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Aloha,

I am in the process of converting my system to solar and was wondering if anyone has experience with 12v pumps, which are the most reliable?  I have 2500 gallon tank with about 2000 gallons water for tilapia and will be pumping up 6 ft.  Thank you for any input....

Loke K.

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The only 12v dc pumps I know of is a bilge pump that are used for boats. They can pump 400 gallons and up, but they wearing out fast for continuous use. Wire-runs for dc systems are not in your favor. Your wires have to be bigger in diameter for dc and runs have to be short as possible for dc .

Why don't you use the solar panel to charge a battery  and hook up a 12 volt dc/ 120 volt ac inverter to it. Then you can run your 120 volt pump. This would be much easier and much better and cheaper in the long run.

Just as a reminder.

If you use the solar panel only and you use a 100 watt pump for example than you would need at least a 300 watt solar panel to get the motor (inductive load) to start.

If you use a battery with conjunction of the solar panel you may get away with a 150 - 200 watt since the battery would provide the extra power needed for the start up when using the same 100 watt motor/pump.

A inverter is about 90% efficient, meaning if you put 100 watt in you will only get 90 watt out.

If you have diffused light from the sun, the output from the solar panel diminish very fast and your pump will stop working.

If you use a solar panel - battery - inverter combination, I would advise that you put a battery monitor on it in case the dc power goes down to either charge the battery with house current or for the pump system getting switched over to the house current directly or you could loose all your fish.

 

Thank you for your input Johann.  After much thought, continuous flow is essential and I agree, solar panels, inverter and batteries is the way to go with generator and house current as backup.

Sorry for the long post but wated to get ths out for anyone who is thinking of going completely off the grid.

 

Going completely off the grid is not cheap!  Energy is the main obstacle to overcome and unless you have a constant raging water source available or constant gale force winds, a way to store energy is essential.

 

As you may have guessed I've been experimenting with switching to total off the grid configuration and went down the path of 12v too. As indicated by Johann, there isn't much out there other than bilge pumps for 12 volts. There are some 24volt pumps too.  I bought several 12 volt bilge pumps to test out, mostly made by Rule. Wow are they rinky dinky and I would not install these on a live system unless I had redundant pumps running (One of the configurations I tested.) Also, the lift capacity on bulge pumps is too small for my application needs. More lift = less flow.

The Rule 12 volt oxygenator pump works great. Probably because the lift is only a couple inches. Aeration galore. I dumped all the compressor based aeration equipment.

 

The second issue I ran into is batteries. First off they are expensive if done right . You can't cycle these things down every night to 10% charge and expect them to last. At most you should run them down is to 75%-80 % of charge to make them last. The better the battery the more the cost.  You can buy high powered 2 volt Surrette (The very best in my Opinion) batteries and put 6 of them together for a price tag of about $ 12,000. yes US dollars. Also they weigh about 250 lbs a piece. (empty).  Depending on your needs of course. 

 

Second they wear out. Especially the cheap ones. The deeper and number of discharges the shorter the life.

 

Third they are toxic to maintain and dispose of. You will need spares because they will fail dead as a hammer and not in the day time either.

 

I ruled out a large use of batteries. Going totally off the grid, my energy design is focused in areas. First of all Don't Use It!. If you don't use it you don't have to generate it. May sound obvious but take a close look at how much electricity you waste and don’t think about it. (subject for another thread) Secondly use a 120 volt system utilizing as much solar energy as possible to store energy with the minimum amount of batteries. 

 

<side note: I do not recommend using a solar system without batteries to buffer the load. demand, surges and clouds happen >

 

Fortunately I am in a location that allows me some flexibility to implement the design, but this design is scalable for smaller applications.  The simplified explanation of how it works is - in the day time the down line sump is emptied by an oversized solar driven pump. Just like an ordinary system. The water is pumped up to a reservoir tank above the fish tank (storing the energy of the day). The water drains from the reservoir via gravity into vertical aeration stand pipes into the fish tank during the day and all night when the pump is not running. The fish tank overflow goes into the grow bed distribution piping and then out into the down line sump waiting for the solar pump to pump it back to the reservoir again. 

 

Zero energy consumption at night and if anything fails it will be in the day time

 

Ball park sizes of each module using a 250 gallon fish tank dictate that the reservoir and the sump be 3000 gallons each at least. This allows for the water in the fish tank to be changed on an hourly basis for 12 hours. The closer to the poles that you live the larger the reservoir, sump and pump will need to be to compensate for the change of seasons. The nearly failsafe oxygenated water supply system for the fish allows to maximize the amount fish in the tank without having to lie awake at night wondering if the pump is going to fail.

 

Sound expensive? For start up it may be , but when you are looking at an alternative of spending $35,000 to bring electricity to a remote site like I am. it looks pretty good to me. In addition, as utility companies continue to install remote control electric disconnect devices to control brown outs and the price of electricity doubles or triples, it may look more and more attractive to you too.  

 

Phase III – Using a horse drawn rig to pump water and/or generate power at night. But that’s a story for the big picture blog.

 

"Zero energy consumption at night and if anything fails it will be in the day time"

Love the idea. A battery bank would still be needed to run the pump on very cloudy days.

A good source of cheap but quality batteries is a forklift repair or rental company. I am running four 6V 370 amp hour batteries that were going to be disposed of. Usually when a battery goes bad they will replace them all. I paid $20 each (which is the core charge) and they have been working flawlessly for months. The cost $280 new.

 

"Ball park sizes of each module using a 250 gallon fish tank dictate that the reservoir and the sump be 3000 gallons each at least"

Wouldn't this lower the concentration of nutrients in the system?

If you are feeding water all day and night you may as well convert that flow into energy also. A quick Google search returned some small water wheel generators that would help keep batteries charged at night. http://www.otherpower.com/otherpower_hydro.html

 

 


Bruce, I did not even think about turning renewable energy into kinetic energy. And then turn around and use this potential energy whenever wanted or needed.

           That is brilliant.

Thank you for your responses. There are some really good 12v pumps, but they are expensive and use more power than the a/c pump. Then the solar pumps are not efficient with clouds and will not be pumping strong consistently. My tank is 2500 gallons and I would have to have a 30000gallon holding tank...not happening. I live in the desert on water catchment, the whole point of recirculating water.

So, the most reasonable solution at this point in time...leasing a grid tie system for
the whole house. This locked in a lower rate for the power and we are producing the power
we use. Now, putting together a back up power system with solar panels, an outback inverter/battery charger and a couple batteries for when power goes out to supply 6 hours of power to start and can be added onto and with adding wind and water power. For now, generator power. After the 6 hours.

Thank you for the link on the mini hydro power. I have been thinking about capturing the energy from the gravity feed. I hope there will be leaps in technology as the necessity is reaching that critical point. I guess we are a part of that aren't we.

My experience is that 12-volt pumps are a waste of time and money for aquaponics.  As previously recommended, go with inverter and AC from solar.

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