Solar power field using Stirling engine.

Tell us how to build a simple stirling engine.. I'm very intrigued and like a cat very curious!

Although you are right both my cats that were too curious got run over or got sick (from foot injury infection from fighting ? ) and died. The scaredy cat is alive and well. THe quick and the dead should be amended to say "The quick who are scared and the Dead".

This one is made of cardboard, largely.

Now thats cool!!

I saw the show it was neat, I think they said the focused light was at 1500 deg. F, wow. Now all they have to do is build more, at get some hefty batteries for the cloudy days. A Stirling engine uses a two chamber piston, and the heating, and cooling of a gas to make the piston move a crank connected to the piston. Small ones can work with just a few degrees difference in temperature. Go to howthingswork.com and look it up, its really neat, and it was invented almost 100 years ago. RM.

Hi Guest. It was invented in 1816 by Robert Stirling so it is nearly 200 years old. Spencer.

Sorry, its howstuffworks.com RM.

https://www.stirlingengine.com/makes interesting reading. The Stirling engine has been practicable since its original invention. The key ratios of

• power output per kg installed weight
• power output per capital money unit invested

have made it relatively inconvenient (and therefore unappealing) in comparison with external- and internal-combustion engines until relatively recently, save for niche applications. Things change over time and with changing values and demand for energy sources, the Stirling has an interesting future.

CR4 Admin: replaced broken link

Hi PWSlack. Hi PWSlack. Stirling engines powered by the sun is not a knew phenomonen. Way back in the 1980s William Beale president of Sunpower Inc, of Athens, Ohio experimented with this as a future source of energy. Mr, Beale is the inventor of the "free piston stirling engine" and it was this type of stirling he used in his experiments. Since then another stirling engine manufacturer, United Stirling, based in Malmo, Sweden, have experimented with this souce in their experiments. The experiments in the 1980s have produced exellent results, but the problem is that it was way head of its time. The free-piston stirling engine is very cost effective to produce as it only has two moving parts, the power piston and the displacer, The main costs are the parabolic mirror and the sun tracking device. When it comes to effectivity remember, the sun to power these engines is "free". So all in all these power plants are more effective than anything else, producing efficences of 40 to 50%. Spencer.

Maintenance is always a factor in any type of mechanical device.

The one thing that I would be interested in finding out is what the return on investment is.

Could you imagine having one of the dishes sitting outside of your house and running your own mini electrical power plant for your own home.

Almost totally free electricity once its paid for.

Except for the mainteneance of course.

The beauty of the free-piston stirling engine is that it requires virtually no maintainance. It has only two moving parts which both move vertically, so there is very little wear on the sides of the cylinder and the pistons. Such an engine is a sealed unit that is cyliderical in form, there is a cool end and a hot end, what can go wrong? Spencer.

Where is Stirling Stan?

There are some neat stirling types out there try 5Hp Stirling bangladesh" and also some that have 4 (2 pistons each) cylinders. They guy has integrated both pistons into one cylinder and then chained 4 together on same crankshaft. More power less size, less weight. They say you need at least 500 F to operate well enough to make stirling worthwhile. Solar can go to 1700 F I've heard for solar dishes focused together on same point.

The first ever stirling engine had both pistons in one cylinder, so did Philips first succesful stirling engine. Spencer.

Thanks, so is it then more efficient to have the cylinders separated (easier to keep cold and hot) or better in one cylinder? I am amazed that this hasn't taken the world by storm using solar focusers for heat.

Having the power piston and the displacer piston in one cylinder makes for a very compact engine, this type of engine is a so called Beta engine. Having the power piston and the displacer piston in two different cylinders in a V configuration is called a Gamma engine. Philips first engine was a Beta engine the 60c, it was first tested in 1952, it devoloped 240W at 2000 rpm. A later design in 1957 of the same type the 102c produced 750W at 3000 rpm. Philips have ceased to exist and this capable engine has been left on the shelf. A Beta engine has a higher compression ratio than a Gamma engine. High density stirling engines have working gas of helium or hydrogen at 20 to 100 bar pressure, these engines have an overall efficiency of 36 to 46%. Spencer.

Why isn't anyone making them to work on solar focused energy and captured rain water?

Back in the 1950s there was anough oil around to further develop IC engines to their present level today, though I cannot understand why stirling engines where never put to use in under devolped countries. Another reason was that they didn't have the present day materials, I think that in the not so far future we will see stirling engines put to use. Here in the UK we can buy water heaters that run on gas while the residue heat is put to use by powering a stirling engine to produce our own electicity. Spencer.

