Solar water heating

PluckaPlucka Posts: 61Registered Users ✭✭
Has anybody used 100 mm [4 inch ] PVC pipe to heat water by solar? I saw it on the side of a caravan and wonder whether it is successful.

Comments

  • BB.BB. Posts: 28,139Super Moderators, Administrators admin
    Was it exposed (no box, painted black or not, no hot water storage tank)? Typically a short shower for camping is ~1.5 to 3 gallons.

    It should work if you want to to heat enough water for shower during the afternoon in direct sunlight... But without insulation/box/storage tank, it won't keep its heat long (I would guess).


    As always, proper design will help... You don't want to mix/circulate cold water into the warm water already there... Either fill, and let gravity empty (and refill). Or if pressurized from trailer water pump, put water in bottom (make sure that you don't just ave a nozzle in the bottom that shoots cold water into the hot water above). And draw hot water from the top (mount pipe vertically).

    If parts are cheap enough (or you have some scrap PVC)--It would be a neat experiment to see how well it works for you.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Posts: 4,764Solar Expert ✭✭✭✭
    3" PVC has about a gallon every 4 feet, so might not need much storage...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • EstragonEstragon Posts: 3,006Registered Users ✭✭✭✭✭
    I'm planning such a system myself, but using extra 1" black poly water line used for water supply, which will be coiled over some black epdm roofing rubber. Using 1" should expose a larger area to sun per volume of water. I have used the hang up camp shower bags, and they heat up nicely in about an hour in full sun, a bit longer in a breeze. I know black water pipe heats up in the sun, but don't know how fast or how hot yet.

    I think the type of plastic pipe used could be important. The type I'll be using is made to handle pressurization (to domestic supply line level , ~150psi) and is fine sitting in the sun. Some types, rigid types made for domestic waste lines, for example, may not stand up to the temperature, pressure, and/or UV exposure involved in a solar water heating application.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mcgivormcgivor Posts: 2,393Solar Expert ✭✭✭✭✭
    Have tried the  " black poly, as well as a black pail left in tropical sun, it was very effective,  sometimes too hot for a shower, nice for camping, but the added price/complexity  of storage, circulation and insulation to retain the heated water, for full time use far exceed the cost/convenience of an instantaneous LPG water heater. Paid $150 for the unit, $10 for 15 Kg of LPG, used over a year and the tank is still heavy. Mind you we are the wet, soap, rince type, not the taking pleasure of actually being somewhere nice and warm for 10 minutes, like I did in Canada  :p
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    900W  3 × 300W No name brand Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal as a backup system. 
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergencies and welding.
  • PluckaPlucka Posts: 61Registered Users ✭✭
    My fishing rods are in a length of 4" PVC pipe and in the sun the pipe gets more than hot enough to have a shower so I've decided to go ahead and use this system as I'm in Australia and I just travel full time following the sun.Thanks for your replies.
  • animattanimatt Posts: 294Solar Expert ✭✭✭
    I agree with mcgivor. I currently have about 2 hundred feet of 3/4 inch irrigation line on my roof. By 10am water is plenty hot. Mid day water needs to be tempered with cold water. It does help that the cold water supply is probably about 80f. Not much extra heat needed. Without extra storage water cools down very fast.
    Tons of ways to heat water with solar each with its own pros and cons.
  • NANOcontrolNANOcontrol Posts: 85Registered Users ✭✭
    Every situation is different. I bought a $365 heat pump add on for electric water heater for my home and my average daily cost is $0.47 a day.  At camp I use PV solar and get all my hot water for $1K and it runs my refrigeration etc.
  • Dave AngeliniDave Angelini Posts: 4,120Solar Expert ✭✭✭✭
    Estragon said:
    I'm planning such a system myself, but using extra 1" black poly water line used for water supply, which will be coiled over some black epdm roofing rubber. Using 1" should expose a larger area to sun per volume of water. I have used the hang up camp shower bags, and they heat up nicely in about an hour in full sun, a bit longer in a breeze. I know black water pipe heats up in the sun, but don't know how fast or how hot yet.

