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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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  1.  
    Hi.

    Just wondering. My best this month is 41 degrees c top and base of the tank on the only sunny day this november. I was really pleased, specs are home built controller based on Picaxe micro, one (where usually two would be fitted), evacuated gas glass tube panel and a solar spec tank with a secondary heating coil attached to our wood burning stove.

    Worst so far is 27 degrees bottom tank, 38 top of tank. Not had to fire up the burner yet. This is my first winter with solar hot water and I am really impressed.

    How is your set up doing?
    • CommentAuthorNickiB
    • CommentTimeNov 23rd 2009
     
    Hi Peter - just a quick question - does this supply your hot water - and if so are you finding that those temperatures are supplying hot enough water to bathe/shower/wash up?

    NickiB
    • CommentAuthorNickiB
    • CommentTimeNov 23rd 2009
     
    Just read your heading - so ignore the first question but still interested to hear if you are finding those temperatures ok for your needs...
  2.  
    Hi Nicki

    Sorry about the delay, been insanely busy at CG-e. It does supply the hot water. I would have thought that the top tank temp would be low to use but in practice it is spot on for a shower. It manages 4 short showers a day using a water saving head, (2 am 2 in the evening). Interesting to note when I was in a hotel in Bournmouth recently, I noticed that they had showers that were supposed to be energy saving and the max temp was set to 38 degrees C, which was fine.

    Recovery seems to be about 4 hours in winter back to temps hot enough for a shower.

    The great thing is the tank is warmed from the bottom where the temp difference is greatest. With the solar off, typical december temps are around 12 C for the tank base, today with a little sun, it is 29. When we light the woodburner in the evening, it shoots up to 67 degrees in about 45 minutes. The system then opens a divert valve that moves the hot water into the underfloor heating and radiators, keeping the cottage toasty.

    This uses about 2 sacks of wood offcuts from 4pm to 11pm, (25kg size ex building sand sacks we recylced from the build). (Wood comes from our friendly local builders merchant - untreated offcuts free!).

    Cottage does have min of 3 inches and max of 7 inches (depended on room available) of cellotex on the internal walls and 6 inches in the roof which was the best value for money part of the renovation and conversion to living/working office space. I am not sure this level of heating would be OK for an uninsulated building typical of it's type in Cornwall.

    You have to wonder why solar hot water wasn't mandatory in the last housing boom, image the amount of energy saved compared to completly over the top 24kw gas boilers working to heat water. Seems such a missed opportunity.
  3.  
    Hi Peter - thanks for sharing this data. Encouraging.
    We're looking at a new build in the new year and have designed out any central heating, just putting in a small log burner (with back boiler) for depth of winter. Which means we need to get as much of our DHW needs from solar as we possibly can.
    I'm trying to size the storage tank - and keep coming back to around 175L/200L, twin coil with an immersion top-up.
    I'd be interested in what capacity storage you have in your system and the area of the solar array.

    Hope I can report tank temps myself this time next year !

    Cheers, David
    • CommentAuthorNickiB
    • CommentTimeDec 2nd 2009
     
    Hi Peter - that is very encouraging (for me for the future). At present my shower isn't set up yet so still taking baths - 38 C not hot enough and my woodburner/back boiler is REALLY not working properly. My old cottage is very untoasty and I am envious of those who are!! However I do note that the Solar thermal is making a good contribution to my thermal store (apart from the last few days when the weather has been max 5C during the day) and will start to chart this (at the moment just charting the wood burner effort - or lack of). Will report back myself in due course.

    David - I have a one bed old cottage and have a Stratford Eco boiler which can run up to 5 rads. I have solar thermal panels (would have to look up size) and a Gledhill Torrent thermal store at 210 litres. There is only one of me but system was designed for 2 (for future occupancy). The problem with the stove is just a set/up tweaking problem (I hope!). The cottage area is 68m2. Hope that helps

    Nicki
  4.  
    Good info Nicki, thanks. The tank/store size of around 200L sounds more and more right.
    Two of us looking forward to a new passive build (112m2) but already frugal with water - I didn't want to oversize panels and storage and then not need it."small is beautiful".
    Good luck with the back boiler and stay warm !

    David
    • CommentAuthorNickiB
    • CommentTimeDec 3rd 2009
     
    Hi David

    Plumbers coming this morning - hurrah!!

    One thing I would say is that wood is all important. I wish very much that I had bought in wood in the summer and stored it well (ventilated but with a roof). I will get in wood in the spring this year and have already collected wood (that needs to be chopped up) for next year. It is never too early to get a good stock of wood in. Got to go - plumber here!
    • CommentAuthorJulian
    • CommentTimeDec 3rd 2009
     
    Hi David

    somewhere on here there is a useful discussion of solar cylinders / stores with three coils - two solar coils one in the usual bottom position and one higher. In summer the lower coil can heat the full volume while the poorer solar performance in winter can be diverted to the higher coil which may then be sufficient to give you enough hot enough water for your needs. Depends on your demand and pattern of use but may be worth considering. A too small store will cause stagnation in summer while too large in winter will give you a large volume of tepid water.

    julian
    • CommentAuthorNickiB
    • CommentTimeFeb 24th 2010
     
    Hi GreenPaddy - sorry I never replied to you - apologies. I guess that my post on
    http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=5374&page=1#Item_4
    maybe answers your questions apart from the air intake.

    Did you ever fit an ecoboiler? I ordered mine from Stoves On Line and found them very helpful. Perhaps if you are still pondering about the air intake question you could ask them? I just have a vent by the side of burner if this is what you mean.

    I think that this winter has been such a learning curve and it is ultimately all about the wood. Next winter will be different!
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