Slashdot Mirror
Efficient Solar Power Using Stirling Engines
tscola writes "The EE Times is reporting that the U.S. Energy department believes it can make solar collectors that generate electricity at efficiency levels that rival other methods. Instead of using photovoltaics, they want to use Stirling engines to convert the heat of the sun into electricity."
capability to store large amounts of power? Batteries stink in terms of reuse, and most other things cannot be renewed.
EVen a intermediary step, like electrolysis of water to H2 and O2 would be better than most.. But that's too many steps to loose efficency...
Damn carnot efficiency!
Some pictures
"large farms of Stirling solar dishes - say, 20,000-dish farms" Now, how about the space issue? I know that at least us poor folks in europe don't have room for this...
In the article they mention that with 6 dishes they could power about 40 homes. Why so big scale? Couldn't the size and stuff be scaled down a bit, mass produced, and then homes could have their own sundish or a sundish shared in small community groups? Like shared water wells and such. That'd eliminate the middle man.
Hexy - a strategy game for iPhone/iPod Touch
If this is true, this is a pretty interesting advancement. I can't help but be a little skeptical about the price tag they are assigning it, but I am a sour old bastard at heart. Are the prices they are spitting out for one of these things sitting in the Arizona desert or northern Maine? The article threw in some stuff that I found questionable. Namely, it talked about moving away from reliance on foreign oil - utterly ignoring that the US (and most nations for that matter) gets most of its power (in the power grid) from coal. While it would be nice to get away from coal, there are two things stopping this. First, coal is cheap. Second, in recent years they have done a pretty solid job at cleaning up the health risks associated with coal.
I am not saying that this isn't a worthwhile discovery, just that I don't see much in the market that is going to push to adopt this technology other then governments wanting to use something that is cleaner then coal. Oil is good stuff because you can throw it into a car and have it run. The real technology that is going to make solar cells like these worthwhile and get the market onboard would be cheap hydrogen fuel cells you can stuff into a car. Charge up a cheap fuel cell with one of these solar cells, ratchet up the price of gas some more, and now you are talking about cleaner cars and the ability to care about the Middle East about as much as the US cares about Africa (which is to say almost not at all).
The only other two real problems I see is that first; in the north I imagine that the cost per kilowatt hour is much more expensive. I imagine a few feet of snow and -30 F temperatures render these things pretty useless. Second, to power a place like LA I imagine you would need a massive bank of these things. I wonder if a massive bank of these would have an effect upon the environment or the weather patterns in a noticeable way. That said, I suppose if you just throw them all in a desert no one is going to care.
So, neat technology, but I don't expect an energy revolution over night.
to service 20000 reciprocating engines. Even without combustion, that's a lot of moving parts. TFA made no mention of actual maintenance costs, but I can't believe the seal is the only thing that can go bad.
Think of the cannon fodder we would save.
From the article:
"Since each dish draws about 10 amps from the power grid for a few milliseconds when it starts up in the morning, startup must be staggered if a large dish farm is to avoid causing a blackout."
Question:
Why not add a fuel cell or battery to each dish that would be charged as needed during operation for use as a starter?
This would enable each dish to start up under it's own power without affecting the grid at all... and for a very small price in terms of daily output.
Any reason why not?
A fool throws a stone into a well and a thousand sages can not remove it.
Here's a great little intro to Sterling Engines, for those who have never heard of one.
Look on google for 'stirling engine dish' and you'll find a dozen of similar projects. For instance http://www.ornl.gov/info/news/pulse/pulse_v7_98.ht m.
History matters..
Wasn't Dean Kamen working on this?
Why yes, he was.
I hope he is working on this solar project (or one like it). He could certainly sort out the remaining issues.
"Well it's not Victory - but then it's not Death either."
First I'd like to say that there has been a record amount of interest in this post. (dont mod me down, I can't help being disapointed in a posibly world saving subject being ignored in favor of less important subjects)
There was a project some years ago in Australia where the heat difference between (one of our) desert surface and pipes/heat exchange buried underground was going to power a whole lot of engines. I'm not positive but I think they were Stirling engines that had been changed in some way (possibly day and night running- desert cold at night). They got to the stage of cupple of dozen in a test area to show efficiency workability etc. then nothing. Googling it doesnt show much. Rumors of state govt being bought out by the local energy companies which rezoned and shut them down. The usual Nexus style hippies chanted conspiracy, maybe it just wasnt as efficient as it could have been at that time.
