An open competition to build a smaller power inverter, with a $1M prize

They aren't taking the IP and are also giving the cash as a pure incentive, meant to inspire new innovations in a certain sector.

[1] https://www.littleboxchallenge.com/pdf/LBC-InverterRequireme...

Edit - computed the radiation resistance; not a blocker at 60 Hz. Does anyone know a thermodynamic limit?

...we'll 50W/inch^3 is the throughput. If you assume 96% efficiency (which is common for COTS inverters), you'd have 2W/in^3 in waste heat to dissipate. And 50W/in^3 isn't very high on just a per-piece level. Here's a Vicor DC/DC converter that has 1240W/in^3 power density:

http://www.vicorpower.com/promotions/AC_to_PoL/ChiP_Technolo...

...of course getting rid of the parasitic heat isn't included in that example.

> Which is to say to take something which is 90% efficient and make it 99% efficient.

99% efficient isn't completely unheard of:

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=377536...

...to me it seems like the catch is FCC Part 15 B compliance. That seems like that'll be the biggest thing to disqualify smaller entries.

I don't understand electricity well, but it seems that electronic components require regulated DC, and producing that requires an AC somewhere in the transforming circuit. Is that correct?

First of all, you want to avoid having multiple wiring systems in one building. Wiring a building for 110V alone is expensive enough (both initially and later during maintenance). In the vast majority of situations, you are going to have to pick one or the other.

So: AC or DC? Either way, you need to be able to run high power appliances (e.g. a 2000W kettle), and to keep losses in your cables low you need to use as high a voltage as possible, which will keep the required current as low as possible. So either way, in a realistic scenario, you need to retain the high voltages (110/230V) that we currently use.

When you require high power / high voltages, AC is a better solution. It is easier to switch (your kettle switch will burn out much more quickly while trying to interrupt a high current DC supply than it will interrupting an AC supply that crosses 0V 100 times per second). Overload devices work more reliably with AC for the same reason (which makes your house less likely to burn down). AC also makes it much easier to transform voltage levels - you just use an inductor or two. DC requires relatively complex electronics. DC distribution is also more complicated since the the distribution network and everything attached to it has parasitic (or deliberate) inductance and changes in load produce voltage spikes

There's nothing to stop you from installing a DC system in your house, but I think you would find it significantly less practical than you had imagined

Minor nitpick: relatively few quality solar panels generate 12Vdc. Most generate around 40V

Stepping AC up or down in voltage is simple, build a transformer. Stepping DC up or down requires switching electronics, which usually will also have a transformer (if the step is reasonably large).

That distribution of power inside houses is AC still is a legacy problem and because half the things in your house still use AC power motors, and generally those things are the big current consumers (air conditioning, fridge, clothes washer, etc). Your PC, phone, etc which run on DC draw tiny amounts of power in the typical house compared to an air conditioning unit, but running an air conditioning unit on DC would likely require an inverter to generate the AC power for the compressors and fans.

Motors like AC, it's what makes them spin best. "Brushless DC" motors use an inverter system, usually. Even brushed DC motors effectively generate AC inside themselves with commutation.

Or perhaps tiny inverters could be a good example of disruptive innovation, an invention that looks bad along traditional dimensions but opens up nontraditional applications.

http://tec.appstate.edu/sites/tec.appstate.edu/files/micro%2...

(EDIT: The above point is valid, but I was wrong about cable sizes improving when using micro inverters!)

I might be completely wrong. Still, I'm sure we all agree that it's not ever a bad idea to incentivize any sort of energy innovation.

I applaud Google for doing this! I think Google knows there's a bunch of undisovered Einstein's in the world, and they just using the Internet to find them?

I like contests like this. I thought Bill Gates condom contest was a great idea.

It's just another way of pushing unreliability to the network edge where it minimizes systemic effects and can be replicated away cheaply, much like they did with GFS or even their UPS system (at least previous server generations at Google included a large per-server battery).

After that, freight was still on the increase and soon it became more economical to expensively engineer a lighter weight, smaller replacement. Regardless of orders of magnitude more complexity, switchers replaced simple transformers.

Inverters are like that too.

At 50W/inch^3 one ocean container of inverters will handle as much power as two ocean containers at 25W/inch^3.

One of the largest components in an inverter (such as found in a Toyota Prius) is the capacitor bank. I'll ignore the electrical design and just assert you need X capacitance to get this done. At least in automotive world, polymer film capacitors are used for this purpose. A polymer film capacitor is made from a (very long) sheet of polymer coated on both sides with a thin layer of metal and rolled up into a cylinder. They get quite bulky at capacitances required by these inverters. The other downside is polymer film cannot handle high temperature. I believe the Prius includes an whole extra cooling loop (in addition to the main loop attached to the engine, which runs hotter than the capacitors) to keep the capacitors cool, so that's even more bulk.

A multi-layer ceramic capacitor of similar capacitance can be much smaller, and can handle far greater temperatures than any polymer. The reason why polymer film is preferred is that when ceramic capacitors fail, they do so catastrophically in much the same way as a ceramic dinner plate shatters. At sufficient voltage, or at lower voltage with a sufficient defect, the ceramic will breakdown: a conduction path will form between the electrodes through the ceramic, which will heat the surrounding area, causing thermal expansion, shattering, and permanent destruction of the capacitor.

The same thing happens in polymer film capacitors, except that because the material is flexible, it does not shatter, and only a small hole around the defect will be ablated away. The remaining capacitor loses some capacitance, but otherwise functions normally.

So one way to create a smaller inverter is to use smaller capacitors, but you've got to match capacitance, voltage-handling ability, and fail gracefully.

But they'd probably run on a higter voltage and frequency.

