2 Types of solar systems

solar systems
installation of a solar system

Solar energy is one of the most important free resources that citizens can benefit from today in order to produce the necessary electricity for their daily needs. So if you want to produce electricity in your home through solar energy, all you have to do is to follow the following steps that explain in detail how you can do that On your own without needing an engineer to install a solar system connected to the grid On-Grid) or isolated from the grid( Off-Grid)

What is the difference between on-grid and off-grid?

Solar-grid integration is a network that makes a significant penetration of PV in the national utility grid. This is an important technology because the incorporation of modular PV systems in grids optimizes the energy balance of buildings, improves the economy of the PV sector, lowers operating costs, and adds value to customers and utilities.    

your local utility. This is what most residential homes will use because if your solar system is under or over-produced with respect to your varying energy needs, you will be covered. For you, all this means your utility system is acting as your battery space. 

If you use your solar panels or device to produce more energy than you use, the excess energy is sent to the power company of your grid, enabling you to build credit that you can cash out at the end of the year, in a process called net metering. It’s beneficial to be grid-tied because you don’t need to buy a costly battery backup system to store any excess energy.

The on-grid system 

On -grid means that your solar system is connected to the GRID (low and medium voltage lines )

On grid
On-grid solar system

#1. Number of Panels required


If I assumed that I had a solar panel manufactured by Solar World, it is a leading company in the world and I wanted to perform the calculations. I will need the following values ​​from the datasheet of the Panel :                         

  1. VOC
  2. Cell temperature used for standard test conditions (STC), temperature coefficient of Voc
  3. Maximum power point voltage (Vmp)
  4. Temperature coefficient of Vmp

If we selected  a random module of  this company( solar world )  and we found theses values on its datasheet : 

VOC: 45.9, ºC @ STC: 25
TCVoc: -0.304
Vmpp: 36.7
TC Pmpp: -0.43%

#2.The inverter

Now if I take an  inverter  made by SMA company It is a well-known company for those working in this field, The inverter model is SMA Sunny Boy 7700TL-US-22
What interests me in the accounts from the Datasheet of the inverter is :

*Maximum system voltage: Vmax( 600 Volt)
*Minimum system voltage: Vmin (150 volts)
Now that I have specified the specifications of the Solar Panel and the inverter, the information I need from the datasheet should specify the weather data for the location where the installation will take place.

We record the lowest temperature at the location where the panels are to be installed and suppose which is just an assumption – 10 is the lowest temperature heat.

We record the highest temperature and assume 38 degrees which are also just an assumption
Now we will start by calculating the number of the top or maximum panels that must be connected in series, we have the temperature at the STC conditions It is 25 ° C.

Now we substract  this minimum temperature from the Maximum  temperature of the site
38 °-13 ° =25 ° C
We multiply the temperature difference  (25 degrees) by the temperature coefficient of Voc and the Temperature coefficient 

25* TCVoc = 25*0.0034=0.107 ° C
then we multiply by Voc in STC >>> 0.017*45.9=4.88V

So 4.88V  is the voltage that will rise for each solar panel when the temperature reaches -13 and it is the lowest temperature, which is the worst possibility

Now we add this increase of 4.88 volts to the open-circuit voltage

V+Voc=4.88V + 45.9V = 50.78 

Now we add this increase of 4.88 volts to the open-circuit voltage
When we divide the maximum system voltage of the inverter, which is 600 volts, by 50.78
we get 11.8 

The maximum number of panels that can be connected within a single String is 11.8, and therefore the maximum number of solar panels is 11 in a String, If the number exceeds 11, the inverter will be separated when the temperature reaches the coldest day of the year, which is – 11degre.
As I mentioned, it is only just an example, and it can be – 1, 0 or even 5 degrees, and this depends on the region that will be done Install the system in it if we multiply 
11 x 50.78 V = 558 Maximum System voltage

We start calculating the maximum number of panels that can be connected in series, and here we will use the Vmp value, not the Voc in our calculus.

