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The Stirling Engine (Merged)

Discussions of conventional and alternative energy production technologies.

The Stirling Engine (Merged)

Unread postby nicklockard » Fri 10 Sep 2004, 19:56:40

The Power Conversion Unit (PCU)

The Stirling engine’s cylinder block incorporates four sealed cylinder assemblies (pistons, piston rods, and connecting rods domes) along with coolers, regenerators and heater heads. Concentrated solar energy heats up self-contained gas (hydrogen) in the PCU, causing the gas to expand into the cylinders, moving the cylinders and generating electricity. There is a 90-degree timing separation between adjacent cylinders and the working gas is exchanged repeatedly back and forth between the same adjacent cylinders. This cycle is repeated over and over as the engine runs at a steady rate of 1,800 rpm (a low-stress, long duty-life regimen for a conventional gasoline engine). Unlike familiar auto or truck engines, Stirling engines do not rely upon internal combustion to drive the pistons and rotate a crankshaft. In fact, there is no combustion at all. Power is generated by heat transfer from the concentrated solar rays to the working gas in the engine’s heater head, which converts the heat energy into mechanical motion. This power runs the electric generator, which produces electricity with an output of 480 Volts and 60 Hertz, so it is already power-conditioned by the generator’s interface. The generator of each unit in a utility-scale project is connected by underground wire to a small substation where the power can be transformed into a higher voltage for more efficient transmission across the grid.


Proprietary History
In 1996, SES acquired the patent, tooling, and equipment rights to the world's most efficient solar dish concentrator system: the Dish Stirling. Initially developed in the 1980s by McDonnell Douglas (now The Boeing Co.) the Dish Stirling system was field-tested by Southern California Edison and Georgia Power for over 175,000 hours between 1982 and 1988. Edison's test data indicated the Dish Stirling out-performed all other solar-to-electric generating systems by a factor of two, yet had comparable start-up costs. SES optimized the McDonnell Douglas dish to operate with a 25kW Stirling power conversion unit (PCU) developed in Sweden by United Stirling, Kockums and Volvo. The resulting system, the "Dish Stirling", has fewer moving parts than comparable diesel engines and operates relatively quietly. The SES Solar Test Site and related tooling and equipment facilities are located at the Boeing facility in Huntington Beach, California. The 25kW SES Dish Stirling system has an operating track record of more than 17 years. Since 1984, it has held the world record for efficiency in converting solar energy



http://www.stirlingenergy.com/solar_overview.htm


Extensively tested (I remember seeing an article in the mid nineties that the DOD was testing a field-portable, 2-man crewed unit which produced 5KW from a 16ft. array in Popular Mechanics.

It's more efficient than PV, with similar capital costs.




Also, for someone with a shop, easy to make your own:

First, you'd need a paraboloidal 'dish.' This can be easily constructed from fiberglass matting in an (actually caternary curvature, but close enough) by suspensing a hoop from your garage ceiling. Drape some light-weight fiberglass matting over the hoop. Apply your choice of thermoset epoxy evenly (you might want to pre-apply it prior to hanging.) Next, by means of a low-speed drill, spin the hoop continuously while it is curing. This will iron out 'kinks' and defects in the shape.

Next, you'd need to apply a reflective coating of chrome paint to the inside surface; you'd probably want to clearcoat this so it stands up to rain, etcetera.

Affix a stirling engine by means of a rod poking out from the dish such that the hot end of it recieves the concentrated sunlight. Place the cool end facing away from your concentrator and toward the sun--you may want to make a tiny 'sun-hat' to keep direct rays off of it. That will increase the temperature differential and total output.

Now, you can buy Stirling cycle engines commercially on the internet. Just google it. Many can be ordered with integrated generators.


Alternate method: make several one-meter dishes such that their focal point (term used loosely since shape not truely parabaloidal--but close enough) points to a common center where a larger engine/generator is affixed. /Fabricate steel or fiberglass frame arms to hold all this together.

Finally you'd need a sun-tracking system.

