Understanding solar panels in solar water pumping systems

Understanding solar panels in solar water pumping systems

Learn about the various types of solar panels and how you can use and size your own panels in Grundfos Product Center.

Solar panels are obviously essential in a solar-powered solution. 

In this module, we’re going to take a closer look at the various types of solar panels, how they work and finally how users can add and size their own solar panels in Grundfos’ sizing programme, Grundfos Product Center.

Simply put, solar panels absorb the energy from solar rays to generate energy. Typically, a solar panel consists of anything between 36 and 72 cells ranging from 50 to 300 watts in power. 

There are two types of solar panels: crystalline and thin film. Let’s take a look at the main differences between the two.

Generally speaking, crystalline is the most common type of solar panel, but there are some criteria in which thin film is a better solution. 

For instance, thin film offers a better performance in cloudy and hot conditions, while crystalline is the best choice for cold weather. The efficiency, size and possibilities, however, is where some of the main differences lie. Efficiency levels in the crystalline range typically lie between 13-20 %, while thin film reaches 6-8 %. Crystalline panels are also much smaller, making them an ideal solution for compact spaces.  

Crystalline solar panels offer two different versions: poly crystalline and mono crystalline. 

Mono crystalline is solid black and performs better in warm temperatures, while reaching an efficiency level of up to 20 %. 

Poly crystalline, on the other hand, is a mixture of light and dark blue, and reaches efficiency levels of up to 17 %. However, it’s cheaper to manufacture and wastes less silicone during production. 

Now that we’ve outlined the characteristics of the various types of solar panels, the next section of this module will take a closer look into the electrical properties of a solar panel. First of all, there are a few essential electrical properties to be aware of during the selection of solar panels.

These terms are:  

Voltage at maximum power point – or Vmp – which is the voltage when the solar panels are loaded optimally. "

Next, there’s the current at maximum power point – or Imp. Similar to Vmp, this is the current when the solar panels are loaded optimally. 

Next, there’s voltage without load – or Voc. This is the voltage when wires aren’t connected.

And finally, there’s the short circuit current – or Isc – which is the current when the wires are short-circuited.

When it comes to the electrical connection of solar panels, we typically deal with serial connections or parallel connections. These connection types are also referred to as a ‘String’ or an ‘Array’. 

As the name suggests, a serial connection is a set of solar panels connected in series – or a string. Each panel in the string increases the voltage, contributing to an overall higher voltage output. So, if for instance, there’s a solar panel connection of four panels, in which each panel has an output of 37V, the voltage output from each panel in the series is added up. 

Overall, this means that a serial solar panel connection consisting of four panels can deliver an output of 148V. "

These strings can also be parallel-connected, bringing us to the second connection type. In order for a parallel connection to work, each string must have the same voltage and current. When connecting the strings in parallel, each string adds to the total array current output, meaning that if four strings are connected in parallel with a current output of 8A, the overall current output will be 32A. 

Whichever electrical connection combination you choose, it’s important that your solar panels are sized and connected according to electrical system specifications. Let’s take a closer look.

In solar pumping, it is generally recommended that you get as high a voltage from the setup as possible – within the limits of the product. By doing so, you’ll get a higher performance and you can use thinner cables. Wiring of the solar panels is simply done by means of using cable connectors.

One of the most frequently asked questions within solar pumping stations is whether the customer can add their own solar panels to size their system in Grundfos Product Center. The answer is yes. In the final part of this module, we’re going to show you how it works. 

When sizing your pump in Grundfos Product Center, you’ll have the option to select available solar modules by Grundfos or add your own solar panels to the sizing programme. 

To add your own solar panels in Grundfos Product Center, simply start the sizing process and head to ‘System configuration’ and select ‘Calculate’. From here, you can edit all the relevant information for the specific solar panel you want to create. Once you’re done, make sure to enable 'Save and close with OK' to save your settings and click 'OK'. Your solar panel will then be added to the sizing programme.

Furthermore, you can compare the results between, for instance, two different brands or sizes of a solar panel.

So, that covers the main characteristics of solar panels. Let’s recap what we’ve learned.

There are two types of solar panels: crystalline and thin film. Crystalline offers efficiency levels between 13-20 %, while thin film offers 6-8 %.

A serial connection is a set of solar panels connected in a string. An array connection is when more than one string is connected in parallel. 

And finally, you can now add your own solar panels to Grundfos Product Center, thereby matching sizing specifications exactly according to your needs.