# small engine for small electric generator



## stewcraine (Aug 12, 2013)

Hi all,

Sorry for this nutty sounding message , but I was looking for some advice, and this seemed a good place for it. I flew model aeroplanes with  my Dad as a kid, so am familiar with small fast diesel and glowplug engines, but recent  years have found me helping villages get electricity. The smallest  off-the-shelf diesel generator is a 2.2 kW Yanmar diesel, but I was  thinking if a model train or plane engine or similar exist that might be  even smaller, to which I could hook up a little AC or DC generator.

I've helped millions of people access solar, and am very familiar  with that, but there's a spot also for a product of relatively low  initial cost ($50-200) and less than 1 litre per hour of operating cost  for fuel (which is what a Yanmar takes - am hoping to get down to 0.1  L/hour). Listers were also popular, and because they're slow, they could take vegetable oil pretty well too. Todays' equivalent is probably a Changfa from China, but again, about 2-3 kW and taking about 1 L/hour.

Stirling engine, scaled diesel, anything, I don't really care. Just trying to get a few tens of watts generated (my solar kits are 1-10W per household, so for a 50 household village, need 50-500W, basically).

Any thoughts? Thanks in advance...

Regards,
Stewart Craine
www.villageinfrastructure.org


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## MCRIPPPer (Aug 12, 2013)

i have thought of making a model generator just for fun. you seem to have found a good use for one. but i think it would be more efficient and reliable to have one larger generator run the whole village.


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## Wizard69 (Aug 13, 2013)

stewcraine said:


> Hi all,
> 
> Sorry for this nutty sounding message ,


How does one nut stand out in a jar full of nuts?    


> but I was looking for some advice, and this seemed a good place for it. I flew model aeroplanes with  my Dad as a kid, so am familiar with small fast diesel and glowplug engines, but recent  years have found me helping villages get electricity. The smallest  off-the-shelf diesel generator is a 2.2 kW Yanmar diesel, but I was  thinking if a model train or plane engine or similar exist that might be  even smaller, to which I could hook up a little AC or DC generator.


A DC generator would be easy, just retask a brushed permeant magnet motor.  Since DC motors come in endless sizes, you could easily build a handheld power source.  Go slightly bigger and drive a small auto alternator.   


> I've helped millions of people access solar, and am very familiar  with that, but there's a spot also for a product of relatively low  initial cost ($50-200) and less than 1 litre per hour of operating cost  for fuel (which is what a Yanmar takes - am hoping to get down to 0.1  L/hour). Listers were also popular, and because they're slow, they could take vegetable oil pretty well too. Todays' equivalent is probably a Changfa from China, but again, about 2-3 kW and taking about 1 L/hour.


Low operating costs means low power.   At some point it just isn't worth it. 


> Stirling engine, scaled diesel, anything, I don't really care. Just trying to get a few tens of watts generated (my solar kits are 1-10W per household, so for a 50 household village, need 50-500W, basically).


10 watts per house?     Is that really helping people?   I don't want to dismissing your efforts but these projects sound more like an attempt to make you feel good about yourself.  


> Any thoughts? Thanks in advance...
> 
> Regards,
> Stewart Craine
> www.villageinfrastructure.org



Seriously anything less that 500 watts seems like a complete waste.  That is unless your goals are extreme portability.   Even 500 watts is very limiting, you really want enough power to run power tools.   Ultimately tools are what liberates people.


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## lohring (Aug 13, 2013)

Ohlsson and Rice once made a small generator.  See http://gasengine.farmcollector.com/gas-engine/searching-for-ohlsson-and-rice-engines.aspx  Lohring Miller


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## MCRIPPPer (Aug 13, 2013)

im hard pressed to think of anything that uses less than 10w!


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## Wizard69 (Aug 15, 2013)

If you look towards the hunting/fishing/outdoors suppliers you can find small generators that go as low as 500 watts of output power in portable designs.    For the usage intended I can't see where a DIY project makes sense, you really need a mass produced solution.   The other end of the spectrum is that the US Army was looking into very small generators to be carried by solders to power/recharge all of their little devices, but I'm not too certain much came of that. 