Anyway, plenty of room and plenty of heat and cold differentials in the desert(s). Just something bothers me. Wouldnt the loss associated with transporting the energy back to where it is needed (suberbia, industrial and city use) by leakage make it not sustainable? [In Australia desert in center, cities/living areas on edges]
All this springs more questions. What are the efficiency ratings of other energy storages such as spliting water into Hydrogen and Oxygen to be stored separately and recombined when needed to make combustion engine generate power?
"Persistance is Fertile" - Me. I can quote myself if I want to.
Systems based on imaging optics (including parabolic reflectors) can't make use of diffuse sunlight; anything coming from off-axis gets bounced to one side of your target and goes off uselessly. While the Sahara would be solar-concentrator paradise, areas where large amounts of the total insolation is diffused by clouds are going to collect more useful energy (and a LOT more during periods of lower supply, when it's more valuable) with flat-plate and non-imaging collectors than with the dishes required to run a Stirling engine.
Time is Nature's way of keeping everything from happening at once... the bitch.
The problem with solar power conversion has always been the high Total Cost of Ownership. You have to figure the cost of the real estate these items sit on, versus what other purposes the land could be used for.
In the case of other power technologies, the land use is relatively concentrated. Mines, transport routes, powerplants, refineries, etc. don't take up nearly as much space. In a number of cases the land surface can be used for dual purposes, as in ranging cattle on scrub land sitting on top of an oil patch, or growing crops on reclaim land.
There is cheap land available for this, but it's often located some distance from the use points, and energy doesn't store well and transport is expensive. Figure in the TCO of building that intertie to your solar farm in the middle of nowhere, and the pickings start looking a lot smaller.
*whup* "Get along, little electrons. Heeyah!"
You need to put the power produced by each generator into phase with the rest of the grid. This requires circuitry. If everyone had their own dish, then that circuitry would have to be duplicated once for every home. Most likely, in a 'farm of them', the same circuitry could serve multiple dishes. This is more cost efficient. Sure, you could put 5000 bucks into buying your own dish, and save on your power bill every month, but that 5000 bucks would make you more money if you invested it in a power company that was building a farm of them. You would then make money rain or shine which you could use to buy power off the grid for cheap.
I addressed pretty much the same issue in this essay on my blog.
Sustainability and energy independence essay
Even if you managed the system such that one dish started off the grid and further dishes started off the ones already running (exponential progression), you'd still have an issue with the grid balance. Typical grid demand fluctuates by a few megawatts on the time-scale of seconds; if you fired up a 100 MW dish farm over 5 seconds you'd have generation increasing by 20 MW/second for some time. Unless you also had demand, reactive power, transformer taps etc. scheduled in synchrony with this, it would make a lot more sense to leave dishes pointed off-sun until you could guarantee demand and had down-regulation capacity ready to handle any excess. It might make more sense to fire up big farms over 15 minutes or more (unless you can start generating with the weak morning sunlight and eliminate transient issues by following the curve of incoming sunlight).
Sustainability and energy independence essay
While it would be nice to get away from coal, there are two things stopping this. First, coal is cheap. Second, in recent years they have done a pretty solid job at cleaning up the health risks associated with coal.
First, coal is not cheap. The price is low because the mining and electricity corporations export every cost they can get away with onto the public at large. Mountaintop removal/valley fill mining practices illegally destroy thousands of acres of Appalachian hardwood forests and hundreds of miles of streams. Electricity generation plants dump millions of tons of CO2 into the atmosphere altering its composition with unpredictable consequences, create acid fog and rain that destroy forests, lakes, and streams, and dump hundreds of pounds of mercury into the environment where it ends up damaging our brains. If mining and generating corporations were forced to be good citizens and not force us to surreptitiously pay for their products' hidden costs then other energy sources would be economically competitive. Instead, they prefer to stuff pennies into the fuse boxes of capitalism and bitchslap any more responsible initiatives with their ill-gotten capital.
Second, BWAH HAH HAH HAH. That would be hilarious about the "pretty solid job at cleaning up the health risks" if it weren't so tragic what is happening. Granted, they are better than they used to be, but those gains come from laws passed in the '70s and '80s which are being rolled back now. (See the "Clear Skies Initiative")
- Hail to our fearless misleader! Fool speed ahead!
