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Stirling Energy System's SunCatcher uses this system to drive a stirling engine mounted on a parabolic mirror. It always seemed like a better, simpler solution than photovoltaic cells to me.

Posted in the wrong story, also this has already been done.

http://www.stirlingenergy.com/

Stirling engines will never be economical.
[snip]

Also see www.tinaja.com/glib/hack64.pdf for a review of the dismal Carnot efficiency of modest temperature drops.

It's pretty well understood that you need a big temperature drop. That's why they don't use a small temperature drop. If it doesn't work then what are these people doing?

Frankly, solar thermal makes more sense to me (see Nevada Solar One, or the Solel project), but sterling engines work too.

Check out http://www.stirlingenergy.com/ . They are pursuing mass production of combined parabolic mirror/stirling engine units for large scale deployment, and appear to have signed contracts of impressive size with California utilities.

Pros of stirling engines: efficiency (as you said), old and well understood design, mass productibility, modularity.

Cons: moving parts, maintenance, complexity, lack of smoothing/storage options, fabricating parabolic mirrors is more difficult than other types.

Not necessarily: We could give monetary incentive to buildings' owners to operate heliostat mirrors on their roofs toward energy company's solar tower (there can be even a competition between various "sun buyers" in single area, a multiple choice for aiming-for-dollars) and homesteads already occupy a lot of land.


Nah. These installations fit in wide open spaces. In the city, building roofs should be covered with smaller generators. All the "monetary incentive" needed is that the buildings could get most of the power for their AC from the sun rather than from the grid. It still wouldn't be free (initial cost + maintenance) but if the price for on the spot electricity generation could be driven lower than grid prices, businesses would be falling over themselves to install them.

You are referring to this technology:

http://www.stirlingenergy.com/

I do not know the costs/scale/maintenance/lifetime
issues involved that differentiate the technologies.

Where is a meta-analysis of these issues to permit
a definitive assessment of the 'best' technologies
to permit commercial entities to enter the market?

---537

What if you dont use solar cells? What if you use a stirling engine?

1) Take a bunch of largish mirrors and shape them into a dish 37' in diameter.
2) Point all the mirrors at a Stirling engine.
3) Attach the output of the Stirling engine to 20kw generator.
4) Track the sun through the sky.
5) ???
6) Profit.

"One dish on an annual basis can produce 55,000-60,000 kWh of electricity. This is equivalent to the total energy required for 8-10 homes in the U.S." (Stirling Energy Systems FAQ)

Too bad these guys already stole your idea!

1) Take a bunch of largish mirrors and shape them into a dish 37' in diameter.
2) Point all the mirrors at a Stirling engine.
3) Attach the output of the Stirling engine to 20kw generator.
4) Track the sun through the sky.
5) ???
6) Profit.

"One dish on an annual basis can produce 55,000-60,000 kWh of electricity. This is equivalent to the total energy required for 8-10 homes in the U.S." (Stirling Energy Systems FAQ)

Too bad these guys already stole your idea!

1) Take a bunch of largish mirrors and shape them into a dish 37' in diameter.
2) Point all the mirrors at a Stirling engine.
3) Attach the output of the Stirling engine to 20kw generator.
4) Track the sun through the sky.
5) ???
6) Profit.

"One dish on an annual basis can produce 55,000-60,000 kWh of electricity. This is equivalent to the total energy required for 8-10 homes in the U.S." (Stirling Energy Systems FAQ)

Too bad these guys already stole your idea!

But most people don't want to live in the middle of the desert, which just happens to be is where areas of maximum insolation are. A 100x100 mile patch of solar panels plopped in the middle of the Mojave desert could power the entire United States. I agree that there is always a tradeoff, but the tradeoffs associated with this approach would appear to be much lower than meeting demand over the coming century with coal or nuclear.

Plus, there's the guys doing electricity by converting solar heat using sterling engines http://www.stirlingenergy.com/default.asp and the work converting heat into electricity using an intermediate sound conversion step http://www.sciencedaily.com/releases/2007/06/07060 3225026.htm.

