 | Hansen to Australian PM: stop coal plants now | TOD: Australia/New Zealand | The Bullroarer - Thursday 3rd April 2008 |  |
197 comments on Concentrating On The Important Things - Solar Thermal Power
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A week of cloud cover in the locations that are best suited for solar thermal is unheard of - what are you talking about ?
These things are built in deserts that get (maybe) a few days of cloud cover in a year.
Look at a global solar insolation map - find the best bits. Match against rainfall records.
You'll find vast areas in the south-west US, north africa, middle east, western china, kalahari desert, northern chile and central australia that have great sun and hardly any rain.
Of course, cloud cover isn't the only cause of reduced insolation in desert-like environments:
http://www.mapsofworld.com/referrals/weather/severe-weather-conditions/s...
Good point (and very effectively made).
I was thinking of our local deserts here, which you don't see sandstorms in very often (not sandy enough) - but my one trip into the Sahara ran into one of these things and they are pretty awesome.
Does the Mojave get these things or is it more rocky than sand ?
My sand filled, 6 year old eyes testify to the Mojave having sand storms. Ah, memories...
Two miles, I tell ya! TWO miles!
Cheers
I don't mean to rain on your parade, but a check of the number of clear days for major cities across the US SW returns a lot of cloudy and partly cloudy days. 16 hours of storage only takes you through the night. If the next day is cloudy, your power station isn't generating. You need more storage than that. The following SW US cities have these numbers of clear, partly cloudy, and fully cloudy days, on average. They are in the area which has the highest potential for solar production in the US, according to http://www.energyatlas.org/.
Tucson is clear 53% of the time.
Tucson AZ, clear days: 193, partly cloudy: 91, cloudy: 81
http://www.cityrating.com/cityweather.asp?city=Tucson
Phoenix is clear 58% of the time.
Phoenix AZ, clear days: 211, partly cloudy: 85, cloudy: 70
http://www.cityrating.com/cityweather.asp?city=Phoenix
Flagstaff is clear 44% of the time.
Flagstaff, AZ, clear days: 162, partly cloudy: 102, cloudy: 102
http://www.cityrating.com/cityweather.asp?city=Flagstaff
Albuquerque is clear 46% of the time.
Albuquerque, NM, clear days: 167, partly cloudy: 111, cloudy: 87
http://www.cityrating.com/cityweather.asp?city=Albuquerque
Roswell is also clear 46% of the time.
Roswell, NM, clear days: 168, partly cloudy: 113, cloudy: 84
http://www.cityrating.com/cityweather.asp?city=Roswell
Las Vegas is clear 58% of the time.
Las Vegas, NV, clear days: 210, partly cloudy: 82, cloudy: 73
http://www.cityrating.com/cityweather.asp?city=Las+Vegas
As you can see, it's a lot more than "a few days."
Nice line about raining on my parade - you've brightened up my evening.
However - you seem to be conflating partly cloudy and cloudy with "no sun", which is more than a bit of stretch.
It's still possible to have 12 hours of sunlight on a "partly cloudy" day.
If you look at some of the technical discussions of the solar thermal plants, you'll find they actually have to dump energy in optimal conditions - they aren't expecting to get the absolute best possible solar exposure at all times.
When selecting appropriate locations (using detailed insolation data) they are looking for places which really do get very reliable sun - not somewhere which gets 130 days of sun per year.
16 hours of storage is more than enough except in rare cases (don't forget, plants don't always generate at peak output - and that includes traditional gas and coal fired power too - they get adjusted up and down to match demand - and there is much less demand at night, weekends and days where the weather is mild).
I think the issue of how much solar intensity decreases during winter is probably more important - which points towards locations closer to the equator - and if you do a plot of all the plants being built, you'll see that is where they are heading (as far as is practical - right on the equator is generally too cloudy).
Ausra already used real climatic data (although they arranged them randomly throughout the year) and found >90% correlation with the national load. If the plants are geographically dispersed then the problem of climatic extremes is reduced. But, it makes sense to be prepared for the worst.
Substantially more storage than 12-16 hours to deal with longer climatic irregularities is suboptimal from an economic viewpoint. If CST is to be the main supplier in the national grid, then it will make more sense to install emergence natural gas heaters (relatively cheap). A strategic natural gas reserve, and the existing natural gas networks could be used for this purpose. A month at full load would be more than enough to survive even the longest cloudy periods. In the future, biogas could be used with modest modifications on infrastructure. The quantity required is very low, just for the occasional emergence, not for regular operation, so this should be quite feasible.
Oh, and dealing with the winter load isn't that big a deal. An east-west axis orientation line focus plant, in a good location, has very consistent seasonal output. Most of the parabolic troughs built in the Mojave were north-south oriented to get a high summer bias, which is good for California, but if CST must provide a large chunk of the national generation then most plants would have to be in the east-west orientation.
Thanks for the feedback.
I agree with the natural gas / biogas backup idea - I guess that is why David Mills is only aiming for 90% of the power supply :-)
Thanks. They did say 100% would be possible if required, but that it would increase the cost a bit.
Now, I don't suggest it's a good idea to rely on solar thermal for 100% of electric needs, but in the hypothetical case that it does happen, it's better to use the backup heaters for this last bit as well, as much less energy would have to be dumped from the array and the occasional week or two of bad weather/sandstorms could be dealt with as well. And most of the existing infrastructure could be used, which is great.
With enough biogas in strategic reserve (use existing/depleted natural gas fields), this is one renewable energy scheme that is actually full proof at a plausibly reasonable cost. And that's rare.
Thank you, this is very interesting information. Unless it is certain that solar produced energy will be effective, then we must not get to enthusiastic about it. I must admit however that if it is realistic , it should be seriosuly considered.I believe, however, that with a few selected locations , this proposal could be successful. Even if solar power only works to take over even 5% of fossil fuel production, it is still better than nothing; considering that it remains feasible. The fact mentioned in the article that solar thermal plants could provide more than 90 percent of current U.S. power demand at prices competitive with coal and natural gas is very interesting. This illustrates that there is potential; espescially considering The fact that other nations are investing in solar energy research as well. Costs are apparently an issue. I believe it is essential for government funding to play a role.This woudl facilitate testing otu whether the proposed solar producing sites would be productive.
I must conclude however that we should give solar energy a try because it has many positives.It can be converted to thermal energy and be used to heat homes, and buildings, relieving stress from other non renewable energy sources. After all, soalr energy is a natural "free" resource that never technically runs out. It is essential to at least try other alternatives in order to elminate this dependence on fossil fuels.