Advanced Considerations To Optimize Your Design
The above rules will ensure that your stringing configuration will comply with the specifications of your inverter and that the energy production of the system wont be negatively affected by mismatches in the conditions on the panels.
However, there are additional factors that a solar designer can consider to arrive at the optimal design . These factors include inverter clipping, the use of module-level power electronics devices which include microinverters and DC optimizers, and design efficiency provided by software tools.
Inverter Clipping
Sometimes it may make sense to oversize the solar array that you are connecting to the inverter leading to a theoretical maximum voltage that is slightly higher than the inverter max. This may allow your system to produce more energy when it is below its maximum voltage, in exchange for reduced production during the times when the DC voltage of the array exceeds the inverters maximum.
If the production gains exceed the production lost to inverter clipping, then you can produce more power without paying for an additional inverter or one with a higher voltage rating.
Of course, this decision should be made with care and a clear understanding of how much production will be clipped compared to how much additional production will be gained at other times.
Microinverters
Got It All Great Lets Go
When you have all the information above you are ready to use the following solar panel maximum voltage calculator. This will quickly show if your solar panel design will suit your requirements. Just overwrite the data which is in the calculator this data is for the REC 290W Twin Peak 2 solar panel used as an example above.
How Do I Read The Solar Panel Specifications
Impp, isc, maximum power rating, noct, nominal voltage, Pmax, solar panels, specifications, standard test conditions, stc, Vmpp, voc
There are several terms and ratings that are associated with a solar panels data sheet. Figuring out what means what for the specs can get pretty confusing. We are going to explain each of them to help clear it up.
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Wiring Solar Photovoltaic Panels In Series
As we said above, when connecting solar panels in series, we get an increased wattage in combination with a higher voltage.
Such higher voltage means that series connection is more often applied in grid-tied solar systems where:
1) the system voltage is often at least 24 volts, and
2) the solar array output voltage is fed to an inverter or charge controller of a typically higher input voltage compared to off-grid systems.
Connecting in series means joining the positive terminal of a solar panel to the negative terminal of the next solar panel until eventually you are left with one free positive and one free negative terminal of the array, which are to be connected to the input either of the inverter or the charge controller .
When you connect solar panels in series, the total output current of the solar array is the same as the current passing through a single panel, while the total output voltage is a sum of the voltage drops on each solar panel.
The latter is only valid provided that the panels connected are of the same type and power rating.
Lets consider the depicted below solar panels designated for a 12V solar panel system, operating at their Maximum Power Point, while delivering the depicted voltage and current that correspond to this power tracking point.
Scheme of solar panels connected in series
Which Types Of Solar Charge Controllers Are The Most Widely Used
There are two main types of charge controllers PWM and MPPT ones.
They are very different from each other since they are based on different principles of operation.
In general, while PWM controllers cost less and are used in small solar panel systems, MPPT charge controllers are used in larger solar power systems, are more advanced, and cost more.
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Why Is A 24v System More Expensive
In comparison to a 24V solar panel, a 12V solar panel is often appropriate for smaller houses or projects.
The porch and lawn lights, as well as the cottages, may all be powered by a 12V system. However, if you need to power a family home and intend to expand, a 24-volt solar system is the way to go.
Therefore, a 24V system would need a considerable initial expenditure, but the return on investment would be significant as well. Advertisements
Aside from this fundamental guideline, there are a variety of details to consider while choosing between the two.
Very Large Scale Solar Power Plants
There have been several proposals for gigawatt size, very-large-scale solar power plants. They include the Euro-Mediterranean Desertec proposal and Project Helios in Greece , both now canceled. A 2003 study concluded that the world could generate 2,357,840 TWh each year from very large scale solar power plants using 1% of each of the world’s deserts. Total consumption worldwide was 15,223 TWh/year . The gigawatt size projects would have been arrays of standard-sized single plants. In 2012, the BLM made available 97,921,069 acres of land in the southwestern United States for solar projects, enough for between 10,000 and 20,000 GW. The largest single plant in operation is the 510 MW Noor Solar Power Station. In 2022 the 700 MW CSP 4th phase of the 5GW Mohammed bin Rashid Al Maktoum Solar Park in Dubai will become the largest solar complex featuring CSP.
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Lesson : How Solar Panels Work
A solar panel is made up of solar cells that are often bundled together in the panel into solar modules. A typical solar panel is made up of 60 or more individual solar cells. A solar cell is built like a sandwich. It has an upper layer and a lower layer just like slices of bread. Those layers are made of silicon, which is treated with other elements like boron and phosphorus that cause the silicon to either have too many electrons or too few of them. The solar cell produces electricity when light hits it because the energy from the light knocks electrons loose from the layer in the cell that has too many electrons. The result is that the electrical current flows from the cell
How Does Connecting Solar Panels In Series Help Increase Voltage Output
The Series Wiring approach is the method we will look at for connecting solar panels together. The overall system voltage is increased by connecting solar panels in series.