Are you saying that the UK is leading the way already using stirlings to make electricty on a commercial basis? If you want to see 'one' in use in bangladesh you can search How I Built a 5 Hp Stirling Engine .. its a neat read and they let you have chapter 6 for free as a teaser (halfway down there is a link) . But the question is why isn't this being used at least some in america? sad. Maybe its because it looks like alot of work to build that thing. (casting cylinders, pistons, etc. cooling fins, on and on)

I used to design and construct stirling engines from 1/2hp to 10hp before I retired. I have two at home, one is mounted in a generating set of 1hp, the other is a 5hp boat engine. They are easy to design and construct as a toy, but if you want to build a stirling engine of any use you have to have a good working knowlege of thermodynamics and fluid mechanics. One of the problems you will face is how to get enough heat into it, then there is the question of cooling. To get enough heat in you will have to have an advanced heater head area, this is possible by utilizing inner and out fins on the heater head, otherwise a multi-tubular head. As long as you are producing a boat engine you will be alright as far is the cooler problem, the boat floats in the best cold sink, water. Spencer.

Wondering what you think would be the needed diameter of a solar dish to heat a 5 hp engine? If using finned head maybe a 2 lawnmower engines could be used or a twin v engine (insulated in between the heads)? It would save alot of work to use the existing pistons cylinders and heads that are aready there. On the internal fins.. how would the piston get past them.. wouldn't the fins wear down with the constant pistion scraping past it. That is one question I have for all stirlings: what is the rings if any required, oil, friction scraping metal off the cylinder walls?, if its a sloppy fit as some diagrams seem to indicate .. what keeps the piston from tiling cockeyed or from scraping the walls as it travels? thanks, jeff

Hi. E-mail me at this address and I will help you design a decent stirling engine: garnets@blueyonder.co.uk I will explain every thing for you from start to finish. Spencer.

Whispertech in Christchurch New Zealand has some good (but expensive) engines. -grapevine

On the episode of Really Big Things about the solar field in New Mexico, can anyone tell me where exactly those 6 dishes are located. I thought they said that it was on an Air Force Base and Kirtland AFB came to mind but I'm not sure.

Thanks.

This discussion of Stirling engines takes me back 30 years to when I was designing the thermodynamic and fluid dynamics side of free piston engines conceived by Glen Benson of Energy Research and Generation of Oakland, California.

Thermodynamics tells us that the efficiency of an engine is limited by the temperature of the hot end of the engine. This upper limit is known as Carnot efficiency. If memory serves, it is defined as: Temp (hot end) - Temp (cold end) divided by Temp (hot end). Simple.

That explains why 1500 F is a good heat source for an engine. You want the hottest source that your materials can stand. That is, you do not want your engine to melt or even get gooey (metals get rubbery when extremely hot; that is how steel mills shape steel). 1500 F sounds like about the limit for special high temperature alloys. After that, you are looking at ceramics, which have their pros and cons.

What you want to do, then, is to find out how to obtain the greatest proportion of Carnot efficiency that you can with the temperatures and materials available. That effort can get you involved in some very interesting high tech materials and clever designs for heat exchangers, heat pipes, etc.

Glen Benson's designs for Stirling engines promised to resolve many of the challenges facing Free Piston Stirling Engines. For example, the engine would be formed from ceramics, and that would handle not only the high temperatures but also the steep temperature gradient along the engine casing between the hot end and the cold end. The thermal conductivity of the casing could be kept low to limit leakage of heat.

The ceramic could also be formed to nearly final shape, which includes having tight tolerances for the gas bearings that lubricate piston travel; hence, no oil is needed. A gas bearing is like an air cushion, just pressurized gas. That gas is the working gas in the engine (helium or hydrogen; air is not that effective as a working fluid for thermodynamic reasons; it soaks up heat but does not give the boost in pressure that you need as well as helium or hydrogen does; air molecules -- oxygen and nitrogen -- vibrate too much instead of whizzing around faster).

Benson also employed dual 'power' pistons, like the opposed pistons in the engine of an old Volkswagen Beetle, a Porsche 911, an old BMW motorcycle, or a Subaru. When the two pistons move in synch, there is no vibration. There is also a balancing piston to minimize vibration caused by the displacer piston, much like the balancing shaft in modern 4-cylinder engines.

So, when you look at the details of Stirling engines and the advances of internal combustion engines, it is not hard to see the former have not yet been developed and widely adopted. Believe me; I wrote my masters thesis on this issue. (A side note -- Benson also worked on piezoelectric fuel injectors for diesel engines around the 1970s, and they are now coming into use, long after any patents have expired.)

Twenty-five years ago, I visited a couple of other developers of Stirling engines. United Stirling of Malmo, Sweden, welcome me in. Philips was less receptive. Now, I am back in Malmo and heading down memory lane ... and I now teach science communication, in part, so that fewer worthy inventions will go unsupported.

Will

Sydney, Australia

visiting Copenhagen and Malmo

will,

I would like a Stirling engine in my back yard that powers the house. I think a ceramic about 1/10th the size of the ones out in mojave ca should be the right size. How much would one cost?