Solar Water heating

boisblancboyboisblancboy Solar Expert Posts: 131 ✭✭✭✭✭
I am getting interested in solar water heating and was hoping someone could explain it to me, or give me some links so I could read up on it.

Right now I have LP hot water heater. I also have an outdoor wood furnace to heat my home, but I also use it to heat my hot water so i dont have to use any propane. Though I do use propane once I shut down the wood furnce for the warmer months.

So I was thinking of possibly installing a solar hot water device to further minimize my LP usage.

Thanks for any info!

Comments

  • boisblancboyboisblancboy Solar Expert Posts: 131 ✭✭✭✭✭
    Re: Solar Water heating

    Im having a hard time finding brands and prices of the different types of panels used for heating water, could someone point me in some direction?
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Solar Water heating

    i can't vouch for them, but i got this from a home power mag.
    http://www.butlersunsolutions.com/
  • SlappySlappy Solar Expert Posts: 251 ✭✭✭✭✭✭
    Re: Solar Water heating

    Right now I have LP hot water heater. I also have an outdoor wood furnace to heat my home, but I also use it to heat my hot water so i dont have to use any propane. Though I do use propane once I shut down the wood furnce for the warmer months.

    So I was thinking of possibly installing a solar hot water device to further minimize my LP usage.

    have you thought about building one?
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Solar Water heating

    as slappy said have you thought of building one?
    i would be curious firstly how you intertied the hot water with the wood burning furnace (what kind do you have?) normally you would just substitute the solar hw for the wbhw, but seeing as how you experience freezes that means something to keep it from freezing and breaking even though the wb furnace is providing the heat for the hw. if it's anything like antifreeze that keeps it from freezing them a closedloop system with double walls must be in place so as not to contaminate the pottable water.
    anyway, i'm not one who is expert in it as i know some generalities, but making the panels really wouldn't be as difficult as you may think. all of the other stuff can get complicated though. i made a small solar panel for heating hw and it did ok. the key to mine was to expand the number of pipes used by teeing which slowed the water down to absorb the heat and then recombine them back to a single pipe to go on to whatever it is to be utilized for. i had it against sheet metal and sprayed flat black. i never did get around to putting that small experimental solar wh into an enclosure as i'm quite sure it would have done great. if you're not a good plumber though this may not be for you and there are commercial ones out there.
    my 2 cents worth.
  • EcnerwalEcnerwal Solar Expert Posts: 101 ✭✭
    Re: Solar Water heating

    Good reason NOT to build one would be that you can get the 30% tax credit (in USA) on a system built with SRCC listed components...and the better ones of those use processes that are not easy or possible in a home built, anyway (selective surface black coatings, for instance). Just don't connect to a hot tub or pool (the credit vanishes if you do - so there's the place to homebrew, if you feel you must.)

    Since our host does not delve into hot water, here's some background reading from another source:

    http://howto.altestore.com/Library-Articles/Solar-Air-and-Water-Heating/c29/
  • LucManLucMan Solar Expert Posts: 226 ✭✭✭
    Re: Solar Water heating
    Im having a hard time finding brands and prices of the different types of panels used for heating water, could someone point me in some direction?

    Do a search for Apricus, AET, & Buderus solar ( Bosch), these will get you started in the 3 basic types of collectors.
    Apricus are evacuated tube =more efficient in cold weather = more $.
    AET are flat plate collectors.
    Buderus are a hybrid flat plate collector with argon gas to slow heat loss in cold weather.
    Of course there are numerous other brands but these are the three that come to mind representing the different types.
    Go to the SRCC site to get a list of all the SRCC rated panels & efficiencies.
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Solar Water heating

    A simple way to do it is build yourself a simple flat plate collector, using a preheat tank,,, then your propane or preferably a demand propane heater. Circ water all spring summer and fall,, then drain it when it begins to get too cold.. Guessing at your climate might be late Oct? Most pump controllers have an anti-freeze cycle that runs the pump when the collector gets close to freezing,, circulating water through the collector. Mine will keep the collector from freezing at least until 15f with a 40 mph wind.

    You could also build in a couple of solenoid valves to act as a auto drain with a t-stat control. You need a low point drain which could be a simple automatic underground sprinkler drain valve that opens ~2 psi, closes ~5 psi, a floating ball valve to vent air OUT as the system re-fills, and a solenoid valve that opens to vent to let air IN when the system drains. (A NC washing machine valve can be used,, so it when it energizes it opens, but it doesn't draw current under normal circumstances.

    My collector consist of a wooden box, 2"of foil faced thermax insulation, a piece of 3/16" scrap plate steel, ~150' of 1/2 copper tubing (Probably would do better with 1/4 or 3/8") in a continuos loop, powered by grunfos 7 watt pump and a controller into a surplus electric hot water tank. The collector is covered with scrap used 34X76" patio door glass units that can be had almost free from a local glass shop.

