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Decoding Solar Panel Output: Voltages, Acronyms, and Jargon. Solar pv array

Decoding Solar Panel Output: Voltages, Acronyms, and Jargon. Solar pv array

    Putting It All Together: The Main Parts of a Solar PV System

    Solar PV systems are one of the most widely considered and installed examples of renewable technology in the world. But, for some, how they actually work might be something of a mystery — almost magical.

    But, it really doesn’t need to be. Exactly how they work and what makes up a PV system is actually pretty interesting.

    So, if you have ever wondered what a solar PV system is actually is, or indeed how it works, then we’ve made a very short guide to help you get to grips with the basics.

    How do solar PV panels actually work?

    Put simply, solar PV panels convert sunlight into electricity through a process known as the photovoltaic (PV) effect. Closely related to the photoelectric effect, the PV effect was first demonstrated as early as the late-1830s by Edmond Becquerel.

    Stay ahead of your peers in technology and engineering. The Blueprint

    Becquerel noticed that when plates of platinum or gold were immersed in acid, neutral, or alkaline solutions and exposed to solar radiation, a small electrical current could be generated. A little later, in the 1880s, Charles Fritts managed to develop the first true solar cell made from selenium covered with a thin layer of gold.

    While this panel did work, it had a very low efficiency.

    Modern solar panels work when photons from sunlight knock electrons free from atoms. generating a flow of electricity. The panels are actually made up of smaller units called photovoltaic cells. These solar cells are a sandwich of semiconductors made from silicon that is doped with other materials.

    Boron or indium are usually added to one layer, giving it a positive charge. Essentially, adding a boron atom to a group of silicon atoms creates a “hole” — a space that would be occupied by an electron in pure silicon. This is called p-type doping or a p-type semiconductor (p is for positive). The other layer is usually doped with phosphorous or arsenic, which adds extra electrons, or a negative charge, to that layer (this is called n-type doping, or an n-type semiconductor, for negative).

    Sandwiching the two layers creates an electric field at the junction — called the p-n junction. When exposed to light, an electrical field is generated within this junction as electrons absorb energy from photons and are break free from their parent atom.

    This process leaves behind a hole in the valence bonds of the material the atom escaped from. Because of the preexisting electrical field in the p-n junction, these electrons and holes move in opposite directions — the electron to the n-side and the hole to the p-side.

    This motion of the electron creates an electric current in the cell. Metal conductive plates on the sides of the cell collect the electrons and transfer them to wires, allowing the electrons to flow like any other source of electricity.

    Interestingly, most photocells tend to be more efficient the smaller they are, so each PV panel is usually made up of many small cells. If you look closely at a solar panel, you will be able to see all the smaller subunit photocells that make up the main panel.

    Typically made from doped silicon (though germanium, lead sulfide, and other semiconductors can be used), PV cells are the powerhouses of any modern PV panel.

    on that in the next section.

    What materials are PV panels made from?

    PV panels, like any piece of technology, are a jumble of different materials that make up different parts, from the photocell to the frame and everything in between. However, what most people mean when asking a question like this is what is the magical ingredient that gives the PV panel its seemingly magical ability to create electricity from sunlight.

    That wonder material happens to also be one of the most abundant substances on plant Earth — silicon. In fact, it makes up about 30% of the Earth’s crust, give or take.

    Silicon is the second-most abundant material on the planet, behind oxygen, but is rarely found in its free state in nature. Typically it will be found combined with other elements to form one of the plethora of silica minerals that make up the Earth’s crust.

    It also happens to have some interesting physical and electrochemical properties that make it pretty handy for building electronics.

    One of these is the fact that it is a semiconductor. A semiconductor, as the name suggests, is any material that has a conductivity between that of an insulator (like a ceramic) and that of a conductor (like a metal).

    Being a metalloid (neither metal nor non-metal), silicon shares some properties of both — hence its role as a semiconductor.

    This means that while it can conduct electricity, albeit less well than metals, its ability to do so increases as its temperature rises (unlike metals).

    For this reason, silicon is used to make many important electrical components, including transistors, which amplify or switch electrical currents and are the backbone of all types of electronics, from radios to iPhones.