Options:

1. You are the sun tracker--totally manual, you reposition 5 times a day.
2. You make 8 or 10 azimuth 'rails' which you manually can change the collector's base to with the changing angle of the sun, and you use a small motor and reduction gear to move in response to an solar intensity signal (simple radio-shack photocell placed in bottom of tube) when voltage drops (from improper alignment with sun) it gives a signal to the motor to move until max voltage is achieved again. (you'll have to make a simple TTL logic board for this)
3. Buy a commercial device for doing this.




Efficiencies are roughly double that of the best PV, so that means around 28%. Not bad, eh?
Last edited by Tanada on Sun 21 Feb 2010, 16:57:51, edited 1 time in total.
Reason: Fixed Thread title
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Re: Paraboloidal Solar Stirling Cycle Generators

Unread postby rerere » Fri 10 Sep 2004, 21:44:30

nicklockard wrote:T the engine runs at a steady rate of 1,800 rpm


A bit fast for a stirling, but ok.

Lets see a shipping unit!

nicklockard wrote:Extensively tested (I remember seeing an article in the mid nineties that the DOD was testing a field-portable, 2-man crewed unit which produced 5KW from a 16ft. array in Popular Mechanics.


Lets see a shipping unit then!


nicklockard wrote:Efficiencies are roughly double that of the best PV, so that means around 28%. Not bad, eh?


Ok, to bring the Peak Oil readers up to speed:

Stirling engines need a hot side and a cold side to provide a delta T for work. The great thing about this in my not so humble POV, is the hot side can be sunlight and the cold side can be your water or your home.

Problems:

www.omachron.com used to have a page about a 1 hp stirling, made from stamped metal (not machined) that would have a 8,000 hour life (4,000 to replace seals) using Nitrogen as the working gas that they felt could be bought for $89 in shipping container quanity. They claimed that Sept 11, 2001 stopped it from happening.

www.dekaresearch.com has a stirling that gets play (got play) due to the Segway interest. No closer to shipping a working engine that I've seen.

www.energyinnovations.com had a Discover Magazine article about the Stirling design - $250 for 250 watts and would provide hot water. They 'have changed design'

The only people who ARE Shipping and HAVE been shipping and are increasing their shipping is www.whispergen.com. The original whispergen's were $32,000 and now can be had for $12,000-16,000. The unit to watch is the CHP (Combined Heat and Power) with a target of $5000. You burn gas, you get 1Kw of power and hot water for hot water or building heat.

www.tamin.com has a $25,000 engine and is being tested in a competing CHP design.

It seems the limiting factor for shipping a mass produced stirling unit is a desire to get the best preformance. To get that preformance from sunlight, you need to engineer for a variable Temp. I don't grok why designers don't go for a design that works, perhaps not at a peak, but works. Any design is only buring daylight.
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Unread postby Hegel » Fri 10 Sep 2004, 22:56:43

If you want to buy one, check this link:

http://www.stirling-engine.de/engl/index.html

They sell all kind of sterling systems. The only product I've ever bought from this company is a lawn mower. Probly, I'm going to buy one of their Power-Heat stirling engines real soon, unless Energions SteamCell becomes available in the meantime.
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Unread postby rerere » Sat 11 Sep 2004, 08:15:15

Hegel wrote:If you want to buy one, check this link:

http://www.stirling-engine.de/engl/index.html

They sell all kind of sterling systems.


Not that I have seen. A few prototypes, no acutal units.
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Unread postby Aaron » Sat 11 Sep 2004, 08:22:52

Natural gas appears to be the most used energy source for Combined Power / Heat Units.
The problem is, of course, that not only is economics bankrupt, but it has always been nothing more than politics in disguise... economics is a form of brain damage.

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And your point?

Unread postby rerere » Sat 11 Sep 2004, 10:24:08

Aaron wrote:
Natural gas appears to be the most used energy source for Combined Power / Heat Units.


IF one is going to burn gas for heat, why NOT get power with that heat?

Because right now many BTUs of gas are being used for heat. Just heat. No work being done, just heat.
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Unread postby Aaron » Sat 11 Sep 2004, 10:58:13

Of course... a brilliant concept. Capture lost energy...

Now all we need to do is deploy this technology into the impoverished nations of the world, as well as China & India, to prevent them from gobbling up any savings we might accrue, through growth.

Nothing a few 100's of trillions of dollars and decades of time can't accomplish though... oh wait.
The problem is, of course, that not only is economics bankrupt, but it has always been nothing more than politics in disguise... economics is a form of brain damage.