On a slightly larger scall these guys have an interesting approach: http://www.bladonjets.com/.   Here is something on the very small end for a turbine generator: http://www.powermems.be/gasturbine.html.  Here is a solution that looks like it is ready to ship: http://www.mtt-eu.com/.    Here is an interesting paper on the subject: http://www.bioturbine.org/Publications/PDF/microturbine-01-HILTECH.pdf

You may be wondering why I focused on turbine micro generators above.    There are a couple of reasons.   For one the units are extremely small for a given output.    Another reason is few parts to deal with.  Some of these machines have one moving part with even the common ball bearing replaced with air bearings, this means long trouble free run times.   As long as you have fuel one of these units could run for three years straight.   In that time a diesel generator would have gone through at least four rebuilds along with multiple servicings.   

To put it plainly most internal combustion engine power sources wouldn't be worth the trouble unless the area you are putting them in has the support infra structure in place.   If the area has the infrastructure in place then there is no point to your project.   As much as I hate solar panels, they are likely a better solution for areas well away from modern infrastructure.


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## oldtruck (Aug 15, 2013)

visit your local junk yard, and old construction equipment Look for an generator. There are 6 to 24vdc and you will need a voltage regulator. 
Alternators will work GM a had a 25 amp self excitation with built in reg. Stull available at most auto parts it will take about 5 hp to run at 1100 rpms.


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## Entropy455 (Aug 15, 2013)

A liter of gasoline contains approximately 31,700 BTU of energy. If this liter of fuel is spread out evenly over one hour, the engine fuel consumption would be equal to 8.81 BTU per second (actual heat input into the engine.) Assuming a thermodynamic engine efficiency of 30%, the mechanical crankshaft output would be 2.64 BTU per second (rotational power).

Assuming a typical generator efficiency of 70%, the actual electrical power generation would be about 1.85 BTU per second. Converting into Watts(where 1055 Joules is equal to one BTU, and one Joule per second is equal to one Watt)  a typical gasoline powered electric generator will produce about 1950 Watts of electrical power, while consuming 1 liter of gasoline per hour.

This is just enough power to run a single 15 ampere 120 volt circuit. It would be great for camping  assuming you only have one small load to run at a time. . . . .


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## aonemarine (Aug 15, 2013)

Think Steam!!


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## Lakc (Aug 16, 2013)

Entropy seems to know the numbers involved. Diesel being the most efficient in the internal combustion range, (excepting turbine?) and steam being the least efficient. Stirling supposedly outdoes them all.
Slow running generally means more mass rotating, which is the opposite of what you get downsizing motors.
I would not discount the usefulness of even the small amounts of electricity, dependably generated, and what it could mean to some remote village that has net even heard of the grid. LED lighting, charge a battery, run a radio, all could mean life or death in some situations.


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## mu38&Bg# (Aug 16, 2013)

Small engines are expensive due to low volume and limited market. I've built generators based on RC hobby engines. You need to come up with control, regulation, etc. The Chinese 50 or 80cc two stroke gensets is about as cheap as you can get but you have to burn gasoline. A 10W generator would need to be developed from scratch and the cost would be prohibitive.

A genset running at less than full load would burn less than max rated fuel rate, but may or may not be as efficient. A few solar panels seem to make more sense but I understand that they are targeted for theft.