    It isn't perfect,, but the house it is installed on in the Pacific NW gets 30% of it's hot water in the winter,,, almost 100% from April 1 on. Total cost,,,, ~$400 or so,,, but the copper came as scrap so was essentially free,,, as was the steel and the glass. The pump was ~$150 as was the controller.

    Tony
  • boisblancboyboisblancboy Solar Expert Posts: 131 ✭✭✭✭✭
    Re: Solar Water heating
    niel wrote: »
    i would be curious firstly how you intertied the hot water with the wood burning furnace (what kind do you have?)


    I have a Central Boiler which is working on a closed loop system. One small circulation pump and moves the water from the wood furnace to the house and then through a small heat exchanger that I plumbed into the hot water heater(50gal) from there it goes to another heat exchanger, than I placed into the plenum of my forced air furnace(LP), then back out to the wood furnace.

    I also had to install a tempering valve to make sure I didnt recieve 190 degree water to my faucets! I also installed another t-stat for my forced air furnace to just activate the blower.

    Any more questions on it please ask
  • boisblancboyboisblancboy Solar Expert Posts: 131 ✭✭✭✭✭
    Re: Solar Water heating

    Tony, would happen to have a picture of that solar water heater you made? I understand what you used and how it would, but I would like to see it if you would had pictures of it.
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Solar Water heating

    Sorry I don't,, and I am 300 miles away so I won't likely get any soon!

    Picture this (my thousand words!) Build a box out of 2x4's 12' long. (Get two pieces of patio door glass end to end to get the exact dimension). Put a ply wood bottom on the box. (You might consider treated lumber and ply,,, or not!) Cut a piece of 11/2" Foil face thermax foam insulation to fit in the box. Put a piece of flat steel in the box,, the thicker the better. Paint that steel with Barbque paint. Now solder up a string of copper pipe. I did this one years ago and built it with one continuos loop using 180 degree elbows. I have since been told it would be easier and more efficient to build it with manifolds of Tees instead. There is a Tee at the low point with a sprinkler drain valve so that
    when the pressure drops to less than 2 psi the valve opens. It prevents me from having to go on the roof to open a drain in the event of a very bad freeze.

    Drop the loop on the steel,, paint the copper with the same black paint. (This collector sits on a 6/12 pitch roof,,, about right for its latitude. A stub o copper will come out of the box. Connecting to the house plumbing. The house plumbing is a used electric water heater,,, un plugged. The cold water comes into the tank as usual. The water from the collector comes out of the bottom of the tank, (the drain fitting) and thats where one temp probe is,, and then the pump. The other temp probe is in the collector at it's hottest point. These are simple low voltage thermistors that wire with #20 bell wire. The cold side of the thank supplies the cold side of the collector. When the controller calls for pump, because the temp is greater in the collector than in the tank, the pump starts, forcing water into the hot side of the tank. When the house calls for water,, the water flows into the tank at the bottom, forcing the hottest water out and on to the demand water heater that brings it up to proper temp. If the tank is greater than the set temp of the demand,,, the demand doesn't run at all.

    There is a TP relief valve on the tank, and at the collector. I also have a check valve at the collector to keep the warm water in the tank from thermosiphoning backward. There is also automatic air bleed valve at the highest point to allow the air out of the system when it is refilled after draining. This is a simple Taco floating ball valve. When the valve body fills with water, it closes the hole after letting all the air out. Very elegant, very simple. To make it drain properly you have to not only drop the shut off the water, but you have to drop the pressure and introduce air,, so I have a manual valve that I crack, and that lets air in and the whole thing drains out the low point drain on the collector. I have simple bypass valves plumbed in so that I can drain the system in the event of a prolonged freeze or if the owner is away during a potential freeze,,, but still get hot water through the demand system.
    The controller has a number of settings that are field adjustable including Temp difference between the collector and the tank, and an anti freeze cycle temp.

    All in all it works great. One note of caution is if you are going to plumb it with Pex tubing, make sure that you use Pex with an 02 barrier or you will be forced to use a pump and fittings without iron,,, getting expensive.

    Tony
  • boisblancboyboisblancboy Solar Expert Posts: 131 ✭✭✭✭✭
    Re: Solar Water heating

    Very nice!! Sounds like a good sytem. I think I will be able to collect alot of the parts for free.

    thanks for all the pointers everyone
  • mike95490mike95490 Solar Expert Posts: 8,167 ✭✭✭✭✭
    Re: Solar Water heating
    icarus wrote: »
    Sorry I don't,, and I am 300 miles away so I won't likely get any soon!

