[project] solar water heating

chrischris
edited February 2011 in advice
anyone have a system in use, or planned?



i'm starting to plan out a system, and was wondering if anyone had any good ideas that they'd like to share. you can spend a lot of money on these things, but i'm pretty sure that you can easily build up a system yourself, for far less space bucks.

Comments

  • urbansurgeonurbansurgeon
    edited 3:10PM
    annoyingly they aren't compatible with efficient boilers. theoretically you offset the considerable gains you make with free solar heat against the loss of boiler performance.

    in cost terms they are pretty modular so you get the basic ki in and expand when you can.

    you can of course spread a garden hose over your whole roof siphoning off a tank if you want. that's how my in-laws heat their swimming pool.
  • chrischris
    edited 3:10PM
    aren't compatible in what way? wont the boilers only top-up the heat if required? that's what i've seen so far, anyway. are you saying that the efficient boilers dont run at their best when doing that, or is there another reason?
  • urbansurgeonurbansurgeon
    edited 3:10PM
    that's the reason. you are heating water in the tubes (it gets really hot) and then drawing down into a tank. you feed your system off the tank. the tank temp drops and you top up heat as you say.

    the most efficient boilers work on demand with no tank

    i'm not saying you dont make bug savings long run, its just an annoyance, like you've seen, its not easy being green.

    solar heating is the number 1 coice of renewable energy you are going to get in terms of pay-off. wind and solar pv you'd be lucky if its paid for itself in your lifetime.
  • chrischris
    edited 3:10PM
    yeah, i can't see me going PV anytime soon. however - there will be another thread popping up re: wind turbine project in the coming months :D
  • urbansurgeonurbansurgeon
    edited 3:10PM
    ive got some data on my desk at work on domestic wind. ill dig that too.
  • chrischris
    edited 3:10PM
    i know that it wont result in a great deal of energy, but it'll be fun to do, and can't wait for the adoring letters from the planning dept. etc regarding the lack of permission hehe
  • nickonicko
    edited 3:10PM
    We helped Ferroli launch their solar water heating.

    Would not recommend since Ferroli boilers are shit.
  • urbansurgeonurbansurgeon
    edited 3:10PM
    david cameron is axing the need for a permission unless wales is different
  • chrischris
    edited February 2011
    haha is that anything to do with him having a turbine up with no permission, i wonder? :D
  • mickmick
    edited 3:10PM
    since PV is actually getting more efficient and affordable really fast, it would maybe be smart to build in a way that leaves that option open for future installation.

    my copper water jacket on the back of the porch kitchen woodstove is a nice thing, but i still have it only because a few years ago when my house got a new roof, it would have raised my property taxes by a substantial amount to go solar in any way. :( now there's a new initiative and tax breaks. pisser.


    good idea, chris. it's going to be fun to plan (i hope).
  • chrischris
    edited 3:10PM
    well, the PV may happen if grants get better, but there's no way i'm paying out £15k for panels to power the house right now. there are grants (of around £2k) available, but even with that, the payback is faaaar too long to make any kind of sense. i'm not a fooking tree hugger, see, just trying to save some money ;)
  • chrischris
    edited 3:10PM
    (i like trees, and all, but you know...)
  • nickonicko
    edited 3:10PM
    In all seriousness, don't touch that Ferroli system with a bargepole. Have a look what Worcester Bosch or Viessman have :)
  • chrischris
    edited 3:10PM
    well, i already have a boiler, so right now, all i'm really looking for are 2 panels of tubes, and a tank (but the tank may end being bodged from scavenged parts).
  • nickonicko
    edited 3:10PM
    The tank's gonna need two coils... just sayin
  • chrischris
    edited 3:10PM
    yeah. oh wait, it is?
  • chrischris
    edited 3:10PM
    ah right, that can't be a particularly efficient way of heating the water... i thought that there'd be a single coil in the tank, cold feed at the bottom, and a hot 'to boiler / taps' out the top.
  • nickonicko
    edited 3:10PM
    one for the water to circulate from the panel, the other for the boiler
  • chrischris
    edited 3:10PM
    i was expecting something a little more like this -

    image
  • chrischris
    edited 3:10PM

    Heat pipe evacuated-tube collectors

    Heat pipe evacuated tube collectors contain a copper heat pipe, which is attached to an absorber plate, inside a vacuum sealed solar tube. The heat pipe is hollow and the space inside is also evacuated. Inside the heat pipe is a small quantity of liquid, such as alcohol or purified water plus special additives. The vacuum enables the liquid to boil at lower temperatures than it would at normal atmospheric pressure. When sunlight falls the surface of the absorber, the liquid in the heat tube quickly turns to hot vapor and rises to the top of the pipe. Water or glycol, flows through a manifold and picks up the heat. The fluid in the heat pipe condenses and flows back down the tube. This process continues, as long as the sun shines.

    Since there is a "dry" connection between the absorber and the header, installation is much easier than with direct flow collectors. Individual tubes can also be exchanged without emptying the entire system of it's fluid and should one tube break, there is little impact on the complete system.

    Heat pipe collectors must be mounted with a minimum tilt angle of around 25° in order for the internal fluid of the heat pipe to return to the hot absorber.
  • chrischris
    edited 3:10PM
    this is a much nicer looking diagram of how the evacuated tubes work :D

    evacuated tube solar heating
  • nickonicko
    edited 3:10PM
    What type of boiler do you have? Is it a combi or an open vent / system boiler?
  • chrischris
    edited 3:10PM
    it's a combi
  • nickonicko
    edited 3:10PM
    urgh, my bad... you don't need a twin coil system
  • nickonicko
    edited 3:10PM
    always here to help!
  • chrischris
    edited 3:10PM
    ok (it's not a big deal, as i have not starting cobbling yet ;))

    boiler is an alpha cdc35, if that helps in advicerating me :D
  • NightCrawlerNightCrawler
    edited 3:10PM


    Off the grid.
  • chrischris
    edited 3:10PM
    i've recently watched 3 series of 'it's not easy being green', with dick strawbridge. a far more comfortable looking version of that ;)
  • chrischris
    edited 3:10PM
    slightly related: http://www.ted.com/talks/john_hardy_my_green_school_dream.html just came across it this very afternoon. (bloody hippies).
  • zippiezippie
    edited 3:10PM
    urbansurgeon said...david cameron is axing the need for a permission unless wales is different
    Permitted dev rights for renewables was being consulted on in wales last year. GPDO in wales falls under welsh assembly as does the planning framework in wales.
  • urbansurgeonurbansurgeon
    edited 3:10PM
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