
An open competition to build a smaller power inverter, with a $1M prize - ismavis
https://www.littleboxchallenge.com/
======
jeremymcanally
At first I was like "Why would you do that for only $1m? If you had that big
of a breakthrough, you could easily generate that (and then a lot more) by
selling it yourself." Then I read that they aren't taking the IP, and are just
giving you the cash as a pure incentive. They can publish your high level
approach documents, but you still own the invention.

I wish more of these contests were run that way. I think they'd yield much
high quality and differentiated results with a lot more entrants.

~~~
fryguy
Also, it looks like there are grants available to even get you started with
some capital so it doesn't come out of pocket. Even better.

~~~
vonmoltke
Grants are only for full-time academics.

~~~
angersock
That's what the academics want you to think. :)

~~~
_delirium
In general yes, it's a myth that grants are only for full-time academics.
However _this particular_ grant is indeed only for full-time academics,
according to its terms:
[http://research.google.com/university/relations/littlebox.ht...](http://research.google.com/university/relations/littlebox.html)
Though the full RfP does also encourage groups of students to recruit a
professor and apply as a team.

Incidentally, the RfP has a nice summary of what Google thinks the main
engineering challenges in winning the award are. The first one on the list is
finding a way to deal with 120 Hz ripple in a way other than the current
solution of huge capacitors.

------
ChuckMcM
I saw this earlier and briefly considered it. 50W/inch^3 is soldering iron
level heat dissipation. And my take on it was that it really isn't possible
unless you can cheat and have the "inverter" be the thing on the end of a
solid copper bar that is sitting in ice water on the other end :-). So really
they are looking for a 10X improvement in efficiency. Which is to say to take
something which is 90% efficient and make it 99% efficient. Even looking at
the wide bandgap semiconductors they reference on the web site I'm having a
hard time getting more than a few percentage points more efficient.

~~~
ISL
I think the power density they quote (50 W/in^3) isn't for dissipation, it's
inverted power. I'm not an expert in electrical engineering, but I can't think
of a fundamental physics limitation that's a blocker here. If there is one,
I'd guess that it'll involve the electromagnetic radiated power of the device.
From the specification document [1], they're asking for 95+% efficiency.

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

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

~~~
ChuckMcM
Thanks for the link, you're correct they want to pull 2KVa out of a box no
bigger than 40 cubic inches. These guys
([http://www.apparent.com/products/](http://www.apparent.com/products/)) have
what I consider a very workable technology, basically 2W/cubic inch but one
inverter per panel. Since you have to have panels anyway, having the panel
produce power directly in the form you want eliminates the need for size as
the panel is compelled to be a certain size anyway.

But instead of changing the question (and age old trick of engineers to arrive
at a feasible solution :-) The push here seems to be about efficiency. 95%
efficient would be a huge improvement.

~~~
keenerd
Whatever they go with, the tech is going to make a really killer subwoofer
amp.

Looking at the requirements (mostly the high DC input) it seems that an IGBT
class-D would be the logical starting point, but those are hampered by a
150kHz-ish max switching rate. I think Don Lancaster's Magic Sinewaves
([http://www.tinaja.com/magsn01.shtml](http://www.tinaja.com/magsn01.shtml))
meet the distortion requirements while offering the slowest switching
requirements.

Would be fun to be on one of the teams for this.

------
zw123456
Wouldn't it be more efficient to simply drive all our electronics equipment
directly off DC? Almost all electronics devices now days run off 5VDC (USB) or
12VDC, Solar panels put out 12VDC, all those conversions seem like a waste of
energy. What if you just run our big appliances off 120VAC and run all our
small stuff off of Solar directly along with a battery back up. It seems like
if a new wiring standard were developed that had both AC and DC distribution
it would greatly reduce the cost of installing Solar. In fact, I believe it
would be possible to put a DC bias on top of the AC (similar to the way old
time phone lines work). Just a thought, rather than shrinking the inverter,
think outside the box and get rid of the inverter all together.

~~~
hrjet
This is something that always caught my imagination: using DC for the last
mile.

