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beefheart 09-12-2008 03:29 PM

solar stirling engine
Ok speaking of sustenance living / living off the land why not live off of the sun?

Has anyone ever heard of a solar stirling engine? There is one video on youtube where they use a large fresnal lense to heat a solid steel pipe that then transfers heat to run the engine. If you mount these around a pole then have the fresnal lenses follow the sun somehow you could probably power a heavier duty motor like the custom 5 hp one someone converted a lawnmower engine or something into right?

bkt 09-12-2008 04:50 PM

Haven't seen that before -- thanks for mentioning it. These look pretty interesting, but I don't know what sort of (horse)power they actually generate. Still, they should be able to spin a motor and thus generate electricity to help charge a bank of batteries in the same way conventional solar/wind/microhydroelectric do.

mrwatch 09-12-2008 08:52 PM

I have seen these at tractor shows. Most are kits and very light duty as in it wont hardly turn a toy. I have also seen larger and a man sells plans but again for practical purposes they are just models. There is and was hot air fans that you put over an oil lamp on a stand. It well may be possible to build one that would power a very small generator like for flash light batteries but for something like 5 Hp that would be a tough call.
Check out Sterling engines. Kits and plans. Flame lickers. PM Research Co.

c3shooter 09-12-2008 10:12 PM

No free lunch. Energy in minus losses= energy out. 5 hp of sunlight is a LARGE area.

bkt 09-12-2008 10:51 PM


Originally Posted by c3shooter (Post 40318)
No free lunch. Energy in minus losses= energy out. 5 hp of sunlight is a LARGE area.

No, you're absolutely right. But even if this thing is fairly weak, we should still be able to harness the kinetic energy from it. Hell, link 40 of them together to turn the motor, if need be. So what? After the cost of the engine itself, the fuel supply is free!

WILDCATT 09-13-2008 05:46 PM

free lunch
BKT: do a little research and you WILL find that these are all things tried before. and are not practical.I have seen a magnet motor it runs but you can stop it with your hand.there is an old saying NOTHING NEW UNDER THE SUN.or in mechanics.:rolleyes:

c3shooter 09-13-2008 09:58 PM

Well, to a VERY minor extent, I have one I use. Not a Stirling, but a thermocouple driven motor. Sits on top the wood stove in my shop. Converts the difference in heat between its base (on the stove) and its top (cooling fins) to generate a current that runs a 5 inch diameter fan- circulates heat a little. That motor is about 1/500th of a hp. A solar photoelectric charger about 1 sq yd generates about a watt- and a 1 hp motor uses about 749 watts. I also use a small (home built) windcharger to trickle charge some deep cycle 12 v batteries- use them for my bass boat trolling motor- and in a pinch, I can hook my inverter to them and run my fridge and freezer. But I built that for curiousity- and a touch of paranoia. There is still a sunk cost in building anything- and things DO wear out. BTW- the Virginia Science Museum has a sedan that is solar powered- naw, not an exhibit in a case- real sedan, staff uses it around town. Short range, long charging time, and the solar cell array is the size of a billboard. And while the sunlight is free, I assure you that the batteries and solar array is NOT free- or even cheap. Many things may look promising, but run the numbers- and TANSTAAFL. (Like the gent that hit on a great idea- he would put real small tires on the front of the car, real big tires on the front- since it would always be going downhill, would not need any gas. R I G H T ..... )

PS- one of my long term projects- build a micro-hydroelectric systerm. Want something that can give me a steady 5 kw. But do you know how much WATER that takes for even a SMALL turbine? Grandad was a millwright- built water mills- for grinding grain, running a sawmill, or a smith's forging hammer. Know how much power that 20ft overshot water wheel developed? About 10 hp- tops. At high water. And required constant maintenance for the mill, or the race leading water to the wheel.

CARNUT1100 09-15-2008 07:36 AM

I have seen a stirling outboard boat motor that would push a 10 foot dinghy at about 3 knots. It ran of a propane bottle and a 20 pound bottle would last 7 or 8 hours of use.
The guy who built it is a retired engineer with a passion for stirling engines.
He is now working on a 4 cylinder one with higher efficiency pressurised crankcase.
They can work, but useful energy from sunlight requires a bit of thinking.
could be done though....

bkt 09-15-2008 10:39 AM


Originally Posted by WILDCATT (Post 40439)
BKT: do a little research and you WILL find that these are all things tried before. and are not practical.I have seen a magnet motor it runs but you can stop it with your hand.there is an old saying NOTHING NEW UNDER THE SUN.or in mechanics.:rolleyes:

In principle, if you have a device producing kinetic energy, you can produce electricity. It doesn't need to be powerful, it just needs to turn a core with brushes over magnets (basically, that's all an electric motor is) and you can produce an electric charge.

And while one solar Stirling engine isn't enough to produce enough of a charge, maybe several working together (whether they are geared together to turn a larger generator, or hooked in series/parallel to generate individual small charges), it should still be possible.

That said, it might be more cost-effective to just use solar panels or a wind turbine. That depends on the cost of energy, the cost of the equipment, and the rate at which the equipment generates electricity.

h2oking 09-16-2008 05:38 AM

It is very interesting to see this stuff on this forum even though it has nothing to do with guns. That being said here is my 2 cents on the subject. When talking the making of electric power commercially one usually talks in terms of the capacity of the plant. As an example in order to get 200 megawatts 24/7/365 from a solar plant one would have to build a 1000 megawatt plant. Because the plant only works a relatively short period of time it only has a capacity factor of about 20%, meaning you need all 1000 megawatts of plant to take advantage of when the sun is shinning. Even a 10 year old kid knows you can't burn ants with a magnifying glass at night or on a cloudy day. As such you can't make electricity with solar on those events either. With wind it is better but still it has only about a 28% capacity, meaning you would get about 280 megawatts 24/7/365 from your 1000 megawatt wind plant because the wind does not blow all the time and like our 10 year old knows he can't fly his kite if there is no wind. A coal plant will give you about 80% capacity but no matter how much you scrub it, it will still emit dangerous hydrocarbons into the air. Nuclear has a 94% capacity and puts 0 anything into the air. It does make a weapons grade waist material that can reprocessed into a degraded product making fuel for the plant over and over again making it far better than even perpetual motion. The cost of making electricity with wind and solar is about 10 and 12 cents per kilowatt hour respectively, with coal it is about 8 cents and with nuclear it is about 1.5 cents. Nuclear power would cause the making of hydrogen much more attractive as the largest expense in making it is the cost of the electricity and hydrogen works well in a piston engine which is a much easier modification for the auto maker than trying to transition into building electric cars. Hydrogen is pound for pound the highest form of energy on the chemical scale, only being eclipsed by nuclear reaction.


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