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solardan1959

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Reply with quote  #1 
Don't shoot the messenger, Just repeating what the article is about.  It's still an interesting read.
http://www.greenbuildingadvisor.com/blogs/dept/musings/solar-thermal-dead
Dan

I also think building your own negates a lot of his argument...

Garage_Hermit

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Reply with quote  #2 
Yes to the interesting, Dan, yes, to the provocative,
but a firm "No" to the theory !

(you only need to take a look at this site, to see how much interest PV stirs (or fails to stir...) up...

As a famous member once said, if I may paraphrase him...) "I would not have PV even if I won the lotto tomorrow, and they gave me it for free"

My sentiment exactly.

There's lots of articles like Green Advisor's -- this one for example... but they don't impress me one bit...

http://trueslant.com/oshagraydavidson/2010/07/26/solar-power-at-the-tipping-point/

Personally, I prefer this kind of article:

http://www.richardpresents.com/solar-energy/arguments-against-solar-energy.php

http://www.guardian.co.uk/commentisfree/2010/mar/01/solar-panel-feed-in-tariff

PV is not even a technical debate, IMO, it is "official / political debate".  I suspect it is managed by "interests" that also control our present-day power companies...

The simple truth is, these days folx are gettling rapidly  tired of swallowing the "official line from Central Services".

The interests in question are the same ones that are scared stiff of one thing, in trying to push their PV message, which is that PV is not even good technology !  AND they don't want U to find that out !

PV is bad technology, because it relies on... BATTERIES which are as dirty as industry gets... Yukk, nasty heavy metals, they never go away.
Mercury, Lithium, Lead, Tin, Cobalt, you name it, they are there, and they are indestructible.

As recently seen in the news, batteries are tough cookies to handle - they make plane-makers tremble at the kneees...   Batteries are bad, and replacing them with "modern" batteries is fraught with perils...

PV pushers ("They"), want you to sign up 12 years worth of power bills, to install an expensive technology that will be dead long before that...  PV is about generating cash, period.  A sort of modern-day South Sea bubble.  PV people get rich, because YOU put up front your cherished and hard-to-get dollars, for what is essentially a technological scam!

Fortunately, there is good news is, there is a much better, cleaner and effective technology than PV, namely, CSP, or Concentrating Solar Power, it is *this* that will be the energy of the future.  So don't fork out ANYTHING for PV just yet, hang on a while, and make yourself a nice Solar Thermal installation - lots of good ones on here !
http://tech.groups.yahoo.com/group/SimplySolar/
and especially HERE: http://simplysolar.supporttopics.com/?forum=268122

Solar, yes, electricity, Yes, BUT not from inefficient & dirty PV - nice clean electricity from good old steam turbines like the ones that have served us well for donkey's years ! 

So Bring On the Concentrating Solar Power, derived from prototype Monster Car-Glass City Hub Free Demonstrator Technology (promulgated by yours truly, with technical assistance from a certain sector of the Simply Solar Community...).

http://www.nrel.gov/csp/solarpaces/by_country_detail.cfm/country=ES

G_H

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solardan1959

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Reply with quote  #3 
Boy, poked you good with that one!  I'd love to have a 4K system but just can't stand the price even at the "reduced" prices. But the real question is which works best in the dark solar Thermal or solar PV?
Dan
Garage_Hermit

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Reply with quote  #4 
well, Dan, it says it all here:

http://www.powerfromthesun.net/Book/chapter05/chapter05.html#5.3.3%20Concentrating%20Collectors

Summarising:

Figure 5.7 Performance of a typical flat-plate thermal collector (one glass cover, black-painted absorber, water transfer fluid and ambient temperature 25oC). Curve a) shows the performance as a function of the variable described above. Curve b) and c) for the same collector, show how the output varies with fluid temperature and irradiance. Curves b) and c) are derived from curve a).

(flat plate collector: efficiency 70 to 75%)

Figure 5.8 Collector efficiency for a typical parabolic trough and a typical parabolic dish collector.

(parabolic efficiency = 90%)


Figure 5.9 Photovoltaic panel efficiency at different levels of solar irradiance. Data shown are for a cell temperature of 25 oC and an air mass of 1.5.

(PV efficiency = under 13 %)

Conclusion:  Your Tin Roof (or my Slate Roof...) are FAR more efficient than PV !

but quite a bit less efficient than a parabolic cocnentrating collector.

On balance, I'll stick with my existing system, for all its faults !

It is cheap, clean, healthy, does not destroy the planet, is suited to my requirements, requires NO capital outlay, no politics, no hidden costs, no hassle, basically ZERO maintenance (apart from normal roof maintenance).

Need any more persuation ?

Best Solar Regards,

G_H





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stmbtwle

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Reply with quote  #5 
I can see a few problems:

Yes, most of the interest on this forum is about solar thermal... building a PV panel is beyond the skills of the average home handyman, and therefore the forum IS more attuned to thermal, so considering this forum as "representative" of the solar industry as a whole is rather inaccurate.   

Unless you're off-grid, batteries are NOT required.  If you're grid-tied which most PV systems are, you use the utility for your "battery", for pretty much only the cost of the connection.  Electric utilities are going to be around for a LONG time, a lot longer than any battery you can buy.  

