$1,000,000 dollar prize for a portable 20W generator

[ivor]

I saw this.  http://www.dod.mil/ddre/prize/topic.html

How about we brainstorm about this and get some money for the monastery?

I know it's for the US Military but, somebody will win the money.  It may as well be us.  At least we could use it for something good.

[Aggie]

Hmm...  first thing would be to determine the total energy requirement and then check against what (quantity of) chemical sources would be appropriate.  First thing that comes to mind is a methanol fuel cell.  Not sure how that would hold up during peak power requirements....

Building in a secondary power source for low-watt, long-duration power would help (can solar output at this level?) with the ability to 'boost' with a chemical source to hit the peak requirements or when the secondary is not producing.  Would definitely require some (low-level) computational power to balance the two systems.

[ivor]

I think everybody and his brother will pitch a fuel cell, not that it's a bad idea.

It has to be under 4kg in weight and provide 20W for 96 hours with a 200W peak.

I was wondering if we could get some power from motion like those flashlights I have seen that you shake? 

Something that makes people cooler at the same time would be awesome.  Could we run a sterling engine from  from body heat?  Maybe charge a battery for the 200W peak? 

[Aggie]

S'funny - I was just looking at Sterling engines (I think they could easily run a pump for a geothermal exchange system). 

The trouble is that you'd need to have a significant temperature gradient, which isn't predictable for all climates and applications. Also noticed that it must be able to run without air for a period (probably not the whole 96 h) - good for sterling engines I suppose.

Thermopiles could also be an option, but probably weight prohibitive and with the same temperature gradient issues (and probably wouldn't produce enough power). 


Hmm...  just had a brainwave for an alternative power source that'd run on water, but not practical for this application.  Might start a new thread....

[Griffin NoName]

Slightly puzzled. Space industry/&offshoots been working on this stuff for donkeys years.

[Swatopluk]

I think for the base vs. peak power it would be useful to use a multiple number of parallel running microreactors with only as many active as is needed at any moment. That would also make the outer shape more flexible.
The total retrievable energy would have to be 2-20 kWh, if I am not mistaken (20-200 W for 100h).
Methanol yields 19 MJ/kg = 5.28 kWh (as heat).
That means for 200W the methanol fuel would use up almost 3.8 kg of the 4 kg allowed (for the 20W only 380 g).
If the unit works at lower than 100% efficiency the 200 W can't be achieved at all for the whole time (e.g. an Otto engine yields only 20-30%).
In what form do they want the power output? Direct or  Alternating current? What voltage? The electrical transformer would add to the weight significantly.
If parallel microreactors are used, the power output could be selected quite easily with a simple slide control.
The question would be, whether all units have their own pump with constant flux or wether there would be a central pump with a flux varying with the number of units involved. The first solution could do away with a lot of controlling (and a complex central controller unit).
Personally I have a prejudice against methanol. Gasoline can be nasty too but methanol is not only very volatile and highly flammable but also very poisonous*  and not friendly to a lot of materials (especially when hot).

*people have died of doses of less than 10 g and even below that the organism can be significantly damaged.

[Aggie]

The complete power system must weigh 4kg or less and provide a minimum of 1920Whr. The power system must operate continuously for 96 hours. During the 96 hours of operation the system must operate: (1) continuously (i.e., 24 hours a day); (2) at partial power; (3) for a number of periods of high power of up to 200W for 5 min; (4) in a non-air breathing mode in a sealed container for a time to be determined; (5) be attitude or vertical orientation and motion independent; (6) provide output voltages of 14V and 28V. The system must attach to a vest and operate while worn. The government will provide connectors for the equipment on the course with additional cables, outlets, etc.

Full details here:
http://www.dod.mil/ddre/prize/doc/Wearable_Power_Rules-V3_1.pdf


Perhaps methanol itself is not the best fuel (first thing that came to mind); I'd also accept ethanol as a substitute (heh, same flammability issues, better (in)toxicity profile).   

Seriously though - what are the chemical fuel alternatives?  Will alkanes work in fuel cell applications (especially considering it must be able to do without air for certain periods)?  Like the idea of power-from-motion but it's not necessarily suitable for military use (could be long periods of sitting very still) as a primary source. 

