28 IMPORTANT INFORMATION ABOUT SOLAR ENERGY

By / June 4, 2021 / 14 minutes of reading
solar energy
 
Solar energy is a source of energy that depends on the sun. This energy makes it possible to produce electricity from photovoltaic panels or thermal solar power stations, thanks to the sun radiations captured by solar panels.

#1. What should I know about this source of energy?

Soar energy field is a huge field and there is some information that must be known for everyone working in this field, I think it’s obligatory for you to know such things like what is a solar cell? how it produces electricity? and how many types of solar cells? so in order to get all these answers, I invite you to read these two articles, the first is for beginners and the second is for advanced 
 

Solar cells

#2. How the solar cell produces electricity?

The first thing anyone who works in the field of solar energy, whether he is an engineer or a trader who sells solar panels or an ordinary person who wants to install solar panels in his home, must know that Solar cell generates constant current when exposed to the sun, where photons in sunlight hit the surface of the cell and release electrons in the solar cell, and thus the passage of electric current, then the electric current is the movement of electrons

1-Crystalline‬‬  silicon solar Cells: 

this First type of solar cell also divided into two main types.

  • ‫‪Monocrystalline‬‬
  • ‫‪Polycrystalline‬‬

2- Non-Crystalline Silicon Solr Cells 

 
The second section consists of only one type
  • ‫‪Amorphous silicon solar cells 

for this type Companies refer to it in the datasheet as the following symbol  :

‫‪A-si‬‬‬ thin-film solar module.

A refers to Amorphous.
Si: refresh to Silicon 

The two dominating the world market are Poly and Mono, Mono is the richest and the Amorph is the cheapest this is in terms of price, and in terms of efficiency, Amorphous has the minimum efficiency when we compare it with Mono and Poly.

 

#3.Corporate shortcuts to denote the type of cells 

Three corporate shortcuts to denote the type of cells that make up the solar panel on the solar panel datasheet.
  • Monocrystalline, usually companies symbolize it as Mono-Si, So the  symbol Si indicates Silicon  the material from which the solar cell was made and some times indicate  it as Mono or M 
  • Polycrystalline usually companies symbolize it as Poly-si and some times they make Poly or P
  • Amorphous usually companies symbolize it as A-si, and the A indicates Amorphous and si to Silicon.

 #4.Fingers and Pasbars

On the surface of the solar cell, there are parallel lines called fingers and There are also other lines called busbars.

Solar Panels

#5. What are the common types of solar panels?

 Solar panels are three types that differ according to the silicon cells made of these panels, very briefly and in order to simplify this first issue, solar cells are divided into two main types:

‫‪Crystalline‬‬  silicon solar Cells ‬‬ and Non-Crystalline Silicon Solr Cells.
 

#6. What is the Datasheet and what it contains? 

you cand find in the datasheet of solar panels the following information:
  • Cell dimensions with a millimeter (mm)
  • The cell  efficiency ( less than the efficiency of the panel )
  • Maximum Power of the cell 
  • The cell voltage at the maximum power point (Vmp: when connected )
  • The cell intensity at the maximum power point (Imp: when it is connected )
  • Open circuit voltage of the cell (Voc: when it’s not connected)
  • Open circuit intensity (ISC )

Note: All of these preceding values ​​are given under certain conditions called Standard conditions (1000 watt/m²,25 °c, 1.5 density of atm )

#7.IV Curb

Each solar cell, and each combination of solar panels and solar arrays, has its current-voltage relationship. Consequently, they can supply a current I at a voltage V. The purpose most important of a solar panel or network is to provide electrical energy that results from the multiplication of V and I., It’s about not only providing I and V, but also the maximum power P = V x I

The Power of the panel that the manufacturer of solar panels gives that you find in a datasheet is the maximum power in the standard conditions, and the point that many workers in this field don’t realize is when the company says that the power of the panel is 100 watts, this does not mean that you will get 100 watts during the day. Perhaps you may get 100 watts at ten o’clock and after a minute when a cloud passes, you will get 60 watts and at midday 80 watts and in the evening you get 60 watts good to explain this important point.

#8.VOC, Isc and Vmpp, Impp 

Not knowing the difference between the short circuit current Isc and the load circuit current Impp, as well as between the load circuit voltage Vmpp and the short circuit voltage  Voc as a result of the wrong calculations of panels and the inaccurate system calculations.

As a final result of the system failure after a while,  and a lot of People paid the price of the system twice and three times, and if you go back to the reasons, it will be the result of a miscalculation, which was mainly caused by the lack of knowledge of the difference between the Voltages or currents of the solar panel.
 refer to the Datasheet of the solar panel or the inverter.

iv curve
iv curve

For more details Read also the 5 parameters of I-V Curve 

 

#9.The Fil Factor 

The Fill Factor (FF) is a measure of the quality of the solar cell  and it is an important technical parameter  to know the quality of the cell and the solar panel in general, This Factor is measured by knowing some of the parameters of the solar panel
It is calculated by comparing the maximum practical power that would be output power to the theoretical power at both the open-circuit voltage and short circuit current.

