solar well pumps

[out-law biker]

can anyone give some input on these.

 

[Anonymous-0]

We put one out in a pasture this spring. Has about a three foot square panel hooked to a submersible pump. Puts out a steady five gallon a minute. Has a float on it to shut the pump off when the tank is full. So far has been working great. I think it cost somewhere around four thousand dollars for the setup. I am impressed with it.

 

[IH2444]

How far will they lift ? And they just pump to a resivoir tank or do they build/hold pressure ?

 

[farmerdon]

They can do anything you want if you spend enough money. Most are shallow pumps which if I remember my grade 9 science right the theoretical lift is 27 feet but 22 more like it in the real world. Most just pump to a reservoir tank cause its cheaper. Rule of thumb is that you need a minimum of 80 volts to pump water----I have talked to people who did it with less in the heat of the summer but had to add solar capacity in the fall cause not as many hours of sunlight and sun lower in the sky.

 

[Anonymous-0]

I just talked to my boss who has the installation and he said the well is around sixty feet deep. We have it set up to pump into three connected eight hundred gallon tanks. We are not sure if it would build up pressure but I don't see why it wouldn't. It is just like a submersible pump, it just runs off solar electricity. He said if you need more power just add more solar panels. We have it hooked up to a mercury float switch so when the tanks are full it shuts the motor off, otherwise it would pump all the time. It has been running since around May of this year and so far haven't had any trouble with it. I haven't looked on the internet for any information on solar pumps but I would imagine there are some sites that have a lot of information about them.

 

[Anonymous-0]

"Solar" and "well" are two words that basically don't go together. The laws of physics are pretty unbending.

The energy reaching the surface of the earth from the sun is about 1000 watts per square meter (square yard for those metrically challenged) at high noon, with a cloudless sky, in the desert.

Outside the laboratory, the very best solar cells reach about a 30% conversion efficiency, or yield about 300 watts per square meter.

You'll have to take this through an inverter to get AC to run the pump. So figure about 250 watts per square meter of PV cell to be delivered to the pump.

Your typical submersible pump nets out around a 50% efficiency, allowing for loss in the motor and conversion of mechanical energy in to pressure/volume out. So we're looking at a 1/3 HP pump delivering 1/6 HP worth of water pumping. That's not a very big pump.

1 HP = 33000 ft-lb / min, so we can pump 5500 ft-lb per min.

If our water level is 60 feet down we can get
5500 / (60 * 8) or 11 GPM delivered to the surface. Of course, there's no pressure remaining when it hits the surface.

Let's say we'd like 40 PSI so we can run a hose nozzle. Now the total head is 40 / 0.432 + 60 or 152 feet. We'd thus get about 4 GPM at our hose.
Not bad.

But, this is at high noon, with no clouds. At other times of day the sun strikes the panel at a less effective angle and travels through more atmosphere, reducing the average energy input by a factor of 2 or more. Clouds really take a big bite, taking the output down by a factor of 5.

The good news is, this can work, sort of. As a practical matter, you are going to have to have a large storage tank so that you can "pump water when the sun shines". When all the conditions are right and the PV array is really cranking, you fill the tank. When the sun sets, or the sky darkens, the PV array shuts down and you can draw stored water from the tank. If your need for water is intermittent and don't need 5GPM "all day long" it could be a workable system, albeit expensive.

But don't expect the kind of "turn on the tap and don't think about it" performance you'd get from a grid powered 1 HP electric pump.

 

[T_Bone]

Hi out-law biker,

It sure would help us recomend pumping systems if we knew what you were trying to accomplish.

How many gpm? over what time frame? water depth? year around?

It makes a huge difference if your just wanting domestic water or trying to irrigate with it.

T_Bone

 

[Anonymous-0]

well is 240' 80 static to be used at a park for drinking water will use a battery back-up

 

[T_Bone]

Hi outlaw biker,

Here's what I would do.

I'd install a 115vac 1/2hp deep well pump, about $350, then pump that water into a small 100gal cistern, about $150, then use a 3gpm 12vdc RV pump, about $70, to pump water from the cistern to the discharge point. Use a float type pump controller in the cistern, about $35, for controlling the deep well pump on/off. The 12v pump comes with it's own demand pressure switch and can run dry without pump damage.

I would use 4- T-105 Trojan deep cycle battery's (golf kart battery's), about $80eh, to power a 2000w inverter, about $200, that will power the deep well pump, then recharge the battery bank with two 60/70w PV's(solar panel), about $325eh, using a 20a charge controller, about $55, for battery charge regulation. Intall one PV facing East and one PV facing West as then you will not have to use a sun tracker.

The four T-105 battery's are for the short run time high current demand of the inverter. With a 100gal of cistern storage, you will probably only deep pump twice day thus you won't need additional PV's.

If your ouput demand is greater than 70gal/day then you will need a larger cistern. When you say drinking water, I'm thinking drinking fountain(s) and not filling RV fresh water tanks.

T_Bone