View Full Version : A Solar Water Pump

03-27-2010, 09:50 AM
I need to set one up in a wilderness camp. Bathing in the lake with the black caymans is not so much fun anymore, especially after dark... :D

I am looking at an 85 W panel and a Shurflo 8000 water pump. The vendor sells the "kit" for a good price, and claims on his web site that this will work without a battery or a regulator - just wire the panel to the pump and you are done.

My question is: does a pump like that work well within a range of voltages? The panel outputs up to 17.5 volts at peak sunlight. Presumably, that is what the pump will have to handle, and it would then spin faster and pump more water, bypassing the power loss a regulator imposes. Is that correct?

03-27-2010, 10:09 AM
Thanks, Norm.

Well, a solar water pump without battery isn't likely to work in the dark, either! :)

There will be a small water tank to store the water - I guess that is a battery of sorts...

The pump draws 7 amps tops, according to its specs. But we have a regulator and batteries at the camp anyway, for lights and notebooks. Would I lose a lot of energy if I hooked the pump up to the batteries, rather than directly to the panel?

Bear in mind that the 'head' spec of the pump is only 8 feet....

Isn't it more efficient to have it at water level?

03-27-2010, 10:51 AM
Norman, not sure if you covered this but if the pump doesn't get sufficient power to pump the water doesn't it become a heater dumping the electical load as it tries to pump the water but can't do it? I wonder if that has any long term effect on the pump motor.

03-27-2010, 02:22 PM
Yes and no. Until it is primed, the pump is pumping just air, and that's a comparatively lower load on the motor. Yes, energy is being dissipated as heat in the windings. After priming, the windings STILL dissipate energy as heat, but the current goes up because more energy is converted to mechanical energy. More current means more copper loss. A loaded, primed pump will get far hotter than an unloaded/unprimed pump spinning realtively freely, at either a normal, or lower, voltage.

A totally unloaded pump (i.e., no water source, no restrictions in either the inlet or outlet) draws a far lower current.....................

Generally a water pump running without water has other hazards like seal's damage, reduced heat dissipation and excessive vibration etc.

Running off the battery is a good idea because the pump can draw whatever current it needs, without the voltage dropping precipitously (assuming the battery is large enough, that is). Furthermore, the benefit is far greater. A shower pump will only be operated intermittently... but a solar panel will produce power for six or more hours on a sunny day. The total amp-hours consumed out of the battery by the shower pump will be FAR lower than what the solar panel will be capable of providing.

An overhead reservoir can help to take the full advantage without a battery.

George Ray
03-27-2010, 08:25 PM
I would think that one of many supply companies that specialize in 'Off-the-Grid" living would quickly answer these sorts of questions. When Roger Long posted about his boats 12VDC circulation pump for the new diesel heater, the pump links were mostly all to businesses that do solar heat etc etc

03-27-2010, 09:15 PM
You need the overhead storage water tank, painted black to raise the temperature, an interupt switch so that when the water tank is full it shuts down, then use gravity feed to get the shower. The solar panel can feed the battery at all times, the battery can operate the pump at all times that conditions are right. When the energy is not being used to move water, it can be used to charge batteries, cool down a compartment, or any other thing.

03-28-2010, 07:21 AM
... the overhead storage water tank, painted black to raise the temperature...

Not where I'll be. I think I might want to paint it white, and use the spare electrons to run some 12V fans. :D

03-29-2010, 09:22 AM
... 6 gallons of water ... you've got 2-3 decent showers worth of hot water.

Norman, I didn't realize you were French! ;) :D

Seriously, except for late May-June, it is very hot at our camp, and because of bugs we can't run around in shorts and no shirt. By the time we get back from the afternoon surveys just after dusk, we are dreaming of a cool shower. So far it has been accomplished with buckets at the water's edge (the early evening bugs love that maneuver), or through very quick dips into the lake itself, after shining a flashlight around to make sure the big caymans are not too close.

Thanks again, all.

03-29-2010, 09:45 AM
No, and since their eyes reflect it you can locate them in the dark.

03-29-2010, 10:20 AM
wash the 'important parts' first :):):)

Underarms, face, "parts," and c'est fini! :D

We ration water when sailing too - 1000 liters will last us a week with a full boat. But camped next to one of the largest rivers in the world, a full 20 km wide in the rainy season, rationing shower water makes less sense, as long as you have the energy to lift it to head height. I am hoping for Hollywood showers. :cool:

03-29-2010, 12:14 PM
After 2 solo circumnavigations in small boats with very small water reserves...I swore that the next boat would carry more water than fuel.....well it did, sorta.....desalinators had been developed that made them more practical....one of the first "new toys" that I acquired was a desalinator...one of the big ones, that would fill the tanks in an hour or two to the replenishing point.....and then I installed a heater that ran on engine waste heat....and even in the tropics...it felt soooooogoood to be able to turn on the water and soap down and just let the water run..almost as good as the water at the Navy Base in Vietnam..unlimited hot water showers....then stretch out under the ships fans and cool off.

03-29-2010, 06:09 PM
Talk to Donn about this, he uses them as part of his drainage system I think.

03-29-2010, 10:31 PM
Norman- I'd not heard the 1% battery capacity breakpoint for regulators (charge controllers?). Having been advised by "experts," I was going to hook a 55 watt PV panel (17 v. peak) straight to a 1000 amp/hr battery.

So I'm wondering about how you calculate that 1%.

03-30-2010, 07:55 AM
I'm a huge critic of batteries in parallel.... they're a bad idea, for both technical, and strategic reasons.

And here I was, about to set up a bunch of 50 amp batteries in parallel. The advantage is that they are easier to haul around. What is the drawback?

03-31-2010, 11:32 AM
Thanks, Norman. There is smoke coming out of my ears, but I can't understand if what you wrote applies to charging batteries from a solar panel, as opposed to an alternator. Bear in mind I have two panels on the boat as well as in the camp.