World's Largest Solar Array to use Stirling Engine

An anonymous reader writes "Stirling engines are not a neglected or forgotten technology after all, according to a story at PESN. With 20 years of in-the-field fine-tuning, Stirling Energy Systems is now ready to go big -- real big. They signed a purchase agreement Tuesday with Southern California Edison (SEC), to install a 20,000 dish array that will cover 4,500 acres and will be capable of generating 500 megawatts of electricity -- more than all other U.S. solar projects combined -- making this the largest solar installation in the world. Each collector has a 37-foot-diameter array of mirrors to focus the sun's rays on the Stirling engine, which turns the heat into rotational torque for electricity generation. According to a spokesperson for SCE, this purchase will be in their commercial interest, requiring no subsidy in order to compete, implying that the efficiencies of the technology will give them an edge in the market."

Comments

Good

[RandUser]

I'm glad to see alternative energy sources being developed, I just wish public opinion would change faster so we can get some more nuclear plants as well.

Re:Good

[magarity]

As long as they're pebble bed reactors, I'm all for it. The hugemongous three mile island style are white elephants in comparison.

Re:Good

[MyLongNickName]

If gas hits $3/gallon, and stays there for a year, the American public will accept anything. While I cringe when I have to buy gas, I hope the price keeps going up. Maybe then, we will have the economic incentive to kick the oil habit.

Re:Good

[norwoodites]

Let see, it is about $5/gallon in the UK and the US is complaining about $3/gallon wtf. This is just under estimate too because I am converting from £ to $ and liters to gallons.

Re:Good

[Breakfast Pants]

If nuclear plants can prove to be finacially viable on their own then I am all for lifting the regulations against new ones. The problem I have is that US population essentially pays all of their liability insurance; in that there is a federal law mandating that they don't have to have any. If they had to pay that liability and still could be finacially sucessful I would think they would have reached a pretty safe point. If they are as safe as everyone says then why do the need us to pay their insurance?

Re:Good

[rebelcool]

yeah but britain is much smaller and its economically feasible to build nationwide mass transit systems.

The US relies on trucking and personal automotives for its economic basis because of the extreme expense it would take to build the massive mass transit systems such a large nation would need, to equate.

Re:Good

[Rei]

Yeah. Because everyone wants a nuclear reactor that combines the wonderful properties of graphite (see "The graphite fire" subsection) as a moderator, with water (graphite generates explosive hydrogen with high temperature steam) often in the primary or secondary cooling loop (helium is the primary coolant), with safety features such as no containment structure (this list is just a start - there's many times more that didn't make the list)

Yes, PBMRs have a negative void coefficient (reaction slows as temperature increases); big deal, so does almost every reactor build in the west in the past three decades. Yes, helium is the primary coolant; that doesn't help when there's a jam or corrosion that leads to a rupture, in which case water and/or air enters the chamber (a much hotter chamber than PWRs) - and yes, this has already happened. Containment structures have saved our collective arses from the unexpected too many times to be omitted.

PBMR proponents talk about safety, but they're really about reactor cost. They're hardly the only innovative reactor design out there, but they're apparently the only one that your average slashdotter knows about. There are thorium breeders, reactors that run on unenriched fuel, and designs like my favorite, BREST - a lead-bismuth breeder which can cool itself with natural convection, uses the ground as shielding, has the fuel naturally encased in lead, and unlike most breeders, uses no liquid sodium.

As an aside, we really should move to safe breeder designs, either thorium or uranium based.
U-235 is only 0.7% of natural uranium, and natural uranium isn't incredibly plentiful in deposits concentrated enough to justify mining (I read once that known deposits would supply the world at current power consumption for only a few hundred years). It's a shame that most U-238 goes to waste (yes, some is used in things like armor, bullets, and weights, but we produce far more of it than is used for such tasks)

Re:Good

[CosmeticLobotamy]

The UK would fit in my basement if I moved some stuff around. Why do you people even have cars?

Re:Good

[Draveed]

I share your enthusiasm for pebble bed nuclear tech, but I would think the reason this southern power company isn't planning on using it is because it's not a proven technology. Given how nuclear energy is such a sensitive issue, they probably want to stick with proven designs and concepts. Yeah it's not innovative but it's safer for them. I mean how many reactors have actually been built using the pebble bed concept? AFAIK, just one test reactor in South Africa.

Re:Good

[Ironsides]

I'm not sure why the lack of interest in pebble beds, but I'm guessing they need some political pressure...

As I understand it, the pebble bed nuclear reactors make it really hard to re-enrich the uranium after usage. This is a bad idea as re-enriched uranium can be reused and produces less radioactive waste in the long run. All we have to do to solve the reenrichment problem and a large part of our nuclear waste is to build a fast breeder reactor and start recycling the used material.

This was the original plan when nuclear power plants were first developed. President Carter used execuitive order to ban fast breeder reactors back in the 70's, so it wouldn't take much to undo that ban.

Re:Good

[Rei]

Because, naturally, you know more about the economics, safety, and other issues relating to various nuclear reactor designs than Southern Company.

Do you even know *any* next-gen reactor designs besides PBMRs?

Re:Good

[Rei]

Oh! Logic train a'comin!

ding ding ding Ding Ding DING DING DING Diing diiing diiiing.....

Darn, missed it. :P

Plain and simple, gas prices in Europe are high because of taxes.

Oil companies aren't monopolies - it's a very varied industry, and fiercely competitive. It's worse than many industries, because they're all selling essentially the same thing. They'll push particular blends and additives, but it really comes down to the same product, so it's really down to whoever can sell it the cheapest.

By the way, the main reason that oil companies are turning such tidy profits right now is because they had been working to be profitable at 20$/barrel, and suddenly it's at 60$/barrel. Note that the high prices are much more of a benefit to producers than refiners, although the whole industry is quite profitable right now. If you have infrastructure or build infrastructure, it's in such demand, you're going to make money.

Re:Good

[MillionthMonkey]

Car engines can't be nuclear. While nuclear reactors can be made with the appropriate power output for a car, the biggest problem is that the driver would be killed by the neutrons that would drift out of the engine. Neutrons are a bitch to shield against and a car would not be able to carry the necessary material.

Re:Good

[orz]

I doubt that slashdotters (or policicians) making decisions based upon idealogy and buzz will produce better reactor designs than people who have incentive and resources to make smart decisions.

