Solar Thermal Power (Concentrating Solar) Fail – Just Look At Spain

Posted on Fri 11/08/2013 by

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TonyfromOzProfileImageBy Anton Lang (TonyfromOz) ~

Abengoa Solar - PS10 and PS20 Solar Power Tower Plants

Abengoa Solar – PS10 and PS20 Solar Power Tower Plants

How many times have you heard that there is a form of solar power that can indeed supply what is termed as Base Load Power?

How many times have you heard the story of a solar plant in Spain that can supply power for 24 hours straight?

How many times have you heard that we have now reached the stage with solar power where it can take the place of coal fired power?

How many times have you heard that we can do solar power anywhere, because they are doing it now on a large scale in Spain?

Well then, let’s look at all those things and see if there is any truth in any of those statements.

Gemasolar Concentrating Solar Power Plant Spain

Gemasolar Concentrating Solar Power Plant Spain

You may have recently heard that the much talked about Gemasolar solar plant in Spain which can provide 24 hour electrical power actually did do just that for 36 consecutive days in mid Summer. At first reading, this occurrence actually gives the impression that a plant of this nature can deliver power that is on a par with coal fired power.

However, is that statement actually correct, that a plant like this can compare favorably with those large scale coal fired power plants which do provide that 24/7/365 power referred to as Base Load Power?

Spain now has constructed 24 of these type of Concentrating Solar plants and they are spread across the length and breadth of Spain, so we can in fact use this as a guide because there are now a fairly significant number of them in operation, and have been in operation now for a number of years.

The technology is referred to as Solar Thermal Power, but the more correct term is Concentrating Solar Power. (CSP)

The light from the Sun is focused to a central point which then generates a huge amount of heat. This heat can be used in a couple of ways. It can be used to heat water directly to make steam, or it can be used to make a compound (usually a salt) molten. This molten compound is then used to boil the water to steam. In both cases, the steam is used to drive a conventional turbine which then drives the generator that generates the electrical power.

It can be done in a couple of ways as well. The most common form is the parabolic trough, which is a series of concave mirrors in a series of long rows. At the focal point of these mirrors, a pipe carries either water or the salt compound. The second is what is referred to as a Power Tower. All the mirrors are focused onto the top of a large tower. At that point atop the tower, the compound is passed and the huge focused heat makes this compound molten. In both cases, the mirrors are articulated to track the progress of the Sun across the sky during daylight hours. There is also another method, Linear Fresnel Mirrors, which is still only on a small scale, and shown below as the last solar plant on the list.

One aspect of both methods is the ability to divert some of that molten compound to be kept in as close to a molten state as possible for as long as possible. This is referred to as Heat Storage. The disadvantage of this is that it is a huge added extra cost at the construction phase. A second disadvantage is that it limits the total power that can be generated by the plant as not all the heat is used all of the time to generate as much power as possible.

That is best explained with this diagram, which looks complex, but is relatively easy to understand. The main thing to look for here is the actual total power being generated by this plant, and that is shown by the solid red line along the bottom of the chart indicating that this plant can generate 50MW of power (as indicated by the right side vertical axis – Power in MW) With heat diversion this plant might actually generate this 50MW for 19 consecutive hours. Keep in mind that this is a theoretical model and this is for a typical mid summer’s day with no overcast.

Concentrating Solar DiagramSpain now has 24 of these plants, and while we could look at an individual plant, what I have done here is to collate all 24 of these plants and make a chart with all the relevant details of the plant.

The first column is the name of the Plant. The second column is the type of plant. The third column indicates the total area covered by the mirrors for this plant, and some of those areas are indeed quite large. The next column indicates whether this plant has any heat storage capability and the number of hours of that heat storage. The next column indicates the total Nameplate Capacity for the plant. The next column indicates the actual power being generated by the plant that is delivered to the grids for consumption by all consumers of electricity. The next column is the actual Capacity Factor (CF) for the plant. This is the ratio of power delivered versus Nameplate Capacity, and this is the Industry Standard for that rate of power delivery. The last column shows that CF extrapolated down to a daily average. Now while some days power delivery may be spread over a longer period, then there will be days in mid Winter when that same delivery of power would be impossible, so this is that total yearly CF expressed in average hours per day for that Plant.

SpanishConcentratingSolarPlants01

For the following, I will occasionally refer to the Bayswater Power Station. Now, while this power plant is located in Australia, it is typical for a large scale coal fired power plant anywhere they are in operation around the World. This plant has 4 units, and has a total Nameplate Capacity of 2640MW.

Bayswater Power Plant

Bayswater Power Plant

Now, while the total area is interesting, and some may think it is important for the power generated with respect to area, I have only included it here for the sake of interest. The total for all these plants comes in at 13,548 Acres, which equates to 21.2 Square Miles or just under 55 Square Kilometres, which is a lot of land.