    With regards to solar cells, pure silicon is a poor conductor of electricity. To overcome this, most solar cells blend silicon with other elements, like gallium or arsenic, to either produce electron-deficient layers or electron-rich layers respectively. This is important, as we’ve seen, to produce electron-hole pairs to generate electrical fields.

    While very abundant, there are some limitations to using silicon as the base material for solar cells. The main one being that the panels are inherently fragile and rigid. This can complicate transportation and installation, among other things.

    Typically, silicon-based solar cells come in a few distinct forms in most solar panels that are commercially available. These include:

    • Monocrystalline solar cells — Made from almost pure silicon, these are the most efficient form of solar panel but tend to be the most expensive. These panels are usually pretty dark in color and tend to have the longest lifespans (often 25 years plus).
    • Polycrystalline solar cells — Also known as polysilicon or multi-silicon cells, were the first commercially available type. They are more affordable than monocrystalline panels but are less efficient and generally take up more space. These panels also have a relatively low heat tolerance compared to monocrystalline panels.
    • Amorphous solar cells — Composed of non-structured silicon crystals, these panels are easier to install and transport but have a much-reduced efficiency compared to the other two forms. These are the kind of panels used in relatively cheap solar-powered electronics like calculators and other thin-film applications. They are relatively cheap to produce but are by far the least efficient. Their limitations can be overcome by stacking several of them on top of one another and they also tend to be less fragile and rigid than other forms of solar cells.

    Which type is chosen is usually a trade-off between manufacture and installation cost and an acceptable cap in electrical generation efficiency.

    Organic solar cells might be the future of solar PV

    Silicon-based solar cells make up the vast majority of existing PV panels, but are not the only kind of solar PV panels in existence. One rising star is something called an organic solar cell/panel.

    Organic solar cells, or OSC for short, are an exciting development in the world of renewable technologies. Typically made from special conductive organic polymers or small organic molecules, this technology can produce more lightweight and flexible solar panels.

    OSCs, while relatively new, also have higher efficiencies per area when compared to more traditional PV panels. Existing OSCs tend to be very strong absorbers of light, and are touted by many experts in the field as the future of solar technology.

    Because of the way they are built, organic solar cells/panels have other inherent advantages over their non-organic counterparts. Foremost among these is their lightweight nature, flexibility, large area coverage, and low cost of manufacture.

    Some organic solar cells are manufactured using a process called roll-to-roll production. This process is considerably cheaper than conventional non-organic solar cell production and enables organic solar cells to be manufactured with a large area.

    An organic solar cell, sometimes called a plastic solar cell, is a type of polymer solar cell that uses organic electronics. This is a branch of electronics that deals with conductive organic polymers or small organic molecules, for light absorption and charge transport to produce electricity from sunlight via the photovoltaic effect.

    This enables organic photovoltaic cells to convert solar energy into electrical energy more efficiently than other types of solar cells, including the silicon cells found in most common solar panels.

    However, current OSC systems tend to have shorter expected lifespans when compared to more traditional silicon-based panels. This is because of their generally lower stability and lower strength.

    Another issue with OSCs is their relative material extinction coefficients (a measure of light lost due to scattering and absorption per unit volume). Materials with higher absorption coefficients more readily absorb photons, which excite electrons into the conduction Band. The extinction coefficient of OSCs is not, as yet, as good as that of silicon-based solar panels.

    However, it is important to note that OSCs are still very much in development, and breakthroughs in new materials, processing methods, and device architectures will likely fix this shortcoming.

    OSCs can also be used for some interesting applications that would not be possible with non-organic solar panels. For example, they can be made transparent and specialized for specific wavelengths of light.

    This could have applications in structures like greenhouses, where OSC panels can form the main glazing of the structure. Such a setup could allow wavelengths of light commonly used by plants to permeate through the OSC panels, while using other wavelengths to generate electricity.

    Decoding Solar Panel Output: Voltages, Acronyms, and Jargon

    For those that are new to solar power and photovoltaics (PV), unlocking the mysteries behind the jargon and acronyms is one of the most difficult early tasks. Solar panels have many different voltage figures associated with them. There is a good amount to learn when it comes to solar panel output.