That said, I'd be happy to see more research into pebble bed reactors, and into energy amplifiers / ADS (subcritical fission reactor plus a particle accelerator), and other promising nuclear reactor designs that come along.
I just wouldn't assume that just because pebble bed reactors have some clever safety and efficiency benefits means that they are automatically better for commerical power generation than conventional reactor designs today.

Re:Good

[ickpoo]

Gas will be available as long as there is any demand for it. Because of collectors cars that means close to forever. It will be pricy though.

I see it more like this. 30 years from now I'll be able to stop at the classic gas station and top off my '62 Alfa Romeo with some high test gas for roughly $20 a gallon (current dollars, who knows then).

Re:Good

[VagaStorm]

Since I'm probably not the only one that don't know my reactors that well: http://www.nrc.gov/reading-rm/doc-collections/fact -sheets/next-gen-reactors.html :p

Re:Good

[Danger Stevens]

But the big argument against all-electric (also called gas-optional) cars is that the electricity has to come from *somewhere* and coal plants aren't much better than combustion engines.

If the grid runs off clean and safe nuclear, cars can run of batteries.

Re:Good

[Rei]

1. There is a big debate over the graphite's role in Chernobyl. The Soviets who put out the fire were insistant that the graphite was burning - they even had debates over how to put out the burning graphite without encouraging faster burning or secondary reactions. Nuclear professionals in America are insistant that nuclear grade graphite only erodes - that it doesn't burn - and lab tests of fresh graphite hold this out. Even simple erosion of radioisotope-laden graphite would be awful, of course (especially in this case where the graphite is in direct contact with the nuclear reactants and daughter products), but it's hard to deny the Soviet field reports. In all likelyhood, fresh nuclear-grade graphite doesn't burn well, but after it is bombarded by high energy radiation and corrosive chemicals for long periods, it does.

2. There *Is* water in the system of most PBMR designs. As I stated, helium is the primary coolant; however, some use water as a secondary coolant in the core (such as China's design), and even some designs that don't use it in the core have a secondary loop in which water is pyrolized into hydrogen and oxygen.

3. "seven layers of containment". Um, yeah right. There's only one pressure-tight containment level in PBMRs. The graphite isn't pressure tight - it's just a coating, and one that gets highly contaminated in the process. The reactor vessel and associated helium loop and pellet recycling are pressure tight. Unlike most nuclear reactors, the reactor building is not a positive pressure structure.

4. "Without the helium moderator the chain reaction stops". This is called "a negative void coefficient", and it's nothing remotely new. Three mile island had a negative void coefficent too. The problem is that the reactor core, even if *all* reaction were to cease, still has a huge amount of heat inside of it, and this residual heat is what poses the threat. By the way, helium is not a moderator - graphite is. You'll note that in demonstrations, the only thing that they demonstrate is shutting down the helium coolant - they never violate the integrity of the pressure vessel. This is because oxygen (and even potentially water or steam) can get in, and this can have very serious consequences. And, without a containment structure...

5. "Gas moderated reactors are a means to make Thorium breeders" - Once again, the term is "gas cooled", not "gas moderated". Do you even know what a moderator is?

Re:Good

[richie2000]

President Carter used execuitive order to ban fast breeder reactors back in the 70's

As an old Navy Nuclear technician that was personally involved in atleast one radiation clean-up, I would imagine he had some very good reasons for doing that at the time. Would you happen to know his reasons for banning them and if they may still be valid?

Re:Good

[N3wsByt3]

"Do you even know what a moderator is?"

Many times, I've asked the same question, when reading posts on slashdot... ;-)

Re:Good

[Squalish]

I've been convinced after doing some research that the likelyhood of the geiger counter becoming a whole lot more active very quickly is greater in the struggle over the last few oil fields than it is from waste plutonium.

Re:Good

[True Grit]

and if they may still be valid?

"breeder" still manages to refer to several different types, so there isn't a blanket answer. Ordinary "breeders" still have that same *potential* problem, but we don't just have "ordinary" breeders anymore.

While the current fad seems to be over PBMRs, maybe because of the neat name I guess, my favorite still remains the Integral Fast Reactor, not only because of safety features, but because these could run for decades just by burning all the spent fuel from our conventional reactors. Newflash: we don't *need* a hole in the ground for most nuclear waste, just chuck it into an IFR.

Re:Good

[Ironsides]

Would you happen to know his reasons for banning them and if they may still be valid?

Fast breeder reactors produce Plutonium 239. For those others who don't know Pu-239 is the form of plutonium used in nuclear weapons. As for carter, See this post.

Re:Good

[richie2000]

Frankly, I've always thought that Carter's moves on energy were irrational and borderline cookoo given that he and I attended the same nuclear power training several decades appart.

Maybe you never had the misfortune of having to clean up after a nuclear accident? And maybe he had access to a lot more information about these accidents than you or I ever will? I dunno, that's why I asked if anyone knew why he banned breeders. Apparently, it was an attempt to hinder proliferation of weapons-grade plutonium, a subject I suspect never came up in your nuke power training...

Cite source for clean-up as the Navy had not yet had one accident by the time he was discharged. To this day, we are still waiting for a screw up.

I never said it was a Navy screwup. Non-Navy screw ups galore.

December 12, 1952 - The first serious nuclear disaster occurred at the NRX reactor in Chalk River, Canada. A massive power excursion destroyed the core, resulting in a partial meltdown. A series of hydrogen gas explosions threw a four-ton gasholder dome four feet (1.2 m) into the air, where it jammed in the superstructure. Thousands of curies (several terabecquerels) of fission products were released into the atmosphere, and a million US gallons (3,800 m) of radioactively contaminated water was pumped out of the basement into shallow trenches not far from the Ottawa River. The core was buried. Jimmy Carter, then a nuclear engineer in the US Navy, was among the cleanup crew.

Re:Good

[Knuckles]

I posted something similar a few days ago but got no replies, and I think this is the most overlooked effect of nuclear energy (including fusion btw, but maybe less so, and except maybe the cold variety ;)

Nuclear power leads to a militarization of society due to the huge risks involved, and adds tremendously to a concentration of power - electrical, political, and economical - due to the high complexity and costs, and necessary scale involved.

