  We have unlimited land, but I don't think we have unlimited Silicon with which to cover it.
  - baq 13y ago
    sahara has all the land and all the silicon you may need.
- tsotha 13y ago
  Who has unlimited land?
  - Nikker 13y ago
    Sprint? Maybe Verizon?
  - SamuelKillin 13y ago
    I'm in Australia. We have unlimited land and enough sun to power the solar system.
    - tsotha 13y ago
      You guys might be one of the few countries with effectively unlimited land. But remember the power has to get from where it's generated to where it's needed.
- snowwrestler 13y ago
  From a policy perspecive, land is probably one of the biggest factors limiting large-scale PV installations in the U.S. Basically, every square meter of land in the U.S. is already being used for something that people will defend, even if it is sparse desert land. Sparse desert land is a natural ecosystem, and there are many people and nonprofits who work hard to protect natural ecosystems from disruption by man.
dgreensp 13y ago
So when does solar power become cheap and efficient enough that it's a real game changer? It seems like the numbers have gotten a lot better in recent years, at least in terms of efficiency.
- jacquesm 13y ago
  Price per Watt of installed PV is what drives adoption so with efficiency as one term in there (Wattage output is a direct result of efficiency) the remaining ones (lifespan, efficiency over lifespan and production costs / unit area of panel) are still problematic enough to slow down wholesale adoption. To some extent this is right now offset by subsidies, you'll know that it has arrived when the subsidies are stopped and adoption still increases.
- danielharan 13y ago
  We're at a tipping point already. What's helped the most recently is financing. Solar is already cheaper than retail in a few states; see e.g. this map that lets you play with dates and scenarios: http://ilsr.org/projects/solarparitymap/ http://ilsr.org/projects/solarparitymap/ As for game changers, see e.g. http://www.greentechmedia.com/articles/read/are-utilities-ready-for-the-coming-death-spiral http://www.greentechmedia.com/articles/read/are-utilities-re... http://grist.org/climate-energy/solar-panels-could-destroy-u-s-utilities-according-to-u-s-utilities/ http://grist.org/climate-energy/solar-panels-could-destroy-u...
- tsotha 13y ago
  Solar is already cheaper in most places provided you have net metering, which is a subsidy. But there's a limit to how many people can use the grid for free.
  - evolve2k 13y ago
    Don't forget to take into account that grid connected solar houses feed excess power produced into the grid, there's no free about it, these are essentially micro power stations which enhance the grid.
officialjunk 13y ago
Now combine this with IBM's research to collect most of the energy lost to heat production and push the efficiency up to 80% http://arstechnica.com/science/2013/04/ibms-solar-tech-is-80-efficient-thanks-to-supercomputer-know-how/ http://arstechnica.com/science/2013/04/ibms-solar-tech-is-80...
ck2 13y ago
While nearly 45% is impressive, I'd rather see "cheap as paint" solar cells at 10% efficiency that are football fields in size. Put them on every commercial rooftop and all that free space we have out west in the USA.
- deleted 13y ago
  [deleted]
- dmckeon 13y ago
  It is an interesting challenge for a PV-curious homeowner - if efficiency is increasing, and capital costs are dropping, and assuming that rooftop cells might eventually need replacing - it is better to cover one's roof all at once with current tech, or to start smaller and plan to add new panels over time until the roof is full, and then start replacing old panels? Local variables would probably predominate, along with loan/lease/financing and ability to resell.
rocco 13y ago
Guys, anyone knows the sense of "measured at a concentration of 297 suns."? is sufficient much less energy to transform the earth in a giant BBQ.
- asab 13y ago
  My question too - I wonder how it would perform in normal sunlight.
  - mchannon 13y ago
    Concentrator cells make a number of tradeoffs in order to make their performance as high as possible (and keep from melting, etc.). I would guess around 22% efficient in one-sun AM1.0; that's about what other concentrator cells in this upper tier do. If it's slightly cloudy, I could see efficiencies dropping to the single digits, as each of these cells is actually four different cells all wired in series, each sensitive to different wavelengths of light. If the blue drops out, the corresponding cell on the top of the stack acts as a resistor (and it can even burn out, being so thin). Solar cell efficiency records (particularly for concentrator applications) are like discovering new transuranic elements- extremely useful and interesting at first, then significantly diminishing returns.