When he meant forever, he meant FOREVER: http://www.ez2c.de/ml/solar_land_area/
And that's only using the crappy 8% technology we currently have...

Imagine stirling solar: http://www.stirlingenergy.com/

Solar means 'forever'. P2P Electricity is the future...

Another way to make solar cheaper is to drop the PV/Si approach altogether. Few people seem to have gotten the memo, but there are solar generators that exist right now that are making electricity at twice the efficiency of PV. They consist of nothing more complicated than metal and mirrors, and so there are huge opportunities for returns to scale (think cars.) Our continuing dependence on oil is a failure of imagination and political willpower, nothing more--think about how many of these Iraq could have bought. The technology is there.

Worse than coal or nuclear is going a bit far considering the environmental impact of coal includes the destruction of entire ecosystem in West Virginia and the lion's share of the responsibility for global warming, and we all know how nice nuclear waste is. But you do have a point.

However... there's more than one way to skin a cat. PV is just one way to harness energy from the sun, and it's not even cheap, environmentally friendly, or efficient. Check out these guys. That's just mirrors and metal, and the world's neatest mechanical engine. I keep waiting for the day when people realize we can generate solar power for prices nearing that of fossil fuels, today, with no scary waste or CO2, but, alas, hasn't happened yet.

The SEGS plants at Kramer Junction in the Mojave Desert have been operating since the 1980's and are the largest solar plants in the world producing 354 MW.

Nevada Solar One is 64MW of solar thermal (3rd largest solar plant) and set to come online this year.

Stirling Energy Systems has a CPUC approved contract with SCE for a 500MW parabolic stirling solar thermal plant.

This document details a lot of the 100 year history of solar thermal attempts.

SHPEGS is our not-for-profit design project to adapt solar thermal to moderate climates by combining it with geothermal and heat pump technology. There is more information and links here.

The SEGS plants at Kramer Junction in the Mojave Desert have been operating since the 1980's and are the largest solar plants in the world producing 354 MW.

Nevada Solar One is 64MW of solar thermal (3rd largest solar plant) and set to come online this year.

Stirling Energy Systems has a CPUC approved contract with SCE for a 500MW parabolic stirling solar thermal plant.

This document details a lot of the 100 year history of solar thermal attempts.

SHPEGS is our not-for-profit design project to adapt solar thermal to moderate climates by combining it with geothermal and heat pump technology. There is more information and links here.

There are methods of generating electricity from the sun that exist right now, today, and are or will soon be competitive ($/MW) with coal, oil and NG-fired generators. See www.stirlingenergy.com.

This whole addicted to oil this is not nearly as intractable as the entrenched powers-that-be would like you to believe.

1,000 watts per square meter of direct normal solar radiation strike the earth's surface at sea level. That's a lot of raw energy hitting roof tops. Then the issue is converting it. Solar cells have been stuck at 15% or less conversion efficiency for decades with no real breakthrough on the horizon to improve upon that. Still, an average house with perhaps 100 square meters of roof area could generate far more engergy than it needs (during the day). Problem is, solar cells are still very expensive to manufacture, with no cost breathroughs significant enough to really change the economics.

Solar concentrating power is far cheaper. For example, the system from Stirling Energy Systems http://www.stirlingenergy.com/ once in production will produce electricity that is very cost competitive with electricity from fossil fuel fired plants. The technology is quite cool. A sun-tracking parabolic dish concentrates sunlight on the heater head of a Stirling engine. Each system produces 25kW and is about the same mass, complexity and materials as a mid-size automobile - in mass production it would cost about the same as a car. Pilot installations of the systems have been running for more than a decade. It's not suitable for roof tops, however, since it is a bit large and noisy. San Diego Gas and Electric and Southern California Edison both have contracts now to build large installations using this system.

It seems strange to me that most of the attention is still on non-economical solar cell based systems when a truly viable solution is already available.

Umm, if a 25% increase in energy costs = 10-25% increase in the cost of everything then energy costs are (10/25 % to 25/25 %) = 40 to 100% the cost of everything, which is just not the case. Feel free to look up fuel costs as a % of GDP. (If you don't believe these numbers feel free to look at the cost of land as a function of the cost of fossil fuels. Next look into the price of a good doctor / programmer as a function of energy cost's etc. Physical goods and services are no where near 100% of the US economy.)

