Posted on 08/13/2005 3:42:35 AM PDT by Arkie2
ROSEMEAD, CA, USA -- A Stirling engine is commonly referred to as an "external combustion engine" in contrast to the "internal combustion engines" found in most vehicles. Combine a Stirling engine with solar as the source of heat, and you have a highly efficient means of converting solar power into usable energy.
That is what Stirling Energy Systems has been perfecting for the past 20 years.
On Aug. 8, 2005, President Bush toured the DOE's National Solar Thermal Test Facility at the Sandia National Laboratories complex, situated on Kirtland Air Force Base in Albuquerque, N.M., where he signed the energy bill.
Now they are ready to go big-time, with an agreement signed Tuesday with Edison International (NYSE:EIX) a subsidiary of Southern California Edison (SCE), the nation's leading purchaser of renewable energy.
On Tuesday they announced an agreement that could result in construction of a massive, 4,500-acre solar generating station in Southern California. This comes to around seven square miles, with a perimeter of nearly 30 miles. The completed power station would be the world's largest solar facility, capable of producing more electricity than all other currently-operating U.S. solar projects combined.
This signing was a day after President George W. Bush visited their Sandia National Laboratories installation where they have six prototypes in operation, having chosen this location as his backdrop for the signing of the Energy bill.
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-engine/solar-dish technology. This is enough power to run approximately half a million homes.
According to the California Energy Commission, there are 966 power plants in California that generate more than 0.1 MW. Of those, a 500 MW plant would be in the top 3% for size.
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. (Each dish generates 25 kilowatts.) This phase is slated to be completed in the first quarter of 2007. One of the 40-unit arrays capable of a 1 MW output, will be dubbed a "solar power group" and will be the basis of modular calculations for future installations.
Subsequently, the 20,000-dish array is to be constructed near Victorville, California, during a four-year period, starting in early 2008. If Edison opts for the additional 350 MW installation, that will take two more years, and will bring the total number of panels to 34,000.
“At a time of rising fossil-fuel costs and increased concern about greenhouse-gas emissions, the Stirling project would provide enough clean power to serve 278,000 homes for an entire year,” said SCE Chairman John Bryson. “Edison is committed to facilitating development of new, environmentally sensitive, renewable energy technologies to meet the growing demand for electricity here and throughout the U.S.”
“We are especially pleased about the financial benefits of this agreement for our customers and the state,” said Alan Fohrer, SCE chief executive officer. “The contract requires no state subsidy and provides favorable pricing for ratepayers because tests have shown the Stirling dish technology can produce electricity at significantly lower costs than other solar technologies.”
Gil Alexander, spokesperson for Southern California Edison said, "We operate in a competitive marketplace. While [for confidentiality reasons] we cannot give out precise dollar amounts for how much these installations will cost, we believe the final agreement is very beneficial to our customers. We do not need any subsidies to make this work."
Pioneering Stirling-solar to be Commercially Viable
Although Stirling dish technology has been successfully tested for 20 years, the SCE-Stirling project represents its first major application in the commercial electricity-generation field. Experimental models of the Stirling dish technology have undergone more than 26,000 hours of successful solar operation. A six-dish model Stirling power project is currently operating at the Sandia National Laboratories in Albuquerque, New Mexico.
However, this isn't the first commercial application of Stirling engine technology. For instance, Swedish submarines use Stirling engines for propulsion. (ref)
How It Works
The Stirling dish technology converts thermal energy to electricity by using a mirror array to focus the sun’s rays on the receiver end of a Stirling engine. Each panel tracks azimuth and elevation to keep the sun’s rays focused at greatest intensity possible.
The internal side of the receiver then heats hydrogen gas which expands. The pressure created by the expanding gas drives a piston, crankshaft, and drive-shaft assembly much like those found in internal combustion engines but without igniting the gas. The drive shaft turns a small electricity generator. The entire energy-conversion process takes place within a canister the size of an oil barrel. The process requires no water and the engine is emission-free.
Comparison to Other Solar Technologies
Tests conducted by SCE and the Sandia National Laboratories have shown that the Stirling dish technology is almost twice as efficient as other solar technologies. These include parabolic troughs which use the sun’s heat to create steam that drives turbines similar to those found in conventional power plants, and photovoltaic cells which convert sunlight directly into electricity by means of semiconducting materials like those found in computer chips.