The first big post-war waves of increased police and governmental control in Europe were pushed through by using precisely these threats, even before terrorism (another kind: RAF and Brigate Rosse, both with well-documented help by the police and secret services btw) played that role for the first time, but of course then the two scares worked together.

Add to that how nuclear power contributes to political instability in the world, and adds danger to the already existing instabilities (take this week's developments in Iran).

Re:Good

[venril]

There was an interesting documentary on what-went-wrong. They were monkeying around with power levels to perform some tests by manipulating damping rod positions, and water flow into the core. [btw, the pumps used to move water into the core were electric and, you guessed it, were powered by tapping from the plants own generators. Low or no power, no pumps =P ] While the rods could damp the reaction, water was critical to control/moderate temp change over time. Heat removal by the water buffered the the damp rod control loop. No water and temp fluctuations occur faster and acceleration changes rapidly.

So..

(shaking rust off memory)They ran the power (heat) output of the core low. Over controled it below min levels, decreased water flow, cranked up the power by pulling some rods to get power up. Power ran up to high side, dropped some rods in, added water too quickly, cooled core too much, no steam output, turbines stall, tech panics and pulls ALL of the rods (big no-no, he forgot to RTFM), core temp climbs, water cannot be provided quickly enough (no power), water flashes off into steam, core over heats, ignites graphite - boom. More or less.

A nice feedback loop they they magnified causing increasing excursions with ever larger over corrections - doh! Current reactor designs use the working fluid ( or intermediate heat transfer fluid) as the moderator; the reaction cannot proceed with out the moderator being present to slow the neutrons. If the fluid drains out, the reaction halts and the reactor cools. If the reactor gets too hot, the moderator boils off, again halting the reaction. Kinda hard to get into a meltdown condition.

Not surprising

[benjamindees]

I'm not surprised stirlings are finally profitable.

But those giant dishes look expensive and complicated.

Doesn't anybody have a way to make large parabolic reflectors cheaply? Or isn't there a way to do away with the tracking devices?

Re:Not surprising

[inode_buddha]

I've seen people take the old 6-foot TV dishes and mirrorize them, either with silver paint or glueing a zillion tiny glass mirors onto them. Mother Earth News did a project like that back in the 1970's IIRC. The heat near the focal point was in the thousands of degrees F and powered a small energy-efficient home.

Say "no" to Solar

[Anonymous Coward]

While the solar panel industry would like you to believe Solar Power to be "eco friendly", unlike most "alternative energy" technologies, Solar energy is not a renewable resource. We have a limited amount of sunlight and increased use of commercial solar power would mean less to be used elsewhere, potentially creating an ecological disaster if this happened on a large enough scale. The solar industry likes to throw around statistics about how the entire U.S. could entirely move over to solar power if we created such-and-such amount of solar panels, but what they don't mention is if we did this we would completely exhaust our supply of solar energy by 2150.

Use of solar power should be avoided at all costs. Help promote renewable energy sources instead.

http://nosolar.net/

Re:Say "no" to Solar

[Vombatus]

We have a limited amount of sunlight

But, if you save some of that daylight http://it.slashdot.org/article.pl?sid=05/07/20/195 7200&tid=103&tid=185&tid=218, you would have more to use.

Conversion Table: Megawatts to Homes

[Anonymous Coward]

If anyone is wondering, 500 megawatts can power about 500,000 homes.

Re:Conversion Table: Megawatts to Homes

[ergo98]

If anyone is wondering, 500 megawatts can power about 500,000 homes.

I worked on projects for large methane->power facilities in California (and across the US), which turned landfill belchings into fuel for large engines. One of these facilities, in a dinky little building, put out about 6MW all day long. Not quite 500MW, but it was pretty impressive given that it was methane that would otherwise have been flared off uselessly.

For context, typical new nuclear power plants produce around 600-1200MW.

Re:4500 acres?

[uberdave]

Counting or not counting the uranium mines, heavy water refineries, and spent fuel storage facilities?

Environmental loop...

[ergo98]

4500 acres of solar collectors? This must throw hardcore environmentalists into a infinite loop.

Re:Environmental loop...

[Manchot]

Well, if you think about it, 4500 acres is really only a 2.65 by 2.65 mile square. That's not really that much environmental impact, especially if the thing is in the middle of the desert.

Re:Environmental loop...

[JanneM]

4500 acres of solar collectors? This must throw hardcore environmentalists into a infinite loop.

This makes sense to have in dry, hot areas (where you have lots of dependable, strong sun). Much better than using the same land to grow wheat, corn or rice - a monoculture is no better than this, and the use of scarce water is much less with the solar array than with crops.

Re:Environmental loop...

[syphax]

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.

Re:Environmental loop...

[modecx]

You're right. I studied desert ecosystems before I changed my direction in college. They are quite sensitive, and over millions of years many of the little critters in those areas have become quite dependant on very certian conditions, and very precise timing of monsoons and changes of the season--which greenhouse warming is bound to affect drastically anyway.

I say put these collectors as individual units in people's yards--if they agree--and give them a percentage off their electricity bills as lease for the land. They get the power to run their AC for free, and they contribute to the power grid, win/win.. It's basically the same deal with cell towers. We have one on one of our properties, and we get $2,000 a month for it. Best tenants we've ever had, I must say!

Of course, they'd have to be almost completely maintance free so you don't need a horde of technicians running all over fixing them. In this way, the environmental impact will be mitigated, as there are already people in the area with houses and paving and all of that... But that's good also because distributed power grids are much more reliable (and probably more efficient) than grids depending on only a few sources.

This could be quite popular all over the southwest if it were economically feasible.

Re:Environmental loop...

[Jeremi]

We should just cover the whole moon with this stuff such that the focal point would be here on Earth.

Dude, that's not an energy source, that's a death ray! Tired of listening to Kim Jong Il threaten nuclear armageddon? ZZZAPPP!!!

space power on earth!

[J05H]

Sterling engines are pretty cool. They have one huge advantage over silicon solar power: much much less pollution in production. Photovoltaics are basically large chips, they use the same nasty chemicals and lots of electricity. Sterling engines are just machines, and very scalable apparently.

Funny that one solar-dynamic powerplant will double the solar power being utilized.

One of the Sterling engine makers has a deep-space powercell that combines a sterling converter and a big hunk of plutonium oxide. Man, I wish I could get one for the basement...