A circuit is needed to convert the DC to AC. There is a loss in energy due to the functioning of the circuit. The circuit size and complexity depends on the specifications of the DC to AC inverter including the maximum power capability desired.

Traditional converters operate at low frequencies and lose a lot of energy due to the technological limitations of the semiconductors switches used. The switches essentially chop the DC input into a square-wave type output of a frequency in the low kHz range. This square wave output needs to be low pass filtered to allow only the 60Hz to propagate through to the inverter output. For low kHz type square wave, the inductors and capacitors used to make the low pass filter are large.

New semiconductor technology has resulted in switches that can operate at MHz frequencies. The inductor and capacitors used to make the low pass filters can be much smaller for MHz frequencies. These switches also have much lower conduction losses than the previous silicon-based switches but they need to be used in more novel topologies in order to minimize what are called switching losses.

To see a real-world example of what improvements can be made with the new semiconductor technology, compare the brick power supplies that come with our laptops to the much touted FINsix Dart (http://finsix.com/dart/). The latter uses new GaN switches that operate in the MHz range AND a novel topology that minimizes switching losses.

I don't know what the limits on efficiency are, and the Wikipedia article mainly addresses AC-to-DC conversion rather than DC-to-AC, but I assume simply from the fact that they aren't used these days that they aren't an improvement on solid-state inverters.

http://business.financialpost.com/2011/09/08/why-many-contes...

"the province’s Lotteries Act ... require you to post security for contests open to Quebec residents where you do not have a place of business in Quebec, the value of any single prize exceeds $5,000 or the total prize value exceeds $20,000."

Also note that it may not just be a function of the law, but also of the benefit gained by offering a contest in a given jurisdiction. I'm seeing some indications, for example, that Japan and Brazil have some similar sweepstakes regulations, but it may be more worth the organizers' time to comply with Japanese law than Brazilian. Just a guess.

Some clues:

http://www.slideshare.net/Promosfera/sweepstakes-and-contest... (E.g., server receiving registrations must be located in Italy, steep fines for only brief downtime)

http://en.wikipedia.org/wiki/Sweepstakes ("There are similar laws in Brazil, where sweepstakes must include a "cultural contest", often giveaway questions like 'which brand gives you a house?'")

http://www.theglobeandmail.com/report-on-business/small-busi... (In Quebec "contest runners have to pay tax on the value of the prize. For another thing, contests with prizes over $2,000 have to register their rules with a government agency, the Régie des alcools des courses et des jeux . . . . To top it off, contests with prizes worth more than $5,000 actually have to deposit an amount as a security with the Régie, as a means of protecting consumers should the contest runner fold or renege.")

I don't see a single post that fits your description. Am I looking in the wrong spot? Are you being baselessly condescending?

That's the part of the situation that needs to change, but of course it's the chicken-and-egg problem from hell...

I don't think this is the next X prize. I think this is closer to an open contract for somebody to build the damn thing, when that is a somewhat risky venture that none of the people offering the prize feel they have the ability to execute.

The contest has picked quality (the engineering requirements are not easy to hit) and schedule (there's a timeline for demoing). I bet it's expected that the cost, even if it's high right now, will only come down over time. But since there exist 0 inverters which can do this today (presumably), cost isn't a big concern if you can do something new and novel that's never been done before.

Hint: the resistance losses are ~ amperage squared.

One problem is that we would have to create a whole new standard of how to connect DC appliances. Now I know on a smaller RV level that exists but we need something that can take more juice if I remember the conversation correctly.

Also, there are other small details to consider such as the safety of switches and plugs. When you disconnect AC it will arc and then self extinguish when it crosses 0V. DC will keep arcing longer than AC will making it a bit less safe. Just keep a lot of that stuff in mind.

Let's say we run your 'simplified' household at 48V (the highest voltage commonly used in boat/cabin DC systems). To run 8kW on 48V you need 167 Amps. For 167 Amps you need something like 2/0 wire. That's really thick and heavy cabling!

Can you imagine replacing all of the wiring in your walls with this stuff?

http://i1194.photobucket.com/albums/aa378/chance1525/Mobile%...

[1] http://en.wikipedia.org/wiki/High-voltage_direct_current

Power transmission and the whole grid is based on AC. All device you buy are based on AC. The reason is, transmission of three-phase/AC is much more efficient than DC. DC has also other side effects like they are not potential free (hard to explain for me in English as I am German.) But to make it easy, beside the electrical stuff, the whole world is based on AC. So redesign stuff like TV, dishwasher, computer, … just for the few poeple who run their own system is economically not possible. (The hen and egg problem.)

The other thing is, everything that runs with a drive these days, like your electric car with a permanent-synchron drive, needs to convert DC to AC to run the drive. The AC frequency defines how fast the drive runs.

So even, if the first thing change, the second (running a electric drive) will not change.

Besides from those points, I find this contest interesting. Because, I thing in the industrial world, where I am working in, this kind of problem is addressed every day in electrical engineering.

EDIT: for the grid, it is not only solar, also wind energy is important. Wind parks are the next big source of renewable energy, in Germany (of course), but also in Spain, China, and the US. GE Wind Power is very strong in the US, AFAIK. With wind power AC is generated with the frequency depending on the wind. So this AC is converted to DC, which then is converted to AC synchronized to the grid. Actually, the market leader for those inverters is based in Nuremberg, Germany, where I am from. AFAIK, they have more than 60% of the market. Because moving such high power requires 3 or more inverters in parallel. But running such things in parallel is a pain in the ass. Because they have to run with less then 1ms accuracy in parallel. Otherwise the whole system will burn.

There are other concerns as well (e.g. no standard DC outlet, most AC appliances with DC motors would have to be modified, there would then be two electrical standards in the house since DC is still not suitable for most transmission or distribution needs, firefighters would need to be retrained, etc).