- regularfry 13y ago
  It's a concentrator cell, so it's designed to be used with reflectors or lenses to increase the sunlight capture area. A rough rule of thumb is that you get 1kW/m^2 of raw sunlight, so to get reasonable powers (in the MW+ range) out of a solar installation without needing an enormous solar cell budget, you need cheap concentrators of some sort.
dredmorbius 13y ago
For those wondering about the significance of this announcement: As several people have noted, what matters for solar PV isn't efficiency but cost per Watt. The maximum available energy is 1W/meter^2 at ground. Single-layer PV efficiency is on the order of about 40%. Mutliple-layer cells can reach a maximum of around 80%. Even with existing efficiencies, the land space necessary to dedicate to solar power for all electrical energy needs is reasonably small. A percent or so of the Earth's surface. The hard part will be fabricating the PV and/or CSP (concentrated solar thermal power) plants to collect that energy, estimates run well over $100 trillion globally (Jacobson & Delucchi). A key limiting factor in solar, wind, and other intermittent renewables is storage (or baseload / standby power). Assuming you'd want 7 days' total energy output on reserve, there's quite literally not enough lead in the world to build storage for just the US, let alone the rest of the world. Pumped hydro storage is very efficient, but sites are limited. Biomass similarly doesn't scale to present populations. Geothermal is good for 5-20% of power demands depending on locations (and some places such as Iceland might be able to export energy). Thorium reactors look like a plausible bet but require development. Liquid metal / molten salt batteries (such as Donald Sadoway's designs) look like they're both cheap and abundant enough to make the grade, though they're still under development as well. Solar power does have its equivalent of Moore's Law: Swanson's Law. Solar PV costs fall by 20% with each doubling of capacity. It's held since the 1970s and looks likely to continue. Effectively, costs half about every 3 years. http://www.economist.com/blogs/graphicdetail/2012/12/daily-chart-19/print http://www.economist.com/blogs/graphicdetail/2012/12/daily-c... In short: this is mostly of significance for applications in which space and/or weight are at a premium: satellite or possibly solar-powered aircraft (ultralights or airships most likely). For ground-based generation, look for costs to come down further. And pray for highly effective storage solutions.
- anovikov 13y ago
  Not true at all. Your statement about available land is correct of course, but the important part of picture is that the soft costs for construction of solar electric power plants are already much higher than hard costs. And, improving efficiency is a great way to cut them. Imagine a 10 MW power plant built out of panels with 10% efficiency. If you replace them with 20% efficient panels, you increase output 2x without measurably increasing soft costs - like land provision, fixtures on which the panels stand, installation work, insurance, etc. Only part that will increase will be inverters (not a particulary big item) and thicker cables connecting it to the grid. So, soft costs per watt will fall by 40-45%. So, given that the wholesale price of solar panels now stand at 40 cent per watt, and even in cheapest countries the complete plant is $2 per watt, increasing efficiencies 2x means building a 2x more powerful plant for about $1.4 per watt (soft costs fall from $1.6 to $1.0 - i.e. they slightly increase but power output doubles) and hard costs stay the same. Big deal. And almost all of the progress in solar power costs we can have now lies in this field - increase of panel efficiency, not decreasing their costs. Even if panels were free, costs won't fall much... Of course this article bears no relation to that - these are high concentration cells, and cost to build collectors is already much higher than just buying enough of flat panels... better show me a non-concentrated cell with at least 35% efficiency.
paras111 13y ago
Great news...
cauthonLuck 13y ago
recent improvements in all solid state dye-sensitized solar cells show more potential for lowering the cost of solar energy.

