I was looking for a little electronic circut help, and I realized that you guys were the experts so I came here.

I am trying to figure out a way that I can make a solar arrangement to capture the most power. I work for a company that makes chemical injection pumps for energy production. Recently, we started using solar panels to provide the power to run DC motors. So far, we have had good results, but we are having to use massive solar arrangements and large battery banks to acheive any sort of autonomy. It occured to me that maybe we were not capturing all of the power provided by our panels into our battery banks.

For instance, if the batteries were 90% charged, and the solar panels were not producing power over that amount, would they charge the batteries at all? Would it help to add an inline diode/capacitor to force what ever power was absorbed into the batteries?

If you have any thoughts, I would love to hear them.

Thanks,
Kirk

 

A little info would help. What size (watts) solar panel do you have?
What voltage ?
What battery (lead acid-AH rating- deep cycle)
What is the load (amps), and how long is it running?

 

Thank you for your reply Gerty,

We are using Kyocera panels about 2' x 3' / 22.1V/8.37A and 12Vgel cell 265Ah batteries. The motors ideally need to run constantly as to not disrupt production and are under loads that vary widely. It can range from 1.23A to 13.65A.

We do many arrangements that can vary from two pannels, three batteries to twelve panels, seven batteries. According to the data that we have and the numbers that I have run, we should get four or five days of autonomy, but in reality, I am getting two and a half to three days. This is what leads me to believe that we are not capturing power once it is a little overcast and the panels are not producing more power than the batteries already have stored.

 

Thank you for your reply Gerty,

We are using Kyocera panels about 2' x 3' / 22.1V/8.37A and 12Vgel cell 265Ah batteries. The motors ideally need to run constantly as to not disrupt production and are under loads that vary widely. It can range from 1.23A to 13.65A.

We do many arrangements that can vary from two pannels, three batteries to twelve panels, seven batteries. According to the data that we have and the numbers that I have run, we should get four or five days of autonomy, but in reality, I am getting two and a half to three days. This is what leads me to believe that we are not capturing power once it is a little overcast and the panels are not producing more power than the batteries already have stored.

Are you saying one pump can vary this much in current, or are there multiple pumps?

And, yes overcast skies will produce less power

 

The system can vary that widely. This is the reason that we have so many different arrangements. It is dependent on flow rate and pressure.

My question though, is there any way to ensure that I am capturing all power coming from the solar panels?

 

My question though, is there any way to ensure that I am capturing all power coming from the solar panels?

The panels will produce what they produce. Unless you have extra long wire and / or undersize wire going from panel to battery, there is probably little you can do there.

Panels should be positioned correctly for optimum performance and that will change through out the year. There are a number of good articles on the internet to help you accomplish this, just do a search.

The next thing you can do is implement tracking but it is easier and probably more cost effective just to increase the size of your array.


At the size you are talking, you probably should have a solar charge controller to insure proper battery charging.

 

My question though, is there any way to ensure that I am capturing all power coming from the solar panels?

The way to do that is with a charge controller that works with a scheme called "Maximum Power Point Transfer" (MPPT). It is a switch mode regulator that does a power conversion to get every bit of power from the panel to the battery bank.

The only exception to that is when the battery is charged... then it just lets excess power waste away.

 

Thanks Ernie. I'm using charge controlers, but I'll have to check to see if they have the MPPT setup.

 

According to the data that we have and the numbers that I have run, we should get four or five days of autonomy, but in reality, I am getting two and a half to three days.

Depending on how you've made your calculations, your observations may make perfect sense.

The process of charging and discharging a battery results in only about 50% overall power efficiency, end to end. Obviously, you want to run directly from the panels when you can.

 

Yes, the MPPT is what you want. It's all about maintaining at the peak power point of your solar array. There is a graph here that explains it well. http://pveducation.org/pvcdrom/solar-cell-operation/short-circuit-current.

A peak-power tracker will keep you right at the peak power and deliver as much power as possible to the batteries. Running motors to point as directly at the sun as possible will also increase the power, but you have to balance that with the cost of additional solar panels and determine what the best solution is for your requirements.