When a grid-connected inverter or charge controller requires 24 volts or more, solar panels in series are typically employed.
Within a module of an array of solar panels, the panels are electrically linked in series and parallel connections to create the required output voltage and/or current values.
When there is no external load applied, most silicon solar cells produce around 0.5 to 0.6 volts of direct current.
A solar cell creates its maximum output voltage, also known as its open-circuit voltage when there is no load attached or a very low current demand.
To achieve the entire output voltage, stronger sunlight is necessary as the load current demand from the cell grows.
So to sum it up series linked solar panels are about voltage, thus series wiring equals greater voltage.
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Solar Thermal Enhanced Oil Recovery
Heat from the sun can be used to provide steam used to make heavy oil less viscous and easier to pump. Solar power tower and parabolic troughs can be used to provide the steam which is used directly so no generators are required and no electricity is produced. Solar thermal enhanced oil recovery can extend the life of oilfields with very thick oil which would not otherwise be economical to pump.
Parallel Connected Photovoltaic Cells
In our example above, the four photovoltaic solar cells are connected together in a parallel combination. For parallel connected cells, the combined output voltage is the same as that produced by each cell, then: V1 = V2 = V3 = V4 = VCELL.
If we assume that the output current produced by each individual PV cell in the chain is 1.0 ampere, then the combined output current will be the sum of the individual cells output currents and this is calculated as:
ITOTAL = I1 + I2 + I3 + I4 = 1.0A + 1.0A + 1.0A + 1.0A = 4.0A
Then we can use parallel connected photovoltaic solar cells to boost current output. The combined power is the sum of the individual cells power or the product of the voltage times the current.
We said previously that we can have a current mismatch for series connected solar cells due to shading or a faulty cell and that the good cells bias the bad cell causing large amounts of power to be dissipated into the bad cell which in turn causes what is generally called hot spot heating, severely damaging the solar panel. In a parallel connected solar photovoltaic panel, a mismatch in voltage can be more drastic.
If we use nominally identical solar cells to construct our photovoltaic solar panel then why is there cell voltage mismatch?. In our simple parallel example above, we have assumed that each cell generates 0.5 volts but this is not always the case. At low current outputs , this mismatch of voltages is generally not a problem.
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How To Select Your Solar Charge Controller
Upon selecting a solar panel charge controller regulator, you should consider mainly:
- The system voltage,
- The solar array current ,
- The battery type.
What kind of solar battery maintainer to choose depends on the specific case and is a tradeoff between maximizing the solar generated power and extending the battery life.
PWM controllers are less expensive.
They are very suitable for small wattage solar electric systems.
Furthermore, their efficiency is similar to the MPPT solar panel battery regulator charge controller in hot climates.
An improperly selected charge controller can result in a 50% loss of the solar generated power in a mobile solar panel.
This is a common mistake usually made with charge controllers by owners of caravans, campers, RV and motorhomes.
They get a high voltage solar panel at the lowest cost per Watt and connect this solar panel or these solar panels to a PWM charge controller, and subsequently lose almost 50% percent of the available solar power.
Here is an example of how such a situation can occur.
Lets consider a 220Wp solar panel with:
- Maximum power point voltage Vmpp =29.1 V
- Maximum power point current Impp =7.56 A
Lets assume such a solar panel connected to a simple mobile solar power system consisting of a solar panel charge controller and a 12V battery bank.
A PWM charge controller is sized in regard to the current delivered by the solar array.
Thus you can lose about 130W of the available solar panels 220W power!
Which Solar Charge Controller Is The Best
Selecting the right type of charge controller does not mean to decide which charge controller technology is better the PWM one or the MPPT one but rather to estimate which type of these would be more suitable for your solar system.
The idea is not only to avoid building a system that will not perform well but also save money on buying a costly device that you dont actually need.
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What Is The Difference Between Power And Energy
Instantaneous solar power output is measured in watts. By instantaneous, I mean measured at any instant in time.
As soon as you consider watts for a duration on time, this energy delivered is called watt-hours. Its simply the watts a solar panel generates per hour, or day, or year!
Professional solar installers often use rule-of-thumb guidelines for sizing domestic solar installation and sizing solar panels. One such guide is that a 100 watt solar panel will produce about 400 watt-hours of energy per day.
Where does the solar sizing rule-of-thumb come from?
Every location on the planet has a certain irradiance, which is the amount of sunshine energy falling on a flat surface. Its measured in kilowatt-hours per square meter per day kWh/m2/day.