Greg


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## stewcraine (Aug 16, 2013)

Thanks, Entropy455 and others. Yes, 2kW for 1 L/hour is spot on what is available in the market today. I'm aiming for 0.1-0.2L / hour. Even at similar capital cost. I don't mind the DIY aspect, Wizard69, because if you guys can make one, I can take it to China for mass production. I lived there for 4 years building up www.barefootpower.com and we shipped 200,000 units and more of products I slapped together from rough prototypes compiled from off-the-shelf product. I'm looking to you guys to see if such a small engine can be produced - sourcing the DC or AC generator is of zero concern, I just need something to turn it around. A Stirling engine is likely a good chance of being successful. Microturbines of 25kW are way too big for me, am aiming at 50-500W. The powerMEMs link is interesting and good - I've seen the Japanese have made something similar for robots, but it costs a bomb, and the Japanese rightly point out that something rotating at 500,000 rpm is not trivial. A slower stirling engine sounds better to me....

Cheers,
Stewart


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## aonemarine (Aug 17, 2013)

http://www.cyclonepower.com/whe.html


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## stewcraine (Aug 18, 2013)

Thanks for the waste heat engine link. 8kW is about 20 times larger than I'm hoping for. But interesting!

Stewart


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## mu38&Bg# (Aug 18, 2013)

Large low RPM engines have some inherent traits that will be lost when going to a small high RPM engine. What type of fuel are readily available? Oils? And what about service components for your custom engine?

Greg


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## MachineTom (Aug 18, 2013)

Stewart, In looking at what you want a small IC engine is very inefficient compared to a Listen diesel engine. Oil based fuel is generally expensive in most places in the world. What about steam type engines that can burn local solid fuels, It would seem better for a village to gather and burn local fuel, than to generate cash somehow to purchase oil based fuels.


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## Tin Falcon (Aug 18, 2013)

Maybe one should look upon history. 


this any fuel quite unit put out just under 50 watts. 

http://www.royalsignals.org.uk/photos/steam.htm

Tin


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## aonemarine (Aug 18, 2013)

Nice find Tin!  Thats the beauty of steam, easy to source fuels.  
  Side note, what about wind power?


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## stewcraine (Aug 18, 2013)

Hi again all,

Dieselpilot - kerosene lamps are in every house, so kero/paraffin is pretty widely available. Everyone cooks indoors with wood or charcoal, so this is available. Diesel and gasoline are pretty well available too, for motorbike transport, small boats and farm equipment. I've built an after-sales support network of over 500 retail points serving 400,000 households in my last company, so am confident we have the networks to keep support going.

MachineTom - Yes, am thinking something that burns on the same stuff that ride-on trains burn on, using a similar engine of not terribly high rpm (like a plane engine) is the way to go

Tin - Brilliant! Simply brilliant! This, and the Tiny Tiger posted earlier, and both winners for me. Note that it uses a "model steam engine" - that's exactly why I'm on this site - you guys know how to make those, or even guide me towards where I could buy one. Now I need to try and track down whoever took these photos or made this unit (Stuart Turner, or other). Even if the upfront cost of this was as much as a 3kW diesel, the running costs would be a heck of a lot lower. If it can run on wood, awesome - wood costs $20-50 per 1000kg in villages, and it would take ages for this little puppy to chew through a tonne...

Thanks again! Now for the detective work. But if any of you think an off-the-shelf model steam engine has potential, please let me know. Doesn't have to look like a train or be beautiful or anything...

Cheers,
Stewart


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## stewcraine (Aug 18, 2013)

Just found a YouTube of the Tiny Tiger too.....they're out there...!
[ame]http://www.youtube.com/watch?v=fLsXPfZl9E0[/ame]


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## MCRIPPPer (Aug 18, 2013)

steam: simple but very bad at converting fuel into usable energy. 

internal combustion: very efficient but more complex. 

both of these issues become worse when miniaturizing an engine. reliability also goes down on tiny engines. 

the mini v8s people make on here have to be at least as accurate as a real v8 as far as fit of the components, and are no where near as powerful or reliable as a real one. (they make up for it in awesomeness tho!) but awesomeness will not make power unfortunately.


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## Niels Abildgaard (Aug 19, 2013)

Small steam plants buillt by very skilled people

http://www.imlec2013.co.uk/#!results/cebk

returns efficiency of less than one percent for 100 W.

