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Google Challenge Results In Astoundingly Efficient Inverters

AmiMoJo writes: A few summers ago, Google and IEEE announced a one million dollar prize to build the most efficient and compact DC to AC inverter. It was called the Little Box Challenge, with the goal of a 2kW inverter with a power density greater than 50 Watts per cubic inch. Typical solar inverters have a density of about 5 W/cubic inch. Now the results are in, with the winners hitting 143 W/cubic inch using GaN transistors, and two other teams meeting Google's goal.

46 of 245 comments (clear)

  1. Efficiency by fyngyrz · · Score: 4, Insightful

    Astoundingly Efficient Inverters

    This doesn't seem to be about efficiency at all, but rather about power density (how much power can be converted in a particular cubic volume.)

    Not that small isn't a worthy goal, but efficiency is important in any application where available power isn't both free and copiously oversupplied.

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    1. Re:Efficiency by guruevi · · Score: 3, Insightful

      Don't they go hand-in-hand though? You can only dissipate so much (waste) energy in a particular cubic volume. Decreasing the amount of waste energy increases the amount you can pack together. It wouldn't be a challenge if you're just looking for miniaturization.

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    2. Re:Efficiency by Stewie241 · · Score: 2

      Yeah... from the website:

      INTRODUCING THE LITTLE BOX CHALLENGE

      An open competition to build a (much) smaller power inverter, with a $1,000,000 prize.

      Design and build a kW-scale inverter with the highest power density (at least 50 Watts per cubic inch).

      Efficiency is not mentioned anywhere. I see somebody arguing that efficient with space is still being efficient. This is true, but is not what is commonly meant when referring to the efficient of an inverter, and misusing the word in this context is confusing.

    3. Re:Efficiency by PIBM · · Score: 5, Informative

      If you had read the challenge when it was proposed (or went to read the rules), the efficiency was required to be > 95%

      . Produce a DCAC conversion efficiency of > 95%

      From https://www.littleboxchallenge...

    4. Re:Efficiency by slashkitty · · Score: 4, Informative

      95.4% efficient in the conversion per the Datasheet http://littleboxchallengecetpo...

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    5. Re:Efficiency by DeathToBill · · Score: 3, Interesting

      Maybe, though Hack-a-Day say it involves an "incredible thermal management solution," which doesn't sound like they've actually bumped the energy efficiency up that much.

      Why were Google so keen to have an inverter that maximises power density? Why not maximise energy efficiency?

      Ideally you'd like to minimise cost of energy. But I guess it's fairly difficult to construct a competition around this: It depends too much on production scale and the prevailing cost of electricity. But why power density as a substitute?

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    6. Re:Efficiency by Anonymous Coward · · Score: 5, Informative

      From the website https://www.littleboxchallenge.com/:

      In brief, the other specifications are :

      * Must be able to handle up to 2 kVA loads
      * Must achieve a power density of equal to or greater than 50 W/in3
      * Must be able to handle loads with power factors from 0.7–1, leading and lagging in an islanded mode
      * Must be in a rectangular metal enclosure of no more than 40 in3
      * Will be taking in 450 V DC power in series with a 10 O resistor
      * Must output 240 V, 60 Hz AC single phase power
      * Must have a total harmonic distortion + noise on both voltage and current of 5%
      * Must have an input ripple current of 20%
      * Must have an input ripple voltage of 3%
      * Must have a DC-AC efficiency of greater than 95%
      * Must maintain a temperature of no more than 60C during operation everywhere on the outside of the device that can be touched.
      * Must conform to Electromagnetic Compliance standards as set out in FCC Part 15 B
      * Can not use any external source of cooling (e.g. water) other than air
      * Does not require galvanic isolation

    7. Re:Efficiency by Stewie241 · · Score: 4, Insightful

      Ah, I didn't look that closely to see that. On the other hand, I still wouldn't consider them 'astoundingly efficient' as the headline claims. This article discusses a design for a 97.09% efficient inverter. (I admit at this point I'm beginning to be argumentative, but I still think the headline should have been astoundingly dense inverters, though my theory is that slashdot injects in intentional errors to drive comments and traffics from those who like to nitpick submissions).