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Unread postby Hegel » Sat 11 Sep 2004, 18:15:58

@rerere

I assume that you haven't read the german language section of Solos website. If you look very closely, you'll notice the following information in the "news ticker" on the german website:

"Baden-Württemberg fördert Stirling-Anlagen mit EURO 7.500,- • Anzahl begrenzt"

Translation: State of Baden-Württemberg sponsors 7.500€ for Stirling Engines. Limited offer.

Since I'm situated in the said state and roughly 20km near to the City of Sindelfingen, I know very well that this company sells Stirling Systems.

In case you refered to Solar-Stirling based systems, then you are right that there are a few prototypes around. Although as far as I'm informed, Australia is going to build a huge "Solar Park" in the future, with the help of Schlaich+Partner's Solar-Stirling engines and other photovoltaic concepts. Therefore I conclude some company, probably Solo, is going to roll-out this stuff in greater quantities in the near future. Btw. I read about this project in Australia a few weeks ago in the local newspaper and also noticed a thread of this forum dealing with the same topic.

I do not intend being offensive to you, but next time you are going to reply to a posting make sure you got the facts.
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Unread postby Hegel » Sat 11 Sep 2004, 18:21:27

Solar Stirling as a "reference type" bought by a publishing house in Eibelstadt.

http://www.stirling-engine.de/eibelstadt.html

So much for vapor-ware.
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Unread postby rerere » Sat 11 Sep 2004, 21:14:52

Hegel wrote:So much for vapor-ware.
[/url]


And *I* can buy this where? Where is the link that shows for $X I can get one? (And when will it hit the sub $8000 price tag shown in the 'mass produced price' graph I saw back in 2002?) Because an actual production unit is progress over the 2003 check I did on Solo.

Until it can be bought by the general public, I consider it vapor. What good is the 'promise' if no one can buy it? Esp. as the 'solar powered stirling' has been a 'promised idea' from the late 1970's?

At least with the www.whispergen.com, the unit can be bought by the public. At $10,000+ for 1 KWh of power, it is not cost effective power generation however.
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Unread postby Guest » Sat 11 Sep 2004, 21:44:44

You asked for a shipping unit, there you have one.

Besides that, I agree on the fact that availability of stirling engines is quite low at the present. My gut feeling concerning price tag is round about 8000€ - 10000€ incl. shipping/installation right now. Probably higher for orders outside Germany/EU. Lucky me, I can get a state sponsored write-off by 7500€ :P

If you want to place an order with them, call them or send them a E-Mail.
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Unread postby Guest » Sat 11 Sep 2004, 21:55:41

One thing, as I'm not a native english speaker and sometimes mix up expressing my feelings, i'd like to disclaim a second time. I do not intend to embarass or hurt someone's feelings. My foremost concern is a healthy debate on realistic future energy systems.

PS:
I really need to get rid of this old monster of an oil-heater in my basement and replace it with something better :o
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Unread postby rerere » Sat 11 Sep 2004, 22:24:10

Hegel wrote:@rerere

Translation: State of Baden-Württemberg sponsors 7.500€ for Stirling Engines. Limited offer.

Since I'm situated in the said state and roughly 20km near to the City of Sindelfingen, I know very well that this company sells Stirling Systems.


7,500 euro -> 9200 American. Better price than Whispergen. In fact, publicly aviab. engines are few an far between as the ST-5 is no longer being made when I check in 2003.


Hegel wrote:Therefore I conclude some company, probably Solo, is going to roll-out this stuff in greater quantities in the near future.


There are 5 or so firms that have 'promised' dish-type stirling systems. SES and Solo are 2 firms that have 'long term' prototypes.



Hegel wrote:I do not intend being offensive to you, but next time you are going to reply to a posting make sure you got the facts.


And understand mine. Shipping units ANYONE can buy is what I'm wanting to see.

Because Stirling Engines have been 'just around the corner' for years. I was optimistic 10 years ago, now I wanna see shipping - at any price.
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Unread postby rerere » Sat 11 Sep 2004, 22:33:23

Aaron wrote:Now all we need to do is deploy this technology into the impoverished nations of the world, as well as China & India, to prevent them from gobbling up any savings we might accrue, through growth.


