T Nation

Thermal Solar Applications, Is this the Answer?

We have discussed various aspects of Solar energy and the policies related, mostly from a failure perspective. I have been poking around a bit and have become interested in the possibilities of thermal solar applications as opposed to PV (photovoltaic} which I think is what comes to most peoples minds when they think of Solar.

I do not come from a science background. With this limitation, thermal solar looks very appealing to me. Rather than converting sunlight to electricity and then dealing with storage and efficiency issues, with thermal solar you simply capture and store heat, for example in the medium of molten salts, and then use the transfer to drive steam turbines and generate the electricity as needed. The cost of storage is reduced more than 90%.

What I am looking for is some open minded, fair critique from our members that have the education to more fully understand the science.

Here is a video of a lecture fron Stanford University. It is just under an hour, but I am sure that anyone that invests the time will come away felling it was time well spent.

Warning: There is your usual climate/CO2 propaganda mixed in. I think the content stands up if you just ignore the “Goreisms”. Tell me what you think/

The amount of solar power reaching a surface perpendicular to the Sun’s rays is about 1000 watts per square meter.

Since the sun is not constantly directly overhead any array, the power received does not average this high.

I really don’t have a figure for an average for say some location in California but let’s say an average angle of 45 degrees (thus a correction factor of about 70%) and let’s say 10 hours per day of being bright enough to be worthwhile.

(I recognize that “average angle” isn’t a valid concept, but this is an approximation only.)

So this would give a maximum amount of power as 7000 kW/hours per day per square meter.

Efficiency? I have no idea. Let’s be optimistic (I think) and say 50%.

Now we have 3.5 kW/hours per day per square meter.

How much is the energy worth at the plant per kW/hr?

Maybe 5 cents?

So that would mean a maximum of 17.5 cents, or call it 20 cents, worth (at the plant) of electricity per day per square meter.

Or about $70 worth per year generated per square meter.

This may be feasible. Hard to say.

But the great thing about the free market is that society or the government doesn’t need to figure these things and decide them.

If this is profitable to do, it will be done by people using their own money to make a profit for themselves.

(The video may have gone into this but I didn’t have an hour to watch it.)

There is a thermal plant near where I work, and my boss knows some of the investors. It would be a big-time money loser without the government subsidies.

Here is a pic of China’s Dahan Thermal Solar Plant. Its supposed to be running this year. This stuff seems pretty neat.
I dont like how this guy is promoting thermal solar by saying that PV isnt any good.

Here is a pic of China’s Dahan Thermal Solar Plant. Its supposed to be running this year. This stuff seems pretty neat.
I dont like how this guy is promoting thermal solar by saying that PV isnt any good.

Thermal solar for the use of heating domestic water supplies is effective. A friend of mine installs solar panels for water heating for industry. If business/factories are investing in this technology, then it’s quite obvious it pays. He says that they must wear gloves when installing these panels since they get too hot even when not in full use.

This technology will reduce your gas(methane)/electric bills used for heating water and your house via radiators. It’ll never eliminate your need for gas/electric heating, however it will heat up your water to a reasonable level say 60 deg C, and you use gas/electricity to get it up to 90 deg C, using a cold water source of 5 deg C.

[quote]andrew_live wrote:
Here is a pic of China’s Dahan Thermal Solar Plant. Its supposed to be running this year. This stuff seems pretty neat.
I dont like how this guy is promoting thermal solar by saying that PV isnt any good. [/quote]
Can you demonstrate that photovoltaic returns more value than the value that was put into making the panels?

No, because the reverse is true.

Putting more value into something than it ever puts back out is not a good thing.

Now, it may be that at some future date a tough, durable film would be developed that costs very little per square meter to manufacture and puts out DC with high efficiency. When and if that’s the case, it could be a completely different story. But it is not the case now nor is anyone really close to it, so far as is known anyway.

Steps are being made with these considerations as ‘thin film’ PV, where the efficiency is still low 10-15% however they’re much cheaper leading to a quicker payback time. Chemicals are pretty much printed onto an aluminium sheet.

Oerlikon has recently come into the field of thin-film PV. Take the link with a pinch of salt as it’s a press release: http://www.nanowerk.com/news/newsid=14394.php

Thanks OP. Very interesting stuff.

Interesting.

They say they are “well on track to offer its customers an advanced fab design capable of producing modules for $0.70/W by that time,” meaning by the end of the year.

Now I don’t know but am supposing that that is the manufacturer’s cost, not the price the end-user will have to pay to buy it. But let’s ignore that, and suppose that the figure is achieved.

They probably mean 70 cents per watt peak. Maybe over the course of the day, under ideal conditions, 70 cents per say 7 watt hours produced per day?