    8. Re:Efficiency by fyngyrz · · Score: 5, Insightful

      They can go hand in hand; they don't have to go hand in hand. Generally speaking, efficiency of power conversion is fairly high, 95% isn't all that uncommon for a design that tries hard. Some of the problems are that when you're doing conversion at the KW level, 5% is 50 watts, which tends to be RFI (both direct and indirect) and heat - that's efficient in one sense, and a serious problem in another. Going from 95% to 97.5% cuts that to 25 watts; and that's not space saved once per installation, that's money saved and more energy for other things and less crap in the air every moment the conversion is ongoing.

      In the case of houses and cars, where KW is the order of the day, space is a minor problem; efficiency is the major problem. I'd take a 97.5% efficient box at 10x the volume over at 95% converter any time. But it isn't even 10x the volume, generally speaking.

      That's why the first thing I looked for was competition for conversion efficiency, and why I was a little put off by it not even being there.

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    9. Re:Efficiency by bytesex · · Score: 3, Funny

      They want to put it in your mobile phone! Have a solar panel on the one side, your house fuse box on the other, and your phone in the middle! That's why they wanted the highest energy density per volume!

      --
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    10. Re:Efficiency by Ol+Olsoc · · Score: 4, Informative

      Ah, I didn't look that closely to see that. On the other hand, I still wouldn't consider them 'astoundingly efficient' as the headline claims. This article discusses a design for a 97.09% efficient inverter. (I admit at this point I'm beginning to be argumentative, but I still think the headline should have been astoundingly dense inverters, though my theory is that slashdot injects in intentional errors to drive comments and traffics from those who like to nitpick submissions).

      I disagree that you're being argumentive. While efficiency can mean a lot of things, it's a dead lock given that in a story about electric inverters, that efficiency would mean conversion efficiency.

      Because the "efficiency" they were actually referring to was efficiency in th enature of efficiency apartments.

      I certainly don't want to disparage what they did, because it was very impressive. This was more an issue with the person who wrote the original article.

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    11. Re:Efficiency by DeathToBill · · Score: 3, Informative

      According to [1], the winner achieves 95.4% efficiency - not actually that impressive as inverter efficiencies go.

      [1] http://littleboxchallengecetpo...

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    12. Re:Efficiency by AmiMoJo · · Score: 4, Interesting

      Batteries. Current inverters are rather large compared the batteries that can provide their maximum output power.

      Electric vehicle charging would benefit from this. You want to be pushing 120kW+ DC into the battery. You can also go back the other way and run your house from the car battery to save money when your solar panels are not producing anything.

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    13. Re:Efficiency by castionsosa · · Score: 2

      There is always liquid cooling. A data center usually has a decent water chilling system present, so if inverters could be cooled by that (likely via a heat exchanger, so a leak wouldn't be a major disaster), it would be more efficient than ones that are air cooled. Liquid cooling is maturing slowly, but surely, the main advance are better closed loop systems which make it easier to go this route.

    14. Re:Efficiency by KGIII · · Score: 2

      > If I press really hard during those, it almost stings a tiny bit.

      Err... I can save you the expense of a doctor's visit! It's stinging because, you know, you're pressing really hard. Just a guess. Don't do that and the problem will go away.

      "Doctor, it hurts when I hit myself with a hammer."
      "Don't hit yourself with a hammer."

      That'll be $50 and schedule a follow-up in six months with the secretary out front.

      Disclaimer: I am, technically, a doctor. I am not a medical doctor. Consult a qualified medical professional before deciding to stop pressing on an old injury really hard to see if it stings. My daughter is a real medical doctor. She is not my doctor. She probably is not your doctor unless you're a child in a trauma/intensive care unit.