    Types of solar panel voltage:

    • Voltage at Open Circuit (VOC)
    • Voltage at Maximum Power (VMP or VPM)
    • Nominal Voltage
    • Temperature Corrected VOC
    • Temperature Coefficient of Voltage
    • Measuring Voltage and Solar Panel Testing

    Voltage at Open Circuit (VOC)

    What is the open circuit voltage of a solar panel? Voltage at open circuit is the voltage that is read with a voltmeter or multimeter when the module is not connected to any load. You would expect to see this number listed on a PV module’s specification sheet and sticker. This voltage is used when testing modules fresh out of the box and used later when doing temperature-corrected VOC calculations in system design. You can reference the chart below to find typical VOC values for different types of crystalline PV modules.

    Nominal Voltage VOC – typical VMP – typical # of cells in series
    12 21 17 36
    18 30 24 48
    18 33 26 54
    20 36 29 60
    24 42 35 72

    Voltage at Maximum Power (VMP or VPM)

    What is the Max Power Voltage of a solar panel? Voltage at maximum power is the voltage that occurs when the module is connected to a load and is operating at its peak performance output under standard test conditions (STC). You would expect to see this number listed on a modules specification sheet and sticker. VMP is at the place of the bend on an I-V curve; where the greatest power output of the module is. It is important to note that this voltage is not easily measured, and is also not related to system performance per se. It is not uncommon for a load or a battery bank to draw down the VMP of a module or array to a few volts lower than VMP while the system is in operation. The rated wattage of a PV module can be confirmed in calculations by multiplying the VMP of the module by the current at max power (IMP). The result should give you [email protected] or power at the maximum power point, the same as the module’s nameplate wattage. The VMP of a module generally works out to be 0.5 volts per cell connected in series within the module. You can reference the chart to find typical VMP values for different types of crystalline modules.

    Nominal Voltage

    What is the voltage of a solar panel? Nominal voltage is the voltage that is used as a classification method, as a carry-over from the days when battery systems were the only things going. You would NOT expect to see this number listed on a PV module’s specification sheet and sticker. This nomenclature worked really well because most systems had 12V or 24V battery banks. When you had a 12V battery to charge you would use a 12V module, end of story. The same held true with 24V systems. Because charging was the only game in town, the needs of the batteries dictated how many cells inside the PV should be wired in series and or parallel, so that under most weather conditions the solar modules would work to charge the battery(s). If you reference the chart, you can see that 12V modules generally had 36 cells wired in series, which over the years was found to be the optimum number for reliable charging of 12V batteries. It stands to reason that a 24V system would see the numbers double, and it holds true in the chart. Everything worked really well in this off grid solar system as the and evolved along the same nomenclature so that when you had a 12V battery and you wanted solar power, you knew you had to get a “12V” module and a “12V” controller. Even though the voltage from the solar module could be at 17VDC, and the charge controller would be charging at 14V, while the inverter was running happily at 13VDC input, the whole system was made up of 12V “nominal” components so that it would all work together. This worked well for a good while until maximum power point technology (MPPT) became available and started popping up. This meant that not all PV was necessarily charging batteries and that as MPPT technology evolved, even when PV was used in charging batteries, you were no longer required to use the same nominal voltage as your battery bank. String inverters changed the game for modules, as they were no longer forced in their design to be beholden to the voltage needs of deep cycle batteries. This shift allowed manufacturers to make modules based on physical size, wattage characteristics, and use other materials that produced module voltages completely unrelated to batteries. The first and most popular change occurred in what are now generally called 18V “nominal” modules. There are no 18V battery banks for RE systems. The modules acquired this name because their cell count and functional voltage ratings put them right in between the two existing categories of 12V and 24V “nominal” PV modules. Many modules followed with 48 to 60 cells, that produced voltages that were not a direct match for 12V or 24V nominal system components. To avoid bad system design and confusion, the 18V moniker was adopted by many in the industry but ultimately may have created more confusion among novices that did not understand the relationship between cells in series, VOC, VMP, and nominal voltage. With this understanding, things get a lot easier, and the chart should help to unlock some of the mystery.

    Temperature-Corrected VOC

    The temperature-corrected VOC value is required to ensure that when cold temperatures raise the VOC of an array, other connected equipment like MPPT controllers or grid tie inverters are not damaged. This calculation is done in one of two ways. The first way involves using the chart in NEC 690.7. The second way involves doing calculations with the Temperature Coefficient of Voltage and the coldest local temperature.

