The Paradox of Solar Panel Efficiency
Solar energy systems are designed to convert the sun’s light, which reaches the earth in the form of radiation and, into a usable form of energy, called electricity. Given that solar energy relies exclusively on the light of the sun, it is prudent to assume that the more a solar module is exposed to the sun, the more energy it will produce. For the most part, this is true. However, this is where the paradox of solar panel efficiency comes in. Solar panels do well with radiation, but not so much with heat. And not to belabour a point, but heat is a major component of sunlight. Solar panel performance suffers as temperature rises and depending on other factors like installation location, a solar PV module’s output efficiency can decrease by as much as 10-25%. This is not to say that solar panels become inefficient during peak sunlight hours. On the contrary, this is when the solar harvest is at its peak and electricity production is at its highest. However, there is a very real and substantial drop in output efficiency. Mitigating this drop in output can have a considerable impact on the overall performance of a solar energy system. This is why the ideal operating conditions for solar panels are clear skies with ample sunlight exposure with a cool, if not cold climate. Geography, however, does not take human technology into consideration, and mother nature will do as she pleases. This begs the question, how can we increase a solar energy system’s exposure to sunlight, whilst keeping its temperature down. This will not only increase the output of our solar PV system, but also help reduce the elemental stresses that build up overtime and result in a reduced lifespan. In this article, we will explore the best ways to achieve this without changing zip codes.
Increasing System Size
On of the seemingly most complicated ways, yet in fact the easiest one, is to simply increase the size of your solar PV system. More panels automatically equate to more power output, and even if the output suffers marginally because of the heat, additional panels can more than make up for the drop. Therefore, it is best to purchase solar panels with an output above the baseline required to ensure that any drops in output, because of heat or just cloudy weather, will be compensated for by the additional panels. Connecting solar panels can seem like a daunting task, but in all honestly, it is not nearly as bad or as difficult as it sounds.
The trick with stringing together arrays of solar panels is to configure them in a way that maximises output efficiency, while keeping each array as independent as possible. Therefore, if one panel is obstructed, the others will continue operating at maximum efficiency, and that one compromised panel will not bring down the performance of your entire solar energy system.
There are three basic ways that solar panels can be strung together. Each of these configurations has a specific purpose. One configuration, for instance, will produce more current, while the other produces more output voltage. The configuration chosen will depend entirely on the customer’s intended goal. Integra Solar’s own technicians can not only help you choose the configuration that is best for you, but also set it up, do any troubleshooting that is required, and get everything up and operational for you. The first step, however, is choosing your goal and understanding which configuration best suits it. Let us take a look at each of these in detail.
Exploring Series Connections
The first connection we are going to look at is a series connection. In a series connection, the aim is to increase the overall system output voltage. A series connection is used with a charge controller of 24 volts or more, and generally with a grid-tied inverter. In a series connection, the positive and negative terminals of each panels are connected together until there is one negative and one positive terminal free.
A Series Connection with Identical Characteristics
The solar panels add up the voltage produced by each panel and give a combined output. Now, it is important to note that all the panels in this connection are of the same type and power rating. In such a configuration, if the panels have a voltage output of 6 volts each and an ampere rating of 3 amps, then the series will produce a combined output voltage of 18 volts (6 x 3) at 3.0 Amperes. The output at maximum exposure to sunlight in such a scenario will be 54 watts (volts x amps).
A Series Connection with Different Voltages
If you want a series where the voltage rating of the panels is nominally different, their current rating must still be the same. For example, if we have three solar panels rated for 5V/3A, 7V/3A and 9V/3A respectively, connected in a series, the array will collectively produce 21 volts at 3.0 amps, with a power output of 63 watts. As you can see, the output voltage has jumped by 3 volts (5 + 7 + 9), resulting in an overall increase in system wattage.
A Series Connection with Different Currents
The final way we can connect a series is using solar panels with different current ratings but similar current ratings. In this example, let us assume that we have three panels of 3V/1A, 7V/3A and 9V/5A respectively connected in a series. In such a connection, it is important to note that the amperage of the system will be limited to the value of the lowest ampere in the system. Think of the current rating as the link in a chain. This chain, or series, or panels is only as efficient as the current rating of its lowest panel. Therefore, the system will have an amp rating of 1A. This configuration will produce 19 volts (3 + 7 + 9) at 1.0 amp. The total output will be 19 watts, whereas the maximum possible output is 69 watts.
Observations
As you may have gleaned from these examples, it is best to keep the ampere rating even across a series, as a panel with a higher current rating will only be wasted. Also, increasing the volt rating of one panel will significantly boost the output of the entire system. Therefore, when considering an upgrade, it is best to incorporate a solar panel with the same current rating as your existing system, but with a higher voltage rating.
Exploring Parallel Connections
The second type of configuration we will explore is a parallel connection. This kind of configuration is designed to maximise total system current. This form of wiring is known as parallel wiring. A parallel connection is the reverse of a series connection, since you connect the positive and negative terminals together, until only one positive and one negative terminal remain, which are then attached to an inverter or a battery system. The total voltage output, in such a connection, remains constant, as it would with a single panel, but the total current output is amplified to the sum of the output of each panel. As with the series connections, let us explore various configurations of parallel connections.
A Parallel Connection with Identical Characteristics
First, let’s look at what a parallel connection will look like if the solar panels have identical characteristics, namely they have the same voltage and current rating. Let us assume that the panels are of 6 volts and 3 amperes each. In such a configuration, the total voltage will remain 6 volts, while the amperage will increase to 9 amps (3 + 3 + 3). In peak sunlight exposure, the total output will be 54 watts (9 x 5). You might have noticed that this is the same output as an identical series connection.
A Parallel Connection with Different Voltages
Now, let us consider a parallel connection in which the output volts are nominally different. Let us assume that we have three panels with the following ratings:
- Panel 1 – 3V/1A
- Panel 2 – 7V/3A
- Panel 3 – 9V/5A
As you may have guessed, the volt rating will adjust to the lowest value. This chain will be measured by its weakest link as well, which happens to be its voltage rating. For a parallel connection to be effective, solar panels should have the same voltage rating. The solar panel rated for 9 volts will only operate at a maximum of 3 volts, thereby reducing its efficiency drastically and wasting energy that could potentially be harvested.
Summary
As you can see, connecting solar panels in arrays is not as complicated as it may first appear. Each of these connection types serves a purpose, and you should have a clear goal in order to identify what connection is best for you. Just remember:
- If you are going for maximum current output, be sure that your solar panels have the same voltage rating.
- If you are aiming for maximum voltage, make sure your panels have the same amperage rating.
Choosing the type of connection you should opt for depends on your ultimate goal. If, for example, you want a 12-volt battery charging system, you should probably consider a parallel wiring. If you want a higher voltage grid connected system, you’re probably better off considering a series-parallel combination, depending on the number and ratings of your solar panels. Yes, you can connect solar panels in a combination of series and parallel configurations, just remember the above rules and make sure that the amperage and voltage ratings of your solar panels match where necessary.
If all this is too complicated, just keep in mind that parallel wiring means more amperes and series wiring means more voltage. So, what do you need? More amperes, or more volts? Using a combination of series and parallel wirings works best for most folks, but if you can’t decide or just don’t know, there is no shame in it. Just pick up your phone and give integra Solar a call. We’ll walk you through your needs step by step for no additional charge.