177 points by X4 13y ago

"These solar cells are used in concentrator photovoltaics (CPV), a technology which achieves more than twice the efficiency of conventional PV power plants in sun-rich locations. The terrestrial use of so-called III-V multi-junction solar cells, which originally came from space technology, has prevailed to realize highest efficiencies for the conversion of sunlight to electricity. In this multi-junction solar cell, several cells made out of different III-V semiconductor materials are stacked on top of each other. The single subcells absorb different wavelength ranges of the solar spectrum." If that isn't a reason to be investing in Space, I don't know what is. "This world record increasing our efficiency level by more than 1 point in less than 4 months..." I think we may start to see Moore's Law starting to be applied to Solar Cells. Which actually reminds of a chart on the waves of innovation[1] on the Stanford Tech Entrepreneurship course where we are now seeing the tail of IT and computing and beginning of renewable technologies. The same thing can be said about energy density of batteries(According to Tesla batteries). [1] Page 5 https://d2d6mu5qcvgbk5.cloudfront.net/documents/original/69bd3725d86ab970f2d9509424bb67ae4c832faa.pdf?1377910658 https://d2d6mu5qcvgbk5.cloudfront.net/documents/original/69b...

killerswan 13y ago
It is indeed interesting, but IIRC most of the funding for satellite launches (R&D for III-V semiconductors) came from intelligence, not NASA. So, um, thank you, NSA! :P
- hrkristian 13y ago
  What with their love for predictability, it's no wonder they're strong supporters of the sun.
- hxc 13y ago
  I would rather dump trillions of dollars into NASA and their tech :D.
- D9u 13y ago
  I thought it was the NRO? http://www.nro.gov/about/ http://www.nro.gov/about/
wyager 13y ago
>I think we may start to see Moore's Law starting to be applied to Solar Cells. It would have to be a kind of inverse Moore's law, given that you can't double beyond 100%.
- TheLegace 13y ago
  I guess what I really mean was exponential increase in gains.
  - markfx 13y ago
    Moore's law describes a polynomial increase, not exponential.
    - ScottBurson 13y ago
      I'm afraid you're mistaken. Doubling every 18 months is an exponential progression.
- gilgoomesh 13y ago
  It's worse than that. There's no room for a single doubling of 44% efficiency. The theoretical maximum for multi-junction concentrator cells is about 86%: https://en.wikipedia.org/wiki/Shockley–Queisser_limit https://en.wikipedia.org/wiki/Shockley–Queisser_limit For single junction cells it's a mere 33%.
  - MikeCapone 13y ago
    Efficiency matters, but price/watt matters more and there's still room for a kind of moore's law there.
    - jnw2 13y ago
      Which of efficiency or price/watt matters more depends on the application. For example, I believe something like 4 m^2, 40% efficient, 8 hours of charging is enough to get electricity to drive a Tesla something like 30-40 miles. (In practice, I assume you'd cover all of the outside of the car with 40% efficient solar panels to make this work (or maybe even 80% if you can figure out how to build them), and then 4 m^2 approximates the effective useful area after you take into account suboptimal sun angle, the side of the car facing away from the sun, etc.) The number of people whose commutes could be entirely covered by 40% efficient solar panels built into the car being used to recharge the battery is a lot more than the number of people whose commutes could be covered entirely by 12-15% efficient solar panels. Current mass produced technology doesn't make any variation on this cost effective today, but it seems clear that in the future, a 12% efficient