    I think the type of plastic pipe used could be important. The type I'll be using is made to handle pressurization (to domestic supply line level , ~150psi) and is fine sitting in the sun. Some types, rigid types made for domestic waste lines, for example, may not stand up to the temperature, pressure, and/or UV exposure involved in a solar water heating application.
    As you go north you may need to build a proper collector if you use it outside of summer:) Home Depot has Polygal sheets that you can cover the collector box with. I have never used an on demand heater because a proper gas water heater and a collector is just too easy and reliable. The same El Cid pump has been on mine for close to 20 years. You may need copper inside up there for full time living. Just a thought from some of my northern friends living offgrid.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • mcgivormcgivor Posts: 2,393Solar Expert ✭✭✭✭✭
    The performance of on demand water heaters is influenced largely on incoming water temperature, higher BTU ratings are required  the further north, so south, of the equator one is located. My on demand has 3 settings, water temperature, which modulates  water flow, flame, which modulates gas flow and winter, autumn or summer, which determines 1,2 or 3 burner rows. With everything set to minimum it's fine for most of the year. Incoming temperature is generally around 28°C, but I usually shower late at night so ambient has dropped to where that warm feeling is welcome.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    900W  3 × 300W No name brand Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal as a backup system. 
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergencies and welding.
  • EstragonEstragon Posts: 3,006Registered Users ✭✭✭✭✭
    Would definitely need a better collector outside of summer months. My plan is just for use in an outdoor shower initially, so likely just spring/summer use anyway. If I did a preheat for the tankless, it will most likely be electric for opportunity load.

    Copper pipes weren't sloped right etc when I bought the place and burst regularly, so I've replaced it all with pex.

    Interesting about seasonal settings on tankless. I don't think they have such a think in the CDN market - maybe because in most of the country the incoming water is buried deeply for frost so doesn't vary much seasonally.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • PluckaPlucka Posts: 61Registered Users ✭✭
    Moving north in Australia is heading towards hotter days around 80 F + and my system is not under pressure, the high end is left open for the water to expand.If I need a shower I just turn the pump on and plug the shower hose in .The 100 mm [4"] pipes 2 metres [6'6"] long hold about 31 litres [6 gallons].The volume of water to heat is my only worry.I haven't looked at this thought I just had but I am wondering about a 12volt heating element that only runs when the car engine is running [I travel a lot] as a booster. 
  • EstragonEstragon Posts: 3,006Registered Users ✭✭✭✭✭
    Boats use heat from the engine to heat water, rather than making the alternator work harder to do so. FWIW.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Dave AngeliniDave Angelini Posts: 4,120Solar Expert ✭✭✭✭
    edited June 1 #14
    I just hear to many negatives from my clients having to clean on demand water jackets or getting them to work right. Some models are good and others are a PITA. 

     With a tank that is solar heated you can take a shower anytime and not use any gas or electricity. Change the zinc every 7 years or so and it can outlive you.

    Boats can use normal solar ways of heating  water  besides engine heat.  We did not start the engine for months,
    but we do tend to go south...
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • EstragonEstragon Posts: 3,006Registered Users ✭✭✭✭✭
    On demand certainly not a panacea. My Rinnai just had a flow sensor go bad, so $90 for the part and ~2 weeks to get it :-(

    Might have to rig up that outdoor shower quicker than planned.

    I was only pointing out the engine heating of water because OP was thinking of using alternator to power a DC element. Running a standard alternator hot for long periods may not be the best way to do the job.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Dave AngeliniDave Angelini Posts: 4,120Solar Expert ✭✭✭✭
    Yea sorry I get your point :)  That method would require a spare alternator.....

    I think people love the on demand so much because it takes up so little space and can hang on a wall.

     Usually space use is down the list offgrid.  Reliable, low energy, and simple in winter wins every time for me.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • mcgivormcgivor Posts: 2,393Solar Expert ✭✭✭✭✭
    Had a Bosch on demand, heat exchanger failed in 1 year, pin hole leaks apparently pretty common ,  German quality, yeah right, misplaced the reciept no so warranty, replaced with a Rinnai, never had problems in 4 years. My current one is a Mazuma $150, 2 D cells for ignition, no electronics, KISS, the best so far. In Thailand 99% of hot water is on demand, 98.99% electric, the gas units are not popular for reasons unknown, ignorance perhaps.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    900W  3 × 300W No name brand Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal as a backup system. 
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergencies and welding.
  • LucManLucMan Posts: 226Solar Expert ✭✭✭
    The most important thing in any water heater but even more so with on demand is the quality of the water that you put through it.
    High mineral content, acid or alkaline water will shorten the lives of even the stainless steel indirect models. Read the warranty statement it will tell you what the acceptable water conditions are. Avoid Triangle Tube warranty !!!!s.
    You can only flush the on demand HX so many times before they pinhole.
    Test your water before you purchase.
  • EstragonEstragon Posts: 3,006Registered Users ✭✭✭✭✭
    My Rinnai is ~ 5 yrs old. The problem may be partly my fault though. There's an inlet filter I hadn't realized existed, and it got partly blocked and flow reduced. Cleaned it and flow returned, but the sensor wasn't detecting it.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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