When you add up the Nameplate Capacity for all those solar plants, that total comes in at 1781MW, a seemingly quite large amount. By comparison, the Bayswater plant has a Nameplate Capacity of 2640MW, a total that is 48% larger than all those 24 solar plants.

Now this next total is by far of greater importance than virtually anything else. That is the amount of actual power being generated by these 24 Plants for delivery to surrounding grids for consumption. That amount of power delivered comes in at 4,483GWH, which at first glance is a seemingly huge amount of power. But, is it really? By comparison, the Bayswater plant actually delivers between 16,000GWH and 17,000GWH of power to the grid for consumption. So this coal fired plant delivers almost four times as much power for consumption than all these 24 solar plants. So, in just 93 days of normal operation, that ONE Bayswater power plant delivers the same power that all these 24 solar plants deliver in a full year.

This next area is probably the most crucial of all, the Capacity Factor. (CF) That is the ratio of power delivered to the theoretical total. Note from the list that one plant have what seems a relatively high CF of 62%. However, when the total power generated is calculated to give that overall CF, then that comes in at only 28.7%. Now, while this percentage factor may seem fairly meaningless, this is the Industry Standard for power plants. This percentage here means that over a full year, all these 24 solar plants deliver only 28.7% of their maximum rated power (Nameplate Capacity), or, exactly the same thing, they are only delivering their maximum rated power for 28.7% of the year. Now, extrapolating that out, then if that is a yearly average, then it can also be expressed as a daily average as well, the same 28.7%, and while there may be days in Mid Summer when some plants can actually deliver their power for much longer periods, then that average tells you immediately that there must also be days when power delivery is of a very short duration. That CF of 28.7% equates to just under 7 hours a day. That is important, because a Base Load requirement is that plants can actually supply their power on a 24/7/365 basis, and that’s 24 hours of every day, and just under 7 hours a day is nowhere even close to doing that.

The next column ties in with what I just mentioned above. The Time Supplied equates to the CF expressed as a daily delivery of power, and while some days there is a lot, the average here for all 24 plants is only just under 7 hours. You can see on the list that some plants have higher totals, but most of them are down as low as only five and a half hours.

So, I mentioned at the top that there was one of these solar plants which actually delivered its full rated power for 36 consecutive days, the much talked about Gemasolar Plant. Now look again at the Nameplate Capacity here ….. 20MW. Here you have a plant covering a huge area, costing a huge amount of money, and yet all it can supply is 20MW. Now, because this plant did actually achieve this 36 consecutive days there will be supporters out there who will now claim that this indeed is now a viable replacement for coal fired power and can indeed supply that Base Load Power.

This is 20MW only.

The Bayswater plant supplies power to the grids of most of Australia. Bayswater is just one of a number of power plants that supply power to most of Australia, and that area in question has a Base Load requirement of a MINIMUM of 18,000MW, that amount of power required 24 hours of every day, 7 days of every week, and 365 days of every year.

18,000MW compared to what this plant can supply for 36 consecutive days in Mid Summer, 20MW.

All right then, let’s actually compare what this solar plant did with Bayswater.

With respect to the total power delivered to grids by this solar plant in those 36 consecutive days, Bayswater delivered that same amount of power in 6.5 hours.

Bayswater delivers the yearly total from this plant in 41 hours.

This Solar plant has a projected lifespan of 25 years, so let’s compare the total power generated by this plant for consumption during this whole life of the plant. At 110GWH per year, than that total is now 2750GWH. That same amount of power is actually generated by the Bayswater plant in 59 days of normal operation.

25 years from the Solar plant and 59 days from the coal fired plant. There just is no comparison.

This Gemasolar costs around $500 Million, so just to replace the Nameplate Capacity of Bayswater, you would need 133 of these plants at a cost of $66.5 BILLION, and still get less power delivered to the grids than what Bayswater delivers.

Concentrating Solar Power has long been thought of as the answer to power needs that actually can do the job now done by coal fired power. This shows that any talk along those lines is not only misplaced, it is totally untrue.

Technology has advanced almost to the stage now where they might be able to generate enough steam to drive a turbine that could drive a 125MW generator, and the current average maximum is 50MW, but now you have single units at coal fired power plants that have 1300MW generators.

These plants are using the absolute best and most recent technology, and still they cannot deliver power on the scale required to even be considered as coming close to replacing coal fired power.

In actual fact, these figures shown here for ALL 24 solar plants in Spain are currently only on par with Wind Power which currently has a Capacity Factor approaching 30%.

All this shows is that this form of power generation will only ever be of boutique and very small supply, all at an enormous cost.

What it effectively shows is that Concentrating Solar Power is indeed a failure, an expensive failure at that.

Reference for all Electrical power data for Spanish Solar Plants: List Of Solar Thermal Power Plants

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