Most folks aren't in a position to build/install their own systems, they're going to have to pay someone else to do it at retail.  So the "savings" of thermal aren't as great overall as some may think.

Aside from heating, what good is solar thermal?  It won't run my washing machine or my air conditioner.  For that I still need electricity, which I can get from my grid-tied PV system any time I want (yes, even at night, from the grid).

Agreed, thermal collectors ARE more efficient, but if you produce more than you can use, what do you do with the excess?  You can't pump it back upstream for a credit or sell it to someone else...  What you don't use is wasted, and that knocks your theoretical efficiency in the head.   And in most cases you can't use it to generate electricity.   Concentrating solar can, but it only works well in certain parts of the world where you have a clear sky.  Clouds and haze really screw up your "concentration".  PV, not so much.  If someone can come up with a way to generate electricity from the "low-grade" heat from a flat-plate collector, they'll have something, but most engineers will tell you it's horribly inefficient and not cost-effective.  When push comes to shove, the only "efficiency" that really matters is COST efficiency.

Solar thermal is about where it was 50-100 years ago; PV is progressing all the time.  It can not only heat my water but run my air conditioner, my TV, this computer, and my electric car if I had one.  It even keeps my beer cold.  Thermal pretty much only heats my water, and when it has reached its max temperature it shuts off.  PV has no moving parts, it just sits there and churns out the watts day after day.  What I don't use goes up the line and I get credited for it.   

I don't consider myself an expert but I don't think I'm a novice either; I have 3 separate PV systems and 2 thermal systems.  IMO there is a place for both, but I think PV has a "brighter" future.   Only time and the marketplace will tell.

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Willie, Tampa Bay
solardan1959

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Reply with quote  #6 
stmbtwle,
   If you back to the first post, which I made, I said:
Quote:
I also think building your own negates a lot of his argument...


   While many of us focus on solar thermal because we can't build solar cells, very few of us would not have an array of solar panels if we could build them as cheaply and wire them up ourselves.  Even buying the cells and making your own panels is not a cheap or easy endeavor and the invertors themselves for grid feedback are pretty expensive also.  I agree with everything you say except when an EMP or solar flare takes out the grid and all your electronics a solar thermal panel and woodstove will come in real handy. (I will miss my TV though)

Hopefully someday they will go the way of the 700 dollar VCR and 1500 dollar XT computer and come down to a reasonable level so we can all get into the game.  (or somebody will come up with another way to make cheap power)

Dan
stmbtwle

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Reply with quote  #7 
I agree the grid-tie can be the weak point.   It's a safety issue, but still... 

I THINK that a grid-tie inverter would work off-grid if you disconnected from the grid and could backfeed it with an appropriate signal, say from a small battery-based 240v inverter.  However small 240v, 60hz inverters are not common, and probably not cheap.  Then there's the problem of suppose you get the system up and running, the panels are churning out the watts, the air conditioning is running and you're happy as a clam and suddenly a cloud drifts by.  The solar array will shut down and the little "backfeed" inverter is going to choke under the sudden load. 

I have thought about installing a battery backup system, but so far I haven't seen the need. Even with all the dire warnings about solar flares, EMP etc, commercial power is pretty darn reliable and what outages I do experience are few and far between.  What concerns me more is a hurricane doing major damage that could take weeks to repair.  Iin that case my roof-mounted array would probably be damaged and inoperable anyway, as would a solar concentrator.

For those that are really concerned, there's always the gas/diesel/propane backup generator (which will also power your TV).  In my case I'll simply move down to the boat, which has it's own battery-based solar array (assuming it's not sunk). 

A thermal collector would be pretty useless to me in hurricane season, as would a wood stove.  We already have more heat than we know what to do with!

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Willie, Tampa Bay
solardan1959

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Reply with quote  #8 
stmbtwle,
  Ah, boats, hurricanes, and other generally warm, well hot weather issues.  Maybe it's the 8 months of sub 70, and 5 months of sub 50 temps, that have me focusing more on heat type products.  In my case the sun probably shines less than 50% also so a larger array may also be required.  Still I'd love to have a 5k system but at current levels I don't feel the payback is worth it.  And your probably right, a generator is probably a better investment over a battery system. 
  As utility cost rise and panels drop I'm sure more of us will join you.
Thanks, Dan
stmbtwle

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Reply with quote  #9 
That's kind of where we are today. Unless you can build your own, solar is still too expensive for most of us. I was fortunate that I had enough equity in my home that I could finance my system. But as energy prices continue to rise while equipment prices fall, solar of whatever type is getting more attractive. Eventually we'll hit the breakover point ant it wiill take off.
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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
KevinH

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Reply with quote  #10 
I had not seen those heat pump water heaters before.  http://energy.gov/energysaver/articles/heat-pump-water-heaters

For me, none of the solar water heating solutions would make sense.  Subtracting the $8 to be connected to natural gas, my cost to heat water is well under $10 per month so it would take a very long time to pay back the investment.

Regarding solar thermal "if you produce more than you can use, what do you do with the excess?", I think most of us here would love to have that problem.

I would like to try PV some day, especially if I built a new house, but I would want to be able to do at least part of the installation.

Kevin H
MN
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