Instant water heating using solar

SamDSamD Registered Users, Users Awaiting Email Confirmation Posts: 1
edited March 2017 in Solar Beginners Corner #1
I want to understand how I can use solar panel for instant heating of 1 gallon water. The 1 gallon water should be hot in say 30 mins. 

How should I set up the system preferably without a battery? 

Advice from the experts will be highly appreciated. 


Comments

  • dennis461dennis461 Registered Users Posts: 109 ✭✭✭
    I figure you need minimum 665 watts, at 100% efficiency for entire process.
    So, maybe double that number to allow for losses in panels, energy conversion, heat losses of water container, etc.
    You did not mention actual temperature rise you are looking for, are you starting with ice water ?

    Let me know if I guessed closest to your Final Answer :-)

    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
  • PhotowhitPhotowhit Solar Expert Posts: 5,592 ✭✭✭✭✭
    SamD said:
    I want to understand how I can use solar panel for instant heating of 1 gallon water. The 1 gallon water should be hot in say 30 mins. 

    How should I set up the system preferably without a battery? 

    Advice from the experts will be highly appreciated. 



    As Dennis has eluded to there are a LOT of variables!


    So the basic info you need to figure out are;

    2.42 watt required to raise 1 gallon water 1 degree

    Starting temperature of the water.

    Desired temperature of the water, boiling 212, hot shower 110-120, temperature water will burn your hands 140-150.

    Solar panels in direct sunlight angled at 90 degrees to the incoming sun produce about 75% of their panel rating (a 100 watt panel can be expected to produce 75 watt in normal conditions, more in very cold, less in very hot)

    How much heat will be lost in your container, an insulated water heater loses heat very slowly, an aluminum open container will lose much of the heat as you are heating it.

    If you have more info we can give you more info. Solar doesn't do instant and heat very well, suspect you would be happier with gas... but I don't know enough about what you want to do to say that definitively.



    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • BB.BB. Super Moderators, Administrators Posts: 31,771 admin
    edited March 2017 #4
    2.42 watt*hours per gallon per 1 degree F.

    Note, that can be 145 watts for 1 minute or 2.42 watts for 1 hour.

    If you do it with solar thermal. High noon sun is 1,000 watts (roughly 3-5+ hours of sun per day, depending on location, seasons, weather).

    Heating water can be around 50% to 80% efficient with solar thermal.

    Solar electric panels are around 15% or so efficient. You need more square feet or meters with solar electric.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited March 2017 #5
    I agree, about 800 to 250 watts, depending on how hot.    There are some interesting controllers that use fast PWM to directly connect a PV panel to a heating element - while roughly maintaining MPP.

    I am available for custom hardware/firmware development

  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    As Bill points out, using solar directly to heat water is much more efficient than using PV. I used a simple camp shower for years. It heated ~3gals in a couple of hours with just basically a bag laid out in the sun. It could be done faster with a pretty simple system. On my to-do list is an outdoor shower using a coil of back poly pipe as a collector.

    If you need to get to boiling, there are concentrator setups to do it that will be simpler, cheaper, and more portable than a PV system to do the same thing.
    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
  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited March 2017 #7
    On the other hand, if you have to deal with freezing, a pump, controller, etc, then PV might be the simpler and cheaper.

    I am available for custom hardware/firmware development

  • oil pan 4oil pan 4 Solar Expert Posts: 766 ✭✭✭✭
    Use fire.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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