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Old 08-17-2012, 12:43 PM
Johnny L.A. Johnny L.A. is offline
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Solar power and aqueducts

The California Aqueduct runs through the area where I used to live, in the Antelope Valley area of the western Mojave Desert. The desert is a good place for solar power generation. But one large objection is that deserts are fragile, and large solar power plants would adversely affect the environment. The solar power facilities with which I am familiar focus the sun's energy onto a tank containing a liquid, which is used to generate steam. Photovoltaic cells are more expensive than mirrors.

ISTM that the environment has already been affected where the aqueduct is. Aside from the enormous expense, is there any reason not to cover sections of the aqueduct with photovoltaic cells? There would be little environmental impact (aside from species that have adapted to the relatively new environment of the aqueduct), much of the Antelope Valley is in Los Angeles County, so it is close to a metropolitan area that can make use of the power, and covering the aqueduct would reduce a little evaporation resulting in a small amount of usable water. Such a project would provide a boost to the solar power industry, which might spur innovation and improvements in technology. And there would be one or two jobs created.

Again, I'm aware of the expense. I'm mostly wondering about environmental and other factors.
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Old 08-17-2012, 01:21 PM
phreesh phreesh is offline
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The infrastructure required to install the panels - roads, storage areas, etc, would have an environmental impact during construction. The shade would affect the microclimate near the aqueduct.

If the expense would reasonable, I would think the benefits would outweigh the environmental impacts.
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Old 08-17-2012, 01:23 PM
Enginerd Enginerd is offline
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It's underway in India.

I know you said "aside from the expense," but I think that's the main reason we're not doing it. It's a lot of investment for a relatively low return, and there are more economic ways of generating electricity.

Reducing evaporation is a trickier issue. Covering the canals would certainly reduce water losses, but it would increase maintenance costs at the same time. The way water law is written in much of the west*, Los Angeles wouldn't necessarily get to keep the "saved" water. Your water right gets you enough water to fulfill a given beneficial use; if you make your operations more efficient and can achieve that use with less water, your allocation will be reduced by the amount you save. Basically, LA would be paying to free up water for other users.



* I'm not as familiar with California as I am with other states, but my understanding is that it's similar.

Last edited by Enginerd; 08-17-2012 at 01:24 PM. Reason: runaway articles!
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Old 08-17-2012, 01:43 PM
Johnny L.A. Johnny L.A. is offline
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Quote:
Originally Posted by Enginerd View Post
It's underway in India.
'Oh, Calcutta!' he exclaimed, 'Would you look at that!' It will be interesting to see how it works.

Quote:
Originally Posted by Enginerd View Post
I know you said "aside from the expense," but I think that's the main reason we're not doing it. It's a lot of investment for a relatively low return, and there are more economic ways of generating electricity.
I agree that expense is the main reason we're not doing more with solar panels.

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Reducing evaporation is a trickier issue. Covering the canals would certainly reduce water losses, but it would increase maintenance costs at the same time.
Maintenance on the aqueduct? (Any new structure will require maintenance, so obviously a solar array would need it.) How would installing arrays increase maintenance on the aqueduct?
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Originally Posted by Enginerd View Post
The way water law is written in much of the west*, Los Angeles wouldn't necessarily get to keep the "saved" water. Your water right gets you enough water to fulfill a given beneficial use; if you make your operations more efficient and can achieve that use with less water, your allocation will be reduced by the amount you save. Basically, LA would be paying to free up water for other users.
I'm not familiar with water law at all. If loss is reduced, then that will indeed 'free up' more water for other users. Or it will be 'water in the bank' for droughts. You might say that L.A. would be paying for other areas' water; but the electricity goes into the grid, so other areas would be buying the electricity. It would also reduce the costs of fuel for fossil fuel-powered generation plants. Any new power generation facility is going to cost someone some cash, but it also provides revenue. And of course costs are a 'web' rather than a 'teeter-totter'. So while the cost of water may increase in one area and decrease in another, the cost of power will also fluctuate.
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Old 08-17-2012, 02:04 PM
Dewey Finn Dewey Finn is offline
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If you're going to cover the aqueduct with PV panels, why not cover the freeways with them as well?
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Old 08-17-2012, 02:11 PM
Johnny L.A. Johnny L.A. is offline
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If you're going to cover the aqueduct with PV panels, why not cover the freeways with them as well?
People don't really use the aqueducts. Covering freeways would turn them into 'tunnels', and drivers wouldn't stand for it. Also, in case of a structural failure people could be killed. During construction there would be too much disruption. Enginerd's link shows a fairly simple structure that would probably not be suited to freeway environments.
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Old 08-17-2012, 02:57 PM
Enginerd Enginerd is offline
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Originally Posted by Johnny L.A. View Post
Maintenance on the aqueduct? (Any new structure will require maintenance, so obviously a solar array would need it.) How would installing arrays increase maintenance on the aqueduct?
The solar array will require maintenance, but the canal does too - any kind of water conveyance will have sediment accumulating in it that has to be removed periodically, as well as large obstructions every once in a while that also have to be taken out. Concrete has a long design life, but it has to be repaired sometimes, especially in seismically active areas. Constructing a solar array over the aqueduct makes it a bigger pain in the ass to get equipment and personnel into the channel, as well as restricting the size of the equipment that can be used.