      --
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    15. Re:Efficiency by JimSadler · · Score: 2, Insightful

      Wouldn't it be wonderful to do that energy conversion outside the home with a tiny box. Keep in mind that the more equipment inside a home the more power the home will consume. In hot weather a big box inside the home would add to the cooling energy load on the home. If installed outside the home a duct could, in cold weather, direct that excess heat from the converter to keep pipes warm or pumps from freezing up. Most people fail to realize that once power is sent down the power line to the home or industry that that power will be converted to heat again. Whether it is an air conditioner, a TV set, a computer or an electric motor or water heater all of that electricity is converted to heat. To really fight global warming we must control heat generation at both ends of the power line. One way is to reuse the heat emitted from every device to be used by other devices. For example, heat radiated by your hot water heater could be used to heat your home a bit. Heat generated from an air conditioner is already used to heat some hot water tanks. I wonder how many people have even considered this sort of thing.

    16. Re:Efficiency by torkus · · Score: 4, Insightful

      Electrical Efficiency is loosely coupled to volumetric efficiency. We're talking about an inverter roughly the size of a fist that's outputting 2kW. Without very high efficiency your cooling solution would be larger than your inverter. A moderate size CPU cooler (sinking ~65w) is the size of this whole inverter.

      The rules require efficiency >95% which is typical for high efficiency inverter systems. At that, the primary benefit to higher efficiency is lowered cooling requirements (i.e. size) which is the primary goal of the competition.

      So the rules basically *do* set teams out to maximize efficiency. Having small, highly efficient inverters is useful is many applications (solar, vehicular, UPS, etc.)

      As for Google's exact benefit? I could see them running these in datacenters: deliver 450VDC rails to all your racks and power them off a hockey puck inverter or two. Simple to scale - add more battery, more racks with inverters as needed. Everything becomes modular.

      Beyond that, solar and larger UPS systems typically run at 450VDC - so this means you can also scale your UPS and solar installation in conjunction with your datacenter. Basically combine all the technologies together without requiring large monolithic components. Ok, TLDR my own post.

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  2. Re:AC is by its very nature inefficient by dlleigh · · Score: 4, Funny

    Is that you Thomas Edison?

    Stop electrocuting elephants!

  3. Re:Who participated? by GLMDesigns · · Score: 2

    I think he forgot the /sarc at the end of his post.

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  4. Watts per cubic inch? by Anonymous Coward · · Score: 3, Insightful

    Are guys fucking serious?!?

    If you really want to use your old units, why not horse power per cubic inch?

  5. GaN Transistors are the future by stevel · · Score: 4, Informative

    Gallium Nitride transistors have a lot of nice characteristics, but low yields and high costs have slowed their introduction. Two tiny laptop chargers, the FinSix Dart and Avogy Zolt, were said to use GaN transistors. The Dart still hasn't shipped, a year past its claimed release date. The Zolt has but is apparently using older Silicon Carbide-substrate transistors instead (Also see here.) (I received my Zolt recently and it is working well.)

    It won't be a surprise to anyone following this technology that it can make inverters more efficient - that's what FinSix and Avogy have been claiming/demonstrating for two years at least.

    1. Re:GaN Transistors are the future by Anonymous Coward · · Score: 2, Interesting

      I work in RF, Ku band stuff, we use GaN parts like candy. One day I noticed that these things always come straight from Japan in hand-written and hand-packed little boxes... I asked what the BOM cost was and it was very high!

      These things are so cutting-edge that you can't even google for the part number they ship you; it's not even on the manufacturer's page! You need to ask for the datasheet and often it's just screen printouts from the VNA...

      I've also noticed that they smell different when the top explodes because of a mismatched load.

