About Solar Towers

Solar towers use many large, computer controlled, sun tracking mirrors (heliostats) to focus the suns energy on a receiver located at the top of a tower.  A heat transfer fluid, usually molten nitrate salt, is heated in the receiver and used either to drive a turbine/generator to produce electricity or to provide high temperature thermal heat.  The molten salt can be used to store the thermal energy for producing electricity at night or during cloudy weather. Commercial power plants would be sized from 50 MW to 200 MW each.

A ten MW plant, Solar One, located near Barstow CA operated for six years demonstrating the viability of solar towers.  It used a heat transfer fluid to transfer the heat to the generator.  Solar Two, shown left, was a retrofit of solar one, built to demonstrate the advantages of molten salt for heat transfer and solar storage.  At one point it delivered power to the grid for seven days, 24 hours a day during cloudy weather.  Molten salt solar towers are well suited to peaking power applications, being able to generate power when most needed, day or night, cloudy or sunny.

In a molten-salt power tower, the molten nitrate salt, which is a clear liquid with properties like water at temperatures above its 240^oC (464^oF) melting point, is pumped from a large storage tank to the receiver, where it is heated in tubes to temperatures of 565^oC (1049^oF). The salt is then returned to a second large storage tank, where it remains until needed by the utility for power generation. At that time, the salt is pumped through a steam generator to produce the steam to power a conventional, high-efficiency steam turbine to produce electricity. The salt at 285^oC (545^oF) then returns to the first storage tank to be used in the cycle again.

The following paragraphs were excerpted from the Solar Power Tower report referenced at the end of this post.

The Solar Two receiver is comprised of a series of panels (each made of 32 thin-walled, stainless steel tubes) through which the molten salt flows in a serpentine path. The external surfaces of the tubes are coated with a black Pyromark™ paint that is robust, resistant to high temperatures and thermal cycling, and absorbs 95% of the incident sunlight. The receiver design has been optimized to absorb a maximum amount of solar energy while reducing the heat losses due to convection and radiation. The design, which includes laser-welding, sophisticated tube-nozzle-header connections, a tube clip design that facilitates tube expansion and contraction, and non-contact flux measurement devices, allows the receiver to rapidly change temperature without being damaged. For example, during a cloud passage, the receiver can safely change from 290 to 570ºC (554 to 1,058ºF) in less than one minute.

The salt storage medium is a mixture of 60 percent sodium nitrate and 40 percent potassium nitrate.  Molten salt can be difficult to handle because it has a low viscosity (similar to water) and it wets metal surfaces extremely well. Accordingly, Solar Two is designed with a minimum number of gasketed flanges and most instrument transducers, valves, and fittings are welded in place.

Reference:

Technology Characterization - Solar Power Tower (pdf 304 KB), SolarPACES

Technocrati tags: solar, thermal solar, renewable, alternative energy

Comments

[brian donnelly]

published reports on steam generation and heat recovery. all available. more news to soon.

[Anant Joshi]

Is it possible to get detail design/ design features of steam generating heat exchangers
of Solar one and solar two.

alternate ID: [email protected]

[Martin Glass]

Solar 2 cost $48.5M in 1996 and produced 10MW, and was later decommissioned and converted to a telescope.

Why was it decomissioned, why are they not springing up all over the world, and why are they being sold in South Africa by the 100MW with claims of $1M per MW cost?

[Kit P]

MG

There was a time when only a few nuclear power plants bragged about performance and production cost. The interesting thing about good performing plants is that they had great safety records too. Now every plant is performing better than the top quantile 10 years ago.

Now the debate is about plants lasting 80 years and how fast we can build new plants.

When the solar industry starts discussing performance instead of potential, we can then debate the roll of solar power. The short answer to MG's question, solar does not work. Great for cool pictures.

[Martin Glass]

Solar stand alone PV works, where the cost to run grid to a site needing power exceeds or is close to the cost of a PV system to supply the energy required, or where the OPEX costs of running a diesel power plant exceed the CAPEX finance costs of a PV plant.

Outside of this, I agree, makes for great pictures, and one of the greatest ways to be seen to be green.

[subhash narang]

i think much year ago but i cant tried i seen hear you done first

[Ray Garris-Shoemaker]

this is a great site i go here for everything for science

[Kit P]

Like I said,

“``Natural variations over the next 10 years might be heading in the cold direction,'' Wood said. ``If you run the model long enough, eventually global warming will win.''

The world will become at least 2.5 degrees Celsius warmer by 2100, compared with the pre-industrial period, Rajendra Pachauri, chairman of the Intergovernmental Panel on Climate Change, said in March.”

http://www.bloomberg.com/apps/news?pid=20601087&sid=aU.evtnk6DPo&refer=worldwide

I want to the AGW zealots call these folks denialist. What is not know and will never be know is the magnitude and environmental impact of the human portion. What is very well established is the benefit of an adequate energy supply.