Striling engines explained to the lay person:
http://www.bekkoame.ne.jp/~khirata/indexe.htm
Sierra Tango Foxtrot Uniform
Depends on how you do all this. If you have a solar cell, you are producing DC, and all the circuits to turn it into AC at the right frequency is duplicated for each house. For a stirling engine it is much simpler, just connect the stirling engine to a standard synchronous motor, and connect them to the grid. Synchronous motors become generaters when driven faster than their run RPM. Remove the AC input and they output no current. (I'd still want some safety equipment, and you might want to clean the power up a little, but in principal the only equipment duplicated is that which needs to be at each generating point)
One such design, which some of you here are familiar with, is known as an "OTEC" - or "Ocean Thermal Energy Conversion". Pushed greatly by the book "The Millenium Project" - OTECs are devices, sitting on ocean-based platforms, which use the thermal gradients in the ocean at different depths to drive a Stirling-type engine which runs a generator to generate electricity (for a variety of uses in the book). These are actual devices, which have been built and tested (I am not sure if they are in real production or not). This is a very interesting use of stored (in the ocean) solar energy - the amount of energy taken out by OTECs would be miniscule, and would very likely not cause harm to flora and fauna (the ocean is HUGE).
On a similar note, I have, in the past, proposed here on Slashdot the idea of a "reverse OTEC" - which I proposed for be called a DTEC/GTEC/TTEC, for "Desert Thermal Energy Conversion" (or, alternatively, "Ground"/"Terra"). The idea being that we use the energy differential that exists between a few inches under the soil (hot side), and several feet down (cold side). Alternatively, we could bury the "hot" side of the collector in the concrete/asphault that makes up our roadways and parking lots (as well as place them on roofs). We could then gain heat from the sun, increasing the temperature differential (in the winter, when the ground is frozen in some areas - or at night, when surface temperatures drop, these engines would still work - the temperature gradient is still there, just smaller (or inverted in the winter) and not as large).
Using Sterling engine technology in this way helps to offset the "land use" argument - your land actually becomes more valuable, because not only does it provide parking or roads, but energy as well! The tradeoff being that road/parking lot construction and repair would become waaay more complicated, and probably more expensive. These issues would need to be studied. It could very well be that the economics don't work out for this and other reasons. Perhaps the issue then is to design better roadways and parking lots that don't fall apart in a few years, and instead last for a very long time (so you don't have to repair them as often).
I think such a design for Stirling engine use, coupled with more traditional solar heat panels (to drive the Stirlings as well), where they can be used (perhaps putting the panels on the rooftops would be better?) could easily help supplement the energy usage needs of many large urban sites, like malls and office complexes, as well as possibly neighborhoods.
Reason is the Path to God - Anon
This same concern is brought up everytime wind power is discussed. Why not combine the two? Place win farms and these new "solar farms" together? YOu could create a much higher power creating density using such a method.
Great ideas often receive violent opposition from mediocre minds. - Albert Einstein
Because the energy industry can control the sun farms and sell consumers the output. And as "costs" increase, so will the price of the energy.
There is NO energy industry interest in selling the consumer PV arrays, since it is a one-time sale, and the consumer can sell-back excess output, which the energy industry has to pay and doesn't control.
If you want PV arrarys look to appliance companies and auto makers for this solution. They are in the business model of selling once per X years to a consumer.
According to what I've read about grid regulation, it's not uncommon to have the slower-reacting plants ramping in one direction to follow the general trend while the fast-reacting plants go the opposite way to cover the short-term variations. Really rapid changes aren't managed at all, they are just allowed to change demand by altering the grid frequency slightly (lower frequency = less power demand from anything with a motor). Throwing large transients at this system is a certain way to break it; you want to design around this if you can, or even make the solar generator able to regulate faster than anything else (which gives it another revenue stream).
Sustainability and energy independence essay
I've been suggesting this for years! Radiant Heat Solar Powered Stirling engines are the solution to energy capture/extraction. They're safe, quiet, efficient and cheap. Why the hell don't I have one in my backyard today?!?
Assuming you get fifty percent coverage, that is still a lot of shadow. I don't know of any research concerning it. Buildings are not the same, as they are not designed to track and block sunlight as a primary objective.
Electrical power transport and intertie are efficient when looked at from a technical basis. Well-designed modern power transmission systems only lose a small percentage of energy during transmission, but after you add up the infrastructure maintenance costs, right-of-way, aquisition and depreciation, etc, and stretch it out over a thirty-year design life you begin to understand why all those train-cars full of coal exist.
*whup* "Get along, little electrons. Heeyah!"
The 11% produced during the time when everything else is working poorly and supplies are tight is worth more per unit than the 89% produced when everything is cranking and you've got a bumper crop; the more uneven your supply, the greater the investment you need in storage and backups.