Additional Applications
While the number of potential applications for this technology is huge, in the near term Stirling Energy Systems will be keeping their focus on these utility installations.
Or, as I think it was Larry Niven who pointed it out first, we can use parts of the Nevada Test Site to dispose of the radioactive waste from temporary increased use of nuclear-fission for power generation [until we get SPS or fusion or something else thats better]...aferall what less harmful place to put nuclear waste could there be than down a selected-for-geological-stability and already-radio-contaminated old bomb-hole ?
Several years ago I read an article which mentioned that one of the bigger issues with large-scale solar facilities was simple *dust* and dirt and pollen, etc. Over time it builds up on the mirrors/lenses/solarcells/whatever, and you have to send out a freaking huge army of window washers on a regular basis to keep , or work out some automatic system of cleaning the collectors. Either way, you have to budget a surprisingly large amount for maintenance operations, plus probably a heck of a lot of water for the washing, and likely a soap or other cleaning solution as well. Now you've got drainage and run-off to worry about, and environmental effects, and...
"Tests conducted by SCE and the Sandia National Laboratories
have shown that the Stirling dish technology is almost twice as
efficient as other solar technologies."
I think this is a wonderful idea. The stirling engine is an amazing motor.
It makes a neat little model. The stirling engine below runs on the heat
from your hand.
Holtz
JeffersonRepublic.com
I wonder why they switched to hydrogen???
My guess would be cost.
Yeah, your "ounce for ounce" weasel-word lets you out. But on a mole for mole basis (which is what the entire rest of the world uses) hydrocarbons contain more energy than hydrogen.
"C chain fuel in a rocket has a lower ISP than H2 because the C bonds are not proportionally stronger than H bonds compared to their weight."
Sorry, but wrong again. Carbon has a lower specific impulse than hydrogen because the mass of the molecule formed and ejected is lower. It has squat to do with the "strength of the carbon bonds".
"Chemistry happens to the electrons bonds and not all electrons in C and other heavier elements are involved in bonds. So they are carrying a lot of nuclear dead weight."
Uh, PhD in chemistry--minor in Nuclear Science.
RE: mirrors, dust, etc.
Seems like a lot of coatings and materials research should go into how to make the mirrors plus maybe some sort of static dust repulsion system could be built-in.
Yes, but you're not going to get a significantly higher exhaust velocity with any chemical fuels--there's simply not enough difference in energy. Reducing the average exhaust mass of the ejected propellant is a LOT easier than increasing the exhaust velocity in a chemically reactive system. Only ONE chemical fuel combination has a higher specific impulse then H2-02--an exotic propellant using hydrogen, lithium, and fluorine. Now, in things like "ion drives", where the absolute speed of the "heavier" propellant is VASTLY higher, then yes, you can get usably higher ISP's with propellants with higher mass values.
And in fact, there's still a lot of argument that H2-O2 is NOT the best propellant choice, for various other reasons (like safety).
"Time for a refresher course, me thinks."
No, actually it comes from trying to winnow down complex processes into simple terminology. Spend a little time on the Wikipedia "rocket propulsion" page and see how complex it really is.
Would you please provide a link for that statement? To the best of my knowledge, Stirlings don't replace Otto cycle engines in automotive applications because they take longer to start, run at much higher RPMs, are bulkier and aren't suited to the variable power that automobiles demand.
A power plant, however, seems like a made-to-order application for Stirling engines.
On the other hand, newer Hybrids are using Atkinson-cycle engines to get greater efficiency from a gasoline engine at the expense of power. They're more complex because the pistons are connected to the crankshaft via a series of levers instead of directly as in the Otto cycle. This allows the engine to run with a longer power stroke, hence the efficiency gain.
I second your opinion.
For something different: A perpetual motion machine:
http://www.freerepublic.com/focus/f-news/1463214/posts
What? Atkinson would be turning over in his grave! Toyota and others are telling a lie to get around the Miller cycle patents that they really use. No extra connecting rods in these engines, just a late closing intake valve.
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