Solar Photovoltaic Cell Basics
When light shines on a photovoltaic (PV) cell – also called a solar cell – that light may be reflected, absorbed, or pass right through the cell. The PV cell is composed of semiconductor material; the “semi” means that it can conduct electricity better than an insulator but not as well as a good conductor like a metal. There are several different semiconductor materials used in PV cells.
When the semiconductor is exposed to light, it absorbs the light’s energy and transfers it to negatively charged particles in the material called electrons. This extra energy allows the electrons to flow through the material as an electrical current. This current is extracted through conductive metal contacts – the grid-like lines on a solar cells – and can then be used to power your home and the rest of the electric grid.
The efficiency of a PV cell is simply the amount of electrical power coming out of the cell compared to the energy from the light shining on it, which indicates how effective the cell is at converting energy from one form to the other. The amount of electricity produced from PV cells depends on the characteristics (such as intensity and wavelengths) of the light available and multiple performance attributes of the cell.
An important property of PV semiconductors is the bandgap, which indicates what wavelengths of light the material can absorb and convert to electrical energy. If the semiconductor’s bandgap matches the wavelengths of light shining on the PV cell, then that cell can efficiently make use of all the available energy.
Learn more below about the most commonly-used semiconductor materials for PV cells.
Silicon
Silicon is, by far, the most common semiconductor material used in solar cells, representing approximately 95% of the modules sold today. It is also the second most abundant material on Earth (after oxygen) and the most common semiconductor used in computer chips. Crystalline silicon cells are made of silicon atoms connected to one another to form a crystal lattice. This lattice provides an organized structure that makes conversion of light into electricity more efficient.
Solar cells made out of silicon currently provide a combination of high efficiency, low cost, and long lifetime. Modules are expected to last for 25 years or more, still producing more than 80% of their original power after this time.
Thin-Film Photovoltaics
A thin-film solar cell is made by depositing one or more thin layers of PV material on a supporting material such as glass, plastic, or metal. There are two main types of thin-film PV semiconductors on the market today: cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS). Both materials can be deposited directly onto either the front or back of the module surface.
CdTe is the second-most common PV material after silicon, and CdTe cells can be made using low-cost manufacturing processes. While this makes them a cost-effective alternative, their efficiencies still aren’t quite as high as silicon. CIGS cells have optimal properties for a PV material and high efficiencies in the lab, but the complexity involved in combining four elements makes the transition from lab to manufacturing more challenging. Both CdTe and CIGS require more protection than silicon to enable long-lasting operation outdoors.
Perovskite Photovoltaics
Perovskite solar cells are a type of thin-film cell and are named after their characteristic crystal structure. Perovskite cells are built with layers of materials that are printed, coated, or vacuum-deposited onto an underlying support layer, known as the substrate. They are typically easy to assemble and can reach efficiencies similar to crystalline silicon. In the lab, perovskite solar cell efficiencies have improved faster than any other PV material, from 3% in 2009 to over 25% in 2020. To be commercially viable, perovskite PV cells have to become stable enough to survive 20 years outdoors, so researchers are working on making them more durable and developing large-scale, low-cost manufacturing techniques.
Organic Photovoltaics
Organic PV, or OPV, cells are composed of carbon-rich (organic) compounds and can be tailored to enhance a specific function of the PV cell, such as bandgap, transparency, or color. OPV cells are currently only about half as efficient as crystalline silicon cells and have shorter operating lifetimes, but could be less expensive to manufacture in high volumes. They can also be applied to a variety of supporting materials, such as flexible plastic, making OPV able to serve a wide variety of uses.PV
Quantum Dots
Quantum dot solar cells conduct electricity through tiny particles of different semiconductor materials just a few nanometers wide, called quantum dots. Quantum dots provide a new way to process semiconductor materials, but it is difficult to create an electrical connection between them, so they’re currently not very efficient. However, they are easy to make into solar cells. They can be deposited onto a substrate using a spin-coat method, a spray, or roll-to-roll printers like the ones used to print newspapers.
Quantum dots come in various sizes and their bandgap is customizable, enabling them to collect light that’s difficult to capture and to be paired with other semiconductors, like perovskites, to optimize the performance of a multijunction solar cell (more on those below).