Time is Nature's way of keeping everything from happening at once... the bitch.
Wasn't Dean's Stirling Engine just about ready to revolutionize the world...um... about a year (or so) ago?
---- I have nothing more to add.
(I see your bullshit and raise you unnecessary use of attitude.)
They discus the economies of scale (somewhat) by talking first about the "daytime only" nature of the power, and by _coincidence_ the fact that daytime is peak power demand time, where near-term provision will do a lot of good.
The blockquoted text is part of an "not addressed at this time" conjecture. Just liek the part where they talk about a "100 square mile generation system" not as if they are proposing one be built, but as if they were trying to convey the issues of scale and return.
At least it was clear to me when I read the article, and appreciated the "dumbed down explinations" presented, that they were trying to get effecient solar power working instead of wrapping themselves around the *POINTLESS* axle of "what about at night?".
As for the pumping water up a hill (e.g. the "gravity battery" of potential energy) I think you over-estimate the effecency of hydro-power rather a bit as well. Granted the elements are well understood, but I don't think you get the whole "pump head" issue of volume vs lift vs return potential very clearly, otherwise you would not imagine for a moment that the driect mechanical output of the systems in question were "well suted" to running the kinds of pumps you'd need, just because the striling enginges turn and so do pumps.
(_Directly_ using the mechanical energy of the small Stirling Engines to move "enough" water high "enough" to be useful in filling a resivour big "enough" to turn meaningfully sized turbans or water wheels to generate "enough" nightime electricity is a laughable debacle _before_ you consider laminar flow resistance (rising and falling), evaporation loss, pump maintenance (clogging), seeapage loss, providing source water in the first place, simple acreage or water-tower shadows, and so forth.)
The fact remains that cutting N% off our fossil fuel and polution problems is pretty much a win of N%. If we could replace 50% of the runtime on the nations fill-in generators, that would be *huge*. _TEN_ percent would be huge too.
The article and the investigators are trying to solve *their* part, what are you trying to solve by bitching about their off-hand mention of hydrogen?
The fact remains that the "energy storage" problem remians no matter what the generation system. "Batteries" for electric cars, holding solar, wind, or tidal power for return when those are not at peak. That sort of thing will remain no matter what.
The "don't bother with solar until you solve the nightime issues" frame of mind is defeatest as hell and so not terribly useful.
I suspect, were I to have to prognosticate, that we will need to revive nuclear power. Invent better batteries/fuel cells, look into _sonic_ (as opposed to electical) separation of water into hydrogen and oxygen [very promising but not often mentioned], and biomass-fuels, and all sorts of things to "solve" the current problems.
Meanwhile, if we could learn to turn off the freaking lights when we leave the room (guilty here more often than I'd like 8-) and learn to wear a sweater instead of heating the house to 75F (which I *am* good about 8-), and all sorts of simple stuff things will be "Better."
And better is... better.
Innocent people shouldn't be forced to pay for inferior software development.
--"Code Complete" Microsoft Press
There was what? ONE WHOLE SENTENCE about hydrogen in the whole article? But the nay-sayers have latched onto it.
The _article_ was not trying to sell a panaceia. It's just honest work trying to solve "their share" (and then some) of an emerging/ongoing problem. So the solar power plant only works during peak power demand time? GOOD ENOUGH. Decommissioning every gas/coal fired peak-load accessory generator in the sunny south-west would be a *HUGE* win. Hell, 10% would be OUTSTANDING.
So the _SOLAR_ havn't done the _BATTERY_ guys' work for them. Big surprise! Burn the witch!
I mean really...
The guy almost certianly was answering the perenial "what about when it's dark" bull that has been stoping *all* solar work for far too long. You're right solar won't work at night so we should just stop thinking about it all together. Hell, coal won't work if you don't have coal so that was a dumb idea that will never work too... oh wait, look how stupid that sounds... HYPERBOLE isn't ARGUMENT. 8-)
As far has hydrogen is concerned, btw, the _sonic_ separation of hydrogen from water is actually quite promising even if most people don't even know it's even possible.
Expecting to have *that* guy answer the "night time" question through *that* reporter in *one* paragraph is asking for one or two more miricales than we deserve at this point.
Innocent people shouldn't be forced to pay for inferior software development.
--"Code Complete" Microsoft Press
It isn't the "solar power plant" guy's job to answer the power storage requriement for night time. That's a job for a battery/capacitor/whatever guy. You can't expect each application to be a perfect panecia.