A woodgas generatorplant here in Harbooere gives 28% but is 1200 kW

http://www.volund.dk/en/References_...chures - BIO/Biomass gasification plants.ashx

The efficiency of really small combustion engines is low due to too much surface looking at too few atoms trying to do their work.The best ratio of surface to volume is realised by opposed piston engines and it is my pleasure to have made a design for such an animal

http://chevy57.free.fr/FORUM/junkers_two-stroke_crosshead.gif

The beauty of woodgas for spark ignited engines is a 10- 15 % Hydrogen part making carburation and ignition foolproof.

It would be much fun to have an ongoing contest here of making the most efficient
100 Watt engine generator divided into fuel subclasses.


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## Niels Abildgaard (Aug 19, 2013)

Trying to make 50-100 Watt efficiently has been the main game for quite a lot of talents
in something called Shell Eco Marathon.
Can someone involved give us non combatants a state of art report or show the way to the ones to beat?
No platinium technolgy dependent ,(fuel cells etc)need aply


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## Niels Abildgaard (Aug 19, 2013)

Hello Stewart

What electric output is relevant?

AC or DC,Hertz ,Volt?


Picture shows worlds first (and maybe last) electric synchronized opposed piston engine


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## Philjoe5 (Aug 19, 2013)

I don't know a lot about these but Stuart built a steam engine powered generator during WWII so paratroopers could recharge their radio batteries.  I saw one recently at a model engine show and here's a youtube video with a bit more info:

[ame]http://www.youtube.com/watch?v=qHPX6sDsQgk[/ame]

Cheers,
Phil


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## jwcnc1911 (Aug 19, 2013)

I'm kinda on board here.  I'm not a prepper by any means but I think a small hobby sized stirling that makes just enough power to charge a cell phone or run a radio would be great in emergency situations.  Back in 2010 we had tornadoes and as a result we were without power for 8 days.  Later that year we had an ice storm... we were without power for 9 days on that one.  I'd have given my left nut for 15 watts.  My car idled for days with an old invertor plugged in it.

Just my two cents but I'm working on the same thing in my spare time.  Not for sale or commercial purposes but "just to have it" is good enough for me.  After all, what good does a hobby engine do any way?

I'll be following this to see what you come up with.


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## jwcnc1911 (Aug 19, 2013)

any way, Google "rocket stove" for a more efficient heat source for a little stirling.


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## aonemarine (Aug 19, 2013)

It wouldnt take much to convert a small single cylinder IC to steam either, its been done on lawn mowers motors 100 times over now...


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## stewcraine (Aug 19, 2013)

Hi Niels - electric output format in not an issue. AC or DC, whatever, don't mind. Conversions afterwards electrically are easy, and LED lamps + phone chargers come in both AC and 12V or 5V DC formats for supply from cars and laptops. Or from 3.2-3.7V DC direct from batteries for LEDs (phone chargers step this up to 5V to charge phones). And thanks for the tip on the Shell Eco Marathon, will go see what they've found.

Thanks to all for the other great links. PhilJoe5, that's just about spot on, 0.4hp is about 200W. Now how to get one or estimate its price....!

Others - 1% efficiency doesn't actually scare me. Villagers use 1kW of power per house in their stoves for cooking. A thermoelectric module has been fitted to these to generate a few watts of power too (http://www.biolitestove.com/). JW, you need one of these for your next storm! Will keep you warm too!

Thermoelectric modules could also be my "solution" too, but am trying for more than a few watts per household, and to get 50-200W for the village (who use 3-5W per house for LEDs and phone chargers). 200W is handy too, about what Tour de France cyclists average, so can run some higher power stuff in fact, which 1-10W home-based fully-distributed solutions will never do (included one solar panel per house)

Cheers.