Multijunction Photovoltaics
Another strategy to improve PV cell efficiency is layering multiple semiconductors to make multijunction solar cells. These cells are essentially stacks of different semiconductor materials, as opposed to single-junction cells, which have only one semiconductor. Each layer has a different bandgap, so they each absorb a different part of the solar spectrum, making greater use of sunlight than single-junction cells. Multijunction solar cells can reach record efficiency levels because the light that doesn’t get absorbed by the first semiconductor layer is captured by a layer beneath it.
While all solar cells with more than one bandgap are multijunction solar cells, a solar cell with exactly two bandgaps is called a tandem solar cell. Multijunction solar cells that combine semiconductors from columns III and V in the periodic table are called multijunction III-V solar cells.
Multijunction solar cells have demonstrated efficiencies higher than 45%, but they’re costly and difficult to manufacture, so they’re reserved for space exploration. The military is using III-V solar cells in drones, and researchers are exploring other uses for them where high efficiency is key.
Concentration Photovoltaics
Concentration PV, also known as CPV, focuses sunlight onto a solar cell by using a mirror or lens. By focusing sunlight onto a small area, less PV material is required. PV materials become more efficient as the light becomes more concentrated, so the highest overall efficiencies are obtained with CPV cells and modules. However, more expensive materials, manufacturing techniques, and ability to track the movement of the sun are required, so demonstrating the necessary cost advantage over today’s high-volume silicon modules has become challenging.
Learn more about photovoltaics research in the Solar Energy Technologies Office, check out these solar energy information resources, and find out more about how solar works.
Difference Between Nominal Voltage, Voc, Vmp, Isc, and Imp
With an increase in global warming and the depletion of fossil fuels, the world is moving towards renewable energy.
Solar energy is one of the most important sources of renewable energy generation throughout the globe.
There is no recurring cost for fuel as the energy depends on solar irradiance which is available to most places throughout the year.
over, solar energy harnessing requires a single time investment used for procuring and setting up the solar panels and energy storage system.
In order to maximize our return and harness the most amount of energy from the sun, it is essential to select the best type of solar panels.
There are 3 main types of solar cells-
Each of the three types has its own pros and cons that we will discuss in another article. In this article, we will discuss the most important terminologies which we should know before we select a suitable solar panel for our application.
Solar panels or photovoltaic (PV) modules have different specifications. There are several terms associated with a solar panel and their ratings such as nominal voltage, the voltage at open circuit (Voc), the voltage at maximum power point (Vmp), open circuit current (Isc), current at maximum power (Imp), etc.
All these parameters are crucial to know before purchasing or installation of solar panels.
The characteristics of solar panels can be understood by using the current vs voltage graph. The VI graph is shown below:
Let’s find the most common question about solar panels i.e.
What is the difference between nominal voltage, Voc, Vmp, short circuit current (Isc), and Imp in the case of a solar panel? Which parameters are important to check before the installation of solar panels?
Solar Panel Specifications
Let’s understand the difference between Nominal Voltage, Voc, Vmp, Isc, and Imp.
Nominal Voltage in Solar Cell
Used just for classification, it is not a real voltage you are going to measure. It is not a fixed voltage either and, normally, it is not mentioned in the specification sheet of a PV module. Some of the common parameters mentioned in the specification sheet are listed in the table.
Voltage at Open Circuit (Voc)
This voltage is checked with a voltmeter across the output terminals of the solar panel module, without connecting any load. This parameter is used to check/test the module during installation and later for system design. It is an important parameter under standard test conditions. Voc is used while determining the number of solar panels required for a particular load.
Voltage at Maximum Power (Vmp)
This is the voltage available when the panel is connected to a load and is operating at its maximum capacity under standard test conditions. Most solar panel manufacturers specify Vmp to be around 70 to 80% of the Voc.
Short Circuit Current (Isc)
This is the value of current obtained when the positive and negative terminals of the panel are connected to each other through an ammeter in series. This is the highest current the solar panel cell can deliver without any damage. Isc is used to determine how many amps a panel can handle when connected to a device like a solar charge controller or an inverter circuit.
Current at Maximum Power (Imp)
This current is obtained when the solar panels are producing their maximum power. It is the amperage you would want to see when connected to solar equipment.
Maximum Power Point of Solar Cell (Pm)
The maximum power point (Pm) of a solar cell denotes the maximum amount of power a cell can deliver during its standard test condition.