Luckily, this cumbersome looking figure is also known as peak-sun-hours. It can be measured on location but its much easier to look it up for your city using a historical solar database such as the one found at Global Solar Atlas.
Impact On Electricity Network
With the increasing levels of rooftop photovoltaic systems, the energy flow becomes 2-way. When there is more local generation than consumption, electricity is exported to the grid. However, an electricity network traditionally is not designed to deal with the 2- way energy transfer. Therefore, some technical issues may occur. For example, in Queensland Australia, more than 30% of households used rooftop PV by the end of 2017. The famous Californian 2020 duck curve appeared often for a lot of communities from 2015 onwards. An over-voltage issue may result as the electricity flows from PV households back to the network. There are solutions to manage the over voltage issue, such as regulating PV inverter power factor, new voltage and energy control equipment at the electricity distributor level, re-conducting the electricity wires, demand side management, etc. There are often limitations and costs related to these solutions.
When electric networks are down, such as during the October 2019 California power shutoff, solar panels are often insufficient to fully provide power to a house or other structure, because they are designed to supply power to the grid, not directly to homes.
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The Last Step: The Inverter
Solar Panels produce DC power the same type used in a 9-volt battery, just much more powerful! An inverter is required to change that DC power into the AC power used by the lights, appliances, and even battery chargers in a house. It does this by detecting the exact power profile coming from the utility and using a series of switches to mimic that same power profile. Once that power is output to the house, it is the same or higher quality than the power coming from the utility grid.
In recent years, improvements in solar inverters have allowed them to support the utility grid by making it more stable. Solar inverters can support low or high voltage when the utility grid calls outside the recommended limits. This grid-interactive support benefits the entire neighborhood with consistent, well-conditioned power.
What Are The Pros Of Low Voltage Solar Panels
- Lower cost of installation and initial purchase, which can also be less expensive if a person decides to do the installation themselves.
- The panels are not as powerful and dont produce electricity as quickly, but theyre great for home use or smaller projects that just need minimal power production.
- They pose no risk of electric shock because there is very little voltage when compared to high voltage panels.
- Easier to transport and install because they are less heavy due to their lower electrical capacity than high voltage solar panel systems.
- Easier to use for commercial purposes, such as powering a clock or outside lights.
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How Are Solar Panels Rated
The basic rating is in watts, but you need to look at the specifications to understand what that really means.
A 100 watt solar panel wont always give 100 watts output power. In fact, most of the time it wont! So where does this manufacturers rating come from? What will 100 watts power?
All solar panels are rated according to an international standard known as STC or Standard Test Conditions. The most important conditions for the declared rating are:
- Irradiance of 1000watts/m2
- Ambient temperature of 77 degrees F
These are ideal laboratory conditions and you can expect to reduce that rating by about 15%, even in your best conditions.
In addition there are several normal solar losses that can reduce output even further.
Solar Panel Maximum Voltage Calculator Why Its Important
Snow covered solar panels not a problem on the Gold Coast however its important to know that the lower the solar panel temperature, the higher the voltage the panels are producing.
With a solar power system its very important that the solar panels match the electrical characteristics of the solar inverter or charge controller that theyre connected to. So how do we work this out and what do you need to know? Theyre good questions and this is where our solar panel maximum voltage calculator comes in handy! One of the electrical characteristics thats very important is the maximum voltage the solar inverter or controller can handle. Thats because if the voltage supplied from the solar panels is too high it wont work and could be irreparably damaged.
Australian Standards PV array voltage requirements
Another important point is raised in the Australian Standard AS5033-2014 clause 3.1 which states the following:PV arrays for installation on domestic dwellings shall not have PV array maximum voltages greater than 600V. For non-domestic installations where the PV array maximum voltage exceeds 600V, the entire PV array and associated wiring and protection shall have restricted access.
With these points to consider its very important that we know the maximum voltage of the solar power system. Luckily we have our solar panel maximum voltage calculator to help!
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Solar Electricity Regulator Using Ic 741
The majority of typical solar panels provide around 19V off load. This enables to get a drop of 0.6V over a rectifier diode while charging a 12V lead-acid battery. The diode prohibits battery current from moving via the solar panel during night.
This set up can be great so long as the battery does not get overcharged, since a 12V battery can easily become overcharged to above 1V5, in case the charging supply is not controlled.
Voltage drop induced through a series pass BJT, typically is approximately 1.2V, which appears to be way too high for nearly all solar panels to operate effectively.
Both the above flaws are effectively removed in this simple solar regulator circuit. Here, energy from the solar panel is supplied to the battery via a relay and rectifier diode.
