Cool New PowerPlant - uses mirrors and solar power to assist coal power plant in creating steam

Why to use coal at all?

 

It gets dark at night. And it sometimes gets cloudy in the daytime.

The article can't be telling the whole story. It claims the mineral oil is heated to 575F and then used to heat water to 360C. Without additional (unstated) input, this violates the laws of physics since 360C is about 680F.

Most likely, coal is used to finish raising the temp to the 680F/360C or else the 360C is actually 360F instead.

 

This explanation appears more sensible:

Cameo Steam Plant Goes Solar

The plant was slated for closure; that caused a stir; local power company decided to use it to test a solar booster instead of close it. The solar add-on preheats the incoming water by 10 to 15 degrees F. As of April of this year, that story also says that this is just a test, and the plant will be closed at the end of the year.

The story has claimed savings of 900 tons of coal/year. You have to guess what that is as a fraction of total plant consumption, but any back-of-the-envelope estimate says that's tiny. I make it out as enough electricity for 450 average US households. Clearly just a pilot test to see how it works.

The other back-of-the-envelope that puts some brackets on this is that 900 tons of coal is (depending on what you are buying, of course) something like $18000 a year in fuel savings. But this was described as a $4.5M project.

 

900 tons of coal is a drop. Looking at a nearby facility's permit, they're set for about a million tons/yr (midsize plant, 1.15 GW).

 

It's still coal!!! If memory serves, an average railway car carries ~200,000 pounds,, that would be, 100 tons. So, one might think that 9 rail cars full of coal is a lot,,, until you drive Interstate 94 down the Yellowstone River in MT, and see, on the average drive, perhaps a dozen coal trains, each with ~100 cars during the average drive from Billings to Glendive (~250 miles) all destined to easter coal fired power plants, you can begin to see how much coal we burn every day!

Simple (relatively) reflected solar steam plants have been on line for years. Solar steam is one answer, direct PV is another, both have applications, but coal shouldn't!

 

Perhaps some of the more scientifically literate can explain it to me. Several years ago on a tour of the Arizona Public Service facility on University in Tempe, I suggested to the engineer in charge that supplementing the gas fired plant on site there with non-imaging optics solar might be beneficial in terms of using less gas and more solar. Knowing that non-imaging optics can generate temperatures like unto multiples of the surface of the Sun, it just seemed like a scaled back version could supply a bit of heat for their efforts in Arizona - a state with lots of Sunshine.

While the engineer in charge was polite, it was obvious that he thought me a dolt of little wit and less gray matter.

So, again, perhaps someone can explain why solar lenses, solar parabolic troughs, solar non-imaging optics are not being used to juice up the temperatures of the working fluids of the moment just a bit where needed. Non-imaging optics has worked pretty well in demonstrations at NREL in Golden, CO. I am really wondering.

PasPrius

 

May not answer your question, but it is being done.

Tracking the Sun: Concentrating Solar Power Faces Bright Future | Renewable Energy World

To MJfrog,

Systems like this, installed in the desert S.W. have nearly no shade issues from clouds. Concentrated solar fluid heating systems are much more forgiving of occasional cloud and filtered sun than PV solar is. The fact however is, in the desert S.W clouding is almost never an issue. Focused, concentrated solar installations can be build with enough capacity to run through the night on the stored heat. They need to be requisitely larger, but in fact the load is usually less at the same time production drops off. (after dark).

The fact is, there is only one reason we use coal for anything, and that is because it is cheap! For a variety of reasons some don't want to hear or believe it, even without subsidy, PV solar is competitive with grid power at peak times. The reality is that most grid power is artificially subsidized, mostly at the expense of the environment.

 

The physics is correct, the engineering is not. The present plants are designed from the ground up to operate with set temperatures at each stage for optimum efficiency. To make what you propose causes two big problems:
1) The solar heating is cyclic and has occasional blockage. The control and feedback systems of the plant cannot handle these. They would see them as some stage failing to perform as required. It's like trying to use a truck diesel engine in a race car. The engine provides great power, but only when operated at a constant load, since that is the design goal.
2) The sizing of the preheaters, boilers, superheaters, etc. often suffer problems if the fluid is not at the exact temperatures designed. The problems vary with each stage, but the gain of solar can be easily negated by a great reduction in the efficiency of the following stage since it has to operate out of whack to make the output stage at the right temp.

Now a plant designed from the ground up to make use of this is a very different story.

 

You get $18000 a year in fuel savings for a $4.5M project. Ignoring time cost of money, if it lasts 250 years (=4500000/18000), it'll pay for itself in fuel savings. Doesn't address the broader issue but seems to be a pretty good explanation of why this particular type of solar plant is not widely deployed in locations like this.

 

Many donkeys will be hit on their heads with many 2x4s before we give up coal. It'll get ugly.

 

FL_Prius_Driver -

Thank you for that concise and lucid answer. Had not considered the multiple stages required to get the job done - just the heat.

icarus -

Thank you for that link. Good to see that more solar concentrators are being built. We need a lot more. The real costs of coal and imported oil are staggering.

PasPrius

 

It’s just hard to understand why China and US use so much coal for electricity... That’s not nice…

 

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