Slashdot Mirror
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."
It sounds a lot smaller when you put it that way.
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.
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)
Next to my desk we have an Ire Extinguisher. Our boss is really assertive, so we like the idea of having it.
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.