    2. Re:GaN Transistors are the future by rahvin112 · · Score: 2

      GaN isn't cutting edge. It's just super expensive. The only real use for GaN, due to the cost, is in radio transmitters and a few other niches where they need the ability of GaN to run at faster MHZ than silicon can support and can afford to pay the ridiculous process costs. GaN will remain a niche in process tech until they can find a way to make chips cheaper and they've been trying for a very long time. A lot of companies have come and gone trying to improve GaN because of the promise.

      I can remember in the 90's is was the big fad that GaN was going to replace silicon. You can hopefully see how well that worked out.

    3. Re:GaN Transistors are the future by MattskEE · · Score: 3, Informative

      RF GaN parts are certainly expensive - the GaN is grown on silicon carbide substrates which is incredibly expensive by itself, and high-speed RF stuff has much more demanding fabrication needs like very small T-shaped gates, better contact resistances, and so on.

      GaN for power electronics is much cheaper, grown on 6 inch silicon substrates, and produced in much higher volumes. You can buy GaN parts from EPC on Digikey for a couple of dollars each, the other GaN power device manufacturers aren't selling publicly that I know of (just to partners, or nobody) but the cost per unit is not tremendous - a bit more than the same voltage and current rating silicon device but the GaN part can switch faster.

  6. Re:AC is by its very nature inefficient by DeathToBill · · Score: 3, Insightful

    If you don't understand why this isn't going to happen, you need to be kept away from grid design.

    Replacing the AC network with a DC network would mean either replacing or substantially modifying the entire fleet of existing generation plant, all distribution and conversion equipment, all industrial equipment powered by electricity and most appliances. You might well be right that you can achieve better efficiency in a new network with DC than with AC; when you have to replace the entire electricity system, from spinning turbine to phone charger, it just ain't gunna happen.

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  7. Re:Who participated? by cc1984_ · · Score: 5, Funny

    I think he forgot the /sarc at the end of his post.

    You are assuming GP male. This kind of sexist assumption is exactly the type of thing that needs to be stamped out in the industry.

    Now if you need me, I'll be in my safe space. /sarc

  8. Astoundlingly dense by Anonymous Coward · · Score: 4, Funny

    There's probably a joke to be made at your expense, here.

  9. Trifecta by PopeRatzo · · Score: 3, Funny

    We may have just hit peak Google. Three stories in a row.

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    1. Re:Trifecta by houghi · · Score: 2

      As the postings are all about different subjects, it just shows how big Google is.

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  10. Ironic heading to the comment by mykepredko · · Score: 2

    Personally, I read it as "Anonymous Coward by its very nature inefficient".

  11. Split phase by shawn2772 · · Score: 5, Interesting

    Another nice improvement the winners made above the requirements was that Google asked for 230 or 240 VAC output, but the winning device provides 240 VAC split phase, which means it can also be used to provide two legs of 120 VAC. Not that it's terribly hard to add a 240 VAC -> 120 VAC transformer, but with this design there's no need.

  12. Cubic inches? by HammerToe · · Score: 5, Insightful

    Cubic inches?! So this isn't a project intended to be looking beyond the borders of one country?

    -Matt

    1. Re:Cubic inches? by fibonacci8 · · Score: 4, Funny

      And in English no less, the third most commonly spoken first language in the world. Could we please get these summaries in Mandarin and Spanish? If we're going to base things in the US on what more people are doing elsewhere, why stop at measurements?

      --
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    2. Re:Cubic inches? by stooo · · Score: 3, Funny

      >> Yea. Inches are kind of THE STANDARD for doing PCB layout worldwide.
      Not any more.
      Today, 80-90% of components are SMD, and SMD is metric.
      The odd 2,54 component is just destroying the harmony of the grid, but that's OK, the modern CAD packages handle this well.
      Yeah, sometimes I use 2,00mm headers instead of 2,54mm -> more compact, but a bit more exotic.

      Farewell, imperial.....

