Small solar system for swamp cooler

FreeCoolerFreeCooler Registered Users Posts: 10 ✭✭
Hi All, a complete Solar neophyte. We live out in the boonies and grid power is expensive at around $0.30/kWh. Winter bills are fine but Summer with the swamp cooler going 12-hours a day it almost doubles our monthly bill. It has a 1/3hp pump and 1/15hp circulation pump, all 110vac. Both pumps cycle on and off together, about 20-minutes on and 15 minutes off for about 12-hours. Nights are cool enough to not need it and plenty of sun all day.

I have it all controlled by Arduino's on our home Iot-network I designed, programmed and and built. I am wondering if I could get a car battery (or two) and one of the low cost 12v 100W solar systems for the swamp and maybe add another panel if needed. I could also run a battery charger off the grid overnight if it made sense to do so. I might even make a dual-axis tracker for the panels as I have some old Satellite dish positioners.

We are using rain collected water for the swamp instead of the 600-ft well pump water, and solar power would be a nice addition for free cooling.What's the minimum equipment it would take to do this. I do not want to buy one of the solar-kits as they seem to include stuff I don't need like clips and cables, relays, terminal blocks etc, all well within my skill set to manage. I already have an 800/1200 Watt (run/peak) inverter, I rediscovered it in a shed yesterday and it got me thinking. :)

Thanks for reading this far.

Comments

  • AguarancherAguarancher Solar Expert Posts: 313 ✭✭✭

    I also use swamp cooler for most of my cooling needs in the summer. I have always thought you could use 2 - 12v, variable speed, auto radiator cooling fans, one ea. mounted on either side of the blower housing and a 12v pump all ran directly off of solar panels. You could p-u some larger wattage solar panels off of craigslist and control the voltage with a  linear voltage regulator which are available for cheap on amazon. So during sunlight hours you can run direct off of the solar panels and when you needed, off the grid with the existing 120v motor. Just a pipe dream but in theory it should work..



  • FreeCoolerFreeCooler Registered Users Posts: 10 ✭✭
    edited March 2020 #3

    I have always thought you could use 2 - 12v, variable speed, auto radiator cooling fans



    If the CFM are real CFM then they could be worth a try. The collective Watts is below the 1/3hp too. Our cooler at the outlet is running at about 500-CFM. How well the 12vdc fans will push air through the filter would be interesting to see the resultant CFM.

    Last Summer, I was thinking about replacing the AC motor with a 90vdc I picked up at a swap meet and I could vary the speed rather than cycle. I think it will first come down to relative theoretical efficiencies before spending money though.I'd need a 12vdc circulation pump too.

    The noise level may be a lot higher with the 12vdc fans. I have our fan well-balanced and rubber mounted and it is whisper quiet.

  • FreeCoolerFreeCooler Registered Users Posts: 10 ✭✭

    I also use swamp cooler for most of my cooling needs in the summer. I have always thought you could use 2 - 12v, variable speed, auto radiator cooling fans, one ea. mounted on either side of the blower housing and a 12v pump all ran directly off of solar panels. You could p-u some larger wattage solar panels off of craigslist and control the voltage with a  linear voltage regulator which are available for cheap on amazon. So during sunlight hours you can run direct off of the solar panels and when you needed, off the grid with the existing 120v motor. Just a pipe dream but in theory it should work..



    OK AR, the problems I see are that after laying them out in CAD we would lose about 50% of the swept filter area using 2 x 14" and 2 x 16" fans. Also finding a 12vdc pump at reasonable cost for the 5-GPM flow rate is proving difficult at best.

    We could series two of the fans inside the outlet but that would bring the fan noise inside.

    As a result, I am back at the inverter idea to replace the grid.
  • mike95490mike95490 Solar Expert Posts: 9,459 ✭✭✭✭✭
    1/3 hp, for a 120V pump, will require close to 600w from a pure sine wave inverter, so your solar requirement has now increased to about 800w of harvest, or about 1,000 w of panels.

    Or your mileage may vary.
    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 ,

  • AguarancherAguarancher Solar Expert Posts: 313 ✭✭✭
    @freecooler you are correct about the noise, it would be louder. As for a cheap 12v pump for proof of concept I would use one of these and just throttle back the flow a bit: https://www.amazon.com/SeaSense-600-GPH-Bilge-Pump/dp/B001H1ERBY/ref=sr_1_25?dchild=1&keywords=bilge+pump&qid=1583155240&sr=8-25&th=1&psc=1



  • FreeCoolerFreeCooler Registered Users Posts: 10 ✭✭
    mike95490 said:
    1/3 hp, for a 120V pump, will require close to 600w

    Mike, thanks for the comment, but the 1/3hp motor is for the swamp fan, not a pump!

    One HP is 756-Watts so I am thinking around 250-W should be OK except for 1/3-rd of a second start up in-rush which jumps to about 800-W according to my Tektronics. The inverter I have is rated at 1200-W for 3-seconds in-rush. The water circulation pump is actually less than the 1/15hp I guessed, I have found one rated at 1/30hp for 4gpm which is plenty for circulation.