Fossil fuel energy costs are ~3% of the US GDP so a 25% increase in those energy costs would increase everything by .03 * .25 = 0.75%.

Granted I have not run the numbers in a few years but converting all of the US electricity generation would to non CO2 sources would create a 30 - 65% premium over existing costs depending on location. See: http://www.stirlingenergy.com/solar_overview.htm for a good example of such systems.

Solar hot water heaters save money for most of the continental US. Granted not so much in Alaska.

The only real issues is Cars / Jet's but there is enough of a buffer from heating and electric costs that even at 2.5x gas prices your only talking about 2x net energy costs. (Note your price at the pump is only about 50% raw fuel costs so (2.5x /2 + .5) = 1.75x at the pump or ~5.25$)

PS: In time there will be no fossil fuel's left anywhere in the world so doing nothing is not really an option. Those economies' that are prepared for ever increasing costs of fossil fuels will do better in the long run.

While that is 'interesting' that Dean wants to burn Dung, there are others who are building heilostats with Stirling engines. (That means you don't have to go gather dung for power.)

Whispergen is shipping engines, has test dishes, Solo was selling some a couple of years ago for sub-10,000 euros.

And these people were at one time claiming a $89 price point for a 1hp engine if you bought 'em in 40 foot container lots.

Dean's looking like the looser on the stirling race.

One thing I really wish would happen is that the efficiency of thermovoltaic technology could somehow be improved... Think about how much energy is wasted as heat; eventually all of it, I suppose. I actually heat my bedroom in the winter with my PC. When I read about large scale solar facilities, I can't help but wonder at the losses in heat that are going on there. There are more efficient ways of utilizing solar power right now anyway: http://www.stirlingenergy.com/ comes to mind... and they work pretty well. It would be nice, however, to move the technology to solid state like we have with photovoltaic cells; That way we could apply them to things like brake shoes on cars, the condensers on refrigerators and air conditioners, etc... -Photovoltaic paint has been invented, but is not realistic yet. I think that's where the future is: Objects that need electricity should become more efficient, and should have photo/thermovoltaic technology built right into them.

at this point we start looking at alternative means of harvesting solar energy. I still remember the idea of using a parabolic dish to focus sunlight on a sterling engine to produce energy. Here is the makers website: http://www.stirlingenergy.com/ but I didn't see any efficiency numbers. anybody willing to look in on this?

~5% efficiency.

what's wrong with a reflective dish and a stirling engine, anyways? much higher efficiency, materials aren't as expensive as solar panels and not nearly as bad for the environment.

Better yet, powered by hot air?

I know you're joking, but maybe that's actually not such a bad idea.

"The REAL problem with hydrogen, which everyone loves to ignore, is that there IS ABSOLUTELY NO WAY to produce hydrogen efficiently, from a renewable resource, without leaving toxic byproducts; current methods either involve hideously inefficient electrolysis, toxic catalysts, or non-renewable resources."


In a few years these guys will get their R&D phase finished and roll out an enormous array of these. They already have operational test units at Sandia National Labratories, and are scoping out some expansive real estate out in the desert northeast of Los Angeles.

"The REAL problem with hydrogen, which everyone loves to ignore, is that there IS ABSOLUTELY NO WAY to produce hydrogen efficiently, from a renewable resource, without leaving toxic byproducts; current methods either involve hideously inefficient electrolysis, toxic catalysts, or non-renewable resources."


In a few years these guys will get their R&D phase finished and roll out an enormous array of these. They already have operational test units at Sandia National Labratories, and are scoping out some expansive real estate out in the desert northeast of Los Angeles.

Why the fuck not? http://stirlingenergy.com/faq.asp?Type=all

"In fact, a solar farm 100 miles by 100 miles could satisfy 100% of the America's annual electrical needs."

" What happens on a cloudy day or at night?