      --
      aaaaaaa
  13. Re:Why is this important? by afidel · · Score: 2

    Heck a 10,000 BTU AC unit in a small travel trailer only needs 700W once running so a 2kW setup would net you almost 3:1 runtime:collection (or about 2:1 once all inefficiencies are accounted for). The big problem is that 2kW of panels takes a lot more room than you have on a travel trailer (at least the ones that only need one 10k A/C!)

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  14. Re:Why is this important? by Tx · · Score: 2

    You don't need to use the solar cells directly, you charge up your batteries from your solar panels, or from cheap off-peak grid power, and you then need an inverter so you can run all your AC appliances from the batteries. The basic Tesla Powerwall model is 3.3kW, so that should give you a pretty strong hint of at least one application.

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  15. Re:Why is this important? by Kohath · · Score: 2

    That helps. I don't foresee a lot of applications that have room for those batteries but not for the inverter though. I can definitely see the merit of the complaint that the inverter is too large compared to the batteries. I'd still like to know what makes it very important rather than just something that's nice to have. Maybe nice to have is an adequate motivation for Google ...?

  16. How $1 million cost, for an inverter company? by raymorris · · Score: 3, Insightful

    If you started with nothing and had to buy all of the tooling and equipment, recruit people, etc., I could see this easily costing $1 million, but the winner is an inverter company. They already have all of the tooling, equipment, expertise, etc.

    They "just" needed to optimize one of their existing designs for size. Also, they only needed a working prototype, not a full production model. How do you figure that costs a million dollars?

  17. Google suckered everyone by ArchieBunker · · Score: 3, Insightful

    Sounds like Google had very specific design requirements and didn't want to spend the money in house doing development. So they dream up a contest and offer a cash prize. Meanwhile Google saves way more than the $1 million they paid out.

    --
    Only the State obtains its revenue by coercion. - Murray Rothbard
    1. Re:Google suckered everyone by tsqr · · Score: 2

      Sounds like Google had very specific design requirements and didn't want to spend the money in house doing development. So they dream up a contest and offer a cash prize. Meanwhile Google saves way more than the $1 million they paid out.

      Are you implying that Google somehow assumed ownership of the designs? TFA didn't say that the submitted designs ended up belonging to anyone aside from the submitters; it was, in fact, mute on the subject of ownership. Do you have a source to cite that says Google ended up owning any of the designs?

  18. Japan by DarthVain · · Score: 2

    Hell if I remember correctly half of Japan runs at 60Hz and the other have at 50Hz due to a standards change years ago, and they've never been able to convert even that due to the monumental effort required, and that is AC to AC!

    Though I expect the use of things things would be for Cars and Homes, not entire network conversions...

  19. I'll believe it when ... by fahrbot-bot · · Score: 2

    ... the Mythbusters test it - oh, wait ... damn (sigh).

    --
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  20. Re:Who participated? by silas_moeckel · · Score: 2, Interesting

    Because registering a team is somehow hard for minorities or women? The fact they had to use the internet or english? Please describe a change faced by these groups that a white male from Appalachia would not also face?

    --
    No sir I dont like it.
  21. Re:AC is by its very nature inefficient by IcyHando'Death · · Score: 3, Interesting

    You know the same thing could have been (and was) said about the switch from an analog phone system to digital. Every phone, every piece of switching equipment, every repairman's kit had to change -- all at enormous expense. It paid for itself though, by increasing profits (companies could charge for the new services that were made possible). All it would take is for some upstart startup to begin hooking up DC power in some new neighborhoods to get the game going. I don't even know if that would be legal now in most places though. The entrenched power monopolies would be a big obstacle to overcome.

  22. Re: AC is by its very nature inefficient by KGIII · · Score: 2

    Cock, alternating, cycles... I'm pretty sure there's a retort about how your dick hertz in there somewhere.

    --
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  23. Re:Who participated? by HiThere · · Score: 2

    And when AIs start objecting we'd need to write she/he/it.

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