    Temperature Coefficient of Voltage

    What is a solar panel temperature coefficient? The temperature coefficient of a solar panel is the value represents the change in voltage based on temperature. Generally, it is used to calculate Cold Temp/Higher Voltage situations for array and component selection in cooler climates. This value may be presented as a percentage change from STC voltages per degree or as a voltage value change per degree temp change. This information was not easily found in the past, but is now more commonly seen on spec pages and sometimes module stickers.

    Measuring Voltage and Solar Panel Testing

    How do I measure voltage on a solar panel? Voltages can be read on a solar panel with the use of a voltmeter or multimeter. What you’ll see below is an example of a voltmeter measuring VOC with a junction box. This would be the view from the back of the PV module. Using a multimeter is the best way to measure solar panel output.

    When researching solar panel output, it can be overwhelming to understand the different voltage figures and acronyms used. For those new to solar power and photovoltaics (PV), decoding the terminology can be a challenge. In this blog post, we will break down the basics of solar panel output, including voltage, acronyms, and jargon, to help you get up to speed.

    What are solar amps and watts?

    Solar amps and watts are two measurements of the amount of electrical energy that a solar panel produces. Solar amps (A) measure the rate of electric current produced by a photovoltaic cell, while solar watts (W) measure the amount of power delivered to an electrical load. Both solar amps and watts are related to the efficiency rating of residential solar panels. The higher the efficiency rating, the higher the number of solar amps and watts produced.

    There are many types of 60-cell solar panels on the market for home solar applications, each with varying efficiency ratings and amp/watt outputs. High efficiency panels are capable of producing more solar watts than low-efficiency panels, although they tend to cost more upfront. By choosing the right panel, homeowners can ensure that their solar array is producing enough power to meet their electricity needs.

    Why do solar panels have so many voltages associated with them?

    Solar panels have a variety of voltage figures associated with them due to the different types of solar panels, their placement in a solar panel system, and their power production. The most common type of rooftop solar panel uses a direct current (DC) and produces a low voltage. This low voltage is typically between 20 and 40 volts, depending on the specific type of panel. To increase the voltage output, multiple solar panels can be wired together in a series or parallel connection, or both, depending on the specific solar energy system.

    When solar panels are connected in a series, the voltages are added together. This means that connecting two 20-volt solar panels in series would yield a total voltage output of 40 volts. Connecting three panels in series would result in a 60-volt output, and so on. This method is often used when the total voltage needs to be higher than what a single panel can provide.

    In contrast, when solar panels are connected in parallel, the wattage is added together. This means that connecting two 10-watt solar panels in parallel would yield a total wattage output of 20 watts. Connecting three panels in parallel would result in a 30-watt output, and so on. This method is often used when the total wattage needs to be higher than what a single panel can provide.

    The voltage output of a solar panel also depends on its power production, which is measured by the manufacturer at Standard Test Conditions (STC).

    What does STC mean?

    STC is defined as an irradiance of 1,000 W/m2 and cell temperature of 25 degrees Celsius. Because real-world conditions are rarely equal to STC, the actual power output of a solar panel may differ from its rated output. This is why it’s important to understand the various voltages associated with your particular solar energy system to ensure it meets your needs. To determine solar panels rated output, you need to know two figures: the solar panel wattage (measured in watts) and solar panel efficiency (measured in percent). Solar installation involves connecting solar panels to a photovoltaic system that can use or store the generated electricity. The efficiency rating of solar panels varies depending on factors such as environment, angle, and geographic location, but typically ranges between 15–20%. Knowing what wattage solar panels generate helps determine their overall performance in terms of power production for any given solar installation project. Understanding the various voltages associated with solar energy systems can be challenging for those new to the technology but once you’ve grasped this knowledge, you’ll have the knowledge you need to make informed decisions about your own solar energy installation.

    How many size should my solar panel be?

    When choosing a solar panel size, you must consider your energy needs and the hours of sunlight available in your area. The size of the solar panel will determine how much electricity it can produce, measured in kilowatt hours (kWh). Your energy needs will determine the type of solar panel that you need.

