Solar on houses

[hokie66]

Maybe some of you smart folks in the tech pub can explain for me the logic of placing solar panels on the roof of a house.

There are obvious advantages of centralized power generation, so why would solar be an exception? I suppose it could be because you don't have to transport solar fuel, but is that really enough reason?

Residential solar systems are expensive to buy, install, and maintain. And then, if excess power is generated which could be exported to the grid, the existing grid sometimes can't cope (according to reports I have read).

I wouldn't want panels on my roof. They have limited life, and I imagine require a bit of maintenance during that life. What happens if you need to get at the roof for maintenance? Surely all those penetrations will create some leaks.

Is this all just a political stunt inspired by greenies? Most of these schemes have government subsidies attached at the consumer end, and some have backfired. The manufacturer subsidy end seems to be dodgy as well (Solyndra).

 

[IRstuff]

There's a company that already does that, although it's unclear what their business model looks like, since they only do leases on the panels. I can't remember who I was looking at specifically, but there are a couple others:

http://www.oksolar.com/lion/item/15685

http://www.dowsolar.com/

Of course, none of them are yet competive with roofing tiles.

TTFN

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[Compositepro]

Let's keep in mind that the economics solar photovoltaics is very different than solar hot water. Hot water is a low grade of energy compared to electricity so it can be much more efficient in using solar energy. It is also a major user of energy in homes. The equipment is cheaper than photovoltaics and storage is also relatively cheap and simple. This is not to say that it is economically justified given current energy prices.

 

[patprimmer]

Mike

About 30 years ago I was involved in a project to make a substitute for concrete or earthenware roof tiles from plastic with a solar hot water system incorporated.

It failed because "some toolmakers insist in measuring everything to the 0.0001" and refuse to believe that the concrete tile they measured may vary from others during a run. Three very expensive boat anchors later he still would not accept the concept that clearance can allow for size variations and you need to design around all extremes of the mating objects. He kept thinking he made a wrong allowance for mould shrinkage and could not be convinced otherwise.

Regards
Pat
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[hokie66]

One report of some of the issues with backwards energy flow from solar panels on houses.

http://www.theaustralian.com.au/nat...electricity-grid/story-fn99tjf2-1226165360822

 

[MikeHalloran]

Pat

Sometimes you get a better product out of a toolmaker if you keep him in the dark. If he doesn't know what he's making, he'll be reluctant to make improvements and >might< just follow the print.

;-)


Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

Mike.

It was his product.

Regards
Pat
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[IRstuff]

Sometimes, economics is not an end-all, be-all justification. Medical insurance, seatbelts, etc. are all economically/statistically poor performers unless you live in an area prone to natural events. Otherwise, fire insurance usually is unjustified, economically. Yet, when sh!t happens, that insurance comes in handy. Likewise, just peace of mind can be worth a lot of money.

There are those that think the world is on the brink of chaos (of course, THEY've been saying that for 30 yrs -- they're bound ot be right eventually), so being able to live off-grid might be a REALLY good thing in the coming years of apocalytic collapse of Western civilization.

TTFN

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Chinese prisoner wins Nobel Peace Prize

 

[Demon3]

I don't recall anything "green" that stands up to logical analysis and this is no exception.

Recycling glass makes no sense. Analysis reveals it takes more energy to collect, transport, sort and melt the glass than to go to the beach get sand and make new.

Electric cars make no sense as you just burn coal and oil at the power station to make the electricity so the pollution is just hidden.

Hybrid makes no sense because of the battery manufacture and disposal and you can go buy a VW BlueMotion diesel with better mpg.

and the list goes on...



Chris DeArmitt PhD FRSC CChem

 

[Ron]

Read an article recently about the solar panel boondoggle.

Here's a link...
Solar Doesn't Work

It basically stated that the economic projections of solar benefit have been way overstated and that the payback takes much longer than stated. One significant reason for this is the quick loss of efficiency of the panels...apparently the decline curve is rather rapid.

