Siting of panels for solar water heating

On Sat, 18 Nov 2006 01:12:45 GMT, raden wrote:
So stop arguing about this shit and stay with your topic. I post as I see fit, and try to make it reasonable.
Bottom posting when someone leaves the whole bloody thread on top is in my mind the worst crime. If I have done it I don't remember.
Otherwise, unless I get sniped at I live and let live.
OK?

(which, if you hadn't top posted would have been in the correct place to quote)

Which is very little water. A couple of cubic metres. Storage of that water would not be difficult. Obvuously a cube or sphere and all one lump is best for losses. That can be a nuisance.

I'm not convinced it has no place - you would admittedly need a very large additional thermal mass - a ton or two of water probably, to keep the heating on overnight, with a 10-20C drop.
This is not of itself very expensive, though the places it can be easily installed are of course going to be very limited.

John Beardmore wrote:

In message , raden <raden@kateda.org writes In message , John Beardmore writes
What's the pay back time on a new car or a new kitchen ?
No idea in your circumstances, but it is less well defined than solar
Yes - but my point is that for people to make a purchase, it need not be defined at all !
Solar panels have a reasonably well spec'd return
Agreed, but some people buy them for other reasons.
I don't see what my folks signed for as being economically viable
No, but I think our clients divide into at least four categories.
People that want to save the world.
People that like interesting toys.
People that want to set an educational example.
People that want to save money.
All three seem worthy in one respect or another.

The world savers will achieve nothing by fitting solar dhw, as its counterproductive. To understand that they'd need to see the connection between supply & fit cost and the energy input in supplying and fitting it. Very briefly, money is a form of measure of energy. Without financial payback It just wont pay back in energy terms either.
Same is true for those seeking money payback. There are some systems that do pay, but still too many dont.
As for education, I doubt theres a single person on the planet - counting only those in any position to pay for a solar system - who will be educated to any significant extent by seeing 1 more solar system in the world.
There are well desgined systems that pay back, but most purchases still come down to those that fail to properly understand the reasons for purchase.
NT

raden wrote:

In message , SJC writes
Solar thermal panels for space heating is one of the ways we can save lots of fossil fuels in the future.
Sorry, this is UK.d-i-y, not alt.bad jokes
as practical, as they say, as a chocolate teapot
where are you going to get meaningful heat from at 7am ?

from the gas CH system. Why do you think a solar system would have to output heat 24 hrs a day to save fuel?
NT

John Beardmore wrote:

In message , SJC writes
Solar thermal panels for space heating is one of the ways we can save lots of fossil fuels in the future.
I really doubt it !
Cheers, J/.

Whys that?
http://www.builditsolar.com/ & http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm
NT

raden wrote:

In message , Eric Sears phoneme@025379386.for.email.address> writes
Of course, if the panels were for space heating, you might want the greatest input in the morning, in which case the east facing roof might be better. There are a number of factors to consider.
Like ...
what time the sun rises in winter, how big a thermal store you would need to store sufficient heat overnight
it's just not very realistic for heating

A typical brick or block house should be big enough, assuming its decently insulated. Mine doesnt lose a whole lot of temp overnight. One simply sets the solar heating stat to above the temp of the gas CH, make use of that comfort zone.
NT

raden wrote:

(Look ... a contextual reply - the post has a chance to flow)
I have just had a run in with a company who ripped off my parents. Having just done a "fag packet" response, they freely admitted that solar central heating is a non starter for the reasons I stated below (which, if you hadn't top posted would have been in the correct place to quote)
I haven't done any detailed calcs, but they obviously have

Correction, they admitted that their completely unsuitable designed system was a nonstarter for CH - that I would 100% agree with.
NT

Ian Stirling wrote:

In uk.d-i-y John Beardmore wrote: In message , Ian Stirling writes
I think the usual assumption is that the building will have significant thermal mass internally, in the form of an insulated concrete slab, or something.
:)
That's not a standard feature of the solar water heating systems we install. You are getting into the realm of the Hockerton Housing Project design strategy here, but this has been criticised because of the environmental impact if making the concrete. Ultra low thermal capacity buildings also have something to commend them as long as they can dump heat when required.
I'm not convinced it has no place - you would admittedly need a very large additional thermal mass - a ton or two of water probably, to keep the heating on overnight, with a 10-20C drop.
This is not of itself very expensive, though the places it can be easily installed are of course going to be very limited.