One thing nobody's mentioned is that PV panels have to be kept clean - they're less and less useful the dustier they get. You can't use chemical cleaners on panels that drain into a water supply canal, so they'd have to be cleaned with water. I'd guess that would eat up any water saved by reducing evaporation.
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Old 08-17-2012, 03:09 PM
johnpost johnpost is offline
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panels have a high wind load. you would need to mount them to accommodate this. these would also need to be high voltage systems which presents problems.
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Old 08-17-2012, 04:15 PM
drachillix drachillix is offline
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Quote:
Originally Posted by Johnny L.A. View Post
People don't really use the aqueducts. Covering freeways would turn them into 'tunnels', and drivers wouldn't stand for it. Also, in case of a structural failure people could be killed.
In the central valley of CA as well as many desert areas, I think you would see us welcoming the shade, casualties or not.
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Old 08-17-2012, 04:22 PM
Johnny L.A. Johnny L.A. is offline
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Originally Posted by drachillix View Post
In the central valley of CA as well as many desert areas, I think you would see us welcoming the shade, casualties or not.
When I lived in the AV, I liked the view from the freeway.
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Old 08-19-2012, 10:54 AM
Johnny L.A. Johnny L.A. is offline
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Originally Posted by Enginerd View Post
The solar array will require maintenance, but the canal does too - any kind of water conveyance will have sediment accumulating in it that has to be removed periodically, as well as large obstructions every once in a while that also have to be taken out. Concrete has a long design life, but it has to be repaired sometimes, especially in seismically active areas. Constructing a solar array over the aqueduct makes it a bigger pain in the ass to get equipment and personnel into the channel, as well as restricting the size of the equipment that can be used.

One thing nobody's mentioned is that PV panels have to be kept clean - they're less and less useful the dustier they get. You can't use chemical cleaners on panels that drain into a water supply canal, so they'd have to be cleaned with water. I'd guess that would eat up any water saved by reducing evaporation.
Yes, the arrays would need maintenance as I said. But I had not thought about silting in the ditch. I don't recall hearing of any de-silting operations when I lived there. It's possible that a solar array 'roof' would help keep sand and tumble weeds out. I'm sure there would be a way to clean the aqueduct with arrays over it. Since it seems it's rarely done, it might be worth the hassle and expense to remove sections of the array if necessary.

As for larger debris, I think it would be less likely that larger debris would get into the aqueduct if there's a 'roof' there. The larger debris I heard of when I was there was the occasional car or dead person. I remember a case where an SUV (and skeletal remains) was found in an aqueduct years after the woman crashed into it. It didn't seem to adversely affect the flow of the water. (Though looking back, I knew my water tasted like leg around the time of the crash!)

Cleaning the PV panels shouldn't be much of a problem. Just hose them off. Or have an automated sprinkler system that draws water from the canal and washes the panels at night. I'm more interested in creating power than reducing evaporation, but evaporation during the washing would be reduced by doing it at night.

As acknowledged, PV panels are expensive. But if such a project were undertaken, wouldn't the demand for panels require increased production and lower the per-unit cost not only for the state, but for customers all across the country?
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Old 08-20-2012, 03:33 AM
IAmNotSpartacus IAmNotSpartacus is offline
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Solar power using PV cell generation is not particularly efficient or profitable. Seems a generating company's bottom line is at the mercy of the subsidies and handouts they receive from the government.
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Old 08-20-2012, 08:50 AM
Fuzzy Dunlop Fuzzy Dunlop is offline
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Quote:
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Solar power using PV cell generation is not particularly efficient or profitable. Seems a generating company's bottom line is at the mercy of the subsidies and handouts they receive from the government.
With the drastic drop in panel prices the price per watt is already below the cost of grid power in some very high cost energy places (carribbean, Hawaii, etc.)

And PV installations last 20-25 years. Government incentives today allow for a profitable installation that will produce power for 20-25 years as energy costs rise. Today's invesments make it easier to cost reduce future investments all while the cost of non-renewable electricity from the grid steadily rises to meet it.
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Old 08-20-2012, 08:54 AM
Fuzzy Dunlop Fuzzy Dunlop is offline
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Quote:
Originally Posted by Johnny L.A. View Post
As acknowledged, PV panels are expensive. But if such a project were undertaken, wouldn't the demand for panels require increased production and lower the per-unit cost not only for the state, but for customers all across the country?
China recently invested billions in silicon for panels and flooded the market with cheap PV panels. Retail price fell from $3.50/watt to $2.43/watt in 2011.

One relatively small installation isn't going to have any impact though.
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Old 08-21-2012, 08:37 AM
rbroome rbroome is offline
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Quote:
Originally Posted by Fuzzy Dunlop View Post
China recently invested billions in silicon for panels and flooded the market with cheap PV panels. Retail price fell from $3.50/watt to $2.43/watt in 2011.

One relatively small installation isn't going to have any impact though.
that they did. Now everyone is paying the price.
First the US plants started going out of business.
Then the German plants.
Now the Chinese manufacturers are losing so much money they are turning to the Chinese Gov't for "loans" to keep going.
Classic boom and bust cycle. Accentuated by Gov't (all gov'ts from what I can tell) intervention.
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