Solar Power for Subs: Panel Connections

In this edition of Franklin AID, we continue our series on solar pumping systems, specifically the configuration and wiring of solar panels. Though this step is relatively straightforward, it is a critical one. A system could have all the right panels, but if they are not wired together correctly, the controller/motor won’t receive the voltage and/or current needed to fulfill the system’s water requirements.

Solar panels are DC devices. That is, just like batteries, they produce a direct current. Also just like batteries, they can be wired together to produce the exact combination of voltage and current required. There are two key points to remember when connecting multiple solar panels:

1)     When panels are connected in series, the total voltage delivered is the sum of the voltage produced by each panel. However, the amount of current (amperage) available will only be the current produced by a single panel. This is very similar to what happens when two or more pumps are connected in series. The total head produced will be the sum of the pressures produced by each pump, but the flow produced will remain equal to the flow of one of the single pumps.

2)     When solar panels are connected in parallel, results are flipped. The currents become cumulative, but not the voltages. Once again, this is very similar to connecting two or more pumps in parallel. If the intakes and discharges of two or more pumps are connected, we produce more flow, but the pressure generated will only be the pressure generated by a single pump.

So how are solar panels connected in series and in parallel? Using our pump analogy again, think about connecting two or more pumps in series. The discharge of the first is connected to the intake of the second and so forth. Likewise, to connect two or more solar panels in series, the positive terminal of one solar panel is connected to the negative terminal of the next. The positive connection of the panel can even be thought of as the “output” and the negative terminal as the “input”. This is shown in the diagram below.

panels in series

To wire two or more solar panels in parallel, all of the positive terminals are simply connected together and the all of the negative terminals are connected as seen below.

panels in parallel

To summarize, when panels are connected in series:

  • Total voltage is the sum of each panel in the series
  • Current (Amps) remains the same as a single panel in the series
  • Power (watts) is the sum of each panel in the series (since power = voltage x current, this makes sense) 

When panels are connected in parallel:

  • Voltage remains the same as a single panel in the parallel connection
  • Current (Amps) is the sum of each panel in the parallel connection
  • Wattage is the sum of each panel in the parallel connection

What about a combination of panels in which some are wired in series and others in parallel? The same rules apply, of course. Voltage will add up for those panels that connected in series and current will add up for those panels connected in parallel. In some installations, a combination of connections may be needed to produce the voltage and current required.

The good news is that Franklin Electric’s SolarPAK Selector provides the needed panel array configuration for any given installation. In that segment of the Selector, note that in the first column of the Panel Array Configuration box, the term “String” denotes how many panels should be wired together in series.  The second column indicates how many strings (groups wired in series) should be wired in parallel. Looking at the example we used in the last post, the SolarPAK Selector tells us that we need ten of the panels we have specified and that they need to be configured in one parallel string (one string of ten wired in series).

 Solar Screenshot-frank

Once again, we’ve only provided three pieces of information – location, water requirements, and the panel characteristics supplied by the manufacturer, and Franklin’s Solar Selector has done the rest, even how to connect our panels.

Solar Power for Subs: Part 1

solar installHarness the power of the sun; over time, that age-old dream has become a reality. With solar technology, we can use the sun’s energy to do work, to move things and drive machines. Today several manufacturers, including Franklin Electric, offer solar pumping systems that harness the power of the sun to get water from the ground—even where there’s no power grid.

Over the next several weeks, Franklin AID will examine in detail how these systems work, their sizing, their proper application and set-up, and their advantages and disadvantages. By the end of this series, you will have a very complete understanding of where solar pumping fits into your product portfolio, along with how to install one of these systems.

Why Solar?

To begin with, why use a solar pumping system? There are two simple answers: 1) because there’s no power where the water well is located, and 2) because the power is free. But there can be other reasons to use a solar pumping system that may be less obvious. Perhaps power is available where you need water, but it’s unreliable. If that location is remote, the end user may not even be aware when the power is off. Couple that with a critical water supply and the simple reliability of solar pumping can make a strong case for it. A prime example here is open range livestock.

In other cases, there may be power nearby, but the well is several hundred feet away from the power source. The cost of trenching and running copper to the wellhead could often outweigh the cost of a solar pumping system. In other areas, electrical power may available but very expensive. Since the sun shines for free, solar simply makes the economic sense.

Finally, some people want to use greener products as much as possible and nothing fits the bill better than solar. Marketing reasons can even enter the picture. For example, organic farm operations that market themselves as such may want to use solar pumping for irrigation in order to be able to promote this to their customer base. In such cases, electricity from the grid may be readily available.

Why Not Solar?

Of course, solar pumping by definition has a big drawback: it needs the sun to operate.  As a result, pumping systems that are strictly solar can’t deliver water 24 hours a day. But irrigation normally isn’t required 24 days a day, and in other applications, a storage tank or cistern may store more than enough water when the sun is down or the weather doesn’t cooperate.

In a residence or business, however, we do want water to be available under pressure 24 hours per day. So although stand-alone solar pumping systems aren’t likely to completely replace conventional residential systems, that doesn’t mean they can’t be combined with battery-powered systems or traditional grid systems. We’ll cover these options later.

In summary, where solar systems really come into their own are in applications such as livestock watering, irrigation, vineyards, and anywhere a grid power is unreliable or nonexistent. That’s a pretty exciting development for our industry.

Stay tuned for the next post in this series, where we’ll cover the starting point of all solar pumping systems: the panels.

Line Shafts vs. Submersibles: Some Big Advantages for the Sub

In high volume groundwater pumping applications, the pump is almost always located underground. Even so, the type of pump and the method of driving it can be very different. The two most common pumping systems for high volume groundwater applications are vertical line shaft turbines (VLSTs) and submersible turbines.

VLSTs use an aboveground motor with a drive shaft connecting the motor to the submerged pump. These pumps are suitable for some applications, primarily in shallow sets.

Submersible turbines use a submersible motor coupled to the submerged pump so that both are located together in the well. In most applications, a submersible makes more sense. Some of the main reasons follow. Continue reading

Submersible Installation… How much does it cost?

One of the more confusing things about electricity is how it’s measured and how we pay for it. This issue of Franklin AID will clear up some misunderstandings about electrical power, especially in terms of calculating the electrical cost of operating a submersible pump. As part of this, we’ll examine the phase relationship between voltage and current, otherwise known as power factor. We’ll learn that power consumption is not just about amp draw, but is a combination of voltage, current and power factor. Continue reading

LST or Submersible? Go for the Sub!

Line shaft turbines (LSTs) use an above-ground motor to turn a drive shaft that reaches down the well casing to the submerged pump. A submersible, of course, uses a combinedmotor and pump assembly completely submerged underwater. Although LSTs have their applications, in most cases a submersible motor makes more sense. Here’s why:

Submersible pumps are easier to install. Continue reading

Cold Weather & Submersibles

As we begin our 18th year of Franklin Aid, we would like to ask for your help. In some publishing circles, it is said that every year 10% of a readership either changes addresses or employment status. Franklin Electric has not formally updated our mailing list since 1989. If the publishers are correct, we should have had 100% turnover of our readership! Now we know that hasn’t happened, but if you are receiving duplicate mailings, copies for someone no longer in need, or envelopes with misspelled or incorrect addresses please call us on the Hotline and let us know. Continue reading