    How many panels would I need for 300-W?


  • FreeCoolerFreeCooler Registered Users Posts: 10 ✭✭
    cheap 12v pump for proof of concept I would use one of these


    Thanks, I did not see those when I was searching.

  • PhotowhitPhotowhit Solar Expert Posts: 5,697 ✭✭✭✭✭
    I'd quit with the pumps and make a gravity feed system. You could make the whole thing with nothing but a fan to power. I'd drop to a couple 12 volt fans, not sure how large an area you are trying to cool. Or where you are located if a swamp cooler is doing you much good....

    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.
  • mike95490mike95490 Solar Expert Posts: 9,459 ✭✭✭✭✭
    Corrected:
    1/3 hp, for a 120V blower, may require close to 600w, depending on the style of motor.

    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 ,

  • FreeCoolerFreeCooler Registered Users Posts: 10 ✭✭
    mike95490 said:
    1/3 hp, for a 120V blower, may require close to 600w, depending on the style of motor.

    It is a standard 2-speed swamp cooler fan motor from HomeDepot. At a nominal 120vac it draws 4.1A for about 1/3 of a second at start-up, then runs happily on high speed at 2.24A and low speed at 2.1A. All around 300-W. Well below the rated 800W of the inverter and even more so for the peak rating of 1200-W.

    So, can I get an answer to my original question? What is the basic solar set up we need to run the cooler for 12-hours with the duty cycle I stated in in the OP?

  • FreeCoolerFreeCooler Registered Users Posts: 10 ✭✭
    Photowhit said:
    I'd quit with the pumps and make a gravity feed system.

    Thanks, but clearly you do not understand how a swamp circulation system works. The pump is needed to cycle the water from the base-pan to the top of the filter medium. It flows down the medium and abut 8% is used up being evaporated. The remaining 92% falls back to the base-pan.

    A float valve maintains the level with fresh water in the base-pan as water is used in the evaporation process. This accumulates Salts in the base-pan and I have a solenoid valve that my system opens once every hour for 13-seconds. That releases some of the base-pan water to keep Salts concentration to a minimum. I am pretty sure I know what I am doing.


  • mike95490mike95490 Solar Expert Posts: 9,459 ✭✭✭✭✭
    edited March 2020 #13
    so, now it's
    300w for blower, 12 hrs 70% duty cycle
    50w for circ pump, 12 hrs 70% duty cycle ?

    Adjust if needed before I calc it out ?
    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 ,

  • BB.BB. Super Moderators, Administrators Posts: 32,204 admin
    edited March 2020 #14
    I am not sure where the system will be installed (nearest major city)...  Trying Phoenix AZ:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Phoenix
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 57° angle:
    (For best year-round performance)

    JanFebMarAprMayJun
    4.92
     
    5.55
     
    6.45
     
    6.83
     
    6.74
     
    6.57
     
    JulAugSepOctNovDec
    6.08
     
    5.78
     
    6.03
     
    5.82
     
    5.24
     
    4.74
     

    I will use our basic rules of thumb for a reliable/off grid cabin type installation (pull battery bank down ~25% per day, 2 days storage, 50% max discharge)... However, if running in only sunny weather, you might get away with 1/2 the AH capacity of battery bank and safe some money on batteries and solar panels.

    First, sizing the battery bank. Nominally 300 WH @ 12 hours per day on 120 VAC:
    • 300 WH * 12 hours * 1/0.85 AC inverter eff * 2 days storage * 1/0.50 max battery discharge * 1/24 volt battery bank = 706 AH @ 24 volt battery bank
    Next, sizing the solar array for the amount of sun and your location and size of battery bank... From above, choose 5.55 hours of sun per day (Feb thru Oct):
    • 300 WH * 12 hours per day * 1/0.52 over all system eff for off grid * 1/5.55 hours of sun minimum = 1,247 Watt array Feb "break even"
    And based on battery bank capacity... 5% is good for emergency backup power/weekend use... 10% to 13%+ rate of charge for full time off grid use:
    • 706 AH * 29.0 volts charging * 1/0.77 solar panels+charge controller eff * 0.05 rate of charge = 1,329 Watt array minimum
    • 706 AH * 29.0 volts charging * 1/0.77 solar panels+charge controller eff * 0.10 rate of charge = 2,659 Watt array nominal
    • 706 AH * 29.0 volts charging * 1/0.77 solar panels+charge controller eff * 0.13 rate of charge = 3,457 Watt array "typical cost effective maximum"
    If this was a typical "charge during the day", run lights and appliances at night system... Then 706 AH @ 24 AH battery bank and 2,659 Watt array nominal.

    Give this is a "daytime only" system, and you probably will not run much when the sun is behind clouds, then we can try and make some reductions in capacity...