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?

~~~
m4x
No, you can generate 'regulated' DC from another DC source (see for example
buck converters or more generally any DC-DC converter).

Regulated really just means clean DC which stays at the same voltage and
doesn't contain a lot of noise. Not all devices require a regulated supply. A
drill, torch or heater will happily run on a noisy supply. Your iPhone will
not.

~~~
hrjet
You are right. I remember more details now. The problem occurs when you want
to make regulated DC from a lower voltage DC supply. Step-down is easy.

For example, my battery is 12V, but my laptop needs 19V. AFAIK, you can't get
regulated 19V supply from the 12v battery without a transformer (or maybe
something equivalent).

~~~
dreamcompiler
Step-up is easy too. That's what boost converters
([http://en.wikipedia.org/wiki/Boost_converter](http://en.wikipedia.org/wiki/Boost_converter))
are for. Most single-cell LED flashlights contain tiny boost converters to
increase the 1.5v coming from the battery to above the drop voltage of the
LED.

------
anigbrowl
_2\. ELIGIBILITY: To be eligible to enter the Contest, you must be: (1) above
the age of majority in the country, state, province or jurisdiction of
residence (or at least twenty years old in Taiwan) at the time of entry; (2)
not a resident of Italy, Brazil, Quebec, Cuba, Iran, Syria, North Korea, or
Sudan; (3) not a person or entity under U.S. export controls or sanctions; and
(4) have access to the Internet as of July 22, 2014_

I wonder why Italy, Brazil, and Quebec are included. The other countries are
under special sanctions regimes already but I can't think of a good reason to
exclude these three or why the contest would be considered illegal there.

~~~
dustcoin
These jurisdictions likely have special laws regarding contests with prizes.
For example: [http://business.financialpost.com/2011/09/08/why-many-
contes...](http://business.financialpost.com/2011/09/08/why-many-contests-
exclude-quebec-residents/)

~~~
marcosdumay
Brazil has some laws quite similar to that. And certainly another entire set
of problems our governemnt would put over the winner if he lived here.

------
pkulak
Seems like we just need to switch to DC already. 60hz AC is good for
resistance heat and... that's about it. We are at a point now where we're
creating DC on our roofs, turning it into AC to go through the walls of our
house, then turning it right back into DC to charge our cars and power our
other electronics. With losses and expensive hardware at each step.

~~~
bradfa
Lower frequency (50/60 Hz) AC is the only really useful choice for
transmission on low cost long runs (think 100 km and more). To push high
voltage DC on long runs generally means special cables and possibly super
conductors. Pushing 60 Hz AC at 230 kV goes over simple cables (granted with
fancy insulators for holding it to the towers).

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.

~~~
dreamcompiler
> Lower frequency (50/60 Hz) AC is the only really useful choice for
> transmission on low cost long runs (think 100 km and more). To push high
> voltage DC on long runs generally means special cables and possibly super
> conductors. Pushing 60 Hz AC at 230 kV goes over simple cables.

Not correct. High-voltage DC runs just fine on regular copper. (In fact, in
some cases you only need a single conductor because you can use the Earth as
the return. This isn't typically in the design spec, but it's sometimes used
as a backup plan.) _Low-voltage_ DC requires superconductors, because pushing
low-voltage _anything_ any distance requires superconductors.

The only reason most transmission is over AC today is Tesla (the man, not the
car) didn't have power electronics to step-up or step-down voltage. We now
have the technology to change the grid to DC if we want.

~~~
jimmyswimmy
> We now have the technology to change the grid to DC if we want.

True, but the cost of each endpoint is significantly higher for DC than AC,
especially at high power. I would imagine the reliability and longevity of
power-equivalent DC converters would also be lower than that of AC units. That
is to say, a complicated electronic component with many critical parts is more
likely to fail than a simple transformer.