panel array built into a Tesla is never going to be all that attractive for this application no matter how cheap it might become. I suspect that high rise apartment buildings can cover a much larger percentage of their energy consumption from solar panels mounted on their sides and roof if those solar panels are 40-80% efficient instead of 12-15% efficient. If localized solar right next to the consumer of the power becomes cheaper than paying for electric grid transmission, this may become very relevant in 10 or 20 years. Even for residential suburban solar installation, where finding adequate space for an adequate quantity 12% efficient solar panels is generally not a problem, the really important thing is not the price per watt of the panels themselves, but the price per watt of the system as a whole. The mechanical support of the panels is a part of the system cost, and the cost of that portion will shrink with more efficient solar panels, though of course there is an open question as to whether that will end up lowering the total system cost or not in the long run.
MysticFear 13y ago
There are many reasons to be investing in NASA. They actually have subdomain devoted to highlighting their spinoff technologies. http://spinoff.nasa.gov/ http://spinoff.nasa.gov/
dpatru 13y ago
> If that isn't a reason to be investing in Space, I don't know what is. To justify government research, the results need to be compared to the alternative. Had NASA scientists not been working for the government, they would have been working for private companies engaged doing useful work. The Soviet Union had similar resources to the US, yet their research budget was spent wholly by government, whereas a large portion of the US research during that time was directed by private companies. If you want to restrict the comparison just to the US, ask yourself what would the massive wealth that was dedicated to NASA had produced had it been directed by private interests? What would NASA engineers have produced had they been employed by in Y-Combinator-style startups? (or even big private companies like Google, Apple, Facebook, Amazon, etc.)
- eru 13y ago
  > (or even big private companies like Google, Apple, Facebook, Amazon, etc.) Or IBM, or everyone's favourite, Tesla. A similar argument always crops up with people always looking at how much technology came out of war-time efforts. The opportunity costs are huge.
- nitrogen 13y ago
  While you're considering alternatives, what would the massive wealth dedicated to the DOD have done in the hands of NASA and private non-military researchers?
- scarmig 13y ago
  A couple points: 1) It's not like the Soviet Union was a terrible hellhole for research. It had impressive research output for decades. 2) That's almost beside the point, however. Let's take it as a given that more good research, whatever that is, is a worthy goal for a society, and that the market under-invests in it in favor of short term profits. It's obviously not a binary of either 100% government funding or 100% private; it's not even really a one-dimensional continuum, because for the large capital expenditures typically involved in research, the government always has a heavy involvement, either in tax breaks or grants or collaboration. The question is, how do we allocate money to produce the best research? It's undoubtedly at some value that's somewhere between 0% and 100%. 3) There's a whole lot of money floating around now that makes endeavors like SpaceX practicable. That wasn't the case in, say, the Sixties. Even if the arguments for government spending on research were weak now, they'd be stronger in the 1960's, particularly for things like space exploration that required substantial concentrations of capital.