    If you’re looking to produce a specific amount of electricity, the total number of solar panels that you need will depend on their wattage rating. Generally, the higher the wattage rating, the more electricity it will generate. You can calculate how many solar panels you need to meet your energy requirements by dividing your kWh requirement by the wattage of each panel.

    For example, if you have an energy requirement of 10 kWh per day and you are using solar panels with a rating of 250 watts, then you would need 40 solar panels.

    When choosing the size of your solar panel, make sure to consider the hours of sunlight available in your area as well. The more sunlight available, the fewer solar panels you’ll need to meet your energy requirements.

    In summary, the size of the solar panel that you need depends on your energy needs and the hours of sunlight available in your area. You can calculate how many panels you need to meet your energy requirements by dividing your kWh requirement by the wattage of each panel.

    Mathematical modeling of photovoltaic cell/module/arrays with tags in Matlab/Simulink

    Photovoltaic (PV) array which is composed of modules is considered as the fundamental power conversion unit of a PV generator system. The PV array has nonlinear characteristics and it is quite expensive and takes much time to get the operating curves of PV array under varying operating conditions. In order to overcome these obstacles, common and simple models of solar panel have been developed and integrated to many engineering software including Matlab/Simulink. However, these models are not adequate for application involving hybrid energy system since they need a flexible tuning of some parameters in the system and not easily understandable for readers to use by themselves. Therefore, this paper presents a step-by-step procedure for the simulation of PV cells/modules/arrays with Tag tools in Matlab/Simulink. A DS-100M solar panel is used as reference model. The operation characteristics of PV array are also investigated at a wide range of operating conditions and physical parameters.

    Result

    The output characteristics curves of the model match the characteristics of DS-100M solar panel. The output power, current and voltage decreases when the solar irradiation reduces from 1000 to 100 W/m 2. When the temperature decreases, the output power and voltage increases marginally whereas the output current almost keeps constant. Shunt resistance has significant effect on the operating curves of solar PV array as low power output is recorded if the value of shunt resistance varies from 1000 ohms to 0.1 ohms.

    Conclusion

    The proposed procedure provides an accurate, reliable and easy-to-tune model of photovoltaic array. Furthermore, it also robust advantageous in investigating the solar PV array operation from different physical parameters (series, shunt resistance, ideality factor, etc.) and working condition ( varying temperature, irradiation and especially partial shadow effect) aspects.

    Background

    Mathematical modeling of PV module is being continuously updated to enable researchers to have a better understanding of its working. The models differ depending on the types of software researchers used such as C-programming, Excel, Matlab, Simulink or the toolboxes they developed.

    A function in Matlab environment has been developed to calculate the current output from data of voltage, solar irradiation and temperature in the study of (Walker 2001) and (Gonzalez-Longatt 2005). Here, the effect of temperature, solar irradiation, and diode quality factor and series resistance is evaluated. A difficulty of this method is to require readers programming skills so it is not easy to follow. Another method which is the combination between Matlab m-file and C-language programming is even more difficult to clarify (Gow and Manning 1999).

    Among other authors, a proposed model is based on solar cell and array’s mathematical equations and built with common blocks in Simulink environment in (Salmi et al. 2012), (Panwar and Saini 2012), (Savita Nema and Agnihotri 2010), and (Sudeepika and Khan 2014). In these studies, the effect of environmental conditions (solar insolation and temperature), and physical parameters (diode’s quality factor, series resistance Rs, shunt resistance Rsh, and saturation current, etc.) is investigated. One disadvantage of these papers is lack of presenting simulation procedure so it causes difficulties for readers to follow and simulate by themselves later. This disadvantage is filled in by (Jena et al. 2014), (Pandiarajan and Muthu 2011). A step-by-step procedure for simulating PV module with subsystem blocks with user-friendly icons and dialog in the same approach with Tarak Salmi and Savita Nema is developed by Jena, Pandiarajan and Muthu et al. However, the biggest gap of the studies mentioned above is shortage of considering the effect of partially shading condition on solar PV panel’s operation.

    In other researches, authors used empirical data and Lookup Table or Curve Fitting Tool (CFtool) to build P–V and I–V characteristics of solar module (Banu and Istrate 2012). The disadvantage of this method is that it is quite challenging or even unable to collect sufficient data if no experimental system be available so that modeling curves cannot be built and modeled.