[Marcus]

Just because there are uncertainties KitP does not make it any less of a problem. Since we know how much CO2 we are contributing to the atmosphere we can estimate the temperature change due to our efforts. Read the latest IPCC report.

[Kit P]

“less of a problem”

Marcus provides an example of negative thinking. Mathematical “uncertainties” does not make the something more of a problem either.

Drunk drivers not wearing seat belts have a lower risk of getting alcohol cancer than I do because they will more likely to die in an accident before they develop cancer.

AGW zealots like Marcus are afraid of gradual change in climate something the planet has always adapted for. If life on earth can adapt between summer and winter, then “ 2.5 degrees Celsius warmer by 2100” should not be too hard. Marcus please stop telling me to read something when you ignore the results. If AGW is a crisis, then the word 'crisis' has lost it is meaning.

[Martiin]

"The world will become at least 2.5 degrees Celsius warmer by 2100"

Very safe predictions to make - like maybe the sky will turn green by 2100. If you're wrong, who cares, you'll be long gone and so will those who heard the prediction.

The earth is in equilibrium, whatever the doomsayers who make fortunes out of our fears would have us believe.

The ocean warms up, so Antarctica, Iceland and The Artic dump huge ice cubes into it, and the ocean cools down.

"Natural variations over the next 10 years might be heading in the cold direction"

Now here is a short-term prediction that the writer will probably be around to defend in 10 years time - because it is most likely based on evidence, rather than fearmongering speculation.

And all of these negative theories presuppose that there is no God, who loves us and created everything around us for our benefit. But then trusting God wouldn't be good for business, would it?

I'm not saying we shouldn't act responsibly with our environment, but if the planet heating up is our fear, consider that it will cool down soon enough once there are no more fossil fuels to burn. But perhaps not in our lifetimes - while we are alive, in the eyeblink of a lifetime when compared with eternity, our concern should not be of things which we cannot change, but of things we can.

Things within ourselves.

[Pankaj]

well the salt which is used is to generate power.is it possible to use any other salt which is low cost and can be used for steam generation purpose.please reply.

email id:[email protected]

[Pankaj]

if i have a boiler which is working 24 hrs and i need to minimize its use,is their some process where i can use molten salt to convert water to steam along with the boiler...???please reply.

email id:[email protected]

[hanul chung]

We are interested in build the tower one in Korea. Small scale for experiment. Anyone interested to involved, please let me know. We provide you lodging while you stay in Korea.

[Kath aka wraithe]

Kit P...
You state about reading the IPCC report...Try reading the first chapter of IPCC ar4 WG1...
It says that they dismissed data due to the inability to model thus data...
Is that not creating a false result in itself?
For a theory to have credence, it must be complete and without fault..
Another issue is the drop in Temperatures in the last 6 months, kind of goes against the theory..
And another issue, temperature rises and increase in CO2.. This has been going on for more than 400,000 years(They have gone that far back with ice core sampling), humans dont have that much power yet.. CO2 is made up of two distinct types, Manmade and natural.. Carbon 12/13 and carbon 13/12..
Which is which?
How much of CO2 is manmade and how much is natural?
Solar activity is critical to this planet, yet IPCC havent taken it fully into consideration, thats a bit questionable in it self...
How much have the seas risen, strange answer from IPCC, yet the datum they took data from shows a drop of 34 cm, but hey they are the experts(isnt that a drip under pressure?)

But of course, you need to fudge results to scare people into supporting your oxygen tax and pay for things that are not needed...

Dont be an alarmist, become a solutionist!...
We are polluting our planet, but its not what people are looking at, thats just an excuse to get you looking away from what the real problems are...

[expert]

a prototype Solar chimney in TÜRKEY. it's capacity 1,5 KW. diemensions; height: 15m, collector diameter:16m, chimney diameter:1,2m

for more info...
http://www.unienerji.com
http://www.unienerji.com
http://www.unienerji.com

[expert]

Solar energy in TÜRKEY

Türkey has remarkable solar energy potential. But we can't use our this potential. in last five years, we have been applied some solar applications. you can find some special applications in http://www.unienerji.com , http://yekarum.sdu.edu.tr
Türkey has bigger potential than germany but germany has used solar energy more than us. I think, it's main reason is less promoting the development of solar energy in türkey than germany.

[student]

I am currently a student at Vanderbilt University, and I am doing a research project on SolarReserve's solar thermal technology. My team has several questions that we were wondering if we could get answers to:

1)What are the plans of the government regulation and how will this affect production?

2) Spain has implemented several regulations supporting solar thermal technology: Law 54/1997 and Spanish Royal Decree 436 (http://www.solarpaces.org/News/Projects/Spain.htm ). Do you think regulation such as this is necessary in the United States?