 

[BigInch]

Ron, While I agree that everything has a useful life, that link is total rubbish IMO. I my due dilligence work on major PV projects, I've found that they will deliver commercially for at least 25 years... MINIMUM. Ultimate life is 35 to even 40 years, but commerical maintenance rates and need for still making a nominal profit make them commercially unfit for service after around 30 years (even when conservatively considering the 0.5% decline in performance figure).

Every reputable mfgr will certify and guarantee their Si crystal panels for 80% at 20 years and probably deliver 90; 95% with the better ones. Fall off rate is nearly linear. All that is from data compiled by major mfgrs that NREL have verified numerous times in their own studies at Los Alamos National Lab. All the investors and banks insist on having the mfgr make and model number with original certifications included in the project's documentation files. In Spain, the government agency responsible for state funding also requires that approved mfgrs be used with guarantee of performance, TUV verified certification, and specially solar-licensed contractors do the installation in order to obtain funding.

Your link is to something written on AOL by God only knows whom; no verifiable study; in it is another link (supposingly to NREL, but that just relinks to the same article) nothing of substance to be found anywhere in your link. Check out all the data and studies available at Los Alamos Solar Lab your self, then tell us what you thinka about that link.

Here's the proof. Try to buy used solar panels. If you don't need profit, don't mind 25-30 year old panels, have minimal power requirements, do your own maintenance and want to put them on your own camp's roof, they will still give useable output.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[Ron]

BigInch...good counterpoints.

My only exposure is the current attempts to use PV for roof membranes. My concern here is that PV is much higher technology than roofers have ever been exposed to. Further, when a leak occurs, you can count on some maintenance guy going out with a bucket of bull (asphalt mastic for the unwashed) and slathering it on a material that will be significantly damaged by it.

As for the efficiency of any of the systems, I have no experience. Thanks for the info.

 

[BigInch]

Another... Solar panels mounted above the roof can cut AC costs simply by the shading effect of keeping the roof cooler, but it does make for hi temp operation.

I think that if there are some common trip-ups on efficiency calculations it could be the temperature factor. The panels are rated at 20[&deg;]C, but will obviously operate much of their life at considerably higher temperatures, perhaps up to 60[&deg;]C or more on some southern rooftops in summer. Also in southern climates, what would be cooler averaging operating temperatures of a colder winter season are not present.

Other reasons ... that private systems will generally invest too much in purchase of the panels alone then attempt to save money on wire diameters, buying cheaper inverters and cheaper lead-acid instead of deep cycle solar system batteries. I think a lot of private sys calculations probably ignore the fact that batteries need to be replaced, but net grid payback can eliminate the need for batteries, which is what I think is the best feature of grid connections. Failure of cheaper inverters was a major cost increaser, but the better mfgrs have doubled their lifetime over the last years. I still think you should not consider that they will last more than 12.5 years, even for the higher priced units. To be conservative, just use only whatever the mfgr will certify as useful life to be safe. It could be as little as 5 yrs.

Efficiency is a very important component of each member of the system and having 90%+ in the panels and 80% in the balance of system doesn't add up to an optimimzed design. 5% efficiency for 20+ years of operations equals a considerable amount of Front End Working Capital and more optimization of the entire system should get more attention than it does.


Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[LionelHutz]

BigInch - A number of inverters are warrantied to 10+ years these days. The big companies doing such aren't likely to disappear in that time either so it's also likely you can collect on that warranty.

Avoiding batteries is a very good idea unless you really need to be off-grid.

 

[BigInch]

Yes I believe so, there were some that were starting to talk about stretching the life range to 10 yrs a couple of years ago. I guess with a few more years of data they figured out that they really could do it.

Oh yes. Let the grid be your battery and you save 30-35% of the capital cost. That will push the payback time down a bunch, unless you live in Spain. One of the things I do not like about living in Spain. Rather than put their money where their mouth is, they will only put their mouth where their money is.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso