Google Offers a Million Bucks For a Better Inverter

With the Little Box Challenge, Google (and IEEE, and a few other sponsors like Cree and Rohm) is offering a $1 million prize to the team which can "design and build a kW-scale power inverter with the highest power density (at least 50 Watts per cubic inch)." Going from cooler-sized to tablet sized, they say, would make whole lot of things better, and the prize is reserved for the best performing entrant.

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Reply to
David Harmon
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On a sunny day (Tue, 22 Jul 2014 22:05:43 -0700) it happened David Harmon wrote in :

Does not make sense,

1) There is plenty of space on earth 2) If efficiency has anything to do with it they should make the appliances run on DC. and run those via a singe step DC-DC converter, so say 12V or 24 V input for all stuff (or whatever standard is agreed upon). 3) Same heat (efficiency) generated in a smaller space means higher temperature, you would burn yourself, or set fire to the environment. 4) Google has too many $$$ so go for it, but I doubt any of this will be fair play, protect yourself legally and in any other way to prove YOU designed it.

???? Won't bother.

NEWS: Little Larry For Wisconsin won the google price for building a 1kW DC-AC pure sinewave converter in a match box. The design is sold to Boeing... Ooops that was wireless power transfer.

sigh.

Reply to
Jan Panteltje

Forget it. Even a rotary convertor using the Hummingbird scheme cannot do that.

Reply to
jurb6006

The specified max enclosure size is 40 cubic inches and the output is single phase 2kVA 240VAC/60Hz (from a 450VDC input). This inverter doesn't even require a transformer, since it has a HV input, it just needs two synchronous buck stepdown half bridges (or an Hbridge) fed into LC filters (planar inductors and metal poly caps) to generate the

240VAC/60Hz rail and neutral (centered on 450V/2=225VDC for neutral. Also if reactive power can be fed back into the 450VDC input, it doesn't even require electrolytic energy storage (or supercaps) to handle reactive loads.

To get the enclosure smaller, the switching frequency into the LC filters will need to be high to reduce these components sizes, I think the main factor limiting the enclosure size reduction will be the 95% efficiency requirement, since as the switching frequency increases, using conventional components, the efficiency will start to drop.

Also thermal issues will come into play with too small of an enclosure as the specified max case temperature is 60 Celcius.

For the switches, they could be whatever can handle 1MHz+ with low switching losses and low Rds(on) and two synchronous buck controllers to eliminate buck low side switch diode losses. Also comparator based cycle by cycle current limiting, and analog voltage regulation, based on a reference 60Hz voltage error signal for the 240VAC output, and a fixed voltage reference for the neutral output.

The high side switches on the 450VDC rail could benefit from zero voltage switching, I'm not sure if that is possible though, I have thought about it for a buck converter but haven't seen a circuit for it. Anyone know how to zero voltage switch a high side fet in a buck converter?

cheers, Jamie

Reply to
Jamie M

On a sunny day (Wed, 23 Jul 2014 02:15:21 -0700) it happened Jamie M wrote in :

Did not even read the specs, if that is true,

40 cubic inches is about 3.42 * 3.42 * 3.42 inch (3.42^3 = 40.0017) That is 8.7 * 8.7 * 8.7 cm At 2kW and 95 % efficiency you dissipate 5 * 20 = 100W in that space. Ever touched a big 100W lightbulb? It will have to be tested sitting on an area where there is no airflow, nor water spray or whatever on it at
Reply to
Jan Panteltje

In spite of that, the million dollars will make some people try. I can see where it will attract the cold fusion, free energy, and flux capacitor developers.

Reply to
John S

On a sunny day (Wed, 23 Jul 2014 06:24:54 -0500) it happened John S wrote in :

I tell you, if you can do that, do NOT give it to the google contest, you probably have to give up all rights to them for the 1M$ prize.

*Patent it imediately, and get very very very rich*

You can then, after the patent is granted, always claim that prize, as an 'on the side' for extra pizza..

Reply to
Jan Panteltje

How do you interpret the requirement

everywhere on the outside of the device that can be touched.

Is that the case temperature or are you allowed to blow out air with higher temperature than 60 C ?

  • Can not use any external source of cooling (e.g. water) other than air

So a fan would be allowed ?

Reply to
upsidedown

From the specs:

"Must have a total harmonic distortion + noise on both voltage and current of < 5%"

Maybe I'm misinterpreting this, but the inverter sets the instantaneous voltage. I don't see how it has any control over the instantaneous current that the load draws.

Sylvia.

Reply to
Sylvia Else

I am not an expert in English semantics, but the rule states

It does not state _cubical_

more than twice the area compared to the cubical case. Thus if convection cooling only would be allowed, this would help significantly.

When setting up such specifications, one must be really careful with the wording.

Reply to
upsidedown

Try that again with a capacitive load.

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Reply to
Jasen Betts

They say "harmonic distortion". It means to limit the amount of high frequency noise (why they said "plus noise", when H.D. in this context is a "noise" itself I don't know) present in the output voltage or current waveforms.

Internally, the inverter will likely use a very high frequency (kilo hertz or above) to perform the inversion. They want to limit the amount of that high frequency signal that leaks through into the output. I.e., they are saying it should generate a signal closer to a pure sine wave.

Reply to
Rich

Then the current will be out of phase with the voltage, but it's still determined by the load. If the inverter attempts to control the current, the voltage will change, which it's not allowed to do.

Sylvia.

Reply to
Sylvia Else

Yes. But what I'm saying is that the inverter only controls the voltage. If the load wants to draw some weird and wonderful current with lots of harmonics, then it can, and there's no way the inverter can prevent it without affecting the voltage.

Sylvia.

Reply to
Sylvia Else

On a sunny day (Wed, 23 Jul 2014 14:56:59 +0300) it happened snipped-for-privacy@downunder.com wrote in :

Yes, still have not read the specs, in a cubic form you lose 1 side where it sits on. You can make any other form, but it still must have a side to stand on that is big enough so it does not fall over, and that side is subtracted from the total surface area. If you imagine a 8.7 x 8.7 x 8.7 cube, with a 10W resistor in it, sitting on some sofa (for example) will it rise 20 C in temperature? If so you need 99.5 % efficiency, but 99% would be cool (so to speak ;-) ) too (20 W). it is not only the switchers that dissipate power, the filters and cores too.

No way.

Reply to
Jan Panteltje

Well observed! You're absolutely correct. Such an inverter can only deal with its voltage waveform purity. As you so astutely observed, current waveform purity is a matter that's entirely the reponsibility of the load.

The only time an inverter can assure current waveform purity (within a limited range) is when it's acting as a constant current source when the amplitude of the voltage can be any random value (again within limits) and will reflect the distortion due to the load into a voltage waveform distortion.

You simply cannot specify both voltage _and_ current waveform purity requirements for a sinewave inverter (or generator) in isolation of the load specification.

With AC power supplies, it's only the voltage that needs to be tightly defined, along with purity of the waveform. Constant current supplies are a specialised case, usually contained within the apparatus in question.

I think the 'copywriter' got carried away with the thought "If specifying voltage alone is good enough, specifying voltage and current will be twice as good". :-(

Copywriters, eh! :-(

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J B Good
Reply to
Johny B Good

I suspect that the biggest challenge is going to be the 60C temperature. Presumably that's 60C in 25C ambient, so 35C temperature rise.

Assuming that you can fix the size of the enclosure, as long as it's no more than 40 cubic inches, expect to see a lot of thin, wide and tall entries, with fins.

Even so, you're going to have to be much better than 95% efficiency.

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Tim Wescott 
Wescott Design Services 
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Reply to
Tim Wescott

They said tablet size, so probably tablet shape with fins.

I suspect that they also want it grid-tied. Otherwise, doesn't make sense to push it for solar energy in homes.

You can get rich even with 90% efficiency. I can pay 10 million for 90%, in future earnings of course.

Reply to
edward.ming.lee

Sorry, google said current top efficiency is 98%. So, probably need to build 99%.

Reply to
edward.ming.lee

Yes, plenty of land in the dessert, but not many wish to live there. Same with space. Lots of space on earth, but not so much in my house or office.

Yes, let's change the world's power transmission... what?

Lol, sorry, incorrect. It just means you need to accommodate the higher heat flow density. e.g. larger unit is a brick with smooth surfaces, smaller unit has fins to provide more surface area or maybe a fan to blow the air through.

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Rick
Reply to
rickman

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