Josh

Re:space power on earth!

[alienw]

Are you pulling this out of your ass? Photovoltaics cost a lot because they are labor-intensive to produce and require specialized equipment. If you actually bothered to research the numbers, you would find out that solar panels generate that amount in only 3 years or so (out of 30 or more).

Re:space power on earth!

[Artifakt]

Several sources of Aluminum are demonstrated and proven 'environmentally friendly' technologies (as much as technologies ever are). Take for example Alcoa's TN. plant, one of the largest single sources of refined Aluminum in the entire world (Historically, there have been entire decades when this was THE largest single source). Electric power for this facility comes entirely from four hydroelectric powerplants - Chilhowee, Calderwood, Cheoah and Santeetlah. Several other Aluminum operations, including Alcoa's own plants in Texas, have had more negative environmental impacts, and a few plants in the former Soviet Union have an abysmal record, but it's worth noting these are all much smaller operations.
      The North American Aluminum industry currently uses about one-third recycled material in its products, with the goal of exceeding 50% by 2020 AD.
      This goal may prove impossible to reach however, as the percentage of all aluminum ever produced that is bound up in long term/permanent objects such as buildings and industrial machinery is steadily increasing.
      Aluminum is produced from Bauxite ore. The most significant environmental byproduct is caustic soda, which has been implicated in the amounts produced in contamination of rural water supplies, with (in humans) increased levels of Hypertension, 2 to 5 times that observed before mining came to the area (Given other lifestyle changes common at the time, this may not actually be primarily, let alone wholely, the result of increased sodium uptake from the local water supply).
        In addition, the operations produce large amounts of typical red clay mud, which, while not particularly significant chemically, is produced in large quantities, roughly one ton of mud per ton of seperated ore. Runoff of this in rainy weather has a significant negative impact on streams and rivers, but is hard to isolate from other human adjustable sources of red clay runoff, such as non-contour plowing.

There is no way to rationally analyze "photovoltaic" process impact - common compounds that form a major portion of different cell designs include amorphous silicon, cadmium telluride, and copper indium selenide. Toxicity for these three compounds alone ranges from almost trivial to very high on the hazard list, and trying to discuss them as a group would be like discussing the risks of wild animal attacks, considering only box turtles, poodles gone dingo, and Bengal tigers, and taking an unweighted average for attacks without considering actual lethality. Figure in the differing risks of the mining byproduces for these three types as well, and talking about the risks of the industy as a collective is literally meaningless until we know which technologys will be used in what proportions.
        Cadmium, Tellurium, and Indium are all heavy metals, mining them results in tailings that have Arsenic, Lead and other heav metals in various amounts. and the health risks to nearby communities and industry workers are all at least roughly analogous to those observed in industries such as Lead Acid battery manufacture, but the actual amounts of risk may differ by a couple of orders of magnetude, and it's not known yet how many of them can be mitigated.

So yes, melting Aluminum uses 'nasty' chemicals and electricity. Making Photovoltaics as a whole can't even be compared, but if we look at the designs that incorporate heavy metals we have some strong reasons to suspect that there's "nasty" and "Nasty!", (and just maybe "NAAASSSSTY!!!!").

Colorado voter initiative

[magarity]

The voters here in Colorado were suckered into an initiative requiring the utility companies to get 15% of their power from renewable sources whether it made economic sense or not. Since it looks like this thing actually does then I hope someone from the local utility reads /.

Re:Colorado voter initiative

[fimbulvetr]

The voters here in Colorado were suckered into an initiative requiring the utility companies to get 15% of their power from renewable sources whether it made economic sense or not.

The spin you put on this makes it seem bad, however, relatively speaking our idea of efficient alternative energy is less efficient than coal mining and what have you. So, sure, it might not make economical sense compared to non-renewable energy, but that doesn't mean it's a bad thing!

Another reason this whole thing isn't that bad is because it forces companies (Xcel, etc.) to actually work on R&D for making their energy production more efficient - they now have a vested interest in it. If that were not the case, they'd just be burning the candle at both ends with oil/coal and worry about the future when the future came about. Xcel has been putting in a lot of wind generators in SW Minnesota, and they're not done. I love to see those generators every time I travel through there - it means something is actually getting done.

As for the voters in Colorado getting suckered in, well, I hear you, they're not the smartest...

Re:Failure of the Bush administration

[DAldredge]

This is taking place in California...

Signed Tuesday, the 20-year power purchase agreement, which is subject to California Public Utilities Commission approval, calls for development of a 500-megawatt (MW) solar project 70 miles northeast of Los Angeles using innovative Stirling dish technology. The agreement includes an option to expand the project to 850 MW. Initially, Stirling would build a one-MW test facility using 40 of the company's 37-foot-diameter dish assemblies. Subsequently, a 20,000-dish array would be constructed near Victorville, Calif., during a four-year period.

4500 Acres Sounds Like a Lot

[yrogerg]

but for the record: 4500 acres is only 7 square miles.

It sounds a lot smaller when you put it that way.

Re:4500 Acres Sounds Like a Lot

[Chmarr]

Cheap, not free. Cheap.

Re:Failure of the Bush administration

[MyLongNickName]

Ummmmm. Stirling is located in Arizona, right? I may have graduated public school, but I am pretty sure this is in the U.S. somewhere.... right above Maine.

The Edison URL

[TedTschopp]

The Edison URL should be www.edisonnews.com. Yes, we require you to put the www on the front of it. And yes, I work for them.

Re:4500 acres?

[RandUser]

Touche. Which is why I think we should be focusing research and energy on nuclear fuel reuse [waaaay unexploited in the US] and disposal techniques.

Stirling engines

[JanneM]

Stirling engines certainly aren't forgotten or neglected. Swedish submarines use Stirling engines for propulsion, for instance.

Re:Stirling engines

[apa666]

The only drawback is they lose some of their stealthyness due to the giant solar reflector beaming sunlight down the periscope.

Re:Stirling engines

[aktzin]

The nice folks at Kockums (a division of ThyssenKrupp Marine Systems in Sweden) set up this web page in English with a cutaway view and diagram:

http://www.kockums.se/Submarines/aipstirling.html

OK, so what's the catch?