So that would be $1 per 10 watt hours produced per day, or $1 per 3 kW hours per month.

If the consumer pays 10 cents per kilowatt hour, then that $1 gets him 3 cents per month, or 36 cents per year.

Now in practice the price he has to pay to get the product, have it installed and so forth may be 3-4 times the cost to the manufacturer, so it might be more like taking 12-16 years to pay for itself.

Still, that is surely progress.

Bill, I would suggest you work in the video at some point when you have some down time. It addresses many of the concerns you bring up. I am just not yet well versed enough to evaluate these counter claims.

The video at one point brings up a four square matrix. The top two columns are labeled Continuous and Fresnel. The side two rows are labeled Point and Line. Therefore, there are four variations in play; Continuous Point, Continuous Line, Fresnel Point and Fresnel Line. The Chinese example above appears to be an example of a Fresnel Point System. A fixed point of focus with many tracking or moving mirrored panels. A continuous point system would resemble a huge dish, tracking the sun and focusing all its collected light/heat on a single or finite point. This allows for tremendous heat production, well over 1000 degree Celsius, but would be limited to the parameters of the materials used as the focal point.

The lower tech versions of the Continuous Line, or trough line, interested me more. Less moving parts. Hardier system. You basically have a tube suspended within a long, concave, mirrored trough. The tube obviously has a heat capturing and conducting medium, the circulates back to a heat storage unit. It appears that a very large RFP was just written and granted for such a system out in Arizona, the merits of which were apparently decided without using government subsidies or such.

Again, I don’t have any personal investment either way. It just seems almost “self evident” to me that solar should and could be a viable piece of our overal energy game plan.

The elegant thing (well, not strikingly so, but somewhat) is that the approach I used above for evaluation is independent of which of these systems is used.

If solar is in fact viable – that is to say, if value output exceeds the value that must be input – then it will happen without requiring advocacy or government support.

Government support works only either to yield malinvestments where value put in is greater than value produced; or to line pockets of the connected at the taxpayer’s cost.

[quote]Bill Roberts wrote:
The elegant thing (well, not strikingly so, but somewhat) is that the approach I used above for evaluation is independent of which of these systems is used.

If solar is in fact viable – that is to say, if value output exceeds the value that must be input – then it will happen without requiring advocacy or government support.

Government support works only either to yield malinvestments where value put in is greater than value produced; or to line pockets of the connected at the taxpayer’s cost.[/quote]

Right,
I absolutely get where you are coming from. I have made this very argument a hundred(s) of times. The problem is, every time I made that argument I felt a small twinge of hypocrisy.

I think it would be hard for anyone on this board to label me a bleeding heart liberal. I like to think of myself as a centrist, but I realize I lean conservative more often than not. I can’t say that I’ve given this a in depth examination. Just scratched the surface at most. However, here is a possible example to consider.

I am from Tennessee, and while not much above average in my knowledge of history, I am probably more familiar with TVA (Tennessee Valley Authority). Created in 1933 as a part of FDR’s New Deal, TVA transformed Tennessee. The area was particularly hard hit by the depression. In many ways it resembled a third world country. Extreme poverty, widespread disease such as malaria, you name it we had it. TVA’s scope was immense, but perhaps the most dramatic change it effected was the electrification of the region. This brought about a dramatic improvement in the quality of life of virtually all residents, as well as bringing much industry into the area via lots of good cheap electricity.

I know one could argue that those resources could have better been allocated by free enterprise. I am just not sure that such an argument would be honest. The region was particularly suited for hydro electric production. Tennessee in particular has more rivers and dam-able (is this a word?) terrain than any other state. The tremendous amount of electrical production soon became instrumental in national defense and our eventual rise as the Super Power we became. It was TVA electricity that made it possible to produce the quantities of aluminum necessary to build the airplanes that were instrumental in winning WWII. It was huge amounts of TVA electricity that allowed for uranium enrichment at Oak Ridge, TN that would be used in the Manhattan Project.

It is possible that given time that private free enterprise could have enacted these changes more cost effectively. Possible, but not probable. Given the huge capital requirements, not to mention the expediting of legislation that allowed for the grand scale purchasing of land, relocation of populations, rezoning, etc., it is unlikely that any of this would have been accomplished by free enterprise alone.

I know many will chime in that the Fed Gov had no right to forceably purchase most of this land, relocate populations, etc. That is a different argument for another time. What I am contending is that an immense public good was brought about with government support that would most likely not have been possible otherwise. In a sense, it tended and fertilized the soil in which free enterprise was later able to flourish.

