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  1.  
    So there I was pondering whether to fit a Willis Solasyphon ( at £305.00 + Vat) or an additional 250 litre solar hot cylinder ( at £400.00 + Vat) in the roofspace.
    And commented to Senior Managment that I would probably go with the evacuated tube system.
    Denise, being an Astro Physist, immediately commented that the panels should track the Sun, and indeed be ground mounted for optimium orientation. Though the amount of plumbing would surely render this impractical
    Is there any such a system, for roof mounting, with a two panel set up and modern microelectronics surely this should be reliable and affordable?
    jat
    M
    • CommentAuthortychwarel
    • CommentTimeMar 24th 2009
     
    in theory tracking may be a good idea. however in the UK something over 70 % of all solar energy input is diffuse
    ie it comes from the entire sky dome with a higher %age in the southern half of the sky.

    therefore for temperate climates just mount it somewhere between SE and SW and between 20 to 50 degrees elevation.
    • CommentAuthorPeter C
    • CommentTimeMar 25th 2009
     
    Hi,

    The Willis works just fine I have one on test for a while now, paid for so no loyalty or obligation to Willis.

    250 litres in the roofspace = around 275 Kg so you may need to increase support under the proposed cylinder.

    The only tracking system I have seen was on a solar PV system, looked more trouble than it would be worth for a domestic thermal system, actually the owner was questioning his own decision as the increased gain was very small which he discovered while waiting for a replacement motor.
    • CommentAuthorMiked2714
    • CommentTimeMar 25th 2009
     
    Evac tubes effectively do track the sun across the sky if mounted vertically, although they don't track the sun up and down in the sky.

    Better to buy a few more tubes than go for any complex tracking.
  2.  
    Thanks guys,
    Specifically Tychware, I had not "figgered" on the diffusion due to cloud
    Second Peter, no worries I would be mounting above a stud wall (or corner of walls ) below,
    hell, I could even mount it directly above a dense masonary 150mm wall ( I think?)
    and Miked, yes I found a neat sketch demonstrating how evac tubes effectively track the sun, neat,
    and erm the missis somewhat exasperatedly said "obviousley it would be cheaper, and simpler and more straightforward " to mount a % more tubes rather than piss around with a tracking system
    doh, bloody physists and their Spockian logic
    I am now attempting to resolve the pros and cons of the two different set ups, I actually have room in the hot press to set another solar hot cylinder beside my existing one, plumbed in parrellel?, ie domestic hot water "teeded" in at the top and cold feed/ thermo syphonic recirculating "teeded" in at the bottom.
    ie copying the Willis Solasyphon plumbing system/diagram
    My "ponder" there is in the winter when the main cylinder is heated by the boiler, I am heating twice as much water, and i do not want to piss around with thermostats , motorised valves etc between the cylinders, but then in the winter we need space heating so this heat is not "lost".
    i am crap at making decisions
    thanks again guys
    cheers
    Marcus
  3.  
    Since, post retirement, I am resolved to finish this build I started in 1996, and before my 60th birthday May 2019.
    I am re-visiting the possibility of a solar domestic hot water install.

    Any recent developments to be aware of?

    Or does a PV installation with surplus electric first dumped into immersion heater(s) make more sense?
    since any un-needed electric can be sold back to the grid, unlike surplus hot water during the summer months.

    I am also toying with the idea of switching to an unvented plumbing system, since our local watermain has now been upgraded, mostly to do away with the cistern in the roofspace, though my existing system is still perfectly functional.

    P.S.
    I searched "solar domestic hot water", and only this and one other post was found.
    marcus
    •  
      CommentAuthordjh
    • CommentTimeApr 8th 2018
     
    Posted By: orangemannotOr does a PV installation with surplus electric first dumped into immersion heater(s) make more sense?

    This, in general. I believe the consensus is that PV is cheaper, but with the caveat that you need a larger area of PV panels to match water-heating panels. So if you have a very limited space available you may be better off with water-heating panels, otherwise go for PV and a diverter as you said.

    I am also toying with the idea of switching to an unvented plumbing system, since our local watermain has now been upgraded, mostly to do away with the cistern in the roofspace, though my existing system is still perfectly functional.

    Unvented does away with the cistern and such things as shower pumps. The plumbing needs to be in good condition to cope with the extra pressure and there's more regulation and maintenance for a pressurised cylinder. I'm not sure I would consider changing over unless I had to rip most of the system out for some other reason.
    •  
      CommentAuthordjh
    • CommentTimeApr 8th 2018
     
    Oh, and planning to install some water-heating panels was what got me started on the green building lark and led to me building an entire house, with mains-pressure water but without water-heating solar! So be careful...
    • CommentAuthortony
    • CommentTimeApr 8th 2018
     
    The economics are changing back in favour of ST already, after March 2019 even more so.

    Domestic PV is less economic now than investing in community schemes.
  4.  
    Tony
    ST = solar thermal, as opposed to PV?

    And needless to say in our leaderless post RHI scandal NI situation.
    the water is even murkier, grant or support wise.
    sigh.

    but, regardless,
    cheers to all the above contributors.

    marcus
    • CommentAuthorTimSmall
    • CommentTimeApr 9th 2018
     
    Also worth considering is PV with a heat pump depending on other aspects of the building etc.
  5.  
    So if I stick with the wet option,
    2 panels, feeding a 210l hot cylinder via a Willis SolaSyphon
    for 3 occupants, for now
    Worcester Bosch, or Grant, both appear to supply complete kits
    or what other brands would be recommended.
    I would be installing myself btw.
    regards
    Marcus
    • CommentAuthortony
    • CommentTimeApr 11th 2018
     
    Evac tubes from Navitron or ecosolar

    Go to a boilermaker and get them to make the perfect cylinder that you need.
  6.  
    Why do I need a boilermaker for a bog-standard run-of-the-mill hot cylinder?
    I could install another indirect cylinder with the DHW draw-off plumbed in series, to harnass the Solar, since there is oodles of room.
    Or a Solasyphon.
    And
    What is the expected life of Evacuated tubes
    And why do neither Worcester Bosh nor Grant supply them, preferring flat plate set-ups?
    10 year ago I was all fired up and keen on the evac tube panels, but understand they degrade/give more trouble than simpler flat plate panels.
    marcus
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