The vision of Dean Kamen was to deploy his Stirling engine to 'the 3rd world' to provide power and clean drinking water.

But rather than having a $89 engine ALA the Omcharon "Conrad Cycle" engine and creating a product that costs less than a solar panel or say 3 car batteries, Mr. Kamen wanted millions in grant money for his expensive engine.
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Unread postby Hegel » Sat 11 Sep 2004, 22:43:07

@rerere

I'm terrible sorry. Combined disaster struck and I did mess up with the login procedure, accidently posted as a "guest" and I misunderstood your term "Let's see a shipping unit" with "there is no such thing", rather than "Let me see a working engine to validate it, if indeed it is useful to be produced".

Sorry about that. Guess we are on the same team on this topic


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Buy today or wait for natural gas....

Unread postby rerere » Sun 12 Sep 2004, 00:05:51

Anonymous wrote:PS:
I really need to get rid of this old monster of an oil-heater in my basement and replace it with something better :o


The Whispergen diesel version can be had TODAY (ok a week or so with shipping it seems) for $12,000 to $16,000 depending on the reseller.

Whispergen via www.powergen.co.uk should have a 2005/2006 purchase price of $5,000. The microgen from www.bg-group.com www.bg-group.com/about/grp_other.htm had press releases about a 2005/2006 release of the www.microgen.com/indexc.htm product.

Considering in 1998 I couldn't find a 1 HP+ stirling engine to buy, in 1999 they were $32,000 + NDAs, in 2003 the number of vendors had increased with prices dropping to $16000-$25000 and now a $9000 unit in Germany, I can believe a $5000 CHP system in 2005/2006 is possible. But don't get excited till you can get one that ships.

The $250 for 250 watt Energy Innovations product www.matr.net/article-7928.html due in 2004 is an example of the dissapointment of the Stirling Engine as low-cost mass produced shipping item.
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Re: Paraboloidal Solar Stirling Cycle Generators

Unread postby Guest » Wed 15 Sep 2004, 12:42:40

Update:

Around this time every year in Eugene, Oregon at the fairgrounds, there is a convention of machinists and hobbyists. 3 years ago I went with my dad and son and found a guy demo'ing an 18 inch dish and stirling working model (manual tracking.) I don't remember the power output, but the stirling was compact, so it couldn't > 75w or so. Still, they DO sell them. I'll try to get more info this time. This fair is a cornucopia of home machinist/hobbyist delight. There are usually at least a dozen home-built working benchtop stirling engines. Apparently they are pretty simple to cast and make. Also, you can apparently adapt many existing engines by sealing the valve ports, adding finning for the 'cool' end, and making other optimizations (stirling's are brutally simple in operation.)
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The Stirling Engine

Unread postby bentstrider » Wed 03 Nov 2004, 23:26:35

This things been around since the early 1800's.
http://www.stirlingengine.com/
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Unread postby savethehumans » Wed 03 Nov 2004, 23:41:18

Uh, where does the "hot air" come from? Natural gas is about to peak, too, and good old-fashioned fire doesn't sound very efficient....
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Re: The Stirling Engine

Unread postby rerere » Wed 03 Nov 2004, 23:56:50

bentstrider wrote:This things been around since the early 1800's.
http://www.stirlingengine.com/


And the engine is always 'just about to make it'. The 1950's had a solution shipping from Phillips as a remote generator for radio. But circuits got filters for IC spark plug noise.

The 1970's had expermental cars...now hybrid style technology could make stirlings work in cars.

In the last 5 years, the science of making metal and material science in general makes the 3000 psi working pressure in a stirling more possible.

You have $89 for a 1 hp stirling which was 'projected' by http://www.omachron.com (they blame 9/11/01 for stopping 'em)
You have the people of http://www.solo-germany.com/english/fra ... gine2.html who have a 15,000 euro sun powered stirling.
You have STM power who's shipping engines for co-generation

You have http://www.whispergen.com who's product used to cost $32,000 USD, now costs $12,000 and they hope to have a sub $5000 cost for the Combined Heat and Power unit.
(The people at http://www.bg-group.com use an American engine in test units)
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