------
otterley
This story was previously discussed on HN:
[https://news.ycombinator.com/item?id=7730042](https://news.ycombinator.com/item?id=7730042)

------
lutorm
Why does inverter size matter? The inverter is already smaller than the
battery or PV panel components, so it's not immediately obvious to me what
groundbreaking new applications will be possible with an even smaller one.

~~~
sparkman55
If inverters were smaller and more efficient, they could be placed on a per-
panel basis ("string inverters" or "micro inverters") for significantly better
performance, particularly when some of the panels are shaded. See this paper:

[http://tec.appstate.edu/sites/tec.appstate.edu/files/micro%2...](http://tec.appstate.edu/sites/tec.appstate.edu/files/micro%20vs%20central%20inverters%20shaded%20vs%20unshaded%20dave%20lee%20raichle.pdf)

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

~~~
eck
> Panels commonly run at 12V (or some low multiple thereof),

That is absolutely not true. Generally speaking nontrivial sized photovoltaic
systems are designed with panels in series such that the voltage stays just
barely within the 600v rating on the wire.

For example, grid tie inverter, MPPT rated 195-550v:

[http://pdf.wholesalesolar.com/inverter%20pdf%20folder/Schnei...](http://pdf.wholesalesolar.com/inverter%20pdf%20folder/Schneider-
Conext-NA-range.pdf)

~~~
sparkman55
You're right, panels are generally ganged together in battery to avoid the
'thick copper cable' problem.

However, the individual panel assemblies do run at lower voltages (individual
cells run at the band gap of the semiconductor, 1 or 2 V).

It should be noted that placing the panels in series has a significant effect
on panel performance when some of the panels are shaded (The entire string
outputs at the rate of the shaded panel), so it would be much better to place
panels in parallel when possible.

~~~
marcosdumay
I still think that the best alternative for putting the pannels in parallel is
by using DC/DC converter on then, and never thinking about 60Hz AC.

------
swamp40
Why is there any need to make it much smaller than the solar panels that will
be providing the power?

I can see where ultra-thin (and flexible) would be a benefit, but why not
allow the electronics to spread out over the entire area of the solar panels?
The space is being used up already.

That gets rid of the super high power density problem.

The sun delivers about 1KW per square meter, so even if the solar panels were
100% efficient, you'd have an entire _square meter_ of room for a 1KW
inverter.

~~~
_wmd
Google are the sort of company who would rather have 5,000 crappy, unreliable,
but efficient and tiny inverters attached internally to crappy, unreliable
commodity servers than spend 5000x on a single, huge, expensive, only slightly
more reliable inverter covering all 5,000 servers.

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).

~~~
scott_karana
Nothing about your comment is mutual exclusive with the one you're replying
to...

One inverter per solar panel sounds just like one inverter per server.

~~~
_wmd
Parent comment assumes one inverter per solar panel, my comment suggests it's
more like one per 19" rack unit. Today's inverter vs. the kind of size they're
looking for is a difference of perhaps 4-10TB per U, or approaching enough
space for an extra half petabyte of spinning rust per rack

~~~
scott_karana
Ah, thanks for clarifying. My bad. :)

------
phkahler
Already done. When I worked in EVs we used a HybridPack2 power module from
Infineon. It's about the size of a sandwich but longer, and skinnier. You add
a driver board, a logic board, a capacitor, connectors, cold plate. It's about
the size of a shoe box and can deliver 100kW continuously. I pushed one under
ideal conditions to 200kW.

Of course, liquid cooling means a total system that is quite a bit larger than
I describe. In order to get rid of liquid cooling at that power level you'd
have to get the losses down by a huge margin. We were dissipating 2-3kW at
high power, so for air cooling you'd need to get that down by a factor of at
least 10. The only way to drive the heat down like that is at the
semiconductor device level.

This is a challenge that everyone in the field is already aware of and working
on, while people outside the field have no ability to do meaningful research.

At the small scale, an Arduino with the mega-moto shield can push some
hundreds of watts in a few cubic inches. So what exactly is the challenge?

~~~
fryguy
The challenge is getting AC current, not DC as with the mega-moto shield.

~~~
phkahler
Typically you want AC on the input or output and DC on the other. You can use
that shield to produce AC by driving the outputs with PWM (it is intended for
that). If there was a 3rd channel on the mega-moto, you could drive a 3-phase
AC motor with it. If you put a transformer on it, you can connect it to the
line and do DC->AC or AC->DC. Normally we want the DC voltage to be higher
than the AC, so it's not the ideal shield for line connection - hence the
transformer instead of simple inductors. And yes, the inductors add to the
size, but if you are driving an inductive load like a motor, they are normally
not needed.