[Bryan Ischo]

I know some knowledgeable Slashdot reader can help me here. What I want to know is, what is the drawback to such a power system? It sounds like it generates quite a bit of power, and looks like a completely clean source. Are these things super expensive to build? Is it really hard to keep these things lined up with the sun to produce optimal power?

There is the issue of not being able to produce any power at night. But intelligent use of battery stores along with some supplemental traditional powered generators might take care of that, especially since power draw from the grid is (I'm guessing) much less at night.

So - what's the catch? Why aren't fields of these things going up like crazy?

Re:OK, so what's the catch?

[aktzin]

Wikipedia to the rescue:

http://en.wikipedia.org/wiki/Stirling_engine#Probl ems_with_Stirling_engines

Re:OK, so what's the catch?

[Qzukk]

Why aren't fields of these things going up like crazy?

The real reason? Because cities can think of better things to do with their land than use 4500 acres (3/4 football field is about 1 acre. You could put a lot of stadiums on that land) of it on stuff like this, and unlike other cultures that have become used to growing upwards, planning a city to have all of the buildings the same height so that the entire array can sit on top of them just isn't an accepted idea here.

Re:OK, so what's the catch?

[Artifakt]

Drawbacks? Here's some, although they are neither (IMHO) all that serious, and I like this technology as a whole, and would say these won't stop it in the long run.
1. Heat - Focused mirrors in large banks are extremely hot at the focal points. When you're talking 500 Mw. output, your talking about lots of points inside that 4700 acre area where temperatures must be enormous (3,000 degrees F or so if the focus is at all tight).
        Basically, anything that involves a huge energy differential has some potential for that energy to go in directions we don't want. The potential may be lower for some technologies than others, and this may well be one of the good ones, but by the very definition of energy (the ability to do work), there is no energy technology that can't do some work we don't want, whether it's a dam breaking and all that water working hard to wash away a town downstream, or mirrors getting focused on the wrong points, and the wrong things getting hot (like employees on site, or the supports and braces for other mirrors).
2. Not only can you not produce power at night, but cloudy days reduce your efficiency. Power draw on the grid is (usually) only less at night in the summer, when a lot of electricity is going to air conditioning. In winter, power draw is more for heating and people heat most on cold nights. Days are also shorter, plus sunlight is passing at shallower angles through the air and so has less energy per square foot, so even if this system is very, very efficient at the best of times, it becomes just half (or so) of a two part solution. At best, it's likely somewhat more than half, and maybe cuts fuel oil and coal use by a very nice 60-70%, but it simply can't do away with them entirely.
        Now for the bad news - A power company that only needs 30% of the fuel oil it did won't see a full 70% savings - the way their contracts work, they will probably only see about a 50% savings on oil costs, so that financial 'damping' effect slows adoption of technologies like this. They have to prove themselves to conservative investors, and even then they have to offer big improvements and not just small ones, or they take 20 years or more to catch on.
      This is a catch 22. If the technology caught on really fast, then basic macroeconomics holds fuel oil prices wouldn't continue to rise, because demand would decline. But since the technology simply can't catch on all that fast, places that haven't adopted it yet will continue to drive demand higher, the early adopters will get smaller discounts because they are buying only seasonally or in less bulk, and the rate of adoption will be slowed further.

Re:OK, so what's the catch?

[Jeremi]

I want pictures of such said batteries.

Maybe you could just use the excess energy to pump water uphill, and then let it run back downhill through a dam during the night.

Re:OK, so what's the catch?

[Dun Malg]

Yeah, but an earth-fill damn can never power a car, hydrogen can.

RTF post I wrote: "The only real advantage to hydrogen is that it burns very cleanly, in theory making it an ideal vehicle fuel." Also, you may have noticed that we're not talking about hydrogen's suitablility as a vehicle fuel, we're talking about how SCE is going to store solar energy for nighttime use. Get with the program. Read what people are writing so you can actually follow the conversation.

Re:OK, so what's the catch?

[evilviper]

My VW Vanagon has a hard time climbing hills with 95 horsepower.

Well too bad for you. Meanwhile cars like the original VW Beatle have about 30 horespower (at the wheels), and don't have trouble climbing hills. Your VW might have 95HP PEAK, but at the wheels, especially while climbing, I bet you're getting a fraction of that. Electric cars don't need transmissions, and other horsepower-sapping equipment that ICEs need.

But that's really irrelevant, anyhow. The parent didn't even suggest that solar panels would be the sole source of fuel for future vehicles. If you've got an electric car, put a solar panel on the roof/hood/trunk, and you get more range. You'll save money from not having to plug-in as often. Horror movies will run out of plots, as people that run out of fuel in the middle of nowhere need only wait in their cars for an hour, (while it recharges itself) before continuing to drive. And people that use their vehicles for short, infrequent trips might never need to plug their vehicles in.

Note that "short" means distance, not time. Without the need to keep your engine running, you can sit in traffic for hours and use almost no power.

Pseudoscience?

[rdwald]

Stirling engines seem legitimate enough, but the linked site describing them seems somewhat crack-potish. They promote cold fusion and zero point energy, as well as a number of "alternative energy sources" I've never even heard of. There's also a page trying to disprove the Peak Oil theory, which should be real popular with the Slashdot crowd. Anyway, I sometimes wish that /. nerds had a greater understanding of the pure sciences, rather than just software engineering. Oh well.

Re:Pseudoscience?

[Thanatopsis]

Zero Point Energy? Why Zero Point Modules are what power the lost city of Atlantis in Stargate Atlantis. They are widely recognized as on the most powerful energy sources in television science fiction.

Re:Pseudoscience?

[srleffler]

To be fair, despite its popularity with the wackos, the idea that oil may not come from decaying biological matter after all does have some scientific merit. It's still (AFAIK) a controversial hypothesis, but not a completely baseless one.

We used to think that all 'organic' compounds were organic in origin. We were wrong. 'Organic' compounds have been observed in space and on other planets. It's not a huge stretch (especially given other evidence) to wonder if these vast pools of hydrocarbons under the Earth's crust might be from some source other than decaying vegetation. That doesn't mean we have an unlimited supply of course .

Re:Pseudoscience?

[Dun Malg]

What I've understood from geologists is, is that even if it is true, this source doesn't produce all that much oil per year.

