Kyoto – A Perspective (Part 25)

Posted on Tue 05/13/2008 by TonyfromOz

SOLAR POWER (Part 3)

This shows the now decommissioned Solar Two mirror array near Barstow California in the Mojave Desert. It uses nearly 2,000 heliostat tracking mirrors focussed on the tower and it produced 10 MW of power. It was decommissioned in 1999 and is now used for research by the University of California Davis.

This photograph was taken by an employee of the US Dept. of Energy in his daily duties, and is in the public domain.

Click on the photograph to see a larger image.

As you are now no doubt fully aware, the biggest problem with Solar power is that around 6PM every day, the Sun falls back below the horizon.
While Coal fired power plants, nuclear power plants and Hydro electric power plants just hum along with the turbines rolling at 3600RPM driving the generators day in, day out for years on end, supplying constant dedicated regular baseload power, the Sun rolls over the horizon and the electric power generated at a solar power plant stops, and that is why it cannot be used for baseload power, no matter what the environmentalists might say.

There was no real way to store the energy that was built up during the day. Some of you may have those solar powered garden lights. The Sun shines on the collector during the day, and small electric circuitry connects the cell to a charging device that charges a rechargeable Double A battery. When the Sun goes down, the tiny electric circuit clicks over and the battery then powers a small bulb to provide a gentle glow around the edges of your garden. Some of you in really hot areas where the Sun is really bright for most of the day, and you move the lamps around all day so the collector gets the maximum effect, well, the glow might actually last all night, but the cheaper quality ones will dim and wink out around 10PM to midnight.

Therein lies the source of the incongruity. It works great while the Sun shines, but nix for half the day.
With photovoltaic arrays I discussed in the last post, we saw that they can be quite effective, but consider the space they took. The array at Nellis covers 140 acres, and only produces 14 MW. Reasonably, that same area could contain a 2000 MW baseload nuclear plant, that would power not just 25% of the requirements for Nellis, but all of the power for the base and the nearby city of Las Vegas as well, and then some. I know this is comparing apples with oranges, but you see the comparison regarding one aspect of the power production.

Solar Thermal Power.

This solar furnace directs heat onto the collector in the tower. This plant is located at Odeillo in the French Pyrenees and can reach a temperature of 3,800 degrees Celcius.

This image was taken by Aurelio A Heckert, and is a freely available Commons image.

Click on the photograph to see a larger image.

This process of Solar Thermal power is an encouraging advance. Whereas photovoltaic solar relies on the Sun shining on tiny cells to generate the power, this process uses mirrors to shine onto collectors to heat water to steam to drive a turbine to drive the generator.
Okay, you say, same problem. The Sun goes down at night, the steam converts back to water which cools down, and the turbine stops.
Thousands of curved mirrors track the Sun during the day, focussing the light onto troughs or pipes carrying water. This heats the water to steam etc. Again the inherent problem is the Sun sinking in the West.
Cleverly however, ways have been found to store that heat during the night, again not by placard waving radical environmentalists, but hard working engineers looking for ways to solve problems like this.

This is the PS10 plant near Seville in Spain, focussing 624 Heliostat mirror onto a solar tower. It generates 11MW of power.

The photograph is a Commons image.

Click on the photograph to see a larger image.

The way they do this is to focus a really tight beam generating enormous heat onto towers or collectors. Inside the towers or collectors is salt. The salt becomes molten from the incredible heat focussed onto the collector. This molten salt then heats the water to steam etc.
The molten salt stays molten all night, cooling very little, and when the Sun comes back up the following morning it just tops off that heat.
Ingenious.
This is actually where Solar power might just work.

As is always the case, there are drawbacks.
The cost is enormous. Why you ask?
The simple thing of actually making the mirrors, and then constructing the site to perfectly focus them all on the collector and have them track the Sun.
I’ve actually heard estimates that if we were to take out all the coal fired plants that Kyoto demands, (hey! Remember Kyoto) and we then work to replace them with solar power, and if we geared up enormously by factors of thousands of percent, it would still take nearly 50 years just to construct the mirrors alone. The cost would be astronomical, and would have to be passed on to the end consumer of the power.
This molten salt process provides a growth industry even if the carbon footprint during manufacture is a large one.
See how there’s no such thing as carbon free production of electrical power, and in all actuality, there’s no such thing as carbon free anything.
These molten salt plants are springing up here and there, but again, it’s not going to be of reliable production in the North of the US.
In Arizona, a US Company, Abengoa Solar are constructing a large solar thermal plant at Gila Bend near Phoenix. When it comes on line it will be the largest solar power plant on Earth. It uses the molten salt process, and will supply a maximum rated 28 MW of power. I urge you to take the link and read the interesting data there at all the other links on that site.

This shows a Stirling Engine mounted on a tracking array.

This photograph was taken by an employee of the US Dept. of Energy and is in the public domain.

Click on the photograph to see a larger image.

Another process uses the revived Stirling Engine, using heat reflected from mirrors to drive an engine to produce electricity.
Southern California Edison is contracting to purchase 20,000 of these engines over the next 20 years and will end up producing 500 MW of power.

Again, what is highlighted here most remarkably is the time involved in gearing up this process, that time mostly for the manufacture of the mirrors.

You also need to look at the area involved considering the immense number of those mirrors needed.

Unlike the rhetoric coming from environmentalists, this is just not something that can be done overnight. We need to start now, but when you look around, you’ll see that we actually are starting now. People work quietly, achieving things that these environmentalists dream of, if only they would open their eyes and see what is being done.
The big factor is again, money, and it always comes back to that. However, entrepreneurial Americans actually are making the effort and fronting up their money for processes like this to be developed, but even the most ardent environmentalist must concede that this is something that will come at a higher cost, and that we must bear the cost if we are to make it succeed.

With this post I have included some quite lengthy links to other sites. I know there is a lot of reading involved, but it is really interesting and I urge you all to take some time when you can sit down, follow those links and read the information and take further links. Something is being done right now, and it is well worth looking at.

KPPSTony