Efficiency of Solar Cell
The efficiency η of a solar cell is an important criterion for the selection of a solar cell. It helps compare the performance of a solar cell. It is defined as the ratio of energy produced by a solar cell to the energy it receives from the sun. The efficiency of solar panels depends on the efficiency of the solar cell. Most solar cells available in the market offer an efficiency of 17-19% and the highest efficiency of a commercial solar panel is about 23%.
Fill Factor (FF)
The fill factor (FF) denotes the efficiency of a solar cell. It is denoted by the ratio of maximum power point (MPP) to the product of short circuit current (Isc) and open circuit voltage (Voc). The fill factor can also be denoted as the largest square that can fit inside an IV curve.
How Hot Do Solar Panels Get? Effect of Temperature on PV Panel Efficiency
Imagine one of those searing hot days when all you can do is to sip a margarita somewhere in the shade. How would you perform on a day like that if you were asked to run a marathon? Not that well, right? Our body functions the best when the temperature is within our optimum range. Beyond this range we have to work much harder to maintain our performance level.
As surprising as it may sound, the same principle applies even to photovoltaic solar panels and their capacity to generate electricity!
The effect of temperature on PV solar panel efficiency
Most of us would assume that stronger and hotter the sun is, the more electricity our solar panels will produce. But that’s not the case. One of the key factors affecting the amount of power we get from a solar system is the temperature. Although the temperature doesn’t affect the amount of sunlight a solar cell receives, it does affect how much power is produced.
Solar cells are made of semiconductor materials, like the most used crystalline silicon. Semiconductors are sensitive to temperature changes. Temperatures above the optimum levels decrease the open circuit voltage of solar cells and their power output, while colder temperatures increase the voltage of solar cells.
The output of most solar panels is measured under Standard Test Conditions (STC) – this means a temperature of 25 degrees Celsius or 77 degrees Fahrenheit. The test temperature represents the average temperature during the solar peak hours of the spring and autumn in the continental United States [1].
According to the manufacture standards, 25 °C or 77 °F temperature indicates the peak of the optimum temperature range of photovoltaic solar panels. It is when solar photovoltaic cells are able to absorb sunlight with maximum efficiency and when we can expect them to perform the best.
The solar panel output fluctuates in real life conditions. It is because the intensity of sunlight and temperature of solar panels changes throughout the day. What interests us in this case is how does the temperature affect solar panel efficiency in real life. Let’s break it down.
What happens when the temperature of solar panels increases?
If you have photovoltaic solar panels installed at home or plan to get some in the near future, it’s useful to have a good understanding about the difference between the energy of electrons at a low energy state and electrons in the excited state, because this difference accounts for the power output produced by solar panels.
In a solar cell, you can find electrons bound at a low energy state. When these electrons receive extra energy, they enter a new state – known as the excited state – which allows them to break the bond and move. Electrons in the excited state can participate in conduction. The extra energy that elevates them to the excited state comes from two different sources – from light (sunlight) or from heat.
How much power is produced by a solar cell depends on how big is the energy difference (voltage) between these two states. Increase in temperature affects the semiconductor material parameters by increasing the energy of bound electrons. This means that the energy difference to achieve the exited state is smaller, which results in reduced power output and efficiency of solar panels [2].
When solar panels absorb sunlight, their temperature rises because of the sun’s heat. The common material used in solar cells, crystalline silicon, does not help to prevent them from getting hot either. As a great conductor of heat, silicon actually speeds up the heat building in solar cells on hot sunny days.
In a nutshell: Hotter solar panels produce less energy from the same amount of sunlight.
Luckily, the effect of temperature on solar panel output can be calculated and this can help us determine how our solar system will perform on summer days. The resulting number is known as the temperature coefficient.
Solar panel temperature coefficient
The temperature coefficient tells us the rate of how much will solar panel efficiency drop when the temperature will rise by one degree Celsius (1.8 °F).
For example, when the temperature coefficient is minus 0.5 percent, it means that efficiency decreases by 0.5 percent for every degree above 25 °C (or every 1.8 degrees above 77 °F).
Solar panels from different manufacturers will vary in their temperature coefficients. That is why all solar panel manufacturers provide a temperature coefficient value (Pmax) along with their product information.
In general, most solar panel coefficients range between minus 0.20 to minus 0.50 percent per degree Celsius. The closer this number is to zero, the less affected the solar panel is by the temperature rise.
If you want to find out which solar panels have the best temperature coefficient available today, we recommend checking out our recent report on the best solar panels for home use.