[Swatopluk]

The necessity to carry the oxidizer (and to absorb the products, if the thing should be indeed sealed) will add again to the total weight. The good old Walther engine using hydrogen peroxide to oxidize a variety of flammable liquids would be a possible option.
Hydrogen as a hydride could be a bit too dangerous, I think. It decomposes in contact with water (often quite violently so).

Microreactor units in combination with a fuel tank that adjusts in size (i.e. always completely filled and under slight pressure) would allow the independence of position.

One main problem will be the flexibility in power output. If it has to be stepless, one can't do without a controller unit (and those can be bulky).

[ivor]

Did they say if it was AC or DC?

[Aggie]

I assume DC being that I've never heard of 14V AC. 

[Sibling Zono (anon1mat0)]

For a moment I thought about MB's idea about shake flashlights and while I doubt that you can generate as much power perhaps you can generate some power.

Think about this: you put a similar mechanism in both shoes and in the shirt cuffs, trying to regain power from the movement of the soldier. On top of that you put 3 high efficiency solar panels in the shoulders and hat and store the energy provided in the best Li-Ion cell on the market. You would start with a full charge for that and the other mechanisms would simply generate the remaining power through mechanical/solar means.

I have the feeling that not enough energy would be generated but I don't think it is impossible.

[ivor]

I think DC is a safe bet.  I saw so many weird power requirements in the military that nothing would surprise me.  It wouldn't surprise me if it was three phase 14v AC. Not really. 

I have seen 5v DC at 1000A.  That'll knock your ass in the dirt. 

This is a tough contest isn't it.  Nothing sounds easy or light.

Why don't they just put a hand crank on everything?  I have a little tiny flashlight with a hand crank on it and it works great.   Can't see getting 200W peak out of that though...

[Aggie]

Why don't they just put a hand crank on everything?  I have a little tiny flashlight with a hand crank on it and it works great.   Can't see getting 200W peak out of that though...

I'll bet I could do 200W over 5 minutes if we hooked it up to my bike:
http://science.howstuffworks.com/question658.htm

Not portable as a vest, though.  Heh, they're offering a mil for a reason - they can't do it in house for less.   
However, I like the idea here - we should design some smaller Toadfish invention science challenges after we're done mucking about with this one. 

[anthrobabe]

I saw this.  http://www.dod.mil/ddre/prize/topic.html

How about we brainstorm about this and get some money for the monastery?

I know it's for the US Military but, somebody will win the money.  It may as well be us.  At least we could use it for something good.

I'm not much of a brainstormer on this type of thing so
I'll make tea and such for you all while you think

[ivor]

It seems it's much harder than it should.  We may need a lot of tea. 

[Bruder Cuzzen]

Weights a big problem ,to bad the suit couldn't be the generator covered solar cells with a simple generator integrated within/on .

[Sibling Zono (anon1mat0)]

Unless you use something like this.

[Griffin NoName]

Yes, I noticed those. Great idea.

I asked my son (made battery for the Beagle Mars Lander - (((got a pic - looked like he knocked it up in our garden shed))))) about all this.

20W for 96 hrs at <4kg is 480Wh/kg.  A good Lithium-ion battery is 150Wh/kg-200Wh/kg, so they're talking about double or triple the performance of today's best power sources.  Re-charging (e.g. solar, wind, bio-kinetic) helps, but won't close the gap due to the weight of the charger alone.

There are companies out there investing significantly more than $1m p.a. in researching this field, so the prize is irrelevant.  The research lab I ran in Culham as a sideline to the space business was costing £750k p.a. and developed f.a.

Since it's a prize, the DoD doesn't have to fund the development, but everyone writes in to them to tell them about their idea in the hope of winning.  DoD finds out about the capabilities worldwide (benchmarking US capability for free in the process) and if there's a good idea or a good supplier out there they'll buy or licence the technology into the US.

[ivor]

I was going to submit my idea.  I have a couple of ferrets running around in a wheel-generator.  One can rest whilst the other runs.  Now I am just to depressed to submit it.

[Griffin NoName]