Now the highest temperature we assumed is 37 degrees Thus, the cell temperature will be approximately 25 degrees above the Perimeter of the Panel 
37+25=62  degree
 Hence the difference between cell temperature and temperature at STC conditions :
62-25=37  degree 
We multiply the temperature difference (37 degrees ) by the Vmp temperature factor, which is the same as the power coefficient of power (TC Pmpp -0.43)

TC Pmpp -0.43 %/°C

36.7 x (-0.0043) = -0.157
-0.159 x37 = -5.83V

After that the Voltage become :  -5.83 V + 36.7V=30, 87 V 

if we divided the value of Minimum system voltage on 30.87 
we will  get  4.85V
Thus, we round the number to 5 and we get a minimum of 5 Panels
then 5*30.87=154.35 V
Thus, if the temperature rises to 37 degrees as we assumed, the inverter will remain working, which is the highest temperature we assumed.

I want to comment here at the end of this article 

  1.  The first design or simulation is made to determine the maximum number of Panels based on a Voc value.
  2. The design was made  to determine the minimum number of panels based on Vmp values

#2.Before you  buy the Solar Panel

1: Look at the cells and making sure there are no fractures in the ends of the cell.
2: look at the conductive lines (PASPAR) and confirm they are well .
3: Maintaining cell color homogeneity, such as being a dark, dark, light-colored cell, etc.
4: Look at the Junction Box and making sure there are 6, 9 or 3 diodes in the form of a Mosfet, Sometimes they are adulterated into diode-shaped plastic parts
5: Maintain all data on the label

Off-grid solar system

Off grid
Of-Grid solar system

What does it mean off-Grid ?

Off-Grid means that you are not connected to the power system or utility company of your grid in any way. This is appealing because your energy use is 100% self-supporting. There are drawbacks, however, as off-grid systems allow you to buy back-up batteries that can be costly, voluminous, and not very environmentally friendly.

Now after we talked about the on-grid system we have some pieces of information we can simply talk about this second type of solar systems that exist, off-grid .

The 6 steps of calculus

  1. calculate the loads and here we divide them into AC and DC Then we combine these loads.
  2. The sum of the two resulting lambs is multiplied by 1.2 in order to overcome the resulting losses
  3.  We determine the battery system we will use, depending on the nature of the site to be fed(12 V, 24V, and 48V).
  4. We determine the number of days of storage for batteries, these are not subject to our desire, but to the nature of the area and use. 
  5. If we are in a region where the sun is rarely absent during the day, we choose one day, but if we are in northern Europe, for example, the sun can be absent in the winter for two consecutive weeks and this means that we will choose 14 days to ensure batteries are charged during a The absence of the sun and so on.
  6. Choose the percentage of discharging the batteries; It is known that the repetitive discharge of batteries decreases their life and this invites us to choose a small percentage, but this matter is not economical as it means that we will use a larger number of batteries. The type of batteries used has a role in determining the value and the following table highlights the subject:

Maximum Depth of Discharge Battery Type Default Value Lead Acid Shallow Cycle 0.25 Lead Acid Deep Cycle 0.75 Nickel Cadmium 0.90   Fortunately, solar batteries have large cycles as modern technology has created solar batteries that have more than 1,000 discharge cycles (overpriced)     Note: When you choose  batteries it is advisable to see the technical catalogs of solar batteries available on the market Local, there are many websites for battery manufacturers on the internet

  1. Peak The Amper Hour  (rating for the chosen battery )  
  2. Peak The (Battery Nominal voltage )Volts.
  3. Peak sunshine hours(PSH) for worst month radiation (Hours/day)
  4. Peak amperage of the selected module from the Datasheet 
  5. The nominal power rating of the selected module

After you read this short guide you need to know some other different information such as warranty and size of the selected solar panel, Ground mount or roof mount, orientation and azimuth and all this information is here in this post (all you need to make a solar system ) .

Thank you so much for your time if you find this post helpful we will like it if you to say that in the comments below and if all that we made is less i will like to add some new information as I can.

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