How hot do solar panels get? Can they overheat?
The maximum temperature solar panels can reach depends on a combination of factors such as solar irradiance, outside air temperature, position of panels and the type of installation, so it is difficult to say the exact number.
Generally, solar panels are made of dark-colored silicon cells (black or dark blue), covered by a sheet of glass and framed in metal.
Silicon and metal are good conductors of heat, contributing to faster buildup of heat inside solar cells. Even though, solar panel manufacturers and installers apply mechanisms to prevent solar panel overheating, in extremely hot conditions, the energy output of solar panels might decline significantly.
In summer 2017, The Times published an article discussing the problem of Qatar being too hot for photovoltaic solar panels. According to the article, the combination of temperatures rising up to 50 °C (122 °F) with dust reduced solar panel power output down to less than 40 percent.
What can you do to stop your panels from getting too hot?
Being aware of the effect higher temperature has on the energy output, most certified installers take steps to support natural cooling of solar systems.
A good practice for maximum efficiency is leaving at least a six-inch space between roof and panels to allow air circulation from both sides. But attaching your panels too far from the roof is not always a good idea. If the gap is too big, debris of leaves and twigs could accumulate underneath the array and cause damage to your roof or panels.
If you live in a hot climate, you should consider ground-mounted solar panels, because this way they get the most airflow to keep their temperature lower.
According to estimates, the temperature difference between the ground-mounted and roof attached solar panels can make up to 10 °C (50 °F) at the same location [3].
The best option is to get solar panels with temperature coefficient as close to zero as possible. The difference in total power output throughout the year can be significant.
For example, if your solar panels have a coefficient of minus 0.4 percent, their output on hot days will drop nearly twice that much compared to the output of a panel with a coefficient of only minus 0.2 percent per one degree Celsius.
White or light-colored roofing also helps to lower the temperature around your panels, since these colors reflect sunlight more and do not get heated up like dark roofing.
While above mentioned points involve passive cooling methods, some people opt even for active cooling systems.
For example, fans that blow air over panels, or circulating cold water which absorbs the heat from the panels and is then utilized in the household for showering or heating the building [4].
A side note: Be cautious about hosing down your panels during the hottest part of the day! It could make the glass crack and irreversibly damage your solar panels. The systems with water cooling do not expose solar panels to such a sudden temperature shock like you hosing them down would.
How does cold temperature affect solar panel output?
You may have heard people doubting solar panel performance in cold weather. Some may even think that solar panels stop working when it’s freezing outside. None of these statements is true.
Solar panels actually love colder temperatures on sunny days. The open circuit voltage produced by solar cells on cold days increases and may rise even 20 percent above the values obtained during the standard testing at 25 degrees Celsius. This means that solar panels will produce more power in an hour during the cold and sunny weather. The problem comes with the monthly production.
On average, photovoltaic solar panels still produce up to 80 percent more energy during the summer months than in winter. The main reasons are (as you may have guessed) shorter periods of sunlight per day and more days with heavy clouds in winter. It is the sunlight energy that is limited in winter, not temperature.
The angle of solar panels affects how well will solar cells utilize the sunlight. In winter, the sun is lower in the sky and sunlight is diffused over a larger area, whereas in summer, the sunlight hitting your solar panels is more concentrated. In order to get the best energy output in winter, the angle may need some adjustments to capture more light. In general, solar installers recommend 45 degrees angle. This angle also helps to prevent snow buildup on the panels.
Additional negative factors, reducing efficiency of solar panels in winter, are snow and ice. Solar panels are resistant. They do not get easily damaged by ice. It just takes some time for solar cells to defrost after a freezing night. During the time when the first sun rays shine on your solar panels, their efficiency is reduced, as the ice or snow blocks some of the sunlight that hits them. The time of unobstructed sunlight is then shorter, and you will get overall less power in winter months.
Before you decide on a solution that would work the best for you, do your research well. As you can see, there are already options to perform under different conditions and some help you to save money – even on production of warm water.
If none of them look appealing to you at the moment, do not despair. We live in the era of an amazing development in the solar energy industry.
Just as we speak many scientists are working on tackling issues of solar panel efficiency and performance optimization.
Scientists from the Stanford University have already pioneered a concept of “self-cooling” solar cells, which will be able to re-direct the heat from the cell’s surface. This design might be just one of many future solutions to tackle the problem of solar cell overheating.