Considering that *NONE* of the power grid currently stores power, demanding the solar-power guy "solve" that problem in one paragraph of an interview on promising solar power generation is asking a bit _much_ don't you think?
Do you propose he stop working just because his power system "only works" during peak demand hours?
ASIDE: Electrolysis of water into H2 and O2 is not the only way to get H2 and O2 from water. The sonic method looks rather more effective especially in the smaller scales involved here. And if the power *return* from the hydrogen were handled right, by say keeping the already-hot engines hot into the even-cooler night...?
Double-asside: "lose" efficency... "loose efficency" would not be so bad... (that's humor, my spelling is atrocious... 8-)
Note: the best place to think is _outside_ the box. 8-)
Innocent people shouldn't be forced to pay for inferior software development.
--"Code Complete" Microsoft Press
The water thing is "simplistic" and not terribly informative. The "gravity battery" of using weight or water to store potential energy is pretty much "known bull".
It certianly doesn't apply (mechanically) when you are talking about a large farm of small generators. The mechanical drag alone, before wear and "storing water in the bright sun" loss to evaporation and devices getting clogged with alge in execelent sunlight factors in
Directly running a pump significantly larger than a garden hose to pump water high enough to be usefull as nighttime generation is patently absurd, and would cost you 100% of the day-time peak electrical usage output of the plant.
Besides, not a heck of a lot of water in the desert with wich to perform this miracle.
I know, we could truck it in every morning...
(Oh look, hyperbole isn't argument... that sounds stupid... 8-)
Innocent people shouldn't be forced to pay for inferior software development.
--"Code Complete" Microsoft Press
The "steadly increasing" 20MW/second isn't that problematical if you don't put it on the grid right then but instead wait till it was needed, or use it to charge a (whatever) storage battery to span lulls and, I don't know make the hydrogen for the on-site matenence vehicles or something.
There is a complete non-issue about how to cut in this power source (compared to any other kind of generator).
How not to "waste" the power generated when you aren't cut in is a "what to do with the gravy" kind of issue for the most part.
Since they have to get up to the (230,000-volt was it?) levels to get menaingfully onto the grid in the first place I suspect that a giant bank of capacitors and a fast switching doodad are pretty much mandatory. The plant's start-up cascade should be private anyway as they could go "on-sun" exponentially before they cut in.
Of course, the larger problems of the power grid are larger problems. Especially with deregulation and "known bad places" as per the recent blackout. So wer are borrowing problems here anyway.
Innocent people shouldn't be forced to pay for inferior software development.
--"Code Complete" Microsoft Press
Remembering that the actual heat isn't going very far, the cooling isn't *that* interesting.
.5 to 2 times the size of the farm. The thermal might cast a rain shadow but not for more than twice (?) the length of the chord distance that the prevailing wind passes over the farm.
We arn't reflecting the heat off into space (a la snow-cover), we are reflecting it to a heat sink about 20 feet off the ground.
The heat passes through that heat-sink and into the air. The air temprature will probably *rise* during the day because the ground isn't soaking it up _directly_. Any given square-inch of ground will be in shdow for about two extra hours a day per dish (wild-ass geuss from just looking at the thing) and will be subject to the shadows of three dishes max. So any given square inch will be "shaded" for half the day.
A good bit of that heat will get back into the ground anyway.
The net environmental impact would be about the same as for sparse tree cover (But without the water use and with a dissimilar habatat provision).
Soil water retention would go up just a tiny bit.
The most liekly impact woudl be changes in midle-size air masses within a range of about
So worst case, (total wog again here) about the same climatological impact as if say one-third the same area were covered with "water that couldn't evaporate" or concrete sculptures of trees.
A similar area covered with buildings would probably be worse in general. It would be the classic "downtown effect" (where it is hotter downtown during the day and colder downtown at night).
Innocent people shouldn't be forced to pay for inferior software development.
--"Code Complete" Microsoft Press
Their main power storage problem is really a solution to their main power distribution problem: blowing the grid when 20,000 10A dishes start up in the morning. They're taking the angle of staggering startup, so presumably they dishes store no power in the H2 cells they mentioned. Instead, each dish should have an H2 cell. That would store the last few coulombs of generated electricity for startup in the morning. Not only will that have solved their startup problem, but the local storage means all that startup power won't have to make the roundtrip over the lossy grid. Then there's no reason they can't make the cells larger to store more of the power.
