If you have installed the right configuration of the solar PV system, then you must be enjoying the comfort of having smooth energy at your home.
But do you know how many transitions, conversions, and distance it travels before reaching to your electrical appliances?
The solar energy experiences many conversions and the losses in your solar power system before giving the final output.
Although, the solar power received by the panel is much more than the energy we get as an output to run the electrical appliances.
The most of the energy in the solar power system is either gets lost as the conversion loss within the components or as a transfer loss through wires.
Take a simple example, when you speak, its intensity is maximum near your mouth and it fades away as the distance increases.
Similarly, when you throw a stone in the still water, the intensity of the ripples decrease with the increase in the circumference.
Both are the examples of transfer loss with the increase in distance.
The answer is simply NO, you cannot convert an equal amount of one form into the equal amount of the other form. These are the examples of the conversion loss.
No system is fully efficient, that is it can convert a certain percentage of the input energy into the usable energy and the remaining energy is lost in the surroundings.
We will discuss such types of losses in this post.
We all know that the basic solar power system consists of following components:
The energy from the solar panels reaches to the load and then to the batteries through the charge controller and then to the inverter. It suffers attenuation in each process, whenever it passes through each component. We are going to discuss the effect on the energy, when it passes through the above components.
Let’s take the case of each component one by one:
(1) Solar Panels (Conversion loss)
The basic function of the solar panel is to convert the sunlight into the DC electrical energy
Not all the sunlight falling on the panels is converted into the DC electrical energy, some fraction of it is either reflected back or gets dissipated as heat into the surroundings.
In noon time and the clear sky, a solar panel of 1 m² , lying flat on the earth’s surface receives around 1,000 watts of solar power.
It is able to convert a small percentage, say 18%, efficiency of solar panel, of the solar power into electrical power.
The remaining 82% of the energy is either reflected back or dissipated as heat into the surroundings.
This, I call as the conversion loss of the energy. You can see that out of 1000 Watts of solar energy only 18% that is 180 watts gets converted into DC electrical energy.
The solar charge controller protects the battery from getting overcharged.
(2) Battery (Conversion loss)
When you are not using energy from the solar panels to run your electrical appliances, the energy gets stored in the solar batteries in the form of chemical energy which later on can be utilized to run the appliances, when there is no sunlight or during night.
The battery provides energy by converting the stored chemical energy into DC electrical energy and there occurs a loss in this conversion.
If your battery is 85% efficient then it will convert 85% of its stored chemical energy into DC electrical energy.
(3) Inverter (Conversion loss)
The energy after getting converted into DC electrical energy by the solar panels is passed through the inverter.
The basic function of the inverter is to convert a DC electrical energy into AC electrical energy. This is a conversion of energy from one form into the other.
Suppose your inverter is 95% efficient, means that it is able to convert 95% of the input DC electrical energy into AC electrical energy.
It will convert those 180 watts of DC electrical energy into 95% of 180 or 171 watts of AC electrical energy.
Those 9 watts are lost as conversion loss into the system.
(4) Wires (Transfer loss)
The energy that we receive as the output and which runs our electrical appliances, needs a medium to travel from one point to the other point and this medium is provided through wires.
The different components of the solar power system are connected through copper wires. When the energy travels through a wire, some of it gets lost as a heat into the surroundings.
The longer is the distance between the solar panel and your electrical appliance, the more is the wastage of energy as heat.
Therefore, one should try to keep minimum or optimum distance and the right sizing of the wires between the various components and the electrical load.
If I say that the wire losses are 1% of the DC electrical energy that is 1% of 180 watts or 1.8 watts are lost as heat.
I can summarize the above explanation in two lines:
There is conversion loss within the components and the transfer loss, through the wire running between the components.
(5) Environmental losses
When your solar panels are placed under shade, they get less sunlight and in turn they produce less current.
Try to install your panels with no nearby high structure or tree, I am calling it an obstacle.
Because at one point in a day, the obstacle comes in between the sun and the panel in such a way that its shadow covers portion of the panels and block the sunlight.
When I was new to this technology, I use to think like many others that the panel efficiency increases with the rise in temperature.
Oh! I was wrong.
On the contrary, its efficiency decreases with the increase in the temperature.
If you got to see the back side of the panel, you can see the temperature coefficient as one of the characteristics written over there.
Let us assume that you have 200 watts of solar panel and its temperature coefficient which is written at the back side is -0.4%/°C.
It means that your panel will lose 0.4% of 200 watts for every degree rise in the temperature from the tested temperature of 25 degrees.
Let us say that the panel surface temperature is 60 degrees.
It means that the panel will lose 0.4% x (60 -25)
= 0.4% x 35
14% of 200 watts or 28 watts at this temperature.
In other words,
you will get 200 – 28 = 172 watts for running your appliances.
The moving air takes away dirt from the ground and leaves it over your panels. These dust particles form the thin layer on the panels, preventing the sunlight striking on their surface.
If you clean dust more often from the panels. I can bet that you live in high air speed place.
The one very good advantage of living in high wind speed region that it keeps your panels cool which help them to produce more current.
If you have disadvantage of dirt accumulating on the surface then on other side the high air speed keeps your panel cool.
You know the sides of the same coin.
Can you find the average wind speed in your area?
(6) Design Loss
The panels perform to their maximum when the sunlight is falling perpendicular to their surface.
But the sun rays cannot be every time normal to the surface because earth and the sun are always in the relative motion.
Also, we cannot always keep on changing the tilt of the panel in order to make sunlight fall normal to it.
Yes, we have solar trackers which keep on moving the panels from east to west in line with the sun’s motion to get the maximum sunlight.
But the solar trackers are costly if we are considering small solar power system.
Therefore, it is good to find the most optimum tilt where you can fix the panels and get the maximum sunlight in the day.
The tilt and the orientation depend on the location of the region where you are living.
The right angle of the panels gives you maximum current than any other angle.
(7) Age of the system
Just like we work less as we grow old, our solar panels also degrade with time and produce less current.
In general, the output of the solar panels reduces to 80% of their rated power in the 25th year.
Assuming the life of the panel as 25 years.
For example, a solar panel of 200 watts will produce 80% of 200 = 160 watts in the 25th year from now due to degradation (reversible and irreversible degradation) with time.
Or in other words 40 watts are lost with time.
So, on an average we are losing 40 watts / 25 years = 1.6 watts per year or 0.8% per year.
I can summarize the above explanation in two lines:
There is conversion loss within the components, the transfer loss through the wire running between the components, design losses, losses due to the age of the system, and the environmental losses
The sum of the input energy and the sum of the output energy remains the same; it is usable energy that gets reduced with every conversion and while transferring from one component to the other.
If you closely notice, then you can find that the major conversion loss occurs at the first stage when solar panel converts solar energy into DC electrical energy.
Therefore, it is very important to include these losses and then calculate the overall efficiency of the system.
Okay let's do it here
I have the following parameters with me:
Now, let's calculate the overall efficiency of the system:
Simply, multiply all these parameters together, you get the efficiency of the complete system.
It is 14.2%
It means that you are able to utilize only 14.2% of the sunlight to run your electrical appliances.
In addition, this discounted efficiency gives you real picture of the financial feasibility the system.
Don't worry guys!
Even with this efficiency, the residential solar power systems are financially rewarding and helping in reducing the carbon content from the environment.