So, let’s enjoy this solar revolution.
Introduction: How to Measure a Solar Cell’s Power Output.
About: I learn by doing, and am always trying to see what I can get away with. About The Mad Thinker »
So you have just scavenged a solar cell that was about to become part of a landfill. Good for you, good for the environment, and even better for your next solar project. But what does that solar cell really do? Maybe a bad solar cell was the reason the whole assembly was in the dumpster.
The aim of this instructable is to give you the tools and understanding needed to examine any solar cell that you find; so that you have a better understanding of how it truly behaves, thus allowing you to incorporate it better into your next project.
While this sort of analysis is usually done with a computer-controlled DC load with a forced voltage function, the equipment needed will usually cost about 500. This method may not be as fast as with a DC load, but for the budding hardware hacker, it’s a lot more cost effective.
Step 1: Gather Your Resources.
You will need the following:
- A solar cell or solar panel to test.
- A good quality multimeter, that can read voltage and preferably current. Don’t worry if your mutlimeter lacks a current setting. We can get by without it.
- A variable resistance box. This is nothing more than an easy way to vary the resistance to known settings while it is still in the circuit. For truly accurate readings, I’d recommend going through and manually measuring all the resistance settings, as I have seem them vary by as much as 5% from the values printed on the dials.
- (not pictured) Short lengths of wire to connect all the components together.
- (not pictured) A spreadsheet program to help keep track of your data and do your calculations. Yes you can get by without it by using paper pencil, but lets take advantage of the tools we have.
- (optional) A second multimeter that can read current over a wide range. Once again, this is something that we can get by without, but it’s nice to have.
Step 2: Hook It All Up.
This is simply a solar cell connected in parallel with a load, and a multimeter set to measure voltage. Before you start, insure the load is set to ‘open’. If you have an additional multimeter that can measure current, you can also connect it in series with the load. This makes things a little easier, but it is not necessary.
Step 3: Point It Toward the Sun.
I realize that you might not have a sunny day on which to measure your cell. Unfortunately, I have yet to find a viable substitute for the sun. Yes, you can use a bright light, but that will give you only a fraction of the sun’s energy. I have used halogen lamps with varying degrees of success. Yes, they give me the most power of any artificial light source I have tried, but they also heat up the solar cells which degrades performance.
Beyond using a good light source, you need to align the solar cell toward it properly to get optimal power. Think of it as positioning a sail towards the wind. The best way I have found to align a solar cell towards the sun it to mount a small stick perpendicular to the solar cell’s surface then adjust the cell to minimize the stick’s shadow. When the shadow is minimized (preferably not visible), then the solar cell is faced toward the sun.
Step 4: Measure the No-load Voltage.
This value is simply taking the voltage measurement across the solar cell’s output with no load connected to it. After confirming the load resistance is open, record the voltage measurement. This is the maximum voltage the cell will produce, under the current light conditions.
Step 5: Measure the Short-circuit Current (optional).
This measurement will tell you the maximum current your solar cell can provide.
With the load still ‘open’, switch the multimeter to measure current. Record the result, then set the meter back to voltage measurement. A current measurement like this is the equivalent of a short circuit across the output of the cell, so don’t keep it like this any longer than you have to. While I have not found any evidence confirming that this will damage your solar cell or a good meter, it’s best not to take chances.
Now you have the maximum voltage your cell can produce and the maximum current it can produce. However, these results are what happens at open and maximum load. The real understanding comes from what happens between those two extremes.
Step 6: Sweep the Load, While Recording Voltage (and Possibly Current).
Now the fun really begins. With your load box set to it’s maximum resistance, change the setting from ‘open’ to ‘resistors’. Record the following data points: Resistance setting, voltage, and current (if you are recording it). Once you have recorded these, switch the resistance to the next lowest value and record the results for that setting. Repeat the process, until you have recorded values for all resistance settings.
Once finished, you should have a data set similar to what is seen in the above spreadsheet image. You should also notice a trend of the voltage dropping as the resistance decreases. Now that you have your data, you can begin analyzing it!
Step 7: Calculate the Power!
The electrical power for any setting is simply the product of the voltage and the current. If you were able to measure the current for each step, you are good to go. If not, you can find the current by dividing the voltage by the resistance. Once you have the current, just multiply it by the voltage.
