Parabolic Solar + Stirling Engine = Free (microgenerated & scalable) Energy

[Ghost Dog]

Article in the Inquirer:

MIT solar dish melts steel
http://www.theinquirer.net/gb/inquirer/news/2008/06/23/mit-solar-dish-melts-steel
Eat your heart out Archimedes
By Nick Farrell: Monday, 23 June 2008, 8:42 AM

MIT boffins have developed a parabolic collector which concentrates sunlight so intensely it can melt steel.

Despite the fact they are fairly simple to use, parabolic collectors have not been developed much as alternative energy sources. But the MIT boffins have worked out a way that they can make them super-efficient...

It focuses enough solar energy at its focal point to melt solid steel. When pointed at water steam is created...

Article in engadget:

MIT solar dish holds promise for low-cost energy production
http://www.engadget.com/2008/06/20/mit-solar-dish-holds-promise-for-low-cost-energy-production/
by Darren Murph, posted Jun 20th 2008 at 8:48AM

Look out 1366 Technologies, you've got yet another solar-based MIT spin-off company vying for business in the alternative energy sector. The company's name is RawSolar, and in due time it could end up selling solar dish arrangements that could power factories or even heat / cool office buildings. Recently, a team of students and faculty celebrated as a prototype dish proved that it could concentrate sunlight by a factor of 1,000, which obviously bodes well for converting that into useful energy here on Earth. Another standout feature of the dish is its small size, and furthermore, the material required to build it is relatively inexpensive and accessible worldwide. Sounds like all the ingredients for a successful startup are there, now we've just got to wait and see if anything becomes of it...

Now, observe these comments to the Inquirer piece:

old news
They claim there innovation is bending flat mirror's onto a frame instead of buying curved ones. Using square sections is far cheaper and simpler to build and achieves the same solar reflection if well aimed, I have no idea why this got a patent, funding or news coverage. It is no more efficient than existing 10 year+ old designs which I have built from scrap with one assistant. They also haven't even got motor powered sun tracking yet! A level students could do better than this with 20 mins looking for plans on google, come on MIT make something amazing!
posted by : tom, 23 June 2008
Been known a long time
A cover article in Popular Mechanics (or Science) over thirty years ago showed a parabolic reflector supplying heat to a Stirling cycle engine to generate electricity. They pointed out that it was at least twice as efficient as photovoltaics. Some day, someone might catch on.
posted by : J Smithson, 23 June 2008

So, Let's do something about it.

Sounds like the MIT spinoff is looking at using steam, but surely a well-designed Stirling Engine/generator set would be at least as efficient, more durable and cheaper to manufacture. Installations of the kind of size the MIT group has been working with are ideal for microgeneration at the domestic level and can be easilly scaled-up to community levels.

Rather than ask the usual question echoed above, "Why isn't this being done already?" (how the hell could the mirror itself be patented?) I''d prefer to propose a simple line of possibly effective action starting right here in this forum of DU.

The idea is simply to spread the idea, using the viral power of the internet. With plenty of interested people kicking the ball around, if the concept proves feaible then the application will be soon to follow. By spreading the concept in the public domain, open source-type projects can be developed by anyone anywhere in the world. The mirror can be built in almost any workshop. With only a little more tooling, the engine-generator set should ideally also be buildable in any average local developing-country engineering shop. Richer, more developed countries would be large markets for more sophisticated designs that could be mass-produced and packaged for the customer. Free-charge your plug-in hybrid. Guaranteed free-energy air-conditioning. Power your home. Anyone?

Let's kick the ball around here for a start. What do you think of it? Any here with a good grasp of Stirling Engine design for such an application? And spread the idea, please. Thanks.

[havocmom]

1. sending links to some friends who are far more clever than I

:thumbsup:

[tinrobot]

2. I guess the first question is - what are the numbers?

Looks like a 6-8 foot dish in the photo.

How much average heat energy does that produce?

It looks like a fun project.

[Ghost Dog]

4. I don't reckon you need enough energy to melt steel

to power a Stirling engine + generator...

Think of me as an ideas-person. I'm sure the engineering expertise is out there...

:)

[tinrobot]

8. I do have engineering expertise....

Melting steel means nothing. You could melt a small amount of steel with a magnifying glass.