Sure, if all you do is try to collect it near the surface like we do now. All you have to do is drill deeper to find more. The Russians are currently pumping oil out of wells 8 miles deep. The stuff we're pumping out at the top is only that little bit that seeps into easily reachable pockets.

Secondly, you find remains of plants in oil, which almost makes you wonder how they got the idea it came from a biological source, not

You don't so much find "plants" in oil, you find "organic matter". Biogenic fuel theory says it's from zooplankton and phytoplankton. The reason abiogenic petroleum theory was initially rejected was that in the 19th century it was believed that microbial life could not exist in such extreme conditions, thus the petroleum itself must have come come from decayed organic matter. We've since discovered numerous extremophile forms of microbial life, but the whole "fossil fuel" notion has become so ingrained that the loss of a major part of it's theoretical underpinning has essentially been ignored.

Solar...

[Junior J. Junior III]

In related news, ants in a 4500 acre area have all mysteriously vanished.

New Energy Laws?

[seven of five]

Now that Bush signed the 'Energy Bill' we have this gigantic solar project, underwritten by a big utility. Coincidence?

Hey, we're almost in business...

[Manchot]

All we need now is 1.42 more of these things!

Comment removed

[account_deleted]

Comment removed based on user account deletion

Parabolic Dishes

[minisimon]

Yeah, parabolic dishes just don't seem to come naturally. (This particular one is made from mirrors with ?5? different circular curvatures arranged parabolically, if recall correctly) Some groups have made test dishes by applying a vacuum to the backside of a thin stainless steel sheet and heating it, then keeping it under a slight vacuum. This doesn't produce a perfect parabola, but it's better than circular, apparently. Some examples are here: http://www.psa.es/webeng/areas/instalaciones/disco s.html

What about cloudy days?

[IceDiver]

From the description of the system, the plant will only produce power when the sky is clear during daylight hours. Has anyone seen information regarding how much time the solar plant will be online and how much time it will spend offline due to night or cloud?

Is the only backup to this system the electric grid as a whole, or will the solar plant include some kind of heat sink or other way to store energy which can be drawn on when the sun isn't shining?

Reality check

[Animats]

Reality is that they've installed six dishes at Sandia, with a peak output of 150KW. Southern California Edison is talking about installing 40 dishes, with a peak output of 1MW. If those work, maybe the 20,000 dish gigawatt facility might happen.

There have already been two big solar projects in Southern California Edison territory, called Solar One and Solar Two. Both were so expensive to operate that they couldn't even cover their operating costs, let alone their construction costs.

Re:Reality check

[Big_Breaker]

Actually they ARE pretty much the same thing.

Heliostats are just mirrors with trackers. Each SES unit is.... a mirror with a tracker.

The only difference is that the SES system has the heat engine attached to each unit while the Solar One "power tower" configuration has only heat engine. Molten salt is used as a storage and transport technology but the real engineering is in the steam turbine, a technology which is extremely mature.

While sterling engines and steam turbines work differently, they are both heat engines and are subject to the same limitations (moving parts and Carnot efficiency).

Re:Reality check

[Big_Breaker]

The tracking is more difficult for the heliostats - I agree there - bank shot versus a straight shot. No combustion takes place in either system. Combustion requires the oxidation of fuel, no?

Anyway I have my degree in EE and work at a company that has invested billions into power projects so I do know this field. Power towers (solar one), linear concentrators (trough concentrators), and these sterling units are generally grouped together as solar thermal. They all use solar energy to heat a transport fluid which in turn powers some sort of heat engine to run a generator. While the implementations are different, the various methods share a great deal of technology and none of it is especially hi-tech.

Solar suffers from the fact that insolation has low power density. Concentrating that power has efficiency and cost challenges which point to clever uses of low-tech materials and mechanisms, not hi-tech ones. For instance in Solar One it is the heliostats that cost the money and most of that is in the mechanics of the tracker. A single computer can control any number of trackers and the calculations are quite simple geometry, so the "bank shot" problem need only be solved once for any size system.

Extracting power from hot fluids has been mature for some time now with only incremental improvements possible due to the Carnot limit. Molten salt as a transport fluid and the elevation of the target are not, in any way, major challenges. Wind turbines are far taller, heavier and more complex. Lots of mainstream heat exchange systems operate at higher temperatures and pressures.

Solar One exists on a grand scale already and is an important project but shouldn't be treated with undo reverence. It is just one step towards practical solar power and may in fact be a dead-end.

These Sterling units are self contained and modular. You can add power incrementally, as needed. With power towers you need to size the target and generator according to a certain power level and then deploy all the required heliostats to maximize efficiency. With these you just keep adding modules.

Re:Reality check

[WOV]

I think we agree more than disagree. I think the power towers *are* a dead end - the working fluid is heinous to handle, the plant itself is much more vulnerable to single points of catastrophic failure, it brins NIMBYs the dishes don't, and it's not that suspectible to manufacturing economies of scale. I think it's a bad application of big power plant thinking to a diffuse and distributed resource.

Where I will argue with you is that the economic failure (and failure they were) of a hundred=plus kW power tower has any bearing on the prospects of a field of dozens of 25-kW engines operating on entirely different principles throughout...

CNAME

[imag0]

...Yes, we require you to put the www on the front of it...

Then you have a brokeass CNAME entry which goes against the RFC's, if I recall.

Do the internet a favor and just say no to worthless CNAME crap. A browser will get to the right place without that dumbass "www" tacked to the front of a domain name.

Re:CNAME

[multipartmixed]

> Then you have a brokeass CNAME entry which goes against the RFC's, if I recall.

You don't really know much about DNS, do you?

www.edisonnews.com is a CNAME for d083489.edisonnews.com. There is nothing "broke ass" about it.

edisonnews.com has no DNS entry whatsoever (excluding SOA, obviously).

> A browser will get to the right place without that dumbass
> "www" tacked to the front of a domain name.

Who says that machine d083489 is the right place?

