Posted By: Jeff Norton (NZ)

Posted By: DantenzYes ET's visibly change colour when failed. I personally think you can get too wrapped here in what is marginal differences in performance between ET's and FP's. I re-itterate, the energy is free at the end of the day; what's all the fuss about. The extra output ET'S give during lower solar gain on cloudy and colder days amounts to very little averaged over the year.

Please show how? Have you a link to some research?

Yes, there is research into this, please see page 49 of this report: http://www.sp.se/sv/units/energy/Documents/ETk/SP%20rapp%202002-20.pdf

Short Swedish-English vocabulary:

Vacuumrör = ET
Plana = FP
TVV-last = DHW load
Radiatorlast = Radiator load

Please note this report is for a combi system (DHW+space heating). If you're only using 2-4m2 solar panels for hot water it seems pretty irrelavent which type you use as you'll get very little coverage out of them in the winter anyway (you're unlikley to get 100% in the summer even). Assume a 3-4 cloudy summer days, with 200-300l cylinder you'll run out of hotwater even if you're using ET's. If you look at the curves you'll see that you'll need around 9m2 of ET's to get 100% coverage of the DHW in the summer (and probaly a 750l-800l accumulator tank to store the heat).

Some combi boilers will work with hot water going in, it is also possible to thermally mix hot water from the solar and combi to get the solar warmer

Not sure what you mean by is it as cheap as normal way?

If you are going to have solar then you will have to have a hot cylinder yes.

You can now vote for your favourite option. Go to the top of the page in this thread to cast your vote.

efficiency has little meaning in this discussion.

Re the comparative performance issue I agree data are rare. But given that dearth, over on the Navitron forums members (presumably all with evacuated tube systems) post details of their tank temperatures each month. These will be critically dependent on the actual system, particularly the size of the tank relative to the size of the panel, and also the pipe runs, but people are getting surprisingly good results in winter. Perhaps this winter has been unseasonally sunny.
Mike

<blockquote><cite>Posted By: craigstuart</cite>I discovered this website<a rel="nofollow" href="http://www.heatmyhome.co.uk">http://www.heatmyhome.co.uk</a>which says that a DTI study in 2001 showed evacuated tubes to be more efficient. They have a direct feed, which they claim is far more efficient than antifreeze evacuated tubes. Is direct heat more efficient? anyone?</blockquote>

My understanding is that 2nd generation heat pipe evacuated tubes would be more efficient than 1st generation tubes through which the water in the system flows, due to there being a lower volume of water and hence more responsive. Heatpipe / manifold systems still need antifreeze.

Mike

I don't think it's worth voting on a topic that there is inadequate information on: It gives credibility to one solution or the other with no particular scientific basis for doing so.

Clear majority for EV then, but still some solid support for FP,

J

Terry, I think I must be in the FP camp too. Welcome to it - it feels like it is sparsely populated!!

Anyone out there had experience of vulnerability to vandalism? Would FP be more resistant to stones or air rifles than ET? Nick Parsons very tall house would put his FP further from harm than a bungalow; theft could also become a problem on the above as ET are easily replaced and vice versa.

We supply ET and FP, but only really reccomend ET. On our ET systems there is no water in the tubes, so if one gets broken on a 20 tube panel, all you lose is 5% of your heat. This can easily be replaced at your leasure for £15.

If a FP gets a brick thrown at it, that's pretty much the end.

H

Herbal, we've got Schott tubes, and having got 2 'brick hits' (which amazingly only broke the outer skin only) I would now choose the plug-in, Thermomax-type. I was quoted £300 for the relacement of one tube.... I have mixed feelings about the Chinese gear, but was seriously wondering about replacing the whole array with cheap tubes and offering the Schott tubes for sale to others who have been unlucky enough to get theirs vandalised.

Nick

Hi Herbal

Is this information on your company's pricing available anywhere on the net?

Herbal are you bringing the sloar showers to Glasto this year?? If so can i request one just outside my tent?

Could you whisper the info to me instead: Emailing didn't see to work too well!

Rgds

Jon