tomasien 13y ago

I'm going to turn to Hacker News, as I always do, for context: what would 50% efficiency mean?

brownBananas 13y ago
Probably just a benchmark. Goal # 1: "At least get half the way there".
ChuckMcM 13y ago
Short answer is that more of the solar insolation that hits Earth gets converted into electricity. So on the equator its about 1kW per square meter, in North America closer to 700W sq Meter, and converted at 50% you would start at 350W per sq meter, which after rectification might be 300W per square meter.
regularfry 13y ago
Where nowadays you might put a 2kW installation on your roof (using 14%-ish efficient cells as are currently available), you'd be able to fit a 7kW installation in the same space, start putting 2kW installations on houses with much smaller available roof area, or start using solar effectively in much more overcast areas. 2kW is a usable approximation for the total power usage of an "average" house.

brownBananas 13y ago

Is the composition of this one solar cell from 4 subcells of any significance? Is it just 4 for a reason?

chmod775 13y ago
"The single subcells absorb different wavelength ranges of the solar spectrum."
ars 13y ago
The way a solar cell works is it absorbs only at one single frequency. Photons below that frequency are lost and not used at all. If the photon is above the frequency then the energy up to that cutoff is used and the rest is wasted (either emitted as a new photon or as heat). Meaning if you set the target frequency at infrared then you loose all the additional energy UV has over infrared. By making multiple layers (junctions) you waste less energy, the more the better (in theory anyway).
mchannon 13y ago
Imagine you have commissioned 100 different manufacturers to make you 100 different arbitrary Lego knockoffs; each manufacturer picks a color, thickness, and a peg pitch (spacing between the pegs). Each manufacturer only makes exactly one kind. Some manufacturers' legos will fit together, and some won't. Some manufacturers make theirs very cheaply and in mass quantities, and some will take years to deliver a very small number at very high prices. As a solar cell designer, you want to make a stack of these legos to form a rainbow. It has to go from blue on the top to red on the bottom, and it has to stack together without too much force. Think of a brand-X terrestrial Home Depot crystalline solar cell as just yellow lego bricks. They aren't the whole rainbow (and green would actually be a closer match to sunlight if you could only pick one color) but they're cheap. Gallium Arsenide legos are green, but they're really hard to make. Germanium legos are red, and it turns out that the green Gallium Arsenides fit on them really well. Yellow Silicon ones, on the other hand, don't fit well with either. So that brings us to two. Indium Phosphide legos are blue and so are Gallium Phosphide legos. But neither of those fit well on the green Gallium Arsenide; one's lego pins are too dense, the other too sparse. It took a long time for a manufacturer to come up with the right blend, thickness, and color, but they were able to come up with a lego that is blue, made from a mix called Indium Gallium Phosphide, and stacks nicely on top of the green Gallium Arsenide. So that's 3. The fourth layer might be Indium Gallium Arsenide Nitride (let's just call it orange), shoved between the existing layers; somehow making a mix of a good quality lego, but one that makes the right color, right thickness, and right pin pitch. Now to translate to real physics: The pin pitch is the lattice parameter of each of these crystals, or the distance between individual atoms. If you attempt to epitaxially grow (grow on top of in the same fashion) a different compound than what already exists there, it tends to work ok if the lattice parameters are close. If they're radically different, you can get growth but it's highly disordered and ends up making a lousy layer and a lousy solar cell.

greglindahl 13y ago

Odd that the figure says that the efficiency was 44.7% +/- 3.1% -- given the big error bar, how could they say they'd increased 1% in 4 months? Measure it again, who knows what you'll get!

nazgulnarsil 13y ago
ERROR BARS DO NOT WORK THAT WAY
- asab 13y ago
  There aren't even error bars in the article's graphs
- kyberias 13y ago
  Care to elaborate?
  - scythe 13y ago
    The +/- 3.1% is relative to the efficiency. The way to read it is: 0.447 +/- 3.1%, where now it's more obvious that it translates to more like 0.447 +/- 0.014.
    - greglindahl 13y ago
      Even if it really means 0.447 +/- 0.014, an increase of 0.01 is not very significant!
- pkroll 13y ago
  +1 for the Futurama reference

sejje 13y ago

Maybe I missed it in the article, but what was considered a good efficiency prior to this?

brownBananas 13y ago
> Back in May 2013, the German-French team of Fraunhofer ISE, Soitec, CEA-Leti and the Helmholtz Center Berlin had already announced a solar cell with 43.6% efficiency. Read more at: http://phys.org/news/2013-09-world-solar-cell-efficiency.html#jCp http://phys.org/news/2013-09-world-solar-cell-efficiency.htm...
diydsp 13y ago
someone on wikipedia has been maintaining a beautiful image of the history of solar cell efficiency for various technologies.. let's see if this has been added yet. It looks 1. No, and 2. There was a recent discovery by Sharp of 44.4%. Main page: http://en.wikipedia.org/wiki/Solar_cell_efficiency http://en.wikipedia.org/wiki/Solar_cell_efficiency http://en.wikipedia.org/wiki/File:PVeff%28rev130923%29a.jpg http://en.wikipedia.org/wiki/File:PVeff%28rev130923%29a.jpg
- contingencies 13y ago
  Image is credited to L.L. Kazmerski of the National Renewable Energy Laboratory (NREL), Golden, CO. Have a look at the types of markers shown on the image key again. While vast amounts of resources are being dumped on efficient electricity extraction through expensive, advanced manufacturing processes, some are looking at going back to organics, which NREL classes as 'emerging'. Apparently hybrid organic/electrical photovoltaics date back to 1958, and can produce 11.1% (roughly 1/3-1/2 of currently available manufactured products) efficiency while remaining cheap to produce at high volumes. Mitsubishi is one of the research leaders. More at https://en.wikipedia.org/wiki/Organic_solar_cell https://en.wikipedia.org/wiki/Organic_solar_cell

twelvechairs 13y ago

this is great but its worth noting that efficiency isn't really what's holding solar production back, its price. few peoples roofs are crammed with PV to the point where they can't fit more in.