Additionally, even if edisonnews.com. CNAME d083489 was inserted in the DNS, the site *still* might not work -- it would only work if www.edisonnews.com was the default site for that web server. Otherwise, he'd had to add another vhost to his httpd.conf-equiv. And given that he's running IIS, that might be a chore. ;)

Incidentally, what RFC w.r.t CNAMEs are you talking about? The only relevant guidelines which pop to my head are an RFC in the 1300-range or so (been a while) discussing the use of CNAMEs with MX records and such. (MX to CNAME ist verboten, but has nothing to do with web traffic)

Give & Take

[topical_surfactant]

Sterling engines don't require the nasty manufacturing processes of photovoltaics. This is great because it takes some rather dangerous chemicals and a lot of electricity to manufacture the typical solar cell. I read somewhere that a solar cell will only pay for its manufacture ($$$ + enviro cost) after 20 years of operation. Can't remember where I saw it...

Photovoltaic cells have no moving parts. Anything with moving parts _will_ wear out faster than a solid-state solution. I wonder how competitive the industry will be in the future...

Re:4500 acres?

[srleffler]

The problem with radioactive waste storage is not the shielding, it's how to prevent groundwater over hundreds or thousands of years from getting into the storage facility and dissolving/carrying off radioactive material into the water table. This is the big concern holding back the real planned waste storage facility, which is in a deep, dry hole in the middle of nowhere. They need to prove first that whatever they put there will stay put for tens or hundreds of thousands of years.

Re:Increase efficiency with fresnel lense

[Ironsides]

Just spit balling but couldn't fresnel lense technology (Giant Fresnel Lense) be used to increase efficieny, or reduce the size of the dish. Then use fly wheel technology to store excess energy for night time use.

The fresnel lens could reduce the surface area of the mirrors, but not of the over all area. The amount of light energy from 1 acre is the same whether you condense it using a lense or a mirror. In addition, with the extra complexity and cost of the lens, you might as well just stick with a mirror (plus the lenses are probably more fragile).

As for the fly wheels. Think about how big and how many flywheels you would need in order to store 3gigawatt hours. That is 250Mwatts for 12 hours. Plus inefficiencies in the bearings and conversion of the power would reduce the stored energy.

Cooling?

[Michael Woodhams]

The pictures have huge dishes to collect heat, but what about the other end? How do they keep the cool part of the cycle cool?

I was expecting to see the engine behind the dish (receiving light via a secondary mirror) and big radiator fins attached to the engine in the shadow of the dish.

Just did a couple quick calculations...

[skelly33]

... and based on a 37ft dia dish, 20,000 count we're talking 21,504,183 sqft of total collector area. Divide that into 500,000,000W, the projected peak output of the installation, and you end up with around 23W per sqft.

Now I could swear I've seen a higher efficiency per sqft specified using a related but different technology: steam turbines. I can't find the link right now, but I was hoping to build one of these things one day myself to take some real world measurements. The projections I read admittedly may have been inaccurate which is why I want to build my own to find out, but the project site was claiming the potential to pull approaximately 3KW of usable power out of a steam turbine from a 6 ft diameter parabolic dish.

There are a few completed collector dishes out there in this size and they are making between 600-1100 deg fahrenheit at the focus where a heat exchanger is placed to boil water into steam pressure which drives a turbine. The only thing that leaves me questioning the accuracy of the projections is that the turbine is a somewhat unconventional one, called a "Tesla Turbine".

Nonetheless, if the figures are remotely accurate, you'll find that a 6ft dish putting out 3KW is worth over 100W per sqft. I believe this possibility alone makes it well worth examining the potential for higher thermal conversion efficiency than the sterling engine model because it could potentially reduce the size of this installation to 25%... or quadruple the output!

Regardless, both approaches are quite fascinating because they're so simple - it's mind numbing that nothing like this is yet operational. It's so technologically unsophisticated that it could be built and installed nearly anywhere. Even the sun tracking circuit can be done on the cheap for about $25US in bits & pieces.

A couple of good reasons...

[Goonie]

I can't find the reference, but part of the problem is that the US nuclear regulatory regime is designed around the assumption of monolithic, large light-water reactors. The idea of a modular system where you can add another reactor module quickly doesn't fit in with the approval process, removing one of the biggest advantages.

Secondly, US companies aren't developing PBMR designs; South African and Chinese ones are. Funnily enough, the subsidies for nuclear R&D and deployment currently floating around Washington are aimed at the American nuclear power industry, not its foriegn competitors.

Mind you, if Westinghouse's cost estimates on its new AP-1000 power plant design turn out to be it's going to be pretty competitively priced anyway. Pebble beds aren't the be-all and end-all. One concern is whether there'll be enough helium available to run them...

Cheap Parabolic Dishes (in a relativesense)

[Redge]

A company in Australia is developing this type of technology for self-contained power generation in remote locations (and 3rd world countries/natural disaster areas). They are using a parabolic dish made from mirror polished bands of stainless steel. Stainless steel (while expensive) stands up to bad weather much better than glass mirrors - and by making the dish with bands (with gaps in between them) you reduce the effect that wind had on the dish.

They are making a dish that isn't affected by wind (except for wind that flattens buildings) doesn't get damaged by hail (unless it's bigger than a cricket ball) and is only 5% less efficient than the same size mirror dish. They don't have a website worth mentioning - but they are developing all this in conjunction with the CSIRO - so you may find something here (CSIRO) http://www.csiro.gov.au/ about it all. Look for Sterling engine power generation. The CSIRO did publish something recently in a subscription only publication about this.

In case you were wondering how I know - my brother works for the small electronics firm that came up with the parabolic dish idea. They have also come up with a sun tracking mechanism that costs $15 to manufacture.

Pity a 5KW generation system costs $25000 all up - but they expect it to last for 25 years or more.

All dollar figures here are Australian Pesos.

Oh yeah - they get around the "How do you generate electricity at night without sunlight light" issue, by using the dish to heat up 300KG (or so) of salt and graphite - which then acts as a heat battery. Apparently they can run the Stirling engine for 3 days or so after the Salt Cell gets to about 900 degrees centigrade.

Re:Failure of the Bush administration

[tehdaemon]

"Ah.. but, in its preamble, the Constitution explicitly declares that one of the its primary purposes is to 'promote the general Welfare'.

The Preamble -

We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.

Let me cut out the unnecessary stuff here -

We the People of the United States, in Order to . . . promote the general Welfare, . . . do ordain and establish this Constitution . . .

The preamble explains why 'We the People' adopted the Constitution. It has nothing to do with any powers delegated to any branch of government beyond hinting that the power is derived from the people.

While I agree that your interpretation has been used, it is so laughably off from the plain text of the preamble that it should never be given a first thought, let alone a second one.