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## Niels Abildgaard (Oct 24, 2013)

To make 200 Watt from petrol or LPG about 5 to 15 cubiccentimeters will do.
Professor Chaddock once made a 5 ccm engine to beat a model aircraft record.
Did he ever publish some fruel consumption/efficiency  figures?
Chucks new 4 stroke engine would be a very good basic engine for the     MAKE 200 WATT AS FUEL EFFICIENT AS POSSIBLE      contest.
The solutions are not the same as the usual make most horsepower from xxxx ccm.
Has someone a link to a cheap suitable dynamometer for small powers?


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## mu38&Bg# (Oct 24, 2013)

His articles Model Engineer say Chaddock tested it at 9600RPM, with BMEP 80PSI and 1.1Lb/HP/hr (670g/kWh) on gasoline. The design looks truly unique for 1967.


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## Niels Abildgaard (Oct 24, 2013)

Hello Dieselpilot

Thank you and can the dynamometer he used be made by senior citizens?
A good 300 to 400 ccm cylinder spark ignited petrol engine will be using 
around 230grams/kWh so his results was remarkable.Do You know what thermal efficiency modern 2.5 ccm team race diesels return?


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## Buchanan (Oct 24, 2013)

Is there any body out there that has reverse engineered a brushless motor into a alternator. Modern electronic regulators can look after the rest.That should give high eficiency and low maintanance. India used to make a comercialy available hot air engine which powered a cooling fan up to about 15 years ago.The fan was about 30cm 12" diameter. That would be around the 10w mark. 

Deryck


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## mu38&Bg# (Oct 24, 2013)

I have tested off the shelf four stroke model engines converted to ignition at less than 400g/kWh. My glow to diesel four stroke conversions are also in that range. Prof. Chaddock used a propeller in his tests. I have not seen any reports of efficiency of F2C engines. This does interest me, but not enough to spend almost 1000USD to acquire one. Brushless motors make excellent generators, but for good efficiency need to be sized properly and require proper regulation.

Greg


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## Niels Abildgaard (Oct 25, 2013)

A 100% efficient petrol (or diesel oil) engine will take 86 gram to make one kWh.An engine using 230 grams is thus 37 % and one using 400 grams is 21%.This is still miles better than the best one can expect for a simple steam plant sized for 200 Watt continuosly.Twenty times in fact.
To make steam realistic will need wage for skilled,always sober never sleeping attendant zero and a wood price about 40 times lower than petrol per mass unit.
I really think it facinating that a hobbymade stupid fourstroke(two is best) small engine can have more than half the efficiency of VolksWagens best and do a real job.
Even if wood is the only fuel possible the gassifier or wood-distillation way is still at least ten times more frugal than a small steam plant.
For making a 200 watt cylinder we need a 5 mm inlet and a 4 mm exhaust  valve let us say 12 mm cylinder bore.
Chucks engine with a stroke of 32 mm(more or less) could be a very good first shot.


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## stewcraine (Oct 26, 2013)

Thanks - happy to take this guidance, towards a four stroke small engine rather than steam. Next step - what off-the-shelf product should I buy to try and make this happen? Is there an Amazon link to buy one, as an example? Something like these?
http://www.laserengines.com/engines.htm

How do I know the wattage power output of these?

Cheers,
Stewart


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## Niels Abildgaard (Oct 30, 2013)

stewcraine said:


> Thanks - happy to take this guidance, towards a four stroke small engine rather than steam. Next step - what off-the-shelf product should I buy to try and make this happen? Is there an Amazon link to buy one, as an example? Something like these?
> http://www.laserengines.com/engines.htm
> 
> How do I know the wattage power output of these?
> ...