paul_f 13y ago
This is the fundamental problem with PV. Compared to cheap natural gas, there just isn't much future in it
- jussij 13y ago
  No Future? That might be true, except for that rather large elephant in the room call human-induced climate change.
  - diydsp 13y ago
    yes and PP presupposes "cheap natural gas." as witnessed by recent fracking-induced earthquakes [1] there may be very little cheap natural gas in the future. [1]http://www.sciencemag.org/content/341/6142/1225942 http://www.sciencemag.org/content/341/6142/1225942
  - tsotha 13y ago
    Pretty sure that was sarcasm.
- fauigerzigerk 13y ago
  I don't understand what you see as a fundamental problem with PV. Prices for panels are dropping like a stone and efficiency is increasing. What's the fundamental problem?
- frabcus 13y ago
  Price per watt of solar PV is on an exponentially improving trend line, since the late 1970s. http://cleantechnica.com/2013/05/24/solar-powers-massive-price-drop-graph/ http://cleantechnica.com/2013/05/24/solar-powers-massive-pri... Natural gas is, well, much less predictable. But hasn't gone below its 1990s price. http://www.tradingeconomics.com/commodity/natural-gas http://www.tradingeconomics.com/commodity/natural-gas

marcfawzi 13y ago

When will the world run out of the "III-V semiconductor materials" ? And which nation or corporation currently controls the largest deposits?

diydsp 13y ago
haha a legit question, but i guess you got downvoted because you could have researched it and shared it? dunno. anyway. not a chem dude at all, but it appears III-V semis are when you combine: "III-V compound semiconductors obtained by combining group III elements (essentially Al, Ga, In) with group V elements (essentially N, P , As, Sb). This gives us 12 possible combinations; the most important ones are probably GaAs, InP GaP and GaN." [1] In other words, the materials in general are: Nitrogen, Phosphorus, Antimony, Arsenic, Bismuth, Boron, Aluminum, Gallium, Indium and Thallium. I imagine nitrogen, phosphorus and aluminum are the easiest to find generally throughout the world. China appears to control 90% of antimony [2] and its price seems to have gone up 700% over the last decade. Arsenic seems to have major supply issues, one of the most critical in terms of scarcity according to [3] and [4]. Nevertheless, the price has gone down over the last 100 years significantly and according to this source is less scarce than it was a century ago: [5] Bismuth is "relatively rare" but doesn't appear to be scarce. it is found mostly in Peru Japan Mexico, Canada, Bolivia and not in the USA. [6] remaining elements are left as an exercise to the reader. [1] http://www.tf.uni-kiel.de/matwis/amat/semitech_en/kap_2/backbone/r2_3_1.html http://www.tf.uni-kiel.de/matwis/amat/semitech_en/kap_2/back... [2]http://www.tf.uni-kiel.de/matwis/amat/semitech_en/kap_2/backbone/r2_3_1.html http://www.tf.uni-kiel.de/matwis/amat/semitech_en/kap_2/back... [3]http://www.acs.org/content/acs/en/pressroom/presspacs/2012/acs-presspac-february-8-2012/arsenic-criticality-poses-concern-for-modern-technology.html http://www.acs.org/content/acs/en/pressroom/presspacs/2012/a... [4]http://environment.yale.edu/news/article/arsenic-supply-at-risk/ http://environment.yale.edu/news/article/arsenic-supply-at-r... [5]http://theunbrokenwindow.com/2010/03/08/running-out-of-resources-arsenic-edition/ http://theunbrokenwindow.com/2010/03/08/running-out-of-resou... [6]http://www.carondelet.pvt.k12.ca.us/Family/Science/Nitrogen/bismuth.html http://www.carondelet.pvt.k12.ca.us/Family/Science/Nitrogen/...
cauthonLuck 13y ago
That is the question. All of the materials are expensive themselves (gallium, indium) or expensive to process ( silicon) - which means these cells will never scale and replace oil. Which is why dye-sensitized solar cells are such a promising alternative, despite their lower single module efficiencies of ~15% (20-30% for the expensive semiconductors discussed in OP). http://en.wikipedia.org/wiki/Dye-sensitized_solar_cell http://en.wikipedia.org/wiki/Dye-sensitized_solar_cell

