small engine for small electric generator

[MCRIPPPer]

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.

 

[Niels Abildgaard]

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.

 

[Niels Abildgaard]

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

 

[Niels Abildgaard]

Hello Stewart

What electric output is relevant?

AC or DC,Hertz ,Volt?


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

 

[Philjoe5]

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

 

[jwcnc1911]

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.

 

[jwcnc1911]

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

 

[aonemarine]

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...

 

[stewcraine]

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.

 

[Niels Abildgaard]

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?

 

[mu38&Bg#]

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.

 

[Niels Abildgaard]

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?

 

[Buchanan]

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

 

[mu38&Bg#]

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

 

[Niels Abildgaard]

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.

 

[stewcraine]

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

 

[Niels Abildgaard]

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

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.

 

[Niels Abildgaard]

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?

 

[skyline1]

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

 

[stewcraine]

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