The Major Physical Impossibility Of Solar Thermal Power

Posted on Thu 10/14/2010 by


This first part here may seem boring, but it is absolutely critical when discussing this matter.

If you pass a single wire through a magnetic field, a flow of electrons is induced in that wire, hence, pretty basically, you have generated electrical power, the flow of electrons.

So, it stands to reason that if that magnetic field is stronger, then a greater power can be generated. It also stands to reason that if there are numerous wires, then a greater power is generated, and also, if you increase the speed of the wires ‘going through’ that magnetic field, then that too will result in an increase in power.

So, let’s look at the magnetic field first. Materials that can conduct a magnetic field vary, and over the years, materials have been found that can conduct greater magnetic fields. These were the original Superconductors, not mistakenly thought that they could conduct electric current better, but that they could conduct, (or generate) a larger magnetic field. Then it was found that magnetic fields are stronger at colder temperatures, so they supercooled that material and an even greater magnetic field was able to be generated. Then, to further increase the strength of that magnetic field, wires were then wrapped around that material and by passing an electric current through those wires, an even greater magnetic field could be generated and sustained. This is the classic modern day large electromagnet.

For the wires where the electric current is being induced, then this magnetic field was now used to rotate inside a large number of wires placed in close proximity to that field. This huge amount of wire is called the stator, which does not move, and the magnetic field that rotates inside this, and is called the Rotor.

As to the speed part of the equation, that rotor spins at 3,600RPM, which equates to 60 times a second. (In Australia, that speed is 3,000RPM or 50 rotations per second) It’s an easy thing to just quote those speeds because they seem so intangible, so try this experiment.

Snap your fingers, and then snap them again. All this has rotated 60 times (50 for Oz)

Generator technology has improved considerably over the years to the point that now, larger amounts of power can be generated from even smaller generators. However, that technology is stagnating to a certain point in the Western World, and there’s a reason for that.

Really large generators are needed to generate huge quantities of power.

Keeping in mind all I have mentioned above, one really large generator can generate in the vicinity of 1,300MW.

Now here comes the single greatest factor in all of this argument.

That part of the generator that rotates, the rotor, weighs in the vicinity of 800 tons.

No, go back to the speed element of the power generation cycle All that weight has to rotate at 60 times each and every second. Snap your fingers again. 60 rotations of something weighing 800 tons.

See how it now becomes something not quite so simple.

Large Generator

This image shows a medium/large generator. The length starts from the large round structure at the far end and goes to the end plate there, around 25 to 30 feet. Half is above floor level and half below. I have included this image with the technician to better indicate perspective. A larger generator around 1300MW would be around one and a half to twice this size. (Click on the image and it will open in a new and larger window)

To make that huge weight rotate at that speed, something has to drive it. That is the turbine, and in the case of larger generators, it is a three stage turbine for greater efficiency. It looks a little like a jet aircraft engine, but is much larger. It has numerous rows of many blades for each stage. To make this turbine rotate, huge amounts of steam are required, and here I mean huge amounts of high pressure and high temperature steam.

To make the steam for these really large complexes, two methods are currently used.

The first is by burning coal in a critical furnace. Crushed coal is fed into the furnace at the rate of, and wait for it, one TON of coal every four seconds, and most large scale coal fired power plants burn in the vicinity of 7 Million tons of coal each year.

The second is the two most common forms of Nuclear power generation, Boiling Water Reactors, (BWR) and Pressurised Water Reactors. (PWR) Basically, the control rods in the water are removed to set levels so the reaction can take place in the enriched rods in the ‘tank’. This reaction then boils the water which is then used directly for the steam (BWR), or fed to the boiler to boil the water to steam. (PWR)

In both of these ways, for coal and nuclear, huge amounts of pressurised steam are generated which then drives the multi stage turbine, which in turn drives the generator.

Steam Turbine

A section of a steam turbine for a large power plant. Image courtesy of Siemens and is a Commons image.

This image at right shows just one section of one stage of a multi stage turbine that is driven by steam. Click on the image to open in a new and larger window, and then for an even larger view, click on that image again.

Keep in mind that this 800 tons has to rotate at 60 times a second.

Now, as I mentioned, generator technology has improved over the years. Luckily, nuclear power is still, well relatively still acceptable anyway, so that large generator technology can be utilised in some Western World Countries. Large Nuclear Power complexes in the main usually produce huge amounts of electrical power, in the main all over 2000MW. Nearly all of them have two of these huge generators on site to do this.

Huge generators of 800 tons rotating at 60 times a second.

However, coal fired power stations have fallen so far out of favour that they have little to no chance of getting approval to begin construction, no matter how modern the technology, because, after all they still burn coal.

One Country however is constructing new coal fired power plants, and that is China. They are constructing them at a huge rate, not to thumb their noses at the environment, but to bring electrical power to their vast populace, where only one residence in six has any access to a reliable and constant source of electrical power. Those new coal fired plants are coming on line at the rate of one new large plant every seven days. Not just beginning construction, but being commissioned and delivering power to consumers.

These plants are all new technology, delivering larger amounts of power from smaller generators, and in the process burning considerably less coal than those currently in the West, which are now nearly all of them reaching the end of their lives. The average lifespan of a large coal fired power plant is around 50 years, and currently in the U.S. the whole fleet of every coal fired power plant has an average age of 48 years.

So, while the U.S. and other Western Countries are rolling back coal fired power, incidentally, with nothing in the future to effectively replace them, China is steaming ahead with new technology plants that are indeed at the cutting edge of coal fired power generation.


So then after supplying some background, let’s then look at Solar Thermal power generation, or more correctly, Concentrating Solar Power Generation.

