# Can you pump wih a 48 v panel

18 Posts
May 12, 2010 03:57 pm
Can you pump wih a 48 v panel

The 48 v thin film panels are low in cost but I want to pump water with a 12v pump.  Can I downcovert the 48v to 12?

10 Posts
May 13, 2010 05:48 pm
Re: Can you pump wih a 48 v panel

Theoretically you can down convert the voltage, but it may require devices that would deplete the money you save by buying the Kaneka panel. Do you know how much wattage you need to run your pump? What kind of pump do you plan to use?

Thanks,

Bramley
Technical Sales
The altE Store

18 Posts
May 14, 2010 12:44 pm
Re: Can you pump wih a 48 v panel

I was planning on using a 12v shurflow pump to pump water to a tank.  the head is around 20-30'.  usage varies and there is a gas pump backup incase more water is needed.

10 Posts
May 18, 2010 12:25 pm
Re: Can you pump wih a 48 v panel

The sizing for the Shurflo above ground pumps can be a little tricky. I'll mention a few words about that before I get to the case of the Kaneka solar panels.

When you look at the chart for one of the Shurflo pumps, the quick and sure way to determine the number of watts required is to multiply the volts of the pump by the highest number of amps the pump could consume. For example, have a look at this pump:

http://www.altestore.com/store/Solar-Water-Pumps/Surface-Pumps/Shurflo-Surface-Pumps/Shurflo-2088-443-144-12V-Std-Surface-Pump/p1088/

According to the chart for that pump, the maximum current draw would be about 9.1 amps. So the 12V version, X 9.1, = 109.2 watts. But you don't want to go looking for a 109 watt panel. First, they don't exist. Second, the watt rating of a given solar panel is the NOMINAL watt rating. For the actual power of a solar panel - in other words, what the panel will operate at in the real world, subtract 20% of the nominal watt rating. Or add 20% to the size pump you are thinking about. In the case of the pump noted above, 109.2 X 1.2 (for 120%) = 131.04 watts. So you need a solar panel at least 131 watts. How much larger than 131 watts can you go? As long as the voltage of the panel or array is compatible with the voltage of the pump (or you are using an LCB to step down the voltage), you can go as over-sized as you want. There is a law of diminishing returns, which as far as I've heard maxes out at with an array about 150% of the watt requirements of the pump.

Getting back to your question about the Kaneka, one 60 watt panel is not enough power for the pump. Would two panels work? That is still not enough IF one calculates the watt needs of the pump based on the highest current it could draw. What if one uses the lowest current it might draw? Then the pump wouldn't need as much power, right? That is correct, and I have three thoughts on that: first, it is a generally established practice in the industry to size PV systems conservatively. Since we are dealing with a variable resource, since clouds can cross the sky and obscure light at inconvenient times, it's always better to have too much PV rather than not enough.

In your case, you have 20-30 feet of lift and an undetermined requirement for flow rate. Is the lift closer to 20 or 30 feet? The higher the lift, the lower the flow rate. Without knowing exactly what you want the pump to do, it's better to size the array to the maximum performance of the pump, which will maximize your chances of being happy with the system. Another thought is that we don't have a lot of experience with the Shurflo pumps. We have charts and math, but not a lot real world experience. I will be performing a series of labs in the coming weeks with the Kyocera 65, 85, and 135 watt panels and the Shurflo pump noted above, so stay tuned for the results.

The final thought I have is that you can do your own experiment and see what happens. Since Kaneka panels use thinfilm technology, you will definitely need to get an LCB, or linear current booster. LCBs manipulate voltage and current to maximize the performance of the system. In the case of 2 Kanekas and a 12 volt pump, the LCB would step down the voltage from the 48 voltage array to the 12 V pump. In doing so, it would boost the current of the panels. I'm confident that with two Kaneka solar panels and an LCB, the pump would move a fair amount of water. But how much and under what conditions? Your best bet is to see for yourself, or use a conservatively sized array that you know will work.

For an LCB that would work with two Kaneka solar panels, look here:

http://www.altestore.com/store/Solar-Water-Pumps/Linear-Current-Boosters-For-Pumps/Solar-Converters-Ppt-48-10A-48V-Linear-Current-Booster/p1360/

If you have any further questions, please let me know.

Sincerely,

Bramley
Technical Sales
altE Store

18 Posts
May 18, 2010 12:54 pm
Re: Can you pump wih a 48 v panel

Bramley,
Very interesting and I thank you for your inputs.  I was under the impression that provided you have a voltage controller so the pump gets the right voltage, it will still pump at a slower rate if the full power or current it would want is supplied.  Granted, we have to get over the head pressure of the 30' which is 13 psi according to

For 20 psi, the pump draws 7a at 12 v = 84w...
at 10 psi, 5.8a x 12= 69w

so yes, you are right, I do need a larger panel, 120-150 would seem to be a minimum.

Thanks

10 Posts
May 19, 2010 10:45 am
Re: Can you pump wih a 48 v panel

Yes, one of the benefits of an LCB is that in low light conditions it will step down the voltage of the solar array in order to increase the current to get the pump moving at least some, when otherwise it wouldn't move at all. It would step down the voltage even if the array voltage were the same as the rated pump voltage. There is a fair amount of wiggle room with many pumps (but not all of them, the Suncentrics being a notable exception) when it comes to adjusting the voltage. So with a 12V pump, it might run at 11 or 10 volts and if an LCB can reduce the array voltage lower to increase the current, and that could make a big difference in overall productivity.

LCBs can also step down the voltage of an array from a much higher voltage to a lower one, like with the Kanekas to a 12V pumps. The concern is that the disparity between volts and amps is so great with thinfilm that it could mean different performance from crystalline PV technology. One of our manufacturers had a project in the works to run a bunch of tests using thin film to run DC-direct pumping systems, but so far they haven't done it. The bottom line is that it's still volts and amps, and if the pump gets enough amps it will move water regardless of where the amps come from. But we just don't have any experience with it.

Thanks for the link to the conversion from vertical lift to PSI. At some point we will post an article on our site about total dynamic head and how to calculate it so our customer will have it to refer to.

Sincerely,

Bramley
Technical Sales
altE Store

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