Green Building Forum - Flat panels -vs- Evacuated tube... ...the showdown...

Flat panels -vs- Evacuated tube... ...the showdown...

Herbal — Fri, 11 Apr 2008 17:51:09 +0100

Hi Jon,
Clue is in the address.
H

Flat panels -vs- Evacuated tube... ...the showdown...

Dantenz — Fri, 11 Apr 2008 22:01:28 +0100

Supposed market leader in Evacuated tubes Schott, withdraw their product from market.
Nuff said!!

Flat panels -vs- Evacuated tube... ...the showdown...

jon — Sun, 13 Apr 2008 17:09:38 +0100

OK Herbal

I know the manufacturer I don't know the product type. At this point I think I'll give up the research.

Flat panels -vs- Evacuated tube... ...the showdown...

Herbal — Mon, 14 Apr 2008 14:34:05 +0100

Hi Dantenz,

Schott gave up evacuated tubes because they reccon they couldn't make a profit, which at Â£300 a tube is surprising. ET panels are far more expensive to produce the FP. If the performance was not significantly better, ET manufacturers would not bother going to the extra expense.

Vaillant have stopped tubes because one of their tubes fell off a roof, which is also rather surprising. I suspect that it was a water filled unit without the evapouration tube down the middle, as this makes it virtually impossible to become detatched. They have also therefore gone for the FP option which is cheaper to produce, I think this is more likely to be for financial and marketing reasons as this brings them in line with their competition. People compare like for like.

Jon, it is the 20 x 47mm unit.

H

Flat panels -vs- Evacuated tube... ...the showdown...

antiriad — Thu, 17 Apr 2008 21:24:16 +0100

CommentAuthorJohan CommentTimeMar 9th 2008 quote
Posted By: jon

How long has ET's been available? 10 year? I don't think that's long enough to say they are better then FP's. If in another 10 years the SAME tubes (no replacements!) are still running as good as they are today then you can start comparing them.

Thermomax - started supplying vacuum tubes in 1980 (that makes 28 years history) - Surely that is a long enough track record.

Flat panels -vs- Evacuated tube... ...the showdown...

jon — Thu, 17 Apr 2008 21:39:47 +0100

Flat panels -vs- Evacuated tube... ...the showdown...

Johan — Fri, 18 Apr 2008 09:47:11 +0100

Posted By: antiriadCommentAuthorJohan CommentTimeMar 9th 2008 quote
Posted By: jon

How long has ET's been available? 10 year? I don't think that's long enough to say they are better then FP's. If in another 10 years the SAME tubes (no replacements!) are still running as good as they are today then you can start comparing them.

Thermomax - started supplying vacuum tubes in 1980 (that makes 28 years history) - Surely that is a long enough track record.

Absolutely! Sorry, I wasn't aware they had been in business that long.

Flat panels -vs- Evacuated tube... ...the showdown...

Ebmocarfli — Mon, 28 Apr 2008 16:03:25 +0100

we've had 3banks of schott tubes on the south facing roof of our 1860s tenement for a year or so, but only in occupation since October. It's been the only source of water heating since mid March. Coolest shower temp has been 48deg, but usuall has to have cold added. 215l tank against 250l specified. Worst problem was melting insulation on primary circuit last summer [138dec C]. External temp of replacement heavy duty balck insulation still hot enough to melt insulation of adjacent insulated hW Hep2O circuit & 80C proof pipe inside! Don't thin it can be very good insulation! Installed cost c Â£3k with triple sytem tankimmersion, combi loop & 1y circuit]. Kitchen tap is some 8m from tank [pipe m] and combi is adjacent to sink, but dual feed via reflux valve allows solar heated water to get to sink faster that combi can on a cold start-up. Fully insulatedd HotWater system allows water to remain hot to tap for very useful periods of time.

Seagull droppings generally rmoved by rain.

We haven't calculated paback period. But generally it means not having to remember to turn a fuel using heating system on.

I am working on a 12V pump using a solar recharge to a battery, as I woulkd like to be independent of elec supply to drive the system.

amazed to hear withdrawn from market. Should

Flat panels -vs- Evacuated tube... ...the showdown...

jon — Mon, 28 Apr 2008 20:09:51 +0100

"I am working on a 12V pump using a solar recharge to a battery,"

You might consider using a car pump second hand. You will find suitable pumps in some types of Audi's, Volkswagens, BMWs and the occasional Vauxhall

Flat panels -vs- Evacuated tube... ...the showdown...

Nick Parsons — Mon, 28 Apr 2008 21:27:07 +0100

Update. We've just 'popped a Schott'! We've been hanging on with 2 with the outer skins broken, but on Sat my volunteer noted panel temps of 140 and lots of steam!

