We currently pump from a pond up a hill to our garden to irrigate it. It's 35' of head from the surface of the pond to the garden. I'm looking at switching out our gas-powered pump to a solar setup. I'd like to do a direct feed system with the panels directly driving a 12V pump. The local farm supply store has a diaphragm pump on sale that will deliver 2gpm with the amount of head I have at 13 amps. Can I just wire it straight to a solar panel without a controller so that it pumps whenever the sun is up, or will that burn up the motor as it tries to start in low sunlight? Can anyone recommend a controller? When I search for one, all I come up with are charge controllers for batteries.
I figure 12V x 13 amps = 156 Watts. Will a 160 Watt panel do, or will I need to go higher? If it's cloudy, I won't need as much water anyways. Thanks for the help.
it s a bit more complex than that. nominal 12V panels will put out around 20V. will the pump handle that? i would prefer not to try.
calculating panel size: most PWM charge controller loose 30% or more of the watts/A. and 160W of panel... that would be in perfect conditions (sun, angle, temperature ...). so you ll need more than that.
i d go for a charge controller and a battery. look for a 20 or 30 A mppt charge controller.
how many hours does the pump need to run per day? how many days will you want to pump even when there s not much sun? multiply the hours(per day) * days of independence * 13A *2 to get the size of the battery bank.
you could wire 2 car batteries parrellel for start and see how it works.
build in some 12V car fuses for added security. and get thicker cables (4mm² +). a multimeter or a voltmeter (a few bucks on ebay) will help to monitor things.
my (very cheap) controller has the option to start the load (pump) in daylight and shut it at night. this will protect batteries when they cycle too deep. it also shuts down the load, when batteries are low.
can you add water storage up that hill? maybe with drip pipes for irrigation? storing water is cheaper than storing electricity.
Look online for solar DC pump boost controller. These are simple and relatively inexpensive controllers that claim to increase pumping capacity by 30%. I assume they overcome the high starting current of electric motors. In my experience, centrifugal pumps are more reliable than diaphragm pumps.
Missouri Wind and Solar has a number of charge controllers and they have videos of using a pond aerator without batteries. It would take a bit more energy to pump water uphill, but it can be done. They do have some programmable charge controllers for wind and solar which might work well for this. The one is designed to run a dump load once the batteries are fully charged. It probably won't work without any battery, but you could likely use a much smaller battery such as the type used in tiny computer UPS's or car battery booster packs to keep the electronics running. Then adjust the settings (engage dump load at a lower voltage, disconnect load from battery at a higher voltage) to run the pump as the dump load from the solar panel(s) instead of the small battery.
From what I understand, a lot of DC motors are not built to withstand a continuous load (3+ hours a day run time). I would either get a good brand DC pump like a SHURflo, or get an A/C motor rated for continuous use and an inverter. It might be more expensive initially, but burning up a bunch of motors not up to the task would be far more expensive and frustrating in the long run.
The starting amperage of a motor is much higher than the amount of current used after it starts running. It might only be a few seconds, but without a sufficient amount of current being supplied it will never start. One interesting thing I have seen is This Video on Supercapacitors. While that particular video shows it being used in a car, he has numerous videos about the supercapacitors and solar energy which are very interesting. If you were to use a programmable charge controller or design your own based on a microcontroller like an Arduino or similar, you could set it up only start once you have sufficient energy and it would allow a small amount of run time in case a few puffy clouds shade the panel for a bit. I personally think this is better for mobile uses instead of stationary because it is lighter and much more expensive to implement, but it is noteworthy as the prices of supercapacitors go down over time.
You could go much further with this and look into systems such as ones available at Open Sprinkler. They have systems based on the Arduino, Raspberry Pi, and more. This takes a bit of learning, but it can make a system that is cheaper and more reliable in the end. Also, there are millions of people out there using these devices and you can usually find someone trying something close enough to your plans that it can be easily adapted.
There are lots of places you can ask for help on this. There are tons of forums and websites that cater to microcontrollers, small computers, off grid gardening and so on where you can find people doing very similar things. I have seen too many YouTube videos on this topic to list here. Do a search there for your keywords like solar, irrigation, and similar. I'm certain you can get a better idea of exactly what you need by checking out those places and most of the people doing it are glad to help.
Trees are our friends
Location: The dry side of Spokane, USDA zone 6ish, 2300' elevation.
E Reimer is barking up the wrong tree if he/she thinks "The centrifugal pumps that could handle the head pressure are considerably more expensive than the diaphragm pumps". A quick, online search reveals a 24V DC pump on EBAY with the following specifications;
Flow at 39ft head is 7 times the flow of the diaphragm pump.
I have used, abused, opened, examined and tried to repair a 5 diaphragm pump similar to the Remco pump from North40. These are positive displacement pumps capable of 100 PSI, 7 bar, 200ft head. Internal bypass is designed to prevent damage if the discharge pressure goes too high e.g. discharge valve turned off. These sort of pumps are very susceptible to damage from fine sediments that can block passages and reduce the bypass pressure. The pump flow, pressure, power characteristics are more flat line compared to a centrifugal. Hence they are used as demand pumps in RVs , spraying, etc. They are not the best pumps to fill a head tank from a pond (take note of the very apt comment from Tobias Ber concerning the cost of storing water and storing electricity).
I invite E Reimer to further consider the relative merits of centrifugal vs diaphragm pumps.