All across the World, this is being touted as that elusive method of supplying Base load power from renewable sources. This statement fails on two fronts. Those who push this barrow have no real concept of WHAT base load power really is, and they have not fully investigated what they propose.

Those who do spin up this option are numerous, and here in Australia it is led politically by the Greens Party, mainly Senators Bob Brown, and Christine Milne, who blindly push this false mantra for all its worth at every opportunity they can. What they fail to comprehend completely is the engineering details behind this.

It all goes back to what I mentioned above. Speed, Weight, and the Steam required to drive that huge weight at that speed.

Concentrating Solar uses two methods to generate power, the Solar Tower, and the Solar Trough method. Tens of thousands of intricately constructed mirrors focus the Sunlight onto a focal point, be it the tower or the pipes for the trough method. A compound is then passed through those pipes or placed in the tower at the focal point of the mirrors. This tremendous generated heat from the focused Sunlight then turns this compound into a molten state. This molten compound then boils water to steam to drive the turbine which drives the generator.

Simple you say. Hook up one of those new huge 1,300MW generators like in a nuclear plant or a new technology coal fired plant, to this Concentrating Solar plant and viola, problem solved.

Turbine Generator deck for the Number One Unit at Diablo Canyon Nuclear Power Plant Facility. Image courtesy Jim Zimmerlin.

This image at right shows just one large turbine/generator complex. The generator is is in the foreground, behind the small blockhouse there, and the multi stage turbine is the larger round complex with the large pipes. Note the man descending the steps, and use that for perspective. (Click on the image to open it in a new and larger window)

Now enter the physical impossibility.

That huge generator, installed at a Solar Plant, no matter how good the technology, will just sit there and will not even move…..EVER.

No matter how good the molten compound, or how many thousands, tens of thousands, millions, or even billions of mirrors can be constructed, that molten compound can NEVER generate enough steam to turn over the driving mechanism, the turbine, to, in turn drive the generator. It will just sit there immobile.

So far, the largest Concentrating Solar Power plant in operation or under construction can only generate 150MW in total power, and that is not from one generator, but a number of them, because the best they can manage is between 20 and 50MW output from the one generator.

That power has been carefully calculated, and it is calculated backwards, as the weight that the generator can be to be able to be driven by the turbine which is in turn driven by the steam, because that is the maximum amount of steam that can be made. This is a physical thing, carefully calculated. If the generator was any heavier, it just would not rotate at all, let alone at 3,600RPM.

So the most power they can produce from the specific weight of turbine/generator complex now is 20 to 50MW. Theoretically, they think they may be able to get that up to around 100MW, or maybe more even but that, so far, is a long way into the future, and as you might imagine, the cost increases exponentially as does the technology.

So then let’s look at this.

A large nuclear or coal fired plant can produce 2000MW, and here I’ve gone for the lower figure when some are much higher. To replace that one plant with an equivalent Concentrating Solar plant, you will need to construct 13 of these Solar Plants of 150MW size.

That’s not me making a point here. It’s quoting an absolute.

Let’s consider the cost. One of these large Concentrating Solar plants will cost in the vicinity of $1.2 Billion, and that’s not at the top end, but an average of current plants in operation or under construction.

A new Chinese coal fired plant is coming in at around $2 Billion, and an equivalent large scale nuclear plant would come in at around $5 Billion conservatively.

So to replace that one large coal fired plant with an equivalent Concentrating Solar Power level, you will need to construct 13 of them, now coming in at around $16 Billion.

Those costs will have to be passed down to consumers in vastly increased costs for electricity.

Now, and attention here to those who push this Solar power barrow, and special attention to Senators Brown and Milne here in Australia, these plants will also be subject to any price they want to place on the carbon dioxide emissions.

Hey! Wait a minute you say, these plants use renewable means from the Sun.

Yeah! Right!

That molten compound actually stays molten enough to produce steam after the Sun sets for the day. So it does, and some of them right up until 10PM. Then the molten compound is not molten enough to generate the steam required to turn over the weight of the turbine/generator complex at the speed required. As part of the covenant that qualifies these types of plant for the enormous subsidies they receive from Governments, then they are required to produce power for the full 24 hours of every day. So, when the molten compound goes off the boil, a natural gas fired turbine takes over to drive the generator until the molten compound is again molten enough to make steam to drive its turbine, in the main around 10AM the following morning after the Sun rises.

So now, to generate their 24 hour requirement for power, then they must burn Natural Gas to drive that turbine to drive the generator.

Natural gas emits CO2, so this supposedly renewable plant now still emits its own greenhouse gases.

Natural gas burns at a set rate, and CO2 is emitted at the rate of 122 pounds for every mcf (Thousand cubic feet) of natural gas being burned, so for the period of Natural gas consumption an amount of 1,200 tons of CO2 is emitted. That’s 1,200 tons of CO2 emissions each and every day. So now we can see that this price on CO2 emissions even applies to these Concentrating Solar plants. At around half a million tons of CO2 being emitted each year, and at the low price of the proposed $25 per ton, this renewable plant is now looking at the added cost of nearly $13 million a year, again, another cost passed directly down to consumers of electricity.

So when you read all about how Concentrating Solar (Solar Thermal) is the way of the future, you need to be fully cognizant of all the facts surrounding the millions of words of spin. It will be touted as a wonderful solution to a vexing question of how to replace those coal fired power plants.

Be mostly aware that there is a major physical impossibility in this, one that will never be explained to you, because those pushing this false mantra have no concept of this, because they only have their eyes on the one thing, and have not even bothered to find out all the facts about what it is they are telling us we need as a matter of absolute importance if we are to save the Planet.

These do gooders have only a fraction of the facts, ones that they use to support their argument, and anything (or anyone) else that speaks against it has an obvious agenda.

There is no agenda here.

These are the facts. It would seem that politics trumps engineering every time.