The wattage can somehow be deducted from stated propeller dimension and rpm
A 12times 8 propeller at 10000 rpm sitting in a stationary test bench absorbs around 800 watt.
The shown laser engines are not what You really want.
Fuel is not normal petrol and combustion geometry is a flat pancake where optimum for power ecconomy is a sphere
I would in Your case start with a very normal chinese genset of say 600 watt and then have a gifted man or two try two or three different cylinder diameters on the given basis stroke and compare fuel consumption.
For Your case where longevity and minimum lube oil  is a good idea crosshead engines are the way to go.
I took a nonworking example of

http://www.ebay.de/itm/ZIPPER-ZI-STE-900-IV-INVERTER-STROMERZEUGER-STROM-AGGREGAT-GENERATOR-HOLZMANN-/160904671445?pt=DE_Elektronik_Computer_Haushaltsger%C3%A4te_Staubsaugerbeutel_PM&hash=item2576aa70d5

apart and was ashamed of being western
The damned thing has electronic regulated carburator and inverter etc and is selling here for peanuts.
Stroke is 32 mm.

Buy 4 and donate to some of us useless old members and let us compete.
Mine would be a 12 mm two stroke with central exhaust valve.


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## Niels Abildgaard (Jun 18, 2016)

Some Young people in Denmark are trying to improve mileage of a Shell Eco racer.It is based on a Yamaha 50 cc engine (bore 41mm and stroke 38 I think)
They are planning to reduce bore to 38 mm  and they measure a thermal efficiency of 41.5%     or 205 grams per kWh (better than Wrigth Turbo Compound)  on pump petrol.

https://ing.dk/blog/kan-nye-knaster-knaekke-kilometerkurven-184661


I still think my AC coupled Junkers scheme

http://chevy57.free.fr/FORUM/junkers_two-stroke_crosshead.gif

can do better but space for spark plugs in cylinder wall is problematic as compression ratio is 14 to one.
Has it been tried to have sparkplugs  in center of pistons?


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## skyline1 (Jun 19, 2016)

Hi All
May I chip in with my tuppence worth, I mean no offence to anyone in my comments

Producing a small cheap plant that can reliably and efficiently produce about 50 to 100W is something of a Holy Grail among many engineers, including myself

I have built and run a micro generating plant  using a watertube boiler, a steam turbine and a small D.C. Generator (See my Avatar).

It makes about 4 watts of power and is merely meant to demonstrate the principles of power generation

It is horrendously inefficient however,  It's input is a propane gas burner of  approx 1.5Kw (equivalent).

But in building it I have learnt that in smaller scales more of the lesser laws of physics come into play.

unexpected stuff like resonance, and steam "hammer", whilst larger machines do suffer from these is is to a lesser extent I feel

And of course,  Friction, the one none of us can get away from. 

As things get smaller they must get faster and unfortunately less efficient 

Like Hummingbirds compared to Elephants

About the 50 - 150 Watt range seems to be where most of the problems both Electrical and Mechanical seem to be at their worst but they will be solved

I commend these brave engineers finding answers in this vital area

 I haven't a solution but...

Flash steam driven turbines  or miniature gas turbines connected to High Frequency Brushless Alternators. 

With modern (and relatively cheap) electronics High frequency A.C. can be easily  rectified and if needed chopped to more standard frequencies.

Just a thought, please feel free to disagree 

As I said just my tuppence worth

Regards to all Mark


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## stewcraine (Jun 19, 2016)

Thanks everyone - lots of great comments here over the years!

I couldn't see any easy wins here (though I still love the 50W wood-fired steam battery charger that spies used!), so have ended up sticking with solar, and am looking at a 24V 40Amp DC generator to back up the solar charged batteries when there's no sun. If that's a diesel, we could convert it to run on coconut oil in a few areas, but now diesel is cheaper than it was, not much point. The power system is for running some other innovative machines we've made a lot of progress on since this thread started - solar powered micro mills:
[ame]https://www.youtube.com/watch?v=xWgevfqIvdU[/ame]

Cheers,
Stewart
www.villageinfrastructure.org


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## Niels Abildgaard (Jun 19, 2016)

Hello Stewart and nice to know You are still helping other people.
The 50ccm Yamaha moped engine from the  danish Shell Eco students give 41.5% thermal efficiency at around 600 watt I think.
A man is about 25% effective when working.
That means that the waste corn hubs can produce as much  power going through a gassification process ( Imberth) for a 50 ccm generator as the edible kernels.


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