    First, reduce the battery bank to 1 day storage and 50% discharge:
    • 300 WH * 12 hours * 1/0.85 AC inverter eff * 1 day storage * 1/0.50 max battery discharge * 1/24 volt battery bank = 353 AH @ 24 volt battery bank
    Let us guess that would be 4x 6 volt @ 200 AH "golf cart batteries in series * 2 parallel strings or 8 batteries and 24 volts @ 400 AH.

    That takes the nominal charging array to (because of 1/2 battery capacity):
    • 353 AH * 29.0 volts charging * 1/0.77 solar panels+charge controller eff * 0.10 rate of charge = 1,329 Watt array nominal
    We also want to check the size of the battery bank vs the starting current (larger starting loads, larger battery bank needed). Say C/2.5 surge current rating (assuming flooded cell battery bank), and 800 Watts starting loads:
    • 800 Watts * 1/0.85 inverter eff * 2.5 battery surge derating * 1/24 volt battery bank = 98 AH @ 24 volts
    And if you assume the AC inverter can support 2x rated power for starting surge (typical), that would be ~196 AH @ 24 volts minimum.

    From the math, would estimate (SWAG) A 24 volt @ ~196 AH to ~353 AH, and (if using the larger battery bank) something like 1,247 to 1,329 Watt array (larger arrays, solar panels are relatively cheap these days, means "happier batteries" and typically longer life).

    The above are estimates... And anything within 10% (battery AH, solar panel wattage, etc.) is pretty much "dead on" as solar goes. If you choose to go with the minimum battery bank (assuming not much use in cloudy weather, or outside of summer), over sizing the solar array a bit can save you money on the battery bank (longer life because of good charging current).

    Note, if you run mostly "in the summer" (not from February thru October), less tilt on the array (flatter), then you will get more Watt*Hours of harvest in the middle of summer.

    Anyway--The above is a start... Knowing your loads (average Watts, and Watt*Hours per day), you can get a relatively cheap Kill-a-Watt type meter (good for doing general conservation around the home):

    https://www.amazon.com/s?k=kill+a+watt+meter

    Your thoughts?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • FreeCoolerFreeCooler Registered Users Posts: 10 ✭✭
    mike95490 said:
    so, now it's
    300w for blower, 12 hrs 70% duty cycle
    50w for circ pump, 12 hrs 70% duty cycle ?

    Mike, the duty cycle or fan has not changed, only the circulation pump got a bit smaller.
    756 / 3 = 252
    756 / 30 = 25
    Total Watts = 277
    20-mins on and 15-mins off is 58% duty cycle per hour.

    This would only be used for the swamp-cooler and not a big deal if we have to plug it into the grid if batteries are low. Location is Northern AZ.

    I have just been thinking, (ouch) we have an old 10' diameter C-Band-TV dish in the yard that still has a working positioner. I can bolt panels to it then use an Arduino to track the sun with it. If so inclined, I could even change the Azimuth once a week/month with a few turns of a large bolt on the dish.

  • FreeCoolerFreeCooler Registered Users Posts: 10 ✭✭
    edited March 2020 #16
    I am not sure where the system will be installed (nearest major city)...  Trying Phoenix AZ:

    Thanks Bill, I appreciate the effort in your reply. This would only be used for the swamp cooler and not needed at nights. I guess I could build a wind generator for overnight charge too, but may not bother with that. Please see my reply to Mike for updated figures.

    ETA: We are into our 80s so the 6-year cheap FLA/AGM battery life would be about right. LOL
  • Ralph DayRalph Day Solar Expert Posts: 957 ✭✭✭✭
    Old 10' dish is what I have 4 185 watt panels on.  "theanalogueguy" makes good tracking modules.  I have mine  (48volt tracker, available in 12, 24, 48)  running off 12 volts supply .   It moves slowly, but saves the actuator motor.  I used 48 volts originally, but that actuator motor didn't last.

    Ralph
  • FreeCoolerFreeCooler Registered Users Posts: 10 ✭✭
    Ralph Day said:
    Old 10' dish is what I have 4 185 watt panels on.  "theanalogueguy" makes good tracking modules.


    Thanks Ralph, but we can make our own tracker. I have used one of the positioners as a gate opener using an Arduino and nRF24L1 radios. We run the positioner at 36vdc and seems to be lasting well as not a lot of load and only intermittently used.
  • mike95490mike95490 Solar Expert Posts: 9,459 ✭✭✭✭✭
    756 / 3 = 252
    756 / 30 = 25
    Total Watts = 277
    20-mins on and 15-mins off is 58% duty cycle per hour.

    Using your numbers:

    277w x 12hrs = 3324 wh
    3324 wh x .6 = 1994.4 wh consumed.  
       Choose panels that can harvest 2x that amount in your local solar hours. That will likely be very close to what you need. 
    If you get 3 useable sun hours, you need a 800w array.  (Arrays only produce about 80% of nameplate when baking in the sun)




    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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