To clear things up, lets look at the above spreadsheet. In row 2 we have 22.20 volts and 1 megaohm (1,000,000 ohms). The current for that entry is 22.2/1,000,000 or 2.22e-6 amps (2.22 microAmps). The power is 2.22e-6 amps X 2.22 volts, which comes to 4.93e-5 watts (or 493 miliwatts). Repeat this process for each resistance setting. Having a spreadsheet, means you can input the formulas, then copy/paste for all entries.
Step 8: Graph Your Results.
Once you have the power for each resistance setting, you can graph it. I have found that the most understandable way to read the power output of a solar cell is to use an X/Y (scatter) plot. with voltage along the horizontal axis and power on the vertical axis.
The graph above is constructed from the sample data. It becomes readily apparent that the maximum power is above the 1.5 watt rating. We can also see that from the graph, that the maximum power correlates above 12 volts. This is about where we want the maximum power to be, when we are charging a 12 volt battery.
Step 9: Always Improve.
Occasionally, I will add the current to the power/voltage graph. While this is not critical in most cases, it does sometime yield some useful insights. For instance, in the above graph we can see there is a cluster of data points at the high voltage end. As this is where the current drops off, that suggests that these represent high resistance values on the load. To improve resolution in the maximum power area, we can calculate what range of additional resistors we’d need. I see one point at (about) 16 V volts and 105 ma. That suggests a resistance of about (16V/.105A) 150 ohms. Our resistance box jumped from 220 ohms, to 150 ohms, to 100 ohms. A load made from a 100 ohm variable resistor in series with a 50 ohm resistor would give much better resolution for the area we are interested in. Also note, that you can see from the power curve, that you would need resistors rated for at leas
PV Array Voltage and Size: What You Need to Know
Jan 5th 2022
If you’re hoping to design your own PV array to harness clean, renewable energy, there’s a good chance you’re feeling a little lost. PV arrays are one of the best ways to get off-grid or provide your home with power in case of emergency. The trouble is actually designing your system. Suddenly, you need to know things like “array voltage” and “PV voltage” just to figure out how many panels you should install.
While learning the ins and outs of PV array voltage can be tricky at first, the results are worth the effort. You’ll be one step closer to energy independence and enjoy a little security during future blackouts. Or, you can outfit an RV with solar panels and take some green energy on the go.
What is PV?
Generally, Photovoltaics (PV) refers to photovoltaic generation systems, which use solar cells to convert irradiance into electricity. For example, a solar panel can be called PV panels.
What is a solar array?
Generally, a solar array is a collection of multiple PV(photovoltaic) panels that produce electricity power, solar array is usually made use of massive solar panel groups, nonetheless, it can be utilized to define nearly any type of group of solar panels for any scenario, today we will talk about everything about PV(photovoltaic) array voltage and size that you need to know, you can also learn how to wire solar panels in series vs parallel here.
What Is Array Voltage?
When building a PV array, you need a few important numbers. These numbers are your inverter’s maximum input voltage and your PV array voltage. Your PV array voltage is the total voltage of all of your modules when connected in a series. The more modules connected in series, the higher your array voltage.
This is important because the more modules you have, the more power you can generate. The more power you have, the more you can store or use to stay off-grid. However, your power generation is limited by your inverter’s maximum input voltage. If you don’t know your PV array voltage and you oversize your PV array, you risk overloading your inverter.
If you overload your inverter, there’s a chance that problems will occur, and your electrical system will suffer damage as a result. Even worse, damage caused by an overloaded inverter could potentially lead to an electrical fire. No matter what, a damaged PV array is no good, so it’s wise to start with an array that’s sized appropriately.
How you connect your modules affects your PV array voltage. Modules can be connected in series, in parallel, or in a combination.
When connected in series, adding the voltage of each module will get you your total array voltage. However, when connected in parallel, the voltage is simply the voltage of a single module.
Keep in mind that modules connected in parallel will still affect the total amperage of the array. Typically, it’s recommended to connect modules in series to maximize output.
The arrangement of your modules will depend on how much output you want, how much space you have, and where you install your modules. With a properly assembled PV array maximizing PV array voltage, you can lessen your dependence on the grid, create a battery backup system, or get off the grid entirely.
When building your array, it is very important to keep your modules uniform. Once you choose a module, stick with the manufacturer of that module. Don’t mix manufacturers, even when power and voltages are the same. While it can be tempting, especially if it seems like it will save you some money, you will most likely lose precious efficiency.