3) What are the effects of the bailout bill have on government regulation?

4) How does solar thermal energy relate in terms of cost and reliability with other promising alternative energies?

5) How long is the stored salt 99% efficient (clarify what this means)?

6) How feasible is it that the cost can come down enough to compete with coal?

7) Are the foreign companies (SENER) planning to build plants in the United States/ how will this affect the market?

8) How much does upkeep of a plant cost… ie heliostat replacement, loss of salt?

Thank you very much - any information is helpful!

[Kit P]

Vanderbilt?

This is a hoax, right? A student prank maybe. Or is it the Barstow regional campus of Vanderbilt.

Maybe it is a political science class studying the politics of the loony left.

“1)What are the plans of the government regulation and how will this affect production?”

Where, which government? I lived and worked in Spain for a year. While I love the people and the country, they are having trouble picking a government that is somewhere between fascist and socialist.

“Do you think regulation such as this is necessary in the United States?”

Do you mean like the RPS enacted in Texas under then Governor Bush or the PTC under now President Bush? The answer is yes but we already have them Since renewable energy has higher capital costs incentives need to be provided to get investors to build something other than natural gas fired power plants.

“3) What are the effects of the bailout bill have on government regulation?”

Huh! What regulations? Building power plants requires long term investments. DOE provides loan guarantees for low carbon investments. Those regulation are already established but I would think you still need investors with capital.

“4) How does solar thermal energy relate in terms of cost and reliability with other promising alternative energies?”

Mature renewable energy like hydroelectric, biomass, geothermal provide about 10% of US electricity because they work and the power plants last a long time. Promising is code for not mature. Wind can produce electricity cheaper than natural gas so it is a good combination for when the there is no wind. When wind turbines last a long time then it will be a mature industry.

Solar thermal beats PV. Solar thermal with hear storage is essentially the same steam cycle as a nuclear plant. A nuke plant can store the energy for a 24 months of electricity for a large city.

“5) How long is the stored salt 99% efficient (clarify what this means)?”

Steam power plants do not like thermal cycling. To fully utilize the high cost capital equipment of a solar steam plant energy must be stored or other wise provided usually with natural gas. One way to store thermal energy is is by heating water. Think of your hot water heater. If you put a 100 BTUs of energy into your hot water heater and lost 1 BTU to an unheated space, it would be 99% efficient. Another way to store energy would be “a 16-hour molten-salt storage system” where the time length of time the steam plant could keep running without the sun. The efficiency would not change with time.

Before moving on, picture 400 solar thermal plants for each large coal or nuclear plants assuming every day is sunny.

“6) How feasible is it that the cost can come down enough to compete with coal?”

Where? Just east of Gillette Wyoming on I-90 is a strip mine and coal power plant. You can use Google Earth to look at this plant and compare it to those existing solar plants near Barstow California.

An unprepared student from Vanderbilt University could likely die traveling Gillette Wyoming in winter or Barstow California in summer. Cost is not the issue.

I do not think that solar thermal will ever be an economical competitor with coal. Location matters more than cost and surviving the elements in more important than cost.

Part of doing research is learning where to find the information. A good place to look is the California state web page on energy. All project must have an EIS and other regulatory reviews.

[Renewable Electricity]

Thanks for this useful blog. You have given a clear explanation about Solar Towers.
To know about solar energy visit http://www.solarenergy-solarpower.com.
Solar Energy - Solar Power site is providing all the information
and products you need to start your own solar power project.

[Solar Power Installation]

Thanks you for your wonderful explanation about the function of solar Towers.

[P.Subba Raju]

nil

[husky air compressor]

I'm working on a green house project. I'm really interested by this Solar towers and I really would like to know if it's reliable for single housing application.
thanks a lot!
Husky air compressor
Husky air compressor tools

[Wholesale Suppliers]

Modern technology is this solar system now. Cars, factories every electrical device is being connected to solar power system to save energy and utilize God's natural products. As its cost has been discusses, its high in some places because this system has not yet been adopted by many countries yet due top lack of knowledge and information.

[Petrochemicals]

That's great that you think in this way there's many times that people get boring reading a book.

[Lee Todman]

Hi Hanul

I am interested in helping to build a small scale solar thermal plant.
This may be way to late but let me know.
I have just completed all my modules for my Masters degree in Advanced energy and environmental studies, I did however postpone my thesis because I can't make up my mind for a topic.

Let me know

Lee Todman

[solar power hot water heaters]

Solar Energy is the most easily available and free source of energy. It is the most important out of non-conventional sources of energy too, it is non polluting, available for all and convenient source therefore helps in lessening the greenhouse effect.

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It is a nice article. It is a good information about solar towers. The solar tower works like a huge inverted funnel. Solar tower also can produce electrical generation in large scale quantities.

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Solar towers are a good alternative for scarce energy resources.

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