Sundish, Stirling , Kamen

[don c.]

The story of SunDish (to be continued?)

The SunDish was a joint effort developed by Science Applications International Corporation (http://www.saic.com/) and STM Power (http://www.stmpower.com/). It operated at the Pentagon, and then at the Pima Maricopa Indian reservation in Tempe, Arizona.

"The SunDish (http://www.staev.com.sg/pdf/SunDish.pdf) is a solar thermal power system designed to produce utility-grade electricity from concentrated sunlight. The system is based on a reflective solar dish concentrator that concentrates solar energy to a Stirling engine/generator, producing a net output of up to 22kW at 1000 W/sq. m. of insolation (solar radiation). The SunDish is described, including the dish concentrator, Stirling engine system, and controls. The Salt River Project (SRP), Science Applications International Corporation (SAIC), STM Corporation, and the U.S. Department of Energy have cooperated to install and operate a prototype SunDish at the Pima-Maricopa Indian Reservation Landfill(PMIRL) in Tempe, Arizona. This system has been in routine solar operation since October 1999, operating 585 hours and producing over 7.1 megawatt-hours of electrical energy."



Unfortunately, the DOE (Department of Energy) funding for the Sundish and other related concentrated solar projects was ended recently. I e-mailed Himesh Dhungel, PHD, Business Development at STM about the fait of the Sundish, and received this reply:

"The US DOE has decided not to fund Concentrated Solar Power projects any more, therefore, the Pima Maricopa unit will not be operating any more. With remaining little funds available from the DOE we will operate one unit in Nevada till the end of November and the DOE Dish/Stirling program will more or less cease to exist, from our perspective."

And a later response from Himesh: "Lack of funding from DOE does not necessarily mean complete obsolesence of the unit. We are always looking for commercial orders of these units. Some utilities in California are interested as well as one-off orders from the government cannot be ruled out. All DOE has done is cut the budget but projects may be funded through other government programs on a one-on-one basis."

So essentially, the government "giveth and taketh" away from alternative energy developments.

I believe that the Sundish could provide a valid energy solution in some current energy markets. If Kamen's stirling can provide a significant improvement in manufacturing costs or energy efficiency over the STM-4 stirling, we may see Sundish's springing up across the countryside.

To quote a former electronics instructor of mine: "Questions? Comments? Concerns? Everybody agree? Anybody disagree?"

[Seeker]

quote: If Kamen's stirling can provide a significant improvement in manufacturing costs or energy efficiency over the STM-4 stirling, we may see Sundish's springing up across the countryside.

To quote a former electronics instructor of mine: "Questions? Comments? Concerns? Everybody agree? Anybody disagree?"



Hi Don,

As we're seeing with the Segway, when Deka brings out the Stirling, there will likely be a number of partnerships with other firms. Since solar power being used together with Stirlings, is kind of an add on technology, it may be that Deka would not view Sundish as an outright competitor, but rather a company whose goals will mesh with those of Kamen : providing affordable alternative methods of energy production.

Seeker

[yop]

I don't think a Stirling engine does that much for a solar energy system. The benefits of a Stirling engine are low emissions, efficiency, and reliability. Low emissions is obviously not an issue for solar. Efficiency is 50% at the theoretical maximum. Much better than an internal combustion engine, but I believe that conventional technology can achieve greater than 50% efficiency. I think I read somewhere that modern natural gas electrical power plants can reach 60% efficiency. That leaves reliability as the useful trait for the Stirling. Very important for applications like this, way off the beaten path. Not so useful for those of us living in modern society. Could be good for Third World or space applications, though.

The big problem for solar energy systems (and other renewables, like wind) is the lack of good storage media. What they need to develop to make solar energy competitive is a good flywheel or fuel cell system. Right now, they have to sell their power as they make it, whenever the sun is shining. Often that occurs when demand is not high. If they could store their power and sell whenever they wanted, they could greatly increase their profitability.

[Casey]

quote:. "Efficiency is 50% at the theoretical maximum"

My view of that is that 50% of 0 is 0. IOW the sun supplies free heat, so it is immaterial what the efficiency of the receiving device is. Natural gas on the other hand is a fossil fuel, and is therefore a depletable source. The sun is infinite.