A system that isn’t as efficient as possible is a waste, so get the most value by sticking with one manufacturer.
What Is PV Voltage?
PV voltage, or photovoltaic voltage, is the energy produced by a single PV cell. Each PV cell creates open-circuit voltage, typically referred to as VOC. At standard testing conditions, a PV cell will produce around 0.5 or 0.6 volts, no matter how big or small the cell actually is.
Keep in mind that PV voltage is different from solar thermal energy. While it can be easy to confuse or conflate the two terms, they refer to energy generated through different processes.
Solar thermal energy is generated with solar thermal panels, which rely on sunlight to heat fluid media like oil, water, or air. Instead, PV arrays rely on the photovoltaic effect to generate power. The photovoltaic effect describes a process of voltage generation where a charge carrying material is exposed to light, causing the excitation of electrons.
Voltage at open circuit can be found with a multimeter or a voltmeter when the module isn’t under load. You can find this number on the module’s datasheet, also. Keep this number handy for later in case you need to calculate the size of the PV array you’re hoping to build.
Just like regular AC power, you can use PV voltage to power whatever you like. With a battery bank and a grid-tied system, you can create a very effective energy backup system for blackouts or emergencies. All you need to do is switch over to your battery banks while you’re off the grid.
With some RV solar panels, you could easily enjoy a powered camping trip. With a large enough battery bank, you could potentially go off-grid for good.
How Do You Calculate PV Voltage?
Calculating PV voltage is very important when determining the size of your PV system. The reason this is so important is because voltage has an inverse relationship with ambient temperature.
When it gets colder in your area, your string of panels will produce more voltage. When it’s hot outside, the voltage produced by your panels will go down. If you mistakenly put together a system that exceeds the maximum input voltage of your inverter, you can potentially damage your electrical and cause a fire.
This is why we start by finding the Module Voc_max, the max module voltage, when correcting for the lowest expected ambient temperature at the install site. To find the Module Voc_max, you’ll need to plug in a few details into the following formula:
Module Voc_max = Voc x [1 (Tmin. T_STC) x (Tk_Voc/100)]
Let’s start with VOC. VOC is the rated open current voltage for your modules, which can be found on their datasheet. The lowest expected ambient temperature is Tmin. A little bit of research on your area’s climate should reveal that. Next is T_STC. That’s the temperature at standard test conditions, which is always 25°C.
Lastly, Tk_Voc is the temperature coefficient of the module’s open-circuit voltage. This is usually found as a %/°C on the module’s datasheet, and it is always expressed as a negative number.
Once you have your max module voltage, all you need is the max voltage input for your inverter. Typically, you can find this on the inverter’s datasheet. From here, divide your inverter’s max input voltage by your Module Voc_max, and you will end up with the maximum string size for your array. The resulting number will let you know how big your array string size can be.
How Do You Calculate Solar Array Voltage?
Finding your solar array voltage depends entirely on your system design. You can either connect your modules in series or parallel, with series being the most common style. If you connect your modules in series, add up the voltage of each module. It’s as simple as that. In this case, your solar array voltage is always the total voltage of all of your panels.
Connecting your modules in parallel is just as simple but entirely different. When connected in parallel, you need to add up the amps of each panel, as amperage is the only thing that changes. In this case, solar array voltage is always the voltage of an individual panel, regardless of how many you have connected.
Calculating your solar array voltage is critical if you’re designing your system yourself. This is because having too many panels in a series can exceed your inverter’s maximum input voltage and that is usually a bad idea.
With the inverter being one of the most critical parts of your PV system, you can’t afford to damage it. Without it, you won’t be able to convert the energy produced by your PV array into a usable AC (alternating current).
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Once you have the numbers down, you can safely move on to designing your own PV system. Now, all you’ll need to do is decide whether you want it ground-mounted or roof-mounted. After that, it’s just a matter of connecting it with your existing electrical.
If any of this makes you feel unsure about your installation capabilities, don’t worry. Most electricians will be able to help you with a PV array installation. However, if you want to learn more or expand the capabilities of your PV system, we’re here for you.
Explore all of our educational videos, resources, and articles about topics like net metering to find out what a solar array can really do for you. Get off the grid entirely with a tiny home solar system. Add battery banks to your system to store power to use less grid power, or stay powered during blackouts. You can even use a portable solar generator to power devices while hiking or traveling.
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