Voc open circuit voltage
Isc short circuit current
Vmp maximum open-circuit voltage
Imp maximum open-circuit current

After knowing these values from the datasheet of each panel, the Factor  is calculated through the following mathematical relation:

The cell quality factor is always smaller than one, and the closer it is to one the better and the meaning of this is that  The theoretical values ​​for the amount of energy produced by the cell given by the manufacturer on the dashboard are the same as the values ​​produced by the cell during work, and some companies say that the cell quality factor if it is smaller From 0.7 (70 %) the lower the quality of the cell and the if it is greater then this value the cell is better.
In reality, This will be true, but most solar cell manufacturers have exceeded this number to above this value. to even 0.8(80%)

we can also calculate and know the value of this factor from the IV graph as its shown on the following figure, and you have to know that the IV graph is so important for the engineer.

#10.Moist heat test 

what is the Moist heat test?

The moist heat test for photovoltaics is an accelerated environmental aging test that determines the ability of a solar panel to withstand long-term exposure to high temperatures and moisture penetration.

How they tested it?
 

The wet temperature test is performed by applying 85 ° C ± 2 ° C with a relative humidity of 85% for an unbroken cycle of 1,000 hours, which exceeds one month.

1000 hours of wet heat test at 85 ° C and 85% relative humidity equals several years of outdoor exposure. The plate to be tested is placed in a wet heat test chamber where the plate is exposed to these conditions.

 

#11. What are the defects that can occur during a wet heat test?

This test specifically challenges the lamination of photovoltaic cells and the closing of edges from moisture. The peel strength of the PV cells that are laminated according to the traditional lamination process is crucial.
 
This test can detect problems with the lamination process and the sealing of the edge of the solar cell.
Rust removal and corrosion can be detected in various cell parts due to the penetration of moisture.
A wet temperature test can reveal various defects, such as lamination, degradation of the vitreous (AR coating), frame erosion, discoloration of the metal mesh, and the junction box attachment.

#12.Moist heat test and IEC 61215

Moist heat test is an environmental quality test and one of the qualifications for IEC 61215. Moist heat test is performed before the mechanical load test and wet leakage current test before and after the test.

Even if no major defects are detected after the DH1000 (1000 hour moist heat test), the unit is then pressed to the point where it becomes more brittle to a subsequent mechanical load test.

#12. What type of silicon photovoltaic cells has immunity to the effects of oxygen interaction with boron?

  • Silicon photoelectric cells N-Type

#13.One way to protect from hot spots on PV panels 

  • Is to  Use of transit diodes.

#14. What is the most secure type of Solar Inverters?

  • Microinverters

#15.Which of the following technologies is theoretically the most cost-effective solar PV manufacture?

  • Heterojunction solar heterogeneous link technology

#16.What kind of solar panels should be chosen for our projects?

  • There is no single answer to this question

#17. What is the highest temperature reached with focused AI technology?

  • 1000 ° C.

#18. What does the symbol Class A, Class B, or Class C usually mean on the solar panel datasheet?

  • Refers to solar panel’s fire tolerance

Installation of a solar system 

#19.Angle and Orientation of the Modules

You must also know the importance of the inclination angle of the solar inclination where each region of the world follows a special inclination angle and the efficiency of the panels decreases if the panels are not installed in the regular direction and inclination.
The angle and direction of each region can be obtained easily through software applications and simulator tools.
for more information about the inclination of modules read this article

#20.The use of completely identical panels in any solar energy project

If you have a solar energy project, you should use the panels exactly the same capacity, i.e. all the panels, for example, 200 watts, and the panels of the same type, for example, all the panels 200-watt monocrystalline, and the panels for the same manufacturer, I mean, for example, all the panels of 200-watt mono produced by Trina company.
 
Someone might say if the connection of the panels is in series, in this case, will be no problem if the panels are with the same current and the loads are different and if the connection is parallel there is no problem if the panels have the same voltage but the current is different, this talk is relatively acceptable but despite that the sound rule is the panels are completely identical, i.e. the same type and capacity, and of the same manufacturer.
 

#21. Does the design of solar panels need an architect and civil engineer ??

 
The respectable factories that make the bases for the solar panels supplied with the purchase of a mathematical study of the iron or aluminum bases, indicating the size of the concrete bases and the weight of each base, of course, after asking for the coordinates of the required wind speed.
So solar companies can do without civil engineers if the business is established With that.

#22. Can you place the battery inside the house?

Generally, put the battery in the shed. It is an upper storehouse that is generally found in our homes above bathrooms or kitchens. It is considered a cold place and has ventilation nets on the skylight and is not exposed to heat, sun, or water.
Certainly, the most important thing is that it is far from the arrival of children or even adults and that there are no flammable materials besides it like gas, gasoline, diesel, fabric, etc. This is in terms of location.
In terms of safety, the charger is examined and has two protection stages to ensure that the temperature does not rise and that the battery is not overcharged.