"low emissions, efficiency, and reliability". Those traits would still exist with the sun as the power source resulting in free electricity other than the cost of the hardware itself.

"The big problem for solar energy systems (and other renewables, like wind) is the lack of good storage media." It would be no more of a problem to store electricity produced by a solar powered generator, than a gas or oil powered generator. Solar produced electricity would still be supplemented by electricity powered by other means, ie hydroelectric, diesel, gas etc when the sun is not shining, which where I live is only at night 90% of the time or better.

[yop]

Efficiency: The sun provides energy to make heat, which is then used to make electricity. A Stirling engine can convert 50% of that heat energy into electricity. A more conventional steam turbine engine can convert up to 60% of heat energy into electricity. 60% is better than 50%.

Economics: Power companies buy electricity from many different suppliers. When they need to buy a lot of power (say, because everyone is running their air conditioning), they have to pay more per unit of electricity. When they need less power, they pay less per unit. Simple supply and demand. So, the price you can get for your electricity varies. If you own a coal burning power plant, it's easy to take advantage of this. When the price is high, you feed more coal into your burners, make more electricity, and make more money. With solar, you can't make that kind of decision. You produce electricity when the sun is out, you don't produce electricity when it's not. Sometimes, you can produce a lot of electricity (because the sky is nice and clear), but you can't turn a profit, because prices are low. Sometimes the price is high, but you can't take advantage because the skies are cloudy. An energy storage device would allow solar electricity producers to take advantage of these price fluctuations, just like the fossil fuel users.

[don c.]

A couple of points, if I may. The Sundish system used solar radiation during the day and methane derived from the reservation landfill at night (and later, propane), so it offered better real-world viability than a photovoltaic solar installation. It's the flexibility of fuel choices the Stirling provides that makes it a valuable part of such a system.

Also, I don't believe that at 22kW it was intended to in any way replace existing utility power plants, or to compete in the energy trading market. It was sized for applications such as industrial parks or villages. With cogeneration, the storage media you speak of would be the grid itself. During off peak hours, surplus energy is returned to the grid for credit.

[Seeker]

http://www.stirlingenergy.com/products.asp?Type=solar

These guys claim to have the world record at converting solar energy into grid quality electricity.I don't know what their figures are. Even if this is true, like yop said, Solar energy is not reliable.

Seeker

[don c.]

quote:
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Originally posted by Seeker



http://www.stirlingenergy.com/products.asp?Type=solar

These guys claim to have the world record at converting solar energy into grid quality electricity.I don't know what their figures are. Even if this is true, like yop said, Solar energy is not reliable.

Seeker

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I have to believe that solar will be reliable for another few billion years, even if not during nightime or cloudy weather. Again, the Stirling allows the use of other fuels, including those derived from biomass, during those times. It sounds if SES is pretty optimistic about the future of solar energy:

http://www.stirlingenergy.com/solar_projects.htm

SOLAR PROJECTS

"While still young, the solar industry, comprised of both photovoltaic and solar thermal technologies, is experiencing phenomenal growth and technological innovation. Worldwide, the industry has 1,800 MW of generating capacity installed as of the end of 1999. Furthermore, the industry has grown between 25% and 41% annually for the past 20 years. These growth rates have been achieved and sustained through improvements in reliability, technology manufacturing, and materials. These improvements have reduced the cost of the solar electricity by 80% over the past 20 years. Many believe that the cost reductions will continue well into the new century as the industry grows and realizes the benefits of mass production. Many studies performed by the U.S. DOE and various industry groups project solar capacity to continue to grow at the same pace over the next 20 years."

[don c.]

http://www.stmpower.com/Markets/STMPureEnergyBrochure.pdf

High Fuel efficiency

The STM (Stirling) engine has been designed to provide levels of efficiency equal or superior to other energy conversion technologies. It has a 30% electrical efficiency, and 70% efficiency for combined heat and power (CHP), producing usable heat in the form of hot water.