The question is, can it produce enough heat energy to do useful work, such as power a house? I guess that's where the backyard experimenters come into the picture.

[pt22]

3. Musta been one of those around the WTC

:eyes:
http://en.wikipedia.org/wiki/Solar_power_tower

[Ghost Dog]

6. Sure, it's already been done on that scale;

works just great but was costly. Ideas have been mooted to, for example, build a string of these across North Africa (to generate electricity for export to Europe).

But I'm interested in looking at the really alternative, microgeneration possibilities here. Think even smaller than the mirror in the photo above, with the generator set at the focal point...

[midnight]

28. Nice to know that thinking people are

finding solutions to our oil for blood wars.

[Schema Thing]

5. Sounds promising

this is just a layman's quick take, but, you know what produces heat? My frickin' car engine, that's what. My knuckles will testify. I'm surprised that there has never been some sort of gas/sterling hybrid developed.

[elocs]

7. I have a Sun Oven which works on the same principle.

And folded it looks like this:

With a handle so I can carry it like a suitcase.

One thing that it absolutely needs to work, though, is sunshine. Here in Wisconsin in the summer we have a lot of days that start out nice and sunny, but by the afternoon the clouds roll in. In the winter, when the sunshine is nice for heat just coming through my south windows, it is often cloudy and gloomy sometimes for days. That doesn't help much if you are depending on the sun for heat--for your house or to cook your food.

That being said, and thinking of the simple concept of a solar oven, I thought of the 2 south facing windows in my kitchen/living room which are together. They allow a lot of sun into the room in the winter--so much so that my kitchen cabinets opposite the windows have gotten faded over the years. Why wouldn't it be possible to have reflectors like on the solar oven only in this case surrounding the windows and could be closed at night? Sunlight would be more focussed into the kitchen like it is into the oven box and a simple fan could be used to circulate the air.

Just a thought. Anyways, I have an old satellite dish that I have thought of fooling around with to make something solar out of it, probably like a solar oven.

[Ghost Dog]

14. Yes indeed.

See many more solar cooking options here: http://solarcooking.org/plans/default.htm
and also here: http://www.solarovens.net/
Cooking hints here: http://solarcooking.org/cooking-hints.htm

I'm planning to experiment with a wood, mirror and ceramic box design myself here in the Canary Islands.

:thumbsup:

[madrchsod]

9. i finally started using my solar powered clothes dryer

this technology is simple and very cheap to operate.

it is unfortunate the components below are made in china not in the usa




this is a picture of a working solar powered clothes dryer

[Ghost Dog]

27. No joke, I'm sure, madrchsod.

I gather lots of people make unnecessary use of indoor dryers over there. :hi:

[Phred42]

10. We did this when I was a kind

In the 70's My dad brought home a working Sterling cycle model and showed us how and why it worked.

we played with it. Eventually we got out the 24" parabolic reflector we had salvaged from a surplus TANK spotlight he acquired and a very large magnifying glass my brother had garbage picked. On a sunny day, between the two, we got that model spinning pretty good.

Then we lost interest.

[IDemo]

11. You ask "Why isn't this being done already?"

It is, and many Stirling based solar thermal systems have been under development for some time now. See the below links. If you ever want a good understanding of how Stirlings work, a good (and entertaining) book is The Next Great Thing: The Sun, the Stirling Engine, and the Drive to Change the World , about Sunpower Inc., a company founded in 1970 to engineer solar/Stirling energy systems.

http://www.seao2.com/solarsphere/csp.htm

http://www.sandia.gov/news/resources/releases/2004/renew-energy-batt/Stirling.html

http://www.stirlingenergy.com/default.asp

[Ghost Dog]

12. Ah. Thanks very much, IDemo. That's exactly what I was looking for,

although if they could be rather smaller it would be even better.

What we're looking at in the photos above, then, are 25kW "SunCatchers" by Stirling Energy Systems of Phoenix, Ariz, (project and technical development offices in Tustin, Calif, and engineering and test site operations at Sandia National Laboratories in Albuquerque).

The SES SunCatcher is a 25 kW solar power system that has been designed to automatically track the sun and focus solar heat onto a power conversion unit (PCU). This in turn converts the intense heat to grid-quality electricity. The concentrator consists of a 38-foot diameter dish structure that supports 82 curved glass mirror facets, each three feet by four-feet in area. These mirrors concentrate solar energy onto the heater head of a high efficiency, 4 cylinder reciprocating Stirling cycle engine, generating up to 25 kW of electricity per system.