Second,  place a cloth over the battery, which is intended to absorb vapors that are dating from the battery. We train the customer to replace this piece every month because it will definitely wear out.

And also make sure that the battery compartment cover contains a hole or hole for leaking gases without causing pressure. And isolate the battery poles in a way that is available to avoid shorts with deformation.

Finally, asking the customer not to approach the system and contact us to do the service at the hands of trained technicians.

 
Of course, putting the battery in the hall, the kitchen, or the bedrooms is a danger, a danger and a risk that cannot be discussed, and the least danger is the wear and tear of furniture from the battery fumes. This is the weakest risk not to mention the danger to humans, children, and the place.

#23. What is the effect of the Accumulation of dirt on the solar panels?

Another common mistake is also simple, but its impact is very large which is the accumulation of dirt on the surface of the panels and not being cleaned periodically when the accumulation of dirt on the surface will reduce the efficiency of the panels, I mean in colloquial language the ability of the panels will decrease compared to the absence of dust on the surface of the panels.
 
Dust will form a layer that prevents the arrival of sunlight on the surface of the board. Of course, there are many studies in universities to study the effect of dust accumulation on the efficiency of panels.
 
But as a result, you have to care about the cleanliness of the panels, and the engineer or technician must give instructions to the customer on the importance of the topic of cleaning, especially if the panels are installed in an open area or in an agricultural or desert area.
 
Well, I think you get a brief thank you for your interest see you in the next article. 

24.Variables used to describe the properties of solar cells

#1.I-V Curve Parameters

  1. Maximum Power at STC (Pmax)
  2. Optimum Operating Voltage (Vmp)
  3. Optimum Operating Current) (Imp)
  4. Open Circuit Voltage ( Voc)
  5. Short Circuit Current (ISC)

#2.Operating Module Temperature

It expresses the operating temperature at which a solar cell can operate.

#3.Maximum System Voltage 

It expresses the system voltage to which a module can be added so that the system does not exceed this amount altogether

#4.Module Efficiency

The energy conversion efficiency of a solar cell is defined as the percentage of the converted power from the absorbed light when the solar cell is connected to an electrical circuit, which expresses the efficiency of the solar cell, and the more the efficiency of the module increases Which equals
(Generated electric power (Watt) / (Light radiation input (Watt / m2) * Solar cell surface area (m2)
For solar cells, whose efficiency ranges between 16-11%, this means that the cells absorb the radiation coming from the sun And that is 1000w / m2 on a sunny day near the equator, one square meter of these cells absorb radiation according to this efficiency allows between 110-160W.

#5.Maximum Series Fuse rating

It expresses the maximum protection current of the fuse, which the module can handle, and if it increases, it

100 w Solar module

can affect the solar cells.
The rated power of a cell (Wp) is measured in watts under standard test conditions (STC) Which :

  •  The value of the maximum orthogonal and instantaneous solar radiation equal to 1000W / m²
  • 1.5 AM  It stands for air mass (AM) and it refers to how light travels through
    Earth’s atmosphere.
  • Cell temperature: Tc = 25 C

 

Pre-sizing studies 

25.Design & Sizing of an off-grid photovoltaic installation

 
There are several steps to follow to properly size this type of installation:
 
  1. The budget: that is to say the financial resources available.
  2. Definition of the electrical need: By making an inventory of appliances consuming electricity (Lighting, refrigeration, electric heating, household appliances, Television, computers, etc.)
  3. Assessment of the local solar deposit:: Determine:
  4. The number of hours of sunshine and the DNI (direct normal irradiance)
  5. The optimal tilt angle of the PV modules. (Calculated by the formula: latitude of the place + 10 °)
  6. The orientation of the PV modules: in the northern hemisphere, the full south orientation is the best possible orientation for a photovoltaic field. If we have a choice between the two directions East or West, theoretically it is the same, but it is still necessary to take a look at the needs. Indeed, if the needs are very marked in the afternoon, we will orient the photovoltaic field rather than the West. Likewise, if consumption is higher in the morning, it will rather be oriented to the East.

26.Qualitative parameters of the photovoltaic installation

The yield of a photovoltaic installation expresses the share of energy returned by the installation, in electrical form, compared to the amount of solar energy received by the modules of the installation. Thus, this efficiency is also written: η = (Electric power supplied) / (Solar power received). In addition, it will be necessary to calculate the efficiency of the modules, the losses due to heating of the cables, the efficiency of the regulator, the efficiency of the batteries, the efficiency of the inverter, and other losses.

 

27.The Quantity of  Electricity produced by a PV System

The evaluation of the solar deposit and the quantification of the various losses allows us to calculate the yield of an autonomous photovoltaic installation. Note that the electrical production thus produced is physically adjusted to the consumption of electrical receivers. There is a simple analytical formula for estimating the electricity production necessary for a photovoltaic installation:

28.Effects of shading on Modules

To function optimally, a photovoltaic solar installation must be subjected to the least possible shade. However, certain constraints linked to the place of installation (presence of mountains, trees, chimney, electric pole, etc.) cannot be avoided.
 
 

 

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