They seem so 'user-unfriendly' compared with the heat-pipe type that, notwithstanding my ambivalence over the Chinese tubes, I was seriously considering getting 20 or 30 of those, replacing the whole array and knowing I can DIY replace at any time. Second-hand Scott tubes anyone?

Nick

Flat panels -vs- Evacuated tube... ...the showdown...

walrus — Mon, 05 May 2008 12:51:56 +0100

Horses for course I would say, depends what you want really. FP are reasonably strong and robust, simple too; but need 'gallons of sunshine' - permanently - whats the one thing we ain't got in this country? You all know that................gallons of sunshine!!

Whilst the ET are fragile (Ok its all glass but........) and most importantly don't need 'gallons of sunshine', still needs some mind!

Whatever it all costs money - this energy for free is a myth!! Like a lot of other things! Thought up by salesmen who haven't a clue what they are talking about but need to sell their products! Wether it's solar energy, garden peas or government!

I find our ET's (just coming into their fourth year) work fairly well most of the time - lashings of hot water between say March thro' June to October! Sod all in the winter (despite global warming - another myth)! Ah well we don't bath in the winter (smell a bit), or use loadsa' money on kettles!

So for me, whilst I prefer FP (cos I'm a simple soul) for practical purposes, in this country, it has to be ET's!

Flat panels -vs- Evacuated tube... ...the showdown...

Arnold — Fri, 09 May 2008 11:07:20 +0100

when i bought my FP.in Sept 2006
Navitron was one of the quotes I had which I decided not to take up partly for the fuel miles perspective and I thought they could be at risk of damage from stones etc. at that time It was possible for it to happen.

Also I would not want to get up on roof to replace any damaged ones.

Herbal - stated a cost of Â£15 for a tube,

but did not talk about FITTING CHARGES. I wonder why NOT

The FP I had I was assured had been used in some relatively exposed locations and had stud the test of time.

i am happy with the product, if any one wants to see it in Chester give me a ring on 07791 958983

Arnold

Flat panels -vs- Evacuated tube... ...the showdown...

greenman — Wed, 28 May 2008 16:39:41 +0100

This response may provoke howls of protest, given the views expressed so far, but I feel I have to make it all the same.

I confess I haven't read all 72 comments posted before this one, (I gave up at about 30ish) but the consensus seems to be that ETs are the preferred solution. Whilst I'm sure the heat generating potential of ETs can't be denied, the basis if this poll is presumably to test the balance of thermal efficiency against other factors (including cost of purchase/installation).

I point out that I haven't read all 72 comments because it's possible that my thoughts have already been expressed by someone else, in which case - sorry!

On two previous houses, my father-in-law has installed home-made Flate Plate solar water heaters. In each case, he took a scrap copper water cylinder, cut the top and bottom off, cut down the side and flattened it out. Then he constructed a lattice of copper pipes with a top and bottom rail (outlet/inlet), and soldered/brazed it onto the flat copper panel. The whole assembly was then painted matt black.

He then constructed a wooden case from marine ply, lined it with insulation, placed the copper panel in the box and fitted a perspex cover (though a toughened glass one would have remained clear).

The whole was then plumbed into a dual coil cylinder, and provided all the 'free' hot water a family of four needed for most of the year.

Combining this with a biomass stove with back boiler seems to me to be the best of all worlds, and even scores on the recycling front!

Flat panels -vs- Evacuated tube... ...the showdown...

Ample — Wed, 02 Jul 2008 21:11:52 +0100

Evacuated tube works like a thin radiator - any cloud cover you can see then the temp drops from the controller then the pump stops and starts causing more electricity uses and wear and tear on the pump, is it worth the extra cost? Flat plate is a very good trouble free system no need to change antifreeze as often and has a lot longer life span. Look back at the system that was fitted in the '70S when oil was $100 a barrel and only 15% of houses had solar then. Systems fitted today won't last more than 10years because sales companies over sizing colector area making the system rot away because of high temp within the collector and turning the antifreeze to acid. Those companies that fit filling loops so the end user can fill the systems themself will cause calcium build up in the collectors and blocking the collectors so only little fluid passing though the collector.
Remember - a system is only as good as the company that fitted it.Also solar can contribute to heating and hot water saving up to 60% of your total energy bill, if you want to see how let me know.

Flat panels -vs- Evacuated tube... ...the showdown...

Nick Parsons — Wed, 02 Jul 2008 23:03:38 +0100

From Ample: 'Total energy bill' ? Or total space and water-heating bill? Nevertheless, do tell.

Nick

Flat panels -vs- Evacuated tube... ...the showdown...

Jeff B — Thu, 03 Jul 2008 07:35:22 +0100

Ample -I too would like to hear how, in your experience, solar has contributed to space heating.