That is where the traditional fossil fuel-based power plants come in: at non-peak hours. Renewable energy will not replace fossil fuels in the foreseeable future"

So they are depending on a fossil fuel source to augment their power generation. In that case nuclear would still be better as it could completely replace fossil fuel.

Solar is fine, but again only suitable for augmentation, not as a primary energy source.

Why the fuck not? http://stirlingenergy.com/faq.asp?Type=all

"In fact, a solar farm 100 miles by 100 miles could satisfy 100% of the America's annual electrical needs."

"Based on a power plant producing 1,000 MW, the cost per kWh would be less than ten cents."

Long term we could build a redundant super conducting power grid to major usage areas and have large scale energy storage systems to smooth out differences between production and demand.

In the real world we are probably always going to use a mix of power generation facilities but saying solar can't be a Major player in energy generation is silly.

If you're looking at powering televisions and radios, though, you need to have electricity. Photovoltaics generally work best for that. Turning heated water into electricity does work, though at a lower efficiency.

I thought http://www.stirlingenergy.com/ was a better solution

Why is it that every time solar is mentioned it is assumed we must be using PV cells. Has any one on this site followed recent trends(http://www.stirlingenergy.com/).

As power production goes, they simply don't have enough power generation area to produce an output similar to that of existing plants.

That's untrue. It's just that nobody has bothered to scale the designs up before now. The highest capacity solar plants on the drawing board are in the 200 to 850 megawatt range - this is comparable to 1200MW nuclear and 700MW coal plants.

My local (tiny, probably 200MW) coal-fired power plant uses an area of roughly 2km by 2km (not counting space for railroad tracks) - because they require a private lake to provide cool water to the generation process.

The major solar projects that I'm aware of:

(1) Sterling Energy's 500MW facility is going to be built, with the option to increase capacity to 850MW: http://www.stirlingenergy.com/

Their development will use 4000 acres, but that's only a patch of land 4km by 4km (my local international airport uses 10 times the space). It will also work on cloudy days.

(1) EnviroMission's 200MW, 1km tall solar tower. The first full-scale tower is about to be built in Australia and they're scouting for locations to build the first one in the US: http://www.enviromission.com.au/

It's slightly less space efficient than the Stirling design, but it also works at night - the design uses the temperature differential of air between ground level and 1km up. During the day, this is boosted by the sun heating air at ground level.

So, factor in the overhead of otherwise mining and transporting coal and any lakes / cooling reserves that are needed for those systems to work - and these designs are looking very, very competetive.

(1) If you don't have plumbing, you need to have a stirling engine and generator at each dish. Which is insane.

Which, if you had RTFA (Or anything, for that matter) is exactly what they have. See that box at the tip of each dish? That's the collector, engine, generator and radiator. IIRC from pictures I've seen, the entire box is roughly 3'x3'x6' (though I may be confusing SES's production engine with some other company's design)

The smaller you make a heat engine, the more surface area there is relative to working fluid volume.

That is correct. That is also the reason that making a Stirling engine of any useful power output is a hefty achievement. Stirlings are external combustion, so "dead" volume in the engine is a serious killer. Making huge engines requires huge heat exchangers to get the energy through, but also increase dead volume that robs the engine of useful output. Stirlings do not scale; the design methodologies for a large engine are completely different than that of a small one.

Same thing with generators vs bearing friction and windage losses. That's why commercial power plants use ONE heat engine and ONE generator, both huge.

Any power plant I have ever seen typically has several gen sets, for a variety of reasons. One being redundancy, another being modular load matching ability, and another being the fact that there is an upper limit to just how big you can make things before it becomes unusable. For new plants it is actually more popular to use many smaller setups than a few large ones because matching the load by enabling/deactivating each unit gives higher plant efficiency, even if each individual generator might be a few % less efficient.

That's why I jsut(sic) *assumed* you were going to have plumbing.

Well you assumed wrong. Even the slightest bit of research would have cured you of that. (Incidentally, that's the website of the manufacturer discussed in the article, since I know you didn't read the article!)

Now about not needing a heat sink

My apologies. There was so much other bogus shit in there I missed that one. Of course you will need a means to reject unused heat: in this case, an air cooled radiator, mounted behind the engine.

Hmmm, that's not a very impressive site.

We've established you don't like my source. We've also established your spelling (and reading comprehension) isn't all that great either... but you have yet to cite any sources of your own other than three sentences in an electronics journal, published by some dipshit who cites as "Off-site resources" such useful and relevant websites as "Dilbert", "The Motley Fool", "Netflix" and my personal favorite "The Onion" (Hey, it's America's finest news source!). What a pro.

And yet somehow my energy balance calc still shows 26% real sun-to-electricity efficiency, which matches the calculated Carnot from assumed (and fairly reasonable for solar applications) operating temperatures and the 50% of the Carnot efficiency claimed on the site I linked, plus a little loss for the electricity generation.

So you cite (rather, just mention) some experiment in a Japanese lab where they got 19%. Great. What were the engine metrics? Heat source/sink temp? Working fluid? Internal pressure? Swept volume? Was it an alpha, beta, gamma or free piston configuration? I certainly don't doubt their 19% claim but we must compare apples to apples here.

=Smidge=

If they actually sold a mirror dish/engine system and had a few real installations (not DoE-funded demos) they might be worth taking seriously.

There's no problem building a solar powered Stirling cycle engine. It was first done over a century ago. Toy sized ones are available. Getting out enough power to make it profitable, though, is hard.

OK, here are some notes on this:

1. It's not like you are covering 4500 acres (that's 7 sq. miles) with solid concrete. The actual footprint of these dishes is fairly small; the main impact will be the amount of sunlight hitting the ground. judging from the area, this may not be such bad thing. Shade for the desert tortoises and the like.

2. It's reasonably scalable. Using SGS's numbers, and being conservative, let's say these things can crank out 400 kWh/m2 per annum. At 2004 US electrical consumption of roughly 1.2 trillion kWh (source: EIA), you're talking about needing ~30 billion sq. m. of collectors, which is about 12,000 square miles, to supply 100% of current electrical needs. You could fit that in about 5% of Texas- not an insignificant amount of land, but doable (you don't have to have all the collectors in one place, and you can probably install them on under-utilized land- say, parking lots- just jack up the collectors a few feet to provide SUV clearance).

So although I'm sure some people will get bent out of shape, I don't see the land area requirements as a big deal. If these things are truly economically competitive, as the article suggests, watch out.

These folks should know ;)

How viable is solar power? I was asking myself this question and here's the numbers I came up with.

In 2001 the USA used 96275 trillion BTUs of energy that year. This comes to 3.22 trillion watts.

Now there are about 295 million people in the US, so this comes to about 11Kw per person at any given time.

This means each person uses is responsible for 262 Kwh of power per day.

Now lets say that square meter of sunlight provides 1 kw of energy on average and the average area gets 5 good hours of sunlight per day. Looking at this chart, you can see that this assumption isn't too far off.

The typical solar panel is about 30% efficient. This means that for every square meter of solar panel would render 1.5 KwH every day.

This means that each man woman and child would need 174 square meters of panel to be responsible for all the energy made and used in their name!

If every person in the united states of America put up solar panels. We would have over 51 billion square meters of panel, that's close to 20,000 square miles of panel or the equivalent of covering most of over in panels.

Now these numbers account for all energy used both domestic, industrial, and exported. Also these numbers do not account for the added or lost efficiency of converting systems over to pure electrical power as opposed to other energy processes like those used in the internal combustion engine.

I left the links to my math in just incase I botched anything.

Some pictures

Actually....

If you are going to use trick mirrors, it looks like the best way is to use a Stirling Engine to convert the solar energy to electricity. One example is Stirling Energy Systems but Discover just ran an article about the sunflower prototype from Energy Innovations that plans to break the magic $1/watt barrier. The sunflower uses reflective plastic petals to focus light onto a Stirling engine which generates electricity. This approach gets around some of the worst characteristics of PV cells such as sensitivity to the angle of light, high cost of material manufacturing, and upper limits on how much light can be converted.