The Stirling Engine used by SES has been an industry test bed for various applications including automotive, solar, gas and diesel fuelled power. The particular engine used in this project is the 4-95 engine (4 cylinder, each 95cc displacement) that evolved from the Philips engines of the 1960's. United Stirling of Sweden carried out the bulk of this work in the 1960's and 70's with technology transfer to the USA to develop automotive applications during the oil crisis.

As the info at the links says, 1000 square miles of these could power the entire USA. And arrays of these are easily scalable, feeding directly at up to 30% efficiency into the grid.

But still it's not quite what I'm looking for. I'm looking for smaller parabolic mirrors and smaller engines, for feeding power into batteries or other storage methods for single-house and small community off-grid use, as well as for distributed micro-generation feeding into the grid.

Why does a 25kW Stirling Engine generator (and the mirror) have to be so large?

[Zachstar]

13. Because right now the tech sucks.

There have been few improvements to the engine for a good long while compared to a gas burning engine.

Me? I prefer heating oil to boil water with. There is far less complex parts, and it scales much easier than this.

For this tech it really needs to focus in on smaller units designed to produce around 5kw for individual home units with far less complexity.

[Ghost Dog]

15. My thinking exactly. Current engines appear to be based on designs from the 'sixties.

Know of anyone doing the focusing-in required? Where to look to find such folks?

[Zachstar]

19. To be honest I do not think these engines are good for solar capture.

If there is one law of designing stuff it is that moving parts suck. And to be honest I just cant see these going all that widespread anyway.

PV for homes and solar oil heating for grid.

[wtmusic]

20. More efficient than photovoltaics, according to Wikipedia

"Placed at the focus of a parabolic mirror a Stirling engine can convert solar energy to electricity with an efficiency better than non-concentrated photovoltaic cells, and comparable to Concentrated Photo Voltaics. On August 11, 2005, Southern California Edison announced<59> an agreement to purchase solar powered Stirling engines from Stirling Energy Systems<60> over a twenty year period and in quantity (20,000 units) sufficient to generate 500 megawatts of electricity. These systems, on a 4,500 acre (19 km²) solar farm, will use mirrors to direct and concentrate sunlight onto the engines which will in turn drive generators."

http://en.wikipedia.org/wiki/Stirling_engine

[IDemo]

17. Dean Kamen (Segway inventor) has been working with Stirlings

He has developed an efficient smaller engine for use in Third World nations, both for electrical energy and clean water production. Kamen thought he would be able to substantially increase the output of a Stirling, but he may have run into the axiom from the book I linked to: that advances in Stirlings don't come in leaps, but small steps. His idea was more about using external combustion fuels that would ordinarily seem unsuitable - like dried camel dung, but more available in third world areas. It struck me when I first heard he was working on this that a smaller 'Sundish' type unit would also be workable.

http://blogs.business2.com/greenwombat/2007/08/a-visit-to-dean.html

[Ghost Dog]

26. And for another thing: the cooling end at least could be built out of auto parts.

With the right design, no matter how large, how easily could these things be assembled in a third world workshop, one wonders.

[NNadir]

16. Free?

I don't even need to send in cereal boxtops to get one?

Do tell...

Where do I send in my order for the free system?

[Ghost Dog]

22. All (most) costs up front. Not free system, but free energy

straight from the sun.

[NNadir]

32. Oh. I see. It's too cheap to meter.

What a surprise!

How's your system working?

Great I expect! Why don't you tell us all about it?

[bhikkhu]

18. The article misses the point, and Stirling engines suck, in practice

To put it bluntly.

The point of the MIT project was to build a low-tech parabolic collector, which they did. Hundreds of similar collectors and designs are around, but this one is built very simply from off-the-shelf components. The design is simple enough that it could be replicated almost anywhere in the world, without the need for specialized parts or expertise.

As for the stirling engine, it is a wonderful old design, but you have to look at its advantages to see its deficits: unlike steam turbines and such, it can produce small amounts of power from small inputs, and its size and output can be varied with the size of the inputs. The problem is that a stirling engine large enough to useful energy is first a huge investment in capital and energy, then still a relatively small power producer, then a relatively expensive machine to operate.