This looks very like an assumption trap to me.
A decently designed solar space heating system would not be using water in the first place. Picking hydronic for space heating is pretty much a design death blow.
Secondly, an entirely different method would be used to maintain temp after dark. There is a comfort zone, not just one fixed temp at which people are cosy. Heat to as high in that zone as solar power provides, and you have n hours after sundown of sufficient warmth. N depends on design details.
NT

On 2006-11-18 02:51:00 +0000, John Beardmore said:

In message , raden <raden@kateda.org writes
Solar panels have a reasonably well spec'd return
Agreed, but some people buy them for other reasons.
I don't see what my folks signed for as being economically viable
No, but I think our clients divide into at least four categories.
People that want to save the world.
People that like interesting toys.
People that want to set an educational example.
People that want to save money.
All three seem worthy in one respect or another. Another category may also creep in.
People that follow fashion.

I think that that is probably a fair assessment of reasons to purchase.
I wonder how much the sales people focus on any of the others than the possibility that the customer might save money. Maybe.
In terms of worthiness, I suppose it depends on what one means by worthiness. Incrementalism is a poor argument at the best of times and one might have hoped that people would be smart enough to realise that they won't save the world through installing a solar panel.

Still - I suppose their CO2 is as bad as anybody elses, and every little helps !

Well, hmmm... isn't that Tesco's tag line as they report their latest set of profits?
All of this is focus in completely the wrong area. All the time that the U.S. continues not to make much of a federal effort in terms of emissions control and China is opening a new coal fired power station weekly, all of this other stuff makes so little difference that it is a waste of time on environmental grounds. I would suggest that efforts are turned towards dealing with the major issues, and that does not include getting GW Bush to sign up for silly politicised nonsense like Kyoto, but for serious efforts for change.

John Beardmore wrote:

In message , meow2222@care2.com writes Richard Bates wrote:
First, flat panels give much better ROI than vac tubes
Quick nurse - the tin opener !

heh, yes

Second, British winters are mostly overcast, and flat panels work ok on indirect sun, whereas silvered evacuated tubes work a lot less efficiently under these conditions.
What do you mean by "silvered" ?

outer envelope part silvered to concentrate sun onto the inner tube.

3rd, it is all more complex than that,
:) Quite so !
but suffice it to say that flat panels are very much a going concern in Britain.
Yes.
An optimally designed system would have a mix of both flat panel and vac tube, with each heating a separate part of the system.
Yes - been there, got the T-shirt.
Really they need to be on separate primary circuits.

Yes, thats what I mean. The FP makes warm water, then this goes to the final high temp circuit with ETs.

Flat panel is best for mid-temp water, as it gives much more output per �/$. Vac tube is best for the final max temp water, as it gives high output temps that flat panels cant consistently deliver. However, the ROI on the flat tubes will be much poorer, so spending some of the money on flat panels will much improve total annual output.
Hmmm... Have you seen the prices of the Chinese import ETs ?
To be honest, while what you say was true 10 years ago, the difference in cost per area is now pretty small, and the prices we quote to end users are much the same per area for FP and ET, because while ET is slightly more expensive, installation is easier and safer in lifting and handling terms, if not actually quicker.
Cheers, J/.

I suppose thats true of professional installs on rooftops, I'm thinking more of diy installs, where the cost for a decent area of tubes is way above that of flat panels, and makes a real difference to ROI figures.
Flat panels can give much better performance at ground level or on a flat roof, as 1 or 2 reflectors are easily added to give anything from 1-2 suns. Equipment on a flat roof ditto, mounting the panel either at an angle from roof to wall or else flat on the wall, reflector below.
I guess the ultimate is a 3 zone system, with a drain heat exchanger providing the 1st stage of heat input, flat panels the 2nd (with reflectors for best performance), and vac tubes the last. Perhaps one day the equipment will be cheap enough for this to be the done thing.
NT

On 17 Nov 2006 meow2222@care2.com wrote:

A typical brick or block house should be big enough, assuming its decently insulated. Mine doesnt lose a whole lot of temp overnight. One simply sets the solar heating stat to above the temp of the gas CH, make use of that comfort zone. NT

A house built for solar heat, or any type of efficient heating, should have a triple wall construction, in contrast to present common designs, a well insulated outer wall, a thick masonry wall (concrete block), and either face brick on the inside, or furring strips and plaster (drywall). There are many concrete block houses, but almost all have the block on the outside.
This is as bad as all the industrial buildings having north facing windows.
Joe Fischer

On Sat, Andy Hall wrote:

All of this is focus in completely the wrong area. All the time that the U.S. continues not to make much of a federal effort in terms of emissions control

The federal government doesn't own many fossil fuel power plants. But both the coal industry and the power plants have been spending fortunes cleaning up coal to reduce pollution.

and China is opening a new coal fired power station weekly, all of this other stuff makes so little difference that it is a waste of time on environmental grounds.

There is a lot of USA bashing, but other than the French nuclear industry, I see very little about what other countries are doing to reduce CO2 emissions.

I would suggest that efforts are turned towards dealing with the major issues, and that does not include getting GW Bush to sign up for silly politicised nonsense like Kyoto, but for serious efforts for change.

Actually, the only really viable change can only come from alcohol production from bio sources, there can be some CO2 sequestration but not on the scale that would be needed to make a difference.
Even if the case for CO2 induced global warming could be demonstrated clearly and proven beyond doubt, there is nothing much that can be done without people freezing or giving up income.
There are ways to reduce energy use, like having people move close to where they work, but there isn't a power that can accomplish that.
Retired people could move closer to the equator, and many do, but most can't afford to.
Solar energy is primarily a sub-tropic region energy source, and is not being guided in the right direction. Solar panels on the roof, especially retrofitted, is not a good idea, on walls facing the equator is a much better idea. Just one leak caused by installing panels on the roof, and all the savings for 10 years is lost, roofs don't usually last more than 15 or 20 years, so installing panels on a 10 year old roof is not a good idea.
Bee-hive apartments may be energy efficient with less outside walls, but not everybody is willing to live in an apartment. Really old buildings may be the most difficult to heat, and the trend in the US is larger homes, so nothing is moving in the right direction to save energy. But it is not the US that is most at risk, countries with no energy reserves are in a crisis condition, and have few options but to continue to import almost all their energy needs.
It seems evident that for solar energy to be affordable by the masses, there has to be a large Do-it-Yourself effort, with the right ideas, and a modular approach that can be done a little at a time is better both for time, and the up front cost.
Joe Fischer

On Sat, 18 Nov 2006 04:17:39 -0500, Joe Fischer wrote:
Well, coming from Australia I certainly cannot talk. We are right up there for energy usage.
But a lot of countries might be saying "well we don't need to clean up so much because we simply use /produce less."

There is a lot of USA bashing, but other than the French nuclear industry, I see very little about what other countries are doing to reduce CO2 emissions.

Joe Fischer wrote:

A house built for solar heat, or any type of efficient heating, should have a triple wall construction, in contrast to present common designs, a well insulated outer wall, a thick masonry wall (concrete block), and either face brick on the inside, or furring strips and plaster (drywall). There are many concrete block houses, but almost all have the block on the outside.

Perhaps because the block is much more durable and resistant to the weather than insulation. Myself, I would have to run the numbers but I have a feeling that if you have a well (even super) insulated house then the typical contents of that house, drywall, furniture, collections of brick a brack, would have more than enough thermal mass to do the job.

This is as bad as all the industrial buildings having north facing windows.

There is a good reason for this. South facing windows would have direct sunlight shining in and this would be much too intense and uneven for work. North facing windows, if there are enough of them, provide more than enough diffuse light without 'hot spots'.
Anthony

"Joe Fischer" wrote in message
<snip>

roofs don't usually last more than 15 or 20 years,

WHAT?
Our house was built in 1937 and has its original roof (plus solar water heating panel). Most of the others houses on this estate are the same, the few who have newer roofs have replaced them for reasons other than failure.
Mary