------
iandanforth
Anyone know why this is particularly hard?

~~~
pmahoney
I actually worked a little on this problem some years ago (as a lab tech; take
my knowledge with a gain of salt).

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.

~~~
shonn
It seems to me that the solution would be along the lines of a 1 bit DAC. The
caps then have less smoothing to do.

~~~
Florin_Andrei
Increase the frequency, yes. That's what I thought as well.

But then you run into other issues. The higher the frequency, the less "neat"
are the up/down transitions, so your power elements (MOS-FET or whatever)
spend more time in that twilight zone, which is exactly where they dissipate
most power. And you want to avoid that.

Anyway, it's worth investigating along these lines.

------
jessaustin
Anyone have any ideas why they highlight _only_ "wide bandgap device
manufacturers"? I'm hope they'd accept a winning solution with different tech,
but surely there are other possibilities they could mention right at the
start?

~~~
dskhatri
Some solutions to the problem will utilize a high frequency, high voltage
switching inverter. The performance of this type of inverter is limited by the
losses generated by the devices making up the inverter. The wide bandgap
devices (switches in essence) offer the lowest losses for this type of
topology. Furthermore, some novel inverter designs work only if they operate
at very high frequencies. Only the wide bandgap devices can switch at these
high frequencies.

------
nsajko
But a lot of devices convert to DC internally! Would it be hard to dispose of
that redundancy? It seems to me there'd be less need for a power inverter that
way. EDIT - some semirelevant discussions:
[https://news.ycombinator.com/item?id=7730205](https://news.ycombinator.com/item?id=7730205)
\- in the past thread, reasoning about usage of AC vs. DC
[https://news.ycombinator.com/item?id=8071524](https://news.ycombinator.com/item?id=8071524)
[https://news.ycombinator.com/item?id=8071670](https://news.ycombinator.com/item?id=8071670)
\- DC vs. AC

~~~
markokrajnc
Read about Tesla vs Edison war on AC/DC currents at the end of 19th century:
[http://en.wikipedia.org/wiki/War_of_Currents](http://en.wikipedia.org/wiki/War_of_Currents)

------
gooseyard
Assuming one was starting from scratch and didn't care whether the available
appliances of the day required AC or DC power, but all the power coming into
the home was solar, what would the motors on the appliances look like? Would
it still be desirable to use AC motors, and if not, would it be practical
(other than for the obvious reasons) for appliances to use a standard DC
voltage?

I don't mean to suggest that we abandon ac powered appliances, I'm just
curious about what electrical wizards would come up with, if they were doing
it all over again.

~~~
marcosdumay
Motors would almost certainly still be AC. They are way more efficient,
cheaper to build and require almost no maintaince. DC motors do not have those
same characteristics.

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

~~~
mindslight
"Brushless DC" motors seem to be taking over due to switching electronics
dropping in price, no? And while those are technically AC motors, it's not the
kind of AC that comes right off the line.

Motors that run on constant 60Hz seem to be a historical shortcut, whose
demand is fading as the control benefits of variable frequency drive are
available for less and less. And if HVDC transmission is gaining popularity,
then how long are utilities going to keep doing the conversion to AC "for
free" ?

It seems to me that if we were in a bizarro world where common end-user power
had always been DC, every motor would just be paired up with an appropriate
driver circuit, even designed around the specific inductance of the motor.
With solid state circuitry, all house fans would be infinitely variable, etc.

Of course there's a huge installed base of a few types of items that would
need 60Hz backwards compatibility. I get a good chuckle from thinking about
legacy clocks requiring an inverter that contains a high-accuracy crystal -
maybe that inverter could even run ntpd.

~~~
femto
I looked into this a while ago, when I was replacing the pump on my swimming
pool. This is a bit of a special case, as there are gains to be made from
using a variable speed drive. Whilst a variable speed drive may increase
electrical losses, the slower water flow may reduce losses due to turbulance
by a greater amount, leading to a net increase in efficiency for volume of
water moved.

As far as I can gather, for variable speed motors a brushless permanent magnet
DC motor is more efficient for small power applications (< 1-2kW), but as the
power goes up, a high efficiency three-phase induction motor with a variable-
speed drive become more efficient than the DC motor. A high efficiency
induction motor has extra copper in the rotor, to reduce resistive losses.

For fixed speed applications, you'd think the above variable speed performance
would reflect the performance for a DC supply, as the DC supply requires
switching in both cases. For a three-phase AC supply, you'd think the
induction motor would win, due to the absence of switching.

------
mmanfrin
Could someone explain, in layman's terms, what the difficulty in building a
smaller inverter is? I unfortunately paid less attention in high school
Physics than I wish I had.

~~~
dskhatri
The output of a solar array is a DC voltage (constant over time). Our homes
are fed by an AC voltage (varying sinusoidally over time at a frequency of
60Hz).

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/](http://finsix.com/dart/)). The latter uses new GaN
switches that operate in the MHz range AND a novel topology that minimizes
switching losses.

------
markokrajnc
Maybe a stupid question: Would that work: create a small electric motor, mount
one coil on the rotating wheel and mount another on the stand. Now put DC on
fixed coil and AC would be generated on the other side (like in
transformer)... Or will this not work? :-) (I am not an electrician.)

I know, I know - mechanical parts are not optimal - and also there are losses
for electric motor - but the size is in question here...

~~~
kpreid
Rotary motion was used for conversion long before semiconductor devices were
invented:
[https://en.wikipedia.org/wiki/Rotary_converter](https://en.wikipedia.org/wiki/Rotary_converter)

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.

------
elsewhen
does anyone know why the list of countries that this contest is blocked from
are:

"ITALY, BRAZIL, QUEBEC, CUBA, IRAN, SYRIA, NORTH KOREA, AND SUDAN.[1]"

aren't the first three places strange to see on that list?

[1] [https://www.littleboxchallenge.com/pdf/LBC-
TermsAndCondition...](https://www.littleboxchallenge.com/pdf/LBC-
TermsAndConditions.pdf)

~~~
pdabbadabba
Not sure, but some Googling reveals that these three are commonly excluded
from contests of all sort. They probably either prohibit all forms of contests
and sweepstakes, impose taxes, or regulate them so tightly that it's better to
just not bother.

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

[http://en.wikipedia.org/wiki/Sweepstakes](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...](http://www.theglobeandmail.com/report-on-business/small-business/sb-
digital/web-strategy/running-an-online-contest-dont-run-afoul-of-the-
law/article594793/) (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.")

------
54mf
I'm just tickled by how many commenters have a _totally obvious_ solution to
this problem. Surely, the hundreds (thousands?) of experts at Google, the
IEEE, and the ~8 manufacturers who put this contest together are just fools
who couldn't come up with such amazing, brilliant ideas themselves.

Congrats in advance, and enjoy your million bucks!

~~~
CamperBob2
(Shrug) There _is_ no good solution, because it's the wrong problem. We
shouldn't be using AC at the home/light-industrial level at all. No matter how
efficient the inverter is, it's going to be constrained by the inefficiency of
putting switching regulators in everything from wall warts to machine tools.

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

~~~
repiret
DC in the house doesn't remove the need for switching regulators - you still
need to step down from the house voltage to the device voltage. Don't forget
that devices that accept 5V or 12V from a wall wart almost all still have
switching regulators to step down to 3.3, 1.8 or less. It does remove the need
for transformers and rectifiers, which would buy us some efficiency.

And don't forget that if the house DC supply was at less than 120V, then
you'll loose more power in the house wires, because the electrician who wired
your house was too cheap to buy superconducting romex.

~~~
dreamcompiler
If your house is wired with the lights and the outlets on separate circuits
(mine is, because I'm an EE and I built the house), you could change out all
those lights to low-voltage LEDs and supply 12-24VDC to them and light up your
house just fine on the 14-gauge copper romex that's in your walls now. This
works because the required current would still be well below the 15A at which
the wire is rated. (Getting your electrical inspector to approve it might be
another matter, though.)

In some cases, this trick would work for the outlet circuits too because most
of the things we plug into outlets now are low-voltage DC wall warts, and they
could be replaced with low-voltage DC-DC converters. The problem is that your
refrigerator and your dryer are not run by wall warts, so outlets are tougher
to convert to DC than lights.

------
dskhatri
There are all sorts of specifications/requirements listed (box size, ripple
allowed, EMI limits) but the most interesting that is not mentioned is cost.
There is no upper limit set on the BOM cost.

~~~
bradfa
The oft repeated engineer's mantra of "quality, price, schedule: Pick 2."

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.

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nsxwolf
What's the difference between a picnic cooler sized inverter, and the one in
my Jeep, which is nowhere near the size of a picnic cooler?

~~~
AlexMuir
The one in your jeep probably puts out 150W, as opposed to the 3kW that's
needed to run household appliances.

~~~
nsxwolf
Makes sense. I've never plugged anything more powerful than a laptop charger
into it.

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jgmmo
Got an email today 'registration declined'. :(

~~~
phaedrus
Any idea why it was declined?

~~~
jgmmo
They didn't like how I described 'my approach'. Nothing specific.

It said I can register again, but something tells me I probably won't be
making the cut for this challenge.

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imranq
didn't FINsix solve this problem:
[http://finsix.com/dart/](http://finsix.com/dart/)

~~~
dskhatri
FINsix solved a AC-DC power converter problem. This is a DC to AC inverter
problem.

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pp19dd
The simplest solution (just give me the $1mil now) is to cut out the middle
man. I mean, there is a needless conversion here from DC to A/C, and then back
to DC. Not that many devices need A/C these days - maybe just your alarm
clock, if it's cheap enough (since cheap alarm clocks use the alternating
current frequency for keeping time, instead of a precise resonating crystal.)

Example of what they have now: [solar-dc] -> [inverter] -> [ac/dc transformer]
-> [device].

Cut out the inverter, the ac/dc transformer and you have:

[solar-dc] -> [device]

Required materials: wire cutters, cheap voltage regulator IC, some wire. Done.
I'll take a cashier's check please.

~~~
sparkman55
Each element on an electric stove is roughly 2 kW. Let's say you have a
4-burner stove, and they're all on. That's 8kW of power.

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%...](http://i1194.photobucket.com/albums/aa378/chance1525/Mobile%20Uploads/WP_002700_zps0b9bf904.jpg)

~~~
pp19dd
No, I certainly can't imagine doing that. However, a person doesn't typically
cook 12 hours a day. Instead, they cook in bursts, so it makes sense to put a
bank of batteries in or near the stove (firewalled of course), and trickle-
charge them with normal cables.

~~~
coryrc
No, it doesn't make sense to do that. The nice, efficient system we have is
far superior to having everyone invest in expensive, fragile batteries
everywhere and never be able to cook more than 30 minutes without recharging
for 12 hours.

~~~
mturmon
Now you've got me dreaming about my battery-powered hair dryer. And my
battery-powered electric tea kettle, microwave, and espresso machine.

Not to mention the battery-powered table saw and air compressor in my garage.

------
ackfoo
Anyone who has lived off the grid understands that an inverter is the least
efficient solution to the problem of running consumer devices from a DC
source. We laugh at the newbies running an inverter to supply a laptop PS that
takes AC right back to DC. Hopelessly inefficient.

DC-DC is the way to go, or else if you need higher voltage, take an auxiliary
feed from the charge controller, since most solar puts out 21-25VDC anyway.
For more efficient and powerful motors, use series battery banks. Duh.

This is just another way of pandering to the people who do not understand
efficiency and who are locked into the idea of "house current", in other
words, dinosaurs.

Our industrialized world is so inefficient that we throw away about 80% of
generated power. What a holocaust for the natural environment! When you go
off-grid, that just won't fly, because no one wants to upsize their generation
capacity five-fold to run some inefficient consumer device, except for the
aforementioned newbies who have yet to notice an open artery.

Inverters simply extend the inefficiency of the consumer experience to
alternative forms of power generation. The smart solution is not to make the
inverter smaller but to lose it entirely.