    Picture this (my thousand words!) Build a box out of 2x4's 12' long. (Get two pieces of patio door glass end to end to get the exact dimension). Put a ply wood bottom on the box. (You might consider treated lumber and ply,,, or not!)

    <snip>

    One note of caution is if you are going to plumb it with Pex tubing, make sure that you use Pex with an 02 barrier or you will be forced to use a pump and fittings without iron,,, getting expensive.

    Tony

    Tony - do you have a website, or schematic & photos of this ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Solar Water heating

    Mike,

    A website??? Surely you jest my good man. I can hardly figure out how to get my pictures out of the camera. I have just learned how to configure them to post here!

    In all seriousness, I will try to come up with some pictures,, and a line drawing schematic. I suppose I could do a line drawing,, scan it (I can't scan it but Susan can!) and then put it up. I'll try to get to it in the next while.

    T
  • EcnerwalEcnerwal Solar Expert Posts: 101 ✭✭
    Re: Solar Water heating
    icarus wrote: »
    Put a piece of flat steel in the box,, the thicker the better. Paint that steel with Barbque paint.

    Polite difference of engineering opinion - thick steel is really not a help here. It adds a lot of thermal mass to the collector, but the collector does not need thermal mass - that's provided by the water tank. A collector with less massive construction heats up faster when the sun starts shining - if you are having a party cloudy day, you may get more hot water from a collector with lower mass. You get fresh hot water sooner in the morning. If you are having continuos sun, it makes less difference, but a lighter collector is easier to mount.
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Solar Water heating

    Ecnerwal,

    You know,, as I was writing that I had the same thought. I was thinking that in the morning it the coils won't warm up until the steel plate warms up! As I thought about it, the question came into my mind was,, if the water can't pull the heat away fast enough,, does the mass hold the heat so that you can pick it up later?

    I have no idea. As with so many DIY projects that are conceived and built by the seat of my pants I haven't really tested them against other options. I would love to build dozens of odd ball ideas and test them against one another,,, but as it stands,, my wife has her limits! I exceed them far too often.

    Tony
  • mike95490mike95490 Solar Expert Posts: 8,167 ✭✭✭✭✭
    Re: Solar Water heating
    icarus wrote: »
    Put a piece of flat steel in the box,, the thicker the better. Paint that steel with Barbque paint.

    Drop the <copper> loop on the steel,, paint the copper with the same black paint

    Why a steel plate? Steel is a poor thermal conductor. I'd think a corrugated metal roof panel would have more surface area. Or a copper sheet (or aluminum) sheet would move more heat into the coils. (copper on copper could be soldered. Copper vs steel also has some electrolysis problems, but being "dry" I guess it wold be OK.

    And the thinnest possible coat of paint, allows more thermal transmission thru the "insulative" paint.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Solar Water heating

    You're right,,, copper would be nice.

    The reality however,,, is in the DIY world scrap steel is cheap, or in this case free. I wonder what would happen if I were to replace the sheet steel with a piece of thin roof steel?

    T

    PS If anyone wants to ship me a sheet of copper ~36"X144" that would be great. I will provide the address,,, although you might have a problem with it to my P/O box!
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Solar Water heating

    a thick mass of sheet metal would not be good. what one would be trying to do is just allow for a type of reverse heat sink, for those that are electronics familiar, that feeds the heat back to the pipe rather than from it and it too will be flat black or whatever method of solar absorption is employed. making it too thick will cause the plate to need to preheat to temp with more heat before much will transfer to the pipe. the use of the same metal being used for the plate makes the chance of galvanic reactions a lesser possibility with copper being a popular metal with good thermal transferring abilities and it's readily available.
    listen to me almost like i know what i'm doing?:roll::p
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Solar Water heating

    A contrary argument MIGHT be made,, that because the pipe and the water can never (almost never) pick up 100% of the heat,, by absorbing it into the plate,,, at the end of the day, the plate allows the pipe to absorb it into the water,, even after the sun has diminished.

    In the case of the system I built,, it takes a while to warm up in the morning,, but it stays on proportionally later. Now the $64k question,,, which would be what is the best way to get the greatest number of btus into the water?,,, which is after all the object of the exercise.

    T
  • summitdwellersummitdweller Solar Expert Posts: 28
    Re: Solar Water heating

    Here is a website for DIY projects http://www.builditsolar.com/ They have a great hot water system you can build for around $1000 if you buy everything. Descibes how to build it in detail.
  • BB.BB. Super Moderators, Administrators Posts: 28,599 admin
    Re: Solar Water heating

    Welcome to the forum Summitdweller!

    www.Builditsolar.com has been recommended here many times--full of worthwhile projects and information.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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