It's 500 MW != a nuclear power plant's 500MW

[dameatrius]

A nuclear power plant will produce on average 80-85% capacity with 90%+ uptime. Uptime for solar will be at most 50% as you only have sunlight for 10-12 hours. Then, will it be producing 100% capacity for those 10-12 hours? No.

The standard anti-nuclear answer. How smart!

[Draveed]

The reactors at Chernobyl are not the same design of any reactors built in the US. So there's no point in bringing it up unless you just want to scare people.

And the fears over Three Mile Island are just plain ignorance. It was a minor incident that didn't hurt anyone. Don't believe me? Too bad. The Pennsylvania court system does. After years of litigation, the courts ruled there isn't enough evidence anyone was harmed by the accident to support even going to trial.

My favorite quote is, "The court has searched the record for any and all evidence which construed in a light most favorable to Plaintiffs creates a genuine issue of material fact warranting submission of their claims to a jury. This effort has been in vain."
Here's a link to the ruling - Click Me

Re:Stirling Engine Inventor

[Ixalon]

You're probably thinking of Mr 'Unit-of-Energy' himself, James Watt. However, he didn't invent the steam engine. The modern idea comes from the late 1600s and industrialised by Thomas Savery and Thomas Newcomen. However Watt did make them around 75% more efficient with a simple change to existing engines, pretty much kicking-off the industrial revolution. Pretty neat stuff!

But yes, Stirling engines should definitely get more press; I doubt 1 in 50 people here in Scotland know of them and might only guess they hail frae doon the road thanks to their rather Scottish name.

Animation

[mrogers]

For those like me who haven't heard of Stirling engines before, there are some nice animations here and here.

Incidentally, the 37-foot diameter units described in the article generate 25 kW each - I wonder if they'd be suitable for domestic use?

no silicon is a good thing

[grqb]

Any solar technology that doesn't use silicon is definitely a good thing these days. The Photovoltaic industry is the "poor cousin of the microchip industry", and so microchips get all the good silicon while PV gets the leftover crap that Intel et al. don't want. For this reason, and a general shortage of poly-silicon, there is a huge shortage of PV panels all over the world. Germany and Japan gobble up all they can and at a fair price too, leaving hardly anything for the rest of the world.

It's good to see the Stirling engine being used like this because in my opinion, the PV industry has some serious problems, especially if they have to compete with the Slashdot crowd for silicon!

Re:no silicon is a good thing

[British]

If people were willing to pay enough $, the panels would be flying out of the factories. But using silicon for LCD screens is a whole lot more profitable.

I blame Mad Mike(West Coast Customs) on "Pimp My Ride". He insists on putting as LCD panels as possible into old, broken down cars.

I think he once put a downward facing LCD panel in an undercarriage for one customer, so he can watch tv while working on a car.

PBMR coolant

[Engineer-Poet]

You don't necessarily need helium; HTGR's have used carbon dioxide (British MAGNOX). If we run out of helium, we could use neon (another noble gas). It may require some small redesign because of lower thermal conductivity and viscosity, but it should not be a big deal.

The atmosphere is about 18 ppm neon. That's one resource that's not going to run out.

25% Efficiency?

[dk90406]

The area of a 37' circle is 99.9 m^2, so the area of a reflector is a little larger.

The amount of energy in sunligt at noon at the equator is approx. 1 kW/M^2, so the theoretical maximum of energy reflected is somwhere around 100 kW.

Getting 25 kW out of that seems quite good. If the 25 kW is average and not peek, it seems even more fantastic...

--- Henrik

Re:No way, San Jose

[Smidge204]

The rest of the equipment: heat collector at the focus, flexible piping, insulation, pipes, evaporators, heat sinks, pumps, working fluid, turbines, gears, cogs, lubricants, generators, buildings, staff, land

What do you need all that stuff for?

With the exception of land (which you will need a lot of but it's all desert and not suited for much else) and a minimal staff, none of that junk is required.

The Stirling cycle runs at 10% efficiency. { Note: most Stirling engines are about 5x less efficient that this}.

This is a little ambiguous. The theoretical Stirling engine can achieve the ideal Carnot efficiency. Real Stirlings can reach 50 percent of this maximum theoretical value.

With a ambient (sink) temperature of, say, 110F (316K) and a temperature of 1400F (1033K - Actually a conservative estimate) our Carnot efficiency is 69.4%. A real high-end Stirling can reach 50% of that, or nearly 35% thermal. After you generate the electricity you are *still* looking at 25% overall efficiency or better.

All that stuff cleans and maintains itself at no cost.

Practically would! If a crew of 3 guys can take a hose truck and rinse the dust off the mirrors of each dish in ~15min, they can do about 30 dishes per day. Each dish would probably only need to be washed once a month, so 30*30 = 900 dishes a month. You'd need 23 crews of 3 men each to maintain 20,000 dishes, or 67 people. A 500MW coal plant would employ about 100. (Guestimated from here) Moreover, the people running a coal plant would have to be skilled to maintain the high pressure steam equipment, which means they would cost more. You would not need special training and licensing to operate a hose truck.

As for the Stirling gen sets themselves, they are hermetically sealed and virtually maintenance free. You can contract out any service that might be required rather than having your own staff. In fact, I would think SES would offer a nice warranty that includes service, so if one does go down simply replace it with a spare unit (They are small and modular, you know) and send them back for service.

The tracking systems are also fairly low maintenance and could be contracted out.

So in light of the above, you may wish to revisit your calculations.

They make a breakthrough and develop an efficient Stiring regenerator, which is simultaneously long and short, conductive and insulating. See : www.tinaja.com/glib/muse116.pdf

So you based your argument on three sentences (one copied almost verbatim) from a journal that seems to deal mostly with electronics? Brilliant. You, sir, seem woefully uninformed about how Stirling engines operate. I will grant you that the regenerator is perhaps the biggest hang up when it comes to design, but by no means is it impossible to create. What you are tying to do is make a medium that stores and rejects heat quickly ("highly conductive") with minimal internal volume ("long and thin") and low pressure loss for gas flow ("short and fat") and does not create a thermal short ("highly insulating"). In practice, a stack of fine mesh stainless steel screens works quite well. I have also read storied about people stuffing the passages in the engine with brass wool to great effect.
=Smidge=