SamuelKillin 13y ago

Good on them. In reality, however, fuel from the sun is free and we have unlimited land. Getting the cost down and economies of scale are what everyone is really focussed on.

idProQuo 13y ago
We have unlimited land, but I don't think we have unlimited Silicon with which to cover it.
- baq 13y ago
  sahara has all the land and all the silicon you may need.
tsotha 13y ago
Who has unlimited land?
- Nikker 13y ago
  Sprint? Maybe Verizon?
- SamuelKillin 13y ago
  I'm in Australia. We have unlimited land and enough sun to power the solar system.
  - tsotha 13y ago
    You guys might be one of the few countries with effectively unlimited land. But remember the power has to get from where it's generated to where it's needed.
snowwrestler 13y ago
From a policy perspecive, land is probably one of the biggest factors limiting large-scale PV installations in the U.S. Basically, every square meter of land in the U.S. is already being used for something that people will defend, even if it is sparse desert land. Sparse desert land is a natural ecosystem, and there are many people and nonprofits who work hard to protect natural ecosystems from disruption by man.

dgreensp 13y ago

So when does solar power become cheap and efficient enough that it's a real game changer? It seems like the numbers have gotten a lot better in recent years, at least in terms of efficiency.

jacquesm 13y ago
Price per Watt of installed PV is what drives adoption so with efficiency as one term in there (Wattage output is a direct result of efficiency) the remaining ones (lifespan, efficiency over lifespan and production costs / unit area of panel) are still problematic enough to slow down wholesale adoption. To some extent this is right now offset by subsidies, you'll know that it has arrived when the subsidies are stopped and adoption still increases.
danielharan 13y ago
We're at a tipping point already. What's helped the most recently is financing. Solar is already cheaper than retail in a few states; see e.g. this map that lets you play with dates and scenarios: http://ilsr.org/projects/solarparitymap/ http://ilsr.org/projects/solarparitymap/ As for game changers, see e.g. http://www.greentechmedia.com/articles/read/are-utilities-ready-for-the-coming-death-spiral http://www.greentechmedia.com/articles/read/are-utilities-re... http://grist.org/climate-energy/solar-panels-could-destroy-u-s-utilities-according-to-u-s-utilities/ http://grist.org/climate-energy/solar-panels-could-destroy-u...
tsotha 13y ago
Solar is already cheaper in most places provided you have net metering, which is a subsidy. But there's a limit to how many people can use the grid for free.
- evolve2k 13y ago
  Don't forget to take into account that grid connected solar houses feed excess power produced into the grid, there's no free about it, these are essentially micro power stations which enhance the grid.

officialjunk 13y ago

Now combine this with IBM's research to collect most of the energy lost to heat production and push the efficiency up to 80% http://arstechnica.com/science/2013/04/ibms-solar-tech-is-80-efficient-thanks-to-supercomputer-know-how/ http://arstechnica.com/science/2013/04/ibms-solar-tech-is-80...

ck2 13y ago

While nearly 45% is impressive, I'd rather see "cheap as paint" solar cells at 10% efficiency that are football fields in size. Put them on every commercial rooftop and all that free space we have out west in the USA.

deleted 13y ago
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dmckeon 13y ago
It is an interesting challenge for a PV-curious homeowner - if efficiency is increasing, and capital costs are dropping, and assuming that rooftop cells might eventually need replacing - it is better to cover one's roof all at once with current tech, or to start smaller and plan to add new panels over time until the roof is full, and then start replacing old panels? Local variables would probably predominate, along with loan/lease/financing and ability to resell.

rocco 13y ago

Guys, anyone knows the sense of "measured at a concentration of 297 suns."? is sufficient much less energy to transform the earth in a giant BBQ.