There are plenty of more promising solar thermal-to-electric possibilities applicable to the MIT project though.

[Ghost Dog]

21. Many thanks for all the input, concrete info and food for thought, guys.

It is a shame that so much journalism, even on technical subjects, is of such poor quality and feels the need to be so frivolous, to say the least, isn't it.

I see that, while there is surely room for improvements in Stirling Engine design and production, these are very efficient although, as with anything mechanical, maintenance is an issue. I see that I will have to investigate further the field of Concentrated Photovoltaics - that Australian installation does look very promising, depending on the cost of the concentrator/PV. I should look into oil-boiling water capture for the grid, also.

For myself, we're expanding our house here on the Canary Island of Fuerteventura (buying the place next door) and as part of the expansion I'm planning to start with a simple PV installation, perhaps incorporated into some new architecture on the at the moment, flat, with domed Arab/Berber-style water-storage) roof, to charge standard 12V car batteries. From these, as well as being able to obtain some 220V AC through an inverter when needed, I mainly plan to operate the composter and a small fridge/freezer, and to be able to charge computer, phone, etc. batteries directly from the DC supply. There's not yet much point in looking at grid-feeding here, since, due to the self-interest and perhaps corruption, it is said, of our local politicians, it is next to impossible to obtain the required licence to do that (although at the national Spanish level this is supposed to be encouraged).

I do have to declare an interest beyond the microgeneration level, though. This island has been developing, in terms of tourism and construction and services for tourism, at a frantic pace over the last decade or two. This has made a few (including, it is said, some of the aforementioned politicians) very rich and has provided employment for many locals and immigrants, and has produced large deficits in infrastructure and essential services (health, education,...) as well as tragic environmental damage - and now, we are told, in electricity supply. The old, dirty oil-fired power station located right next to a residential area in the island's capital needs resiting and replacing. But it so far has not occurred to the aforesaid politicians to propose anything better than to build a new oil-fired thermal station. Their problem, they think, is where to locate it, since their proposals so far have actually served, for once to bring masses of ordinary people out into the streets in protest. For me, as a member of the "ecological" movement, and graduate in environmental sciences from the 1970's, I see a need not only to protest, but to be able to propose, from the environmental movement, viable, and genuine, alternatives. This island is all-year-round sunny, windy, (and mostly arid) and surrounded by Atlantic waters with waves and fairly strong currents, as well as being an ancient oceanic volcanic edifice. With a bit of imagination and investment (and work of course), this island should be in a position to become a model producer of reliable alternative energy - and could become a test-bed for exciting experiments which could, yeah sure, also be marketed as tourist attractions (perhaps we should invite an MIT (and other) team(s) here to have a look). And it would help with the political revolution people sorely need... (edit. They're saying some 50mW will be required).

Anyway, I'll continue investigating and I thank you all here in this thread for the very useful input. And in this forum and in DU in general, which always helps me to see more clearly, as long as one is careful about potential information overload :-) .

Thanks again, guys. One more rec., I see, would push this up to where more people would see it and may have comments to add, but that's not up to me.

BTW, where I said above that a one-thousand square mile solar-Stirling (or concentrated PV or oil-steam) field could power the USA, that should read ten-thousand (100 x 100 miles square). I gather that wouldn't be a large area out in New Mexico or wherever. Or consider the economic future of somewhere like Algeria or Western Sahara (pending liberation) being in a position to invest in electricity production capacity that could power Western Europe...

And then add in the distributed microgeneration possibilities...

Vital work, it seems to me. Vital work that needs to be done now and fast.

[Ghost Dog]

30. This is an Australian Outback array:

using 30 Solar Systems’ CS500 concentrator dish systems equipped with 24% efficient silicon-based photovoltaic (PV) cells providing 720kW rated output. http://www.solarsystems.com.au/

I wonder how much that costs.

[kristopher]

34. Power at the neighborhood level. nt

[hunter]

38. Car batteries are frustrating and problematic in that application.

Here in the U.S. you can easily buy "deep cycle" batteries or even better quality batteries of the sort used in electric wheelchairs off-the-shelf at any Wal-Mart or Sears.

You might also want to look at some of the very robust small scale solar systems designed for sailboats -- if not to purchase, than to see how they are put together.