In this context, I do not think it unreasonable that the Fed Gov in some way facilitate or subsidize the initial stages of large scale applications of solar energy production. I have not even bothered to mention how many times advocates of American energy independence have lamented the throttling of nuclear energy production in the US by special interests. As much as I am for limited government, I assure you that I want governmental oversight when it comes to nuclear energy.

I shouldn’t have stated that as being invariably the case. Where it is a question of providing a public good, such as a highway for example, government can make productive investments.

That is to say, investments that produce outputs with value greater than were the inputs.

However, when it comes to issues such as whether subsidizing a small powerplant or not, subsidizing home solar or not, subsidizing ethanol or not, etc, then what I wrote applies I think invariably (can’t think of an exception anyway.)

On the topic of thin-film PV, IBM has this: http://www.technologyreview.com/energy/24521/?a=f
Thin-film PV using more abundant and less expensive materials.


I just opened a renewable energy company primarily distributing solar thermal technology. PV is several years away from being a viable source of electricity, solar thermal is here TODAY. I am not talking about your typical flat plate collector, either - unless you are in California or Florida, the convection losses will nullify most of the benefits.

I am talking about evacuated tubes insulating a heat pipe. A thirty tube collector array can produce 46,000 BTU’s in a day! It transfers the energy from the tube to a manifold circulating glycol, which then circulates through a double wall heat exchanger to an insulated storage tank. Think of this tank kind of like a “BTU battery”.

All you have to do is engineer the demand, the desired solar fraction, and the collector size and you can pretty much have a system that will meet a large percentage of your NON - electrical energy needs.

The most common application is solar hot water. There are liquid/air heat exchangers as well that can be fitted in-line with duct work which can supplement space air heating. There is also solar air conditioning. There are literally hundreds of configurations that solar thermal can be applied in both residential and commercial environments.

Heat pipes aren’t the only thing you find in evacuated tubes either. There are “U” pipe systems ( imagine a “ladder” on it’s side with the top rail as the supply and the bottom rail as the return, folded onto itself with the “rungs” forming a “U” that slides into the collector ), Thermosyphon systems (which are the least efficient, but very inexpensive), etc…

I am selling these things like hot cakes. I have one on my home, and I have notices a SIGNIFICANT reduction in my gas bill. ($250 down to ~$40 in a 6000 sqft house) I actually use my personal bills to show people that it works.

Now I would agree that solar thermal technology isn’t going to change the world by itself, but it’s a step in the right direction. It is prudent goal economically, politically and globally to reduce our consumption of fossil fuels and eliminate our dependence on foreign oil. Imagine if the world no longer needed oil?

Do you really think we would be in two wars right now and worrying about Iran? Imagine how many American soldiers have died securing our interests in the Arab world so that we, as a country, can get our oil “fix”? It’s stupid not to seek an alternative energy source when the technology is so clearly available and just needs to be developed and implemented.

Or we could just build a nuclear plant… its safe, easy, and the govt finally approved 4 -6 designs so its a lot faster…

The one thing people never mention when talking about most solar energy is how energy intensive / “bad for the environment” making the cells are…

The thermal battery things work and are really cheap. A few libraries / gotv buildings use those in reverse, freeze a large pool of water at night when energy is cheaper and there is less demand, then use it to cool the building during the day. This idea / method I am all for, traditional solar cells, not so much. Off-Shore wind turbines like the ones in England / Spain are a great idea also.

seriously though, people need to get over the B.S. fear of nuclear and embrace it !!

[quote]Ratchet wrote:
Or we could just build a nuclear plant… its safe, easy, and the govt finally approved 4 -6 designs so its a lot faster…

The one thing people never mention when talking about most solar energy is how energy intensive / “bad for the environment” making the cells are…

The thermal battery things work and are really cheap. A few libraries / gotv buildings use those in reverse, freeze a large pool of water at night when energy is cheaper and there is less demand, then use it to cool the building during the day. This idea / method I am all for, traditional solar cells, not so much. Off-Shore wind turbines like the ones in England / Spain are a great idea also.

seriously though, people need to get over the B.S. fear of nuclear and embrace it !![/quote]

Nuclear will not survive without government subsidy, or the absolute guarantee of the government should the project fail for the builders. We also shouldn’t forget the massive cost of decommissioning following operation and of course nuclear waste.

For me (as a physics graduate) Obama’s approval for nuclear should give the opportunity for the next generation of scientists to experiment with new technologies such as fast fission reactors. Fast fission reactors can reduce the problems with waste afterwards. http://en.wikipedia.org/wiki/Fast-neutron_reactor

Sorry for high-jacking this thread to non-solar technology.