    From the work of (Ibbini et al. 2014) and (Venkateswarlu and Raju 2013), a solar cell block which has already been built in Simscape/Simulink environment is employed. With this block, the input parameters such as short circuit current, open circuit voltage, etc. is provided by manufacturers. The negative point of this approach is that some parameters including saturation current, temperature, and so on cannot be evaluated.

    Solar model developed with Tag tools in Simulink environment is recorded in the research of (Varshney and Tariq 2014), (Mohammed 2011), etc. In these papers, only two aspects (solar irradiation and temperature) are investigated without providing step-by-step simulation procedure.

    In overall, although having advantages and disadvantages, different methods have similar gaps as follows:

    • The proposed models are not totally sufficient to study all parameters which can significantly affect to I–V and P–V characteristics of solar PV array, including physical parameters such as saturation current, ideality factor, series and shunt resistance, etc. and environmental working conditions (solar insolation, temperature and especially shading effect).
    • Lack of presenting step-by-step simulation procedure and this causes difficulties for readers and researchers to follow and do simulation by themselves.

    Therefore, the study proposes a robust model built with Tag tools in Simulink environment. The proposed model shows strength in investigating all parameters’ influence on solar PV array’s operation. In addition, a unique step-by-step modeling procedure shown allows readers to follow and simulate by themselves to do research.

    Methods

    Mathematical equivalent circuit for photovoltaic array

    The equivalent circuit of a PV cell is shown in Fig. 1. The current source Iph represents the cell photocurrent. Rsh and Rs are the intrinsic shunt and series resistances of the cell, respectively. Usually the value of Rsh is very large and that of Rs is very small, hence they may be neglected to simplify the analysis (Pandiarajan and Muthu 2011). Practically, PV cells are grouped in larger units called PV modules and these modules are connected in series or parallel to create PV arrays which are used to generate electricity in PV generation systems. The equivalent circuit for PV array is shown in Fig. 2.

    The voltage–current characteristic equation of a solar cell is provided as (Tu and Su 2008; Salmi et al. 2012): Module photo-current Iph:

    I_ = [I_ K_ (T. 298)] \times Ir/1000

    Here, Iph: photo-current (A); Isc: short circuit current (A) ; Ki: short-circuit current of cell at 25 °C and 1000 W/m 2 ; T: operating temperature (K); Ir: solar irradiation (W/m 2 ).

    Module reverse saturation current Irs:

    Here, q: electron charge, = 1.6 × 10 −19 C; Voc: open circuit voltage (V); Ns: number of cells connected in series; n: the ideality factor of the diode; k: Boltzmann’s constant, = 1.3805 × 10 −23 J/K.

    The module saturation current I0 varies with the cell temperature, which is given by:

    Here, Tr: nominal temperature = 298.15 K; Eg0: Band gap energy of the semiconductor, = 1.1 eV; The current output of PV module is:

    Here: Np: number of PV modules connected in parallel; Rs: series resistance (Ω); Rsh: shunt resistance (Ω); Vt: diode thermal voltage (V).

    Reference model

    The 100 W solar power module is taken as the reference module for simulation and the detailed parameters of module is given in Table 1.

    Module photon-current is given in Eq. (1) and modeled as Fig. 4 (Ir0 = 1000 W/m 2 ).

    I_ = [I_ K_ (T. 298)] \times Ir/1000

    Module reverse saturation current is given in Eq. (2) and modeled as Fig. 5.

    Module saturation current I0 is given in Eq. (3) and modeled as Fig. 6.

    Modeled circuit for Eq. (6) (Fig. 7).

    Modeled circuit for Eq. (4) (Fig. 8).

    The solar module simulation procedure is shown from Fig. 3 to Fig. 8b. The solar PV array includes six modules and each module has six solar cells connected in series. Therefore, the proposed model of solar PV array is given in Fig. 9.

    Experimental test

    In order to validate the Matlab/Simulink model, the PV test system of Fig. 10 is installed. It consists of a rheostat, a solar irradiation meter, two digital multi-meters and a solar system of two DS-100M panels connected in series, each panel has the key specifications listed in Table 1.

    Result and discussion

    Simulation scenario

    With the developed model, the PV array characteristics are estimated as follows.