asab 13y ago
My question too - I wonder how it would perform in normal sunlight.
- mchannon 13y ago
  Concentrator cells make a number of tradeoffs in order to make their performance as high as possible (and keep from melting, etc.). I would guess around 22% efficient in one-sun AM1.0; that's about what other concentrator cells in this upper tier do. If it's slightly cloudy, I could see efficiencies dropping to the single digits, as each of these cells is actually four different cells all wired in series, each sensitive to different wavelengths of light. If the blue drops out, the corresponding cell on the top of the stack acts as a resistor (and it can even burn out, being so thin). Solar cell efficiency records (particularly for concentrator applications) are like discovering new transuranic elements- extremely useful and interesting at first, then significantly diminishing returns.
regularfry 13y ago
It's a concentrator cell, so it's designed to be used with reflectors or lenses to increase the sunlight capture area. A rough rule of thumb is that you get 1kW/m^2 of raw sunlight, so to get reasonable powers (in the MW+ range) out of a solar installation without needing an enormous solar cell budget, you need cheap concentrators of some sort.

dredmorbius 13y ago

For those wondering about the significance of this announcement: As several people have noted, what matters for solar PV isn't efficiency but cost per Watt. The maximum available energy is 1W/meter^2 at ground. Single-layer PV efficiency is on the order of about 40%. Mutliple-layer cells can reach a maximum of around 80%. Even with existing efficiencies, the land space necessary to dedicate to solar power for all electrical energy needs is reasonably small. A percent or so of the Earth's surface. The hard part will be fabricating the PV and/or CSP (concentrated solar thermal power) plants to collect that energy, estimates run well over $100 trillion globally (Jacobson & Delucchi). A key limiting factor in solar, wind, and other intermittent renewables is storage (or baseload / standby power). Assuming you'd want 7 days' total energy output on reserve, there's quite literally not enough lead in the world to build storage for just the US, let alone the rest of the world. Pumped hydro storage is very efficient, but sites are limited. Biomass similarly doesn't scale to present populations. Geothermal is good for 5-20% of power demands depending on locations (and some places such as Iceland might be able to export energy). Thorium reactors look like a plausible bet but require development. Liquid metal / molten salt batteries (such as Donald Sadoway's designs) look like they're both cheap and abundant enough to make the grade, though they're still under development as well. Solar power does have its equivalent of Moore's Law: Swanson's Law. Solar PV costs fall by 20% with each doubling of capacity. It's held since the 1970s and looks likely to continue. Effectively, costs half about every 3 years. http://www.economist.com/blogs/graphicdetail/2012/12/daily-chart-19/print http://www.economist.com/blogs/graphicdetail/2012/12/daily-c... In short: this is mostly of significance for applications in which space and/or weight are at a premium: satellite or possibly solar-powered aircraft (ultralights or airships most likely). For ground-based generation, look for costs to come down further. And pray for highly effective storage solutions.

anovikov 13y ago
Not true at all. Your statement about available land is correct of course, but the important part of picture is that the soft costs for construction of solar electric power plants are already much higher than hard costs. And, improving efficiency is a great way to cut them. Imagine a 10 MW power plant built out of panels with 10% efficiency. If you replace them with 20% efficient panels, you increase output 2x without measurably increasing soft costs - like land provision, fixtures on which the panels stand, installation work, insurance, etc. Only part that will increase will be inverters (not a particulary big item) and thicker cables connecting it to the grid. So, soft costs per watt will fall by 40-45%. So, given that the wholesale price of solar panels now stand at 40 cent per watt, and even in cheapest countries the complete plant is $2 per watt, increasing efficiencies 2x means building a 2x more powerful plant for about $1.4 per watt (soft costs fall from $1.6 to $1.0 - i.e. they slightly increase but power output doubles) and hard costs stay the same. Big deal. And almost all of the progress in solar power costs we can have now lies in this field - increase of panel efficiency, not decreasing their costs. Even if panels were free, costs won't fall much... Of course this article bears no relation to that - these are high concentration cells, and cost to build collectors is already much higher than just buying enough of flat panels... better show me a non-concentrated cell with at least 35% efficiency.

paras111 13y ago

Great news...

cauthonLuck 13y ago

recent improvements in all solid state dye-sensitized solar cells show more potential for lowering the cost of solar energy.