What do I have?

3toe
3toe Registered Users Posts: 5 ✭
in Solar Beginners Corner #1
In my garage I have a PMG/DC motor. Label reads Pacific Scientific, 220v dc, 12 amps, 3.2 hp, 2380 rated watts, 3400 rpm. Is it possible to run my hot water heater with this & what else will I need to do it? Thanks
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,637 admin
    #2
    Re: What do I have?

    I am not sure what you are asking for/about... Run the motor as a "DC generator" from a wind turbine/Pelton Wheel or such to heat an electric water heater...

    Or run it as a pump motor to pump hot water through solar thermal panels to heat water for domestic hot water/space heating from solar, battery, or grid power... Or what?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • 3toe
    3toe Registered Users Posts: 5 ✭
    #3
    Re: What do I have?

    If it is running full rpm with an output of 220v dc, that seems like it would be too much for a 12v battery? Also how do I determine the amp draw. I connect an ammeter to the 2 leads of the generator and drive it with a 3/4 hp motor. When I do that its stalls everything. I understand this gererator came from a wind mill in Canada. Thanks.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #4
    Re: What do I have?

    Please explain more clearly what you are trying to achieve. Is this a generator, or a motor? Are you going to use it as a generator? Or a motor? How are you going to heat water? What do a 240vdc and 12 vdc battery have in common and how are you proposing to mix them?

    Tony
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #5
    Re: What do I have?

    Will it supply enough power heat the water you use daily, probably not. Your going to need to spin it faster that 3400 RMPs and for 1+ hours.

    Why it stalled when you went to measure current, is that you needed a load in series with your meter. Right now, you placed a DEAD short across the motor/generator.
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  • 3toe
    3toe Registered Users Posts: 5 ✭
    #6
    Re: What do I have?

    I am sorry for being so vague. What I have in mind is to belt drive this generator by a water wheel to produce enough power to charge a battery bank to heat the water. I am in Florida and a 1000 w 115v element does the job on a 30 gal water heater. I plan to suppy the water wheel with water circulated by a solar water pump. Think it will work? Thanks
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #7
    Re: What do I have?
    3toe wrote: »
    What I have in mind is to belt drive this generator by a water wheel to produce enough power to charge a battery bank to heat the water. I am in Florida and a 1000 w 115v element does the job on a 30 gal water heater. I plan to suppy the water wheel with water circulated by a solar water pump. Think it will work?

    Perpetual Motion ? To get that generator to produce any power, you will have to spin it up to close to it's rated speed/rpm. Very tough to do, it will take 4-6 hp

    And a solar panel pumps the water for the water wheel? Not likely to work the way you plan.

    Best is to use a solar hot water heater. 2nd best is use electric element off your PV, and save the Pump loss (10%) and the motor drive loss (10%) and the water wheel losses (maybe 20%?) and the pumping water pipe friction losses (10%?)
    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 ,

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,637 admin
    #8
    Re: What do I have?

    I am not quite sure--but it sounds like you are building a perpetual motion machine.

    I assume in Florida, you have no large vertical heights for hydro power. And the amount of power required to circulate water should not be very much (few hundred Watts or so?).

    If you want to get 3 HP worth of power from the DC motor powered by a water wheel--you will probably need to drive the water with 6+ HP of a solar power circulation pump.

    You already found that a 3/4 HP motor will not drive a 3 HP generator with a ~1.5 HP electric Load (your 1,000 watt element).

    In general, solar power is a very expensive and low intensity method of generating power.

    Using solar PV Electric Panels to heat a water heater is generally one of the most expensive ways to do it... And to try and create a multiple energy conversion/recovery system is not easy and can have very high losses between mechanical conversion (50% is probably a good conversion factor).

    In our area, with lots of hills and valleys, we have lots of water tanks and pumping stations. To reduce water pressure to consumers in the valley (with tanks on 1,000+ foot hills), they will put turbines in that drop the water pressure and drive motors to feed power back into the grid (energy recovery--just like GT solar).

    Unless you have some large requirement (multi-horse power)--trying to recover energy via this method (if I understand it)--is not going to be easy or efficient.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #9
    Re: What do I have?

    Aside from the perpetual motion aspects of such an idea, why not avoid the middle man and heat your water directly with solar power. You can build a simple flat plate collector, power a circ pump with a ~100 Pv and have more hot water than you can use.

    Converting solar energy into electricity, then back to heat via electrical energy is VERY inefficient, maybe 5%. Direct solar hot water heat might be 35% efficient (WAG) and would be much simpler, and much cheaper!


    Good luck,

    Tony

    Ps Remember, in any heating situation, all you are doing is putting in BTUs into a medium (air/water/etc) It is a simple cals. as to how many BTU's it takes. 30 gallons of water, 50f rise= ~12,000 BTUs. To generate 12k BTUs from Pv takes a lot of Pv capacity.
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #10
    Re: What do I have?
    3toe wrote: »
    I am sorry for being so vague. What I have in mind is to belt drive this generator by a water wheel to produce enough power to charge a battery bank to heat the water. I am in Florida and a 1000 w 115v element does the job on a 30 gal water heater. I plan to suppy the water wheel with water circulated by a solar water pump. Think it will work? Thanks


    Sure it'll work...but it'll be radically inefficient.

    To get 1000w to heat the water, you'll need to supply >1000w of solar to run the pump.

    Second Law of Thermodynamics. In a nutshell, the system itself will consume some of the energy, so no matter how much you put IN, you *will* get less than that OUT.

    http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/seclaw.html
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #11
    Re: What do I have?
    dwh wrote: »
    http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/seclaw.html

    Great link dwh! I've been tryin' to wrap my mind around this principle for years, in an empirical way. This will help.

    Thanks.
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