      (i) I–V and P–V characteristics under varying irradiation with constant temperature are given in Fig. 11a and b. Here, the solar irradiation changes with values of 100, 500 and 1000 W/m 2 while temperature keeps constant at 25 °C.

    • With two modules connected in series (Ns = 72, Np = 1), the value of current output is similar to that of it in case of one module (Ns = 36, Np = 1) but the voltage output doubles so the power output doubles.
    • In term of two modules connected in parallel (Ns = 36, Np = 2), the value of voltage output is similar to that of it in case of one module (Ns = 36, Np = 1) but the current output doubles so the power output doubles. Similar value of power output is experienced in both cases of two modules despite different ways in module connection (parallel or series).

    The proposed model has advantages not only in studying effect of physical parameters such as series resistance Rs, shunt resistance Rsh, etc. but also in investigating impact of environmental condition like varying temperature, solar irradiation and especially shading effect. In this study, the evaluation of shading effect on solar PV array’s operation is carried out through following cases. The simulation results are given in Fig. 15a and b.

    No shaded PV module (full irradiation on solar PV array): 1000 W/m 2

    One shaded module (receives irradiation of 500 W/m 2 ), others receive full irradiation of 1000 W/m 2

    Two shaded modules (receive irradiation of 500 W/m 2 ), others receive full irradiation of 1000 W/m 2

    Two shaded modules (receive irradiation of 500 and 250 W/m 2 ), others receive irradiation of 1000 W/m 2

    • The power output of PV array reduces noticeably when it works under partial shading condition.
    • The I–V curve experiences multiple steps whereas the P–V curve gives many local peaks along with the maximum power point (the global peak). In addition, more shaded modules are higher number of power output peaks is shown.

    Experimental results and validation

    The Matlab/Simulink model is evaluated for the experimental test system (two DS-100M panels are connected in series). The results are shown in Fig. 16. On the other hand, the empirical results with a solar irradiation of 520 W/m 2 and operating temperature of 40 °C are given in Fig. 17. The I–V and P–V simulation and experimental results show a good agreement in terms of short circuit current, open circuit voltage and maximum power output.

    Conclusion

    A step-by-step procedure for simulating a PV array with Tag tools, with user-friendly icons and dialogs in Matlab/Simulink block libraries is shown. This modeling procedure serves as an aid to help people to closer understand of I–V and P–V operating curves of PV module. In addition, it can be considered as a robust tool to predict the behavior of any solar PV cells, modules and arrays under varying environmental conditions (temperature, irradiation and partially shading condition) and physical parameters (series resistance, shunt resistance, ideality factor and so on). This research is the first step to study a hybrid system where a PV power generation connecting to other renewable energy production sources like wind or biomass energy systems.

    Authors’ contributions

    XHN initiated, proposed model developed in Matlab/Simulink and analyzed. He also prepared a draft manuscript for publication. MPN assisted in designing, data collection, analysis and reviewed the manuscript and edited many times and added his inputs. Finally, XHN decided finally the content of the research revised final manuscript. All authors read and approved the final manuscript.

    Authors’ information

    Xuan Hieu Nguyen is a lecturer in Department of Electric Power System, Faculty of Engineering, Vietnam National University of Agriculture, Hanoi, Vietnam. He had bachelor degree in electric power system, Hanoi University of Science and Technology, Vietnam in 2008. He received master degree in electrical engineering in University of Wollongong, Australia in 2012. Minh Phuong Nguyen is graduate student in Faculty of Engineering, Vietnam National University of Agriculture.

    Acknowledgements

    The authors are grateful to the support by this work through the project “Study, design and manufacture a solar PV system using SPV technology served for chicken farms in Faculty of Animal Science, Vietnam National University of Agriculture”, Vietnam (2014–2017).

    Competing interests

    The authors declare that they have no competing interests.

    Author information

    Authors and Affiliations

    • Department of Electric Power System, Faculty of Engineering, Vietnam National University of Agriculture, Trau Quy town, Gia Lam district, Hanoi, 10000, Vietnam Xuan Hieu Nguyen
    • Faculty of Engineering, Vietnam National University of Agriculture, Trau Quy town, Gia Lam district, Hanoi, 10000, Vietnam Minh Phuong Nguyen

    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).

    Become Energy Independent Today

    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.

    See our other related articles to learn more:

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