If I was building such a system today I'd also use LED lamps. A single 1-watt LED can keep you from tripping over things in the bathroom at night, and it's not difficult to modify LED flashlights and camp lights into permanent fixtures suitable for reading and general purpose household lighting.

Of course once you've got the ultra- low energy household electric system installed it's difficult to justify the very significant expense of solar panels and good batteries if reliable network power is available.

That's sort of where I am today. If the electricity to our house was cut off it would be an inconvenience -- I would absolutely loathe washing and drying clothes by hand, but we could still manage some internet access. But if electricity is cut off to our city, things would go to hell very quickly.

[Kablooie]

23. You can also melt cement with a large fresnel lens.

Some guys did it with one about 3 feet square.
http://video.aol.com/video-detail/2-fresnel-lens-solar-cement-melt-sun-collection-green-energy/3181667628?icid=acvsv2


Also this idea has been in development for years but it has always turned out not to be efficient enough for actual production.

[Zachstar]

24. Which is sad but hopefully research into it will lead to better solar oil systems.

So far you just can't economically beat solar oil heating. Nanosolar requires large areas to be filled for its price range and not to mention that the whole thing has to be replaced rather quickly.

Solar Oil 4TW

[Ghost Dog]

25. That's the main Euro Schlaich Bergermann und Partner design. Only 10kW.

These appear to be still experimental. One (double) installation is:
http://www.sbp.de/es/fla/mittig.html

10 kW Dish/Stirling Eurodish

Localidad Almeria, España
Tipología 2 Dish/Stirling-systems, 8.5 m diameter, power 10 kWel each
Propiedad EU-Kommission, Brüssel; Schlaich Bergermann und Partner

Inauguración 2000
Responsabilidad Diseño conceptual
Colaboradores

[bonito]

29. K&R n/t

[hunter]

31. The more moving widgets you have, the more things go wrong.

Parabolic trough collectors have fewer moving parts. Some pretty big solar power projects use them.



http://www.sandia.gov/news/resources/releases/2007/trough.html

You also might make fuel from CO₂ and sunlight:

http://www.sandia.gov/news/resources/releases/2007/sunshine.html



I'm surprised that Sandia is reporting this as a new sort of project, since the Navy was playing around with a very similar concept in the early 'eighties, if I remember correctly...

Back then I'm certain it was still fifteen or twenty years in the future...

If we're stuck in a time loop like Bill Murray in Groundhog Day how come I feel so much older????

[Ghost Dog]

35. Or like Bill Murray in Broken Flowers... That solar+CO2=usable energy research

does look very exciting - coupled with the means to suck CO2 out of the atmosphere, especially.

[Zachstar]

37. Which would not do a damn thing in the long run.

Current climate problems require a reversal not a halting. If the polar ice cap continues to melt away. The resulting changes in energy absorbed could lead to MUCH more CO2 released.

[crimsonblue]

33. when you say "free" energy

do you mean free as in "you won't have any costs other than the fixed initial costs" or by free do you mean the whole "perpetual motion / energy pulled out of your ass"?

there's no such thing as a free lunch.. that being said, I'm a bit curious as to why Stirling engines have been so neglected and forgotten. They are truly the most versatile motors, and can indeed run on almost any fuel source.
The only requirements for a Stirling engine is a heat gradient; in other words, a hot zone and a cold zone. Stirling engines are fairly simple engines and provide a very good efficiency factor, surpassing both the Otto and diesel cycle engines found in most cars. A stirling engine requires very little maintenance or expertise to use.

[Zachstar]

36. Reasons like this.

Lots of the energy is wasted as heat.

Also heat gradients are harder to maintain in the summer. Such as one shown above requiring a fan adding yet another moving part.

And yes again the moving parts thing.

For one panel sure its ok I guess. But when you deal with 50 or 100 the force needed to keep it running grows and grows.

Right now the best that can be done is flashing to steam. Solar oil or that new molten salt is much better because there is far less moving parts per area. If we plan to use the sun we need to focus in on that tech. To reduce the grid load we need to focus on getting PV cheaper for homes and stop this maddness of thinking they can be used for grid pressure.

[Howzit]

39. That is impressive

How many watts per square meter? How long does it take before dust and bird poop degrade performance enough to require cleaning? How do you clean it without scratching the mirrors - a high pressure hose with de-ionized water perhaps?