The author was "insightful" enough to (read the PR?) make a "sunflowers" metaphor. They should really learn from that biomechanics, and use some of the heat directly to force a water reservoir up a pipe at the end of the day, then release it through a turbine in the morning, or even down through the Stirling engine mechanism itself, driving it back to generation. The net efficiency of that process would save a lot of the energy, and they can get evolution's design service for free, rather than wrestling with their staggering architecture.
--
make install -not war
The perfect energy storage device already exists, and it has nothing to do with flywheels. It is called the Energon Cube.
Transients are typically handled with "peaker" natural gas turbine driven generators.
Large scale hydroelectric installations with dams are easy to throttle as well... the reservoir = a big battery. My company is a major hydro investor (one of the biggest in N. America) and most of our dams have 30 days of full power behind them and turbines can be brought on-line or taken off-line very quickly. That is plenty to smooth out daily and weekly cycles.
These heliostat type stirling engines use a at least one stage of heat exchange fluid. One way to store energy and therefore moderate transients is to use a well insulated bank to store excess hot fluid.
So don't they put stirling engines in space? The end facing the sun would be boiling hot and the end facing away freezing cold.
The Formidable Article claims that:
On the other hand, an analysis of algal biodiesel ponds (and some other neat things) from here by Michael Briggs at the University of New Hampshire Physics Department mentions:
So, it looks like biodiesel requires more maintenance, but could probably be started up more quickly because the algae takes care of worrying about building itself. I like the fact though that the algae consumes CO2 from the atmosphere and cleans out wastewater.
Eliminating the middleman is BAD if you are the middleman. If every home could generate its own power, I can't make money selling it to them! My greed is more important than your independence. right? right?
There is not nearly enough love in the world, but there is far too much trust.
Some background is here. "Ken Stone discussed how the United Stirling engine and parabolic dish system was taken out of moth balls and revived. He announced that there is now a new company that appears to be getting into the Stirling engine field with the old United Stirling engine designs."
According to the DOE report "Total net generation of electric power in August 2004 was 366.3 terawatthours"
Just for August!
So, Google says 11 square miles is 28,489,869.2 square meters.
So it's 366,300,000,000 watt hours, divided by 28,489,869.2 sq meters = 12,857 watthours per square meter for the month of August.
Checking the Naval obserivitory data, it there's about 13.5 average hours of sunlight in August.
Dang, at this point I'm stumped. I figure we would put these in the best spot in the US, New Mexico. But I can't find any good data for average sunlight power. All the solar sites use estimates.
Democrats or Republicans. They are both taking us to the same place and they are not afraid of us anymore.
Even if the production of AC was done with electronics, there would not be much storage in the system. Three-phase inverters have a flat power flow and require essentially none, and even single-phase sine wave inverters need but half a cycle or so. This is tiny compared to the time-scales we're talking about, and can be dismissed.
No, it's more of a "how much extra equipment do you need to manage it properly" issue. I suspect it won't be a huge amount, because the array will need dump loads to deal with the eventuality of transmission breaker trips (loss of load without removing motive power = overspeed and possible damage). You can use the same dump load to soak up the power while you are syncing to the grid. Given that you've got to have a dump load, it's not going to pay to have anything fancier - you are not going to use it enough for it to pay off. There are places like California where they can use every watt they can get many days. This is only going to increase if we get grid-chargeable hybrid vehicles. Fortunately, such vehicles are essentially rolling battery banks; if their chargers were synced to the generation coming on-line or going off, they could easily provide the balancing required by the grid. If only 1 million vehicles in California could provide such services, they could soak up a 200 MW change in generation by altering their flow by a mere 200 watts each.You could do the same with ice-storage air conditioners, varying the cycling of ordinary refrigerators on a second-by-second basis, etc. Appliances like that have enormous potential; how many refrigerators do you think there are among California's 30 million people? If it's as few as 10 million, they consume 250 watts each and half of them are controllable, that's 1.25 GIGAWATTS of potential demand-side balancing from refrigerators alone. If you added air conditioners the available DSM would be a large fraction of the total peak. With battery storage costing more than the power going into it, DSM is where the real potential is.
Sustainability and energy independence essay
- The engine in these systems is mounted directly to the receiver at the focus point. There isn't room for much.
- The Stirling Energy Systems pages are very scarce on technical details such as drawings, but I did find a reference to "heat-pipe receivers". The amount of thermal mass in such a receiver is very small.
Rather than complicating the system with extra elements, it makes much more sense to manage it with the pieces that you already have for other purposes. It's going to be easier to point dishes off-sun to reduce excess production than it would be to store heat, and you can't beat the marginal cost: zero.Sustainability and energy independence essay
Sustainability and energy independence essay