Jeff B

Flat panels -vs- Evacuated tube... ...the showdown...

Mantra — Thu, 03 Jul 2008 09:58:51 +0100

Has to be ET for this simple reason. Replacing a vac' tube is as simple as replacing a lightbulb.
No draining of the system. Damage to an FP, replacing that, what does it entail and what are the consequences?
An ET panel can still operate with a couple of tubes out.

Mantra

Flat panels -vs- Evacuated tube... ...the showdown...

greenman — Thu, 03 Jul 2008 10:27:36 +0100

If you think of an FP unit as just a radiator in reverse, surely it's no more complicated to replace than a domestic radiator? Come to that, the home made ones I have experience of didn't need any maintenance, didn't leak, and didn't need to be replaced...

Flat panels -vs- Evacuated tube... ...the showdown...

ludite — Thu, 03 Jul 2008 14:11:02 +0100

Could I just paint some radiators black and put them on my roof, then hook them up to the rest of the 'proper' system - tank and pump etc? Or are manufactured FP specially made for the job and therefore better at collecting the heat?

Flat panels -vs- Evacuated tube... ...the showdown...

tony — Thu, 03 Jul 2008 14:46:05 +0100

You could do that and many have -- it is cheap and it will work, not as well or as efficiently as proper ones but you can have a bit of extra area to compensate.

You would need to have a separate solar circuit and an additional cylinder or twin coil cylinder too but they do that anyway.

Flat panels -vs- Evacuated tube... ...the showdown...

greenman — Thu, 03 Jul 2008 15:35:10 +0100

A compromise is to make your own (as I've described elsewhere) using some copper pipe, and a scrap copper cylinder topped and tailed and split down the side to provide a large piece of copper sheet to act as a backing panel. My father-in-law's dome this twice before and been self sufficient in hot water for at least half the year.

Flat panels -vs- Evacuated tube... ...the showdown...

Ample — Thu, 03 Jul 2008 16:52:55 +0100

Posted By: Nick ParsonsFrom Ample: 'Total energy bill' ? Or total space and water-heating bill? Nevertheless, do tell.

Nick

hi it is what i said 60% Of total energy bill?

Flat panels -vs- Evacuated tube... ...the showdown...

tony — Thu, 03 Jul 2008 17:25:17 +0100

OK then define total energy bill please

Flat panels -vs- Evacuated tube... ...the showdown...

Ample — Thu, 03 Jul 2008 19:12:23 +0100

what ever you use for your heating ie gas,oil,electricity,ground source heat pump,wood pellet -solar will cover all aspects of heating as long as it is a wet system.This what will reduce the annual bill by 60%.

Flat panels -vs- Evacuated tube... ...the showdown...

Ample — Thu, 03 Jul 2008 19:24:39 +0100

i had a comment regarding if flat plate was strong, the glass flexes by 30mm under test condition and a ball bearing is dropped from a meter away- in that case I have a picture with two men standing on a flat plate collector both are 14 stone each; if you would like to see this picture drop me a line.

Flat panels -vs- Evacuated tube... ...the showdown...

Terry — Thu, 03 Jul 2008 19:39:47 +0100

there is a lot of talk about how simple it is to replace an ET vs FP.
Perhaps this is because you do need to replace tubes occasionally

hurriedly ducks for cover

Flat panels -vs- Evacuated tube... ...the showdown...

Nick Parsons — Thu, 03 Jul 2008 19:54:15 +0100

Ample,

Thanks for the clarification. That's 'total space and water-heating bill', not 'total energy bill'. This is not for pedantry, but because so many claims are made without the hearer being sbsolutely sure what the base figure is.

Flat panels -vs- Evacuated tube... ...the showdown...

tony — Thu, 03 Jul 2008 22:27:39 +0100

It is extreemly difficult to supply 40% of heating and hot water from solar thermal panels even using very large thermal stores in homes insulated to better than passivhaus standards.

I do not believe 60% saving -- my ref for this is : "Solar heating systems for houses " Ed Werner Weiss

For average homes in the UK a saving of 60% of hot water costs might be a more reasonable claim to try to make.

Flat panels -vs- Evacuated tube... ...the showdown...

Jeff B — Fri, 04 Jul 2008 09:45:20 +0100

Ample - ok, you have defined what you mean by "total energy bill". How have you managed to achieve a 60% reduction in space heating/DHW production using solar? I only ask because I am in the process of trying to come up with a system which is going for overkill in terms of solar panel area (FP type) with the idea of having some significant contribution from solar during spring and autumn.

Jeff

Flat panels -vs- Evacuated tube... ...the showdown...

tony — Fri, 04 Jul 2008 10:04:27 +0100

borrow my book then

is shows how to use it to help with heating too.