Centrifugal pumps have one moving part (impeller or multiple impellers on the one shaft) compared to to a complex squash plate activating 5 diaphragms.
The starting torque (amps) will be less for a centrifugal pump hence they will start sooner on a solar panel with or without a boost controller
E Reimer might also reconsider his/her firm opinion that submersible is not the way to go. The pump from EBAY was a submersible. Surface mount at the edge of a pond is problematic compared to a submersible floating on the the surface of the pond. Think about the suction line filter, changing pond levels, etc with a shore-mounted pump.
I would definitely consider the option of direct PV to the pump and store the water in an elevated tank, thence feeding the water to the garden and other use points by gravity. This simplifies the design since the battery is eliminated. Only 6 feet or so of head will run drip tape and soaker hoses....this is easy to set up with some cement blocks and a few 300 gallon plastic "totes".....
Location: The dry side of Spokane, USDA zone 6ish, 2300' elevation.
Druce, could you link to that pump? I'm not finding anything like that on Ebay. The gas powered pump I'm using now is a shore mounted centrifugal pump, so I'm familiar with the benefits of the centrifugal pump. What I'm trying to do is make this a simple as possible. I don't want to store water or electricity. I just want to pump directly into the drip lines using a direct feed without batteries while the sun is up. With a low-flow pump (2-3 gal/min), I can divide my garden into 4 zones, water 1 zone each day all day while the sun is up, and get just the right amount of water I need. The reason I don't want a submersible, is because I have to pull the intake periodically to clear the algae that grows in our pond. That seems like it would be harder to do with a pump on the end (though I could be wrong about that).
The surface pumps seem to be much more expensive but the EBAY pump and the Australian pump include the controller. There's much more choice in the submersible range. I see very little difference in protecting the inlet of a surface pump from algae or sediment compared to a submersible. In a pond both would be floated with a largish screen area incorporated into the float. The extra mass of the pump would make little difference to the cost of the floating structure.
Re Pumping Without Storage
You are proposing to pump into drip lines when the sun is shining. That is entirely feasible but have you taken into account the extra pressure (head) required for drip irrigation? Alder suggests that "Only 6 feet or so of head will run drip tape and soaker hoses". I tried to use gravity feed from a head tank of about 10ft but had problems with less than desired flow at the end of the line. I installed a pump (centrifugal) with starting from the irrigation controller and have no problems with uneven watering. I have not done any pressure measurements but have a feeling that you should add another 20ft head to the difference in elevation from the surface of your pond to the elevation of the high point of your garden when you specify the pump duty.
In summary, please consider that I have no direct experience with solar pumping without batteries. With that disclaimer, you will be able to find a supplier of either surface or submersible pump plus controller who could supply an integrated system (with or without panels) but at a price. If you want to save money you must be prepared to source the pump, controller and panels and take the risk of integration. Research of the latter will cost you nothing and may save you a lot. In the final run, surface or submersible may not matter much. In Australia, I could be confident of purchasing the pump (EBAY or direct from China) for USD100, two of 24V panels (assuming 48V motor voltage) secondhand for USD 150. The controller is the unknown factor. I note that most solar panel controllers for pumps are variations on the MPPT controller used for battery charging. These are more sophisticated than I think you would need. The alternative is a linear current booster. These change the output volts to increase amps so motor speed and hence flow will change. If you selected a pump with a wide range of DC voltage input and had excess panel wattage, the controller may not be necessary. Please remember my lack of direct experience. A good controller will undoubtedly increase the reliability and life of your system.
I too noticed low pressure at the ends of my furthest drip lines but rather than go to all the trouble of raising the tanks or putting in another pump, I simply poked more holes in the tape with a needle. It was a small garden......
So, if you truly are against using any water or electricity storage, you will need a pump that is explicitly designed for continuous duty. The Remco pump you linked to states that the "Motor is not equipped with thermal protection" and for this reason I would not choose it. In continuous operation, the pump could overheat (potentially) and blow itself out.
Is 2gpm the ideal flow rate for your application?
There are several ShurFlo pumps that are rated for continuous operation, probably other brands too. Most likely you will need a charge controller to go with your solar panel. As mentioned in another post, this is to control the variable voltage coming out of a "12V" solar panel, which can range up to 20+ V, and normalize it for the pump's use.
Some other questions....how much unobstructed sunshine will the solar panel get per day? This will directly dictate how much water you can transport up to your garden.
Also, what about when the sun is shining and you don't want any more water in the garden? If the pump has a pressure shutoff, then simply having a valve on the hose up by the garden should shut it down.
One thing to also consider, not knowing your climate and weather patterns, is that on cloudy days, the pump won't necessarily just run slower, there simply may not be enough sun to turn it on at all. Take that into consideration.
Finally, with regard to start-up wattage of some pumps, this is negligible on DC pumps, but a serious concern on AC pumps. If you go with direct solar DC you shouldn't have to worry about it.
Location: The dry side of Spokane, USDA zone 6ish, 2300' elevation.
I am curious about your setup? Are you limited only to a pump as the method of moving your water? Is there a pressure requirement for sprinkler system? Space requirements? Alot of farms use a water ram and/or a eductor with check valves to move water.
If you use a method to move your water uphill to a tank then you could use gravity and several different way to distribute your water. I do not full understand the problem on the forum. I was just thinking of all the things out there, that using a solar system to water a garden was overkill.