We get the output from the solar panels as DC voltage. Solar panels are made from a combination of solar cells.
Many factors affect the output voltage of the panel. They are heat buildup/surface temperature, energy conversion efficiency, location, solar shading, orientation and mounting position, environmental temperature, humidity, wind velocity, light intensity, altitude, and atmospheric pressure, and maintenance.
How solar panel generates electricity?
Solar cell is the unit of the solar panel that converts the energy of sunlight to electricity. A solar panel consists of arrays of solar cells which contribute to the output of the solar panel.
A solar cell mainly works from the visible light contained in sunlight.
Photon is a small energy unit. So the total energy of the sunlight is simply called a combination of light photons.
When the light photons hit the solar cells, the atoms of the semiconductors absorb the energy. This will result in free electrons. These free electrons come out from the solar cells as an electric charge.
Electric charges of all the solar cells add up and create the output current and voltage of the solar panels. When connected to a circuit these free electrons flow across the panels and the current flows in the opposite direction.
Factors that affect the output of the solar panels
Heat buildup /surface temperature
The behavior of the solar cells with the increase of temperature is due to the characteristics of the silicon-based modules. Solar cells tend to produce higher output voltage at lower temperatures.
This happens due to two reasons.
One is when the temperature increases, the semiconductor bandgap decreases. This decreases the output voltage of the solar panel.
The other reason is when the temperature raises the energy of the orbital electrons rises. So when the light photons hit the material more electrons will be ejected which will increase the photocurrent. But the output voltage decreases as the energy difference is decreases.
Energy conversion efficiency.
The energy conversion efficiency of a solar cell is calculated when it is connected to an electrical circuit. It is the percentage of the electricity converted from the absorbed light photons and collected by the solar panel. This is easily calculated by dividing the maximum power point ratio by the input light irradiance and the surface area.
The energy conversion efficiency of most solar panels remains at a low value. This is the reason that we need large solar arrays to generate enough electricity.
Monocrystalline solar panels reach efficiencies higher than 20% when the polycrystalline solar panels reach 15% – 17% of efficiency.
There are two ways to increase the efficiency of solar cells by reducing the reflection of sunlight incident on the solar panels.
- Apply and antireflection coating on solar panels.
- Use textured surfaces instead of smooth surfaces for panels.
Your geographical location is very important to have a good solar output. Even though we can use solar panels in most areas of the world, some locations do not receive enough sunlight to produce a good amount of power.
Any way when talking about this topic you have to always keep in mind that to produce power from solar panels you only need sunlight, not heat.
We are saying this because many had this wrong assumption about solar panels as they can only be worked at locations near the equator. But that belief is not true at all.
Also, some believe that the solar panels need to be under direct sunlight to work. But that is also not true. You can know more about this fact through our article.
So as you can see, when you are deciding to get a solar system you have to consider how much sunlight your area received throughout the whole year. If your area does not receive enough amount of sunlight there is no point in installing a solar system.
To ensure that there is enough sunlight in an area there is a value called peak sun hour.
Peak sun hour means an hour of the day that the intensity of the sunlight reaches 1000 Watts per square meters. The average number of peak sun hours received throughout the day vary from location to location.
Anyway, at least there should be 4 peak sun hours to work your solar panels efficiently.
There are many calculators that available online so you can calculate the peak sun hours of your area on your own or you can ask this from the solar system providers of your area or any other competent person.
Solar panels can be shaded from trees, nearby buildings, or any other structures. So you have to make sure that there are no structures over them.
Even though solar panels do not need direct sunlight to produce electricity, the shading of solar panels will decrease the output of the panels.
Also, when there are trees over the panels fallen leaves collect on the panel. This requires more frequent cleaning which increases the maintenance fee. Not just that but falling branches can damage the solar panels. Also, there is a huge chance of accidents during the stormy or rainy season.
Orientation and mounting position.
Orientation and the mounting position have a great impact on solar panel output.
As the earth is an irregular-shaped ellipsoid and it is tilted, sunlight is not incident on every location of the earth at the same angle. So the optimal orientation and the placement of solar panels will be different from location to location.
Most suitable orientation for your solar panel;
Southern hemisphere – facing north
Reason – the longest axis of the sun’s path is east to west. For a location in the southern hemisphere at this orientation solar panel will face this axis. So this allows your panels to be exposed to the sunlight more time of the day.
Northern hemisphere – facing south
Reason – the longest axis of the sun’s path is east to west. For a location in the northern hemisphere at this orientation solar panel will face this axis. So this allows your panels to be exposed to the sunlight more time of the day.
Most suitable position for your solar panel –
Tilted 20 – 30 degrees or minimum 10 degrees.
Reason- from sunrise to sunset sun is not at a constant level. It goes up and down. To get the most out of the sunlight it is better to angle the panel as it exposes the panel more. Also, this is important for the self-cleaning of the panel when raining.
As we explained before when the surface temperature of the solar panel increases, the efficiency of the solar panel decreases.
When the environmental temperature is high it does not allows the panels to be cool off. So the surface temperature remains at higher levels. So the output will remain low.
According to the researches done about the effect of temperature on the output of solar panels, cold temperatures are best for the solar panel output. You can read further about this in the article.
Humidity is a measurement that indicates the amount of water vapor available in the air.
According to the available data, humidity is inversely proportional to the output voltage, current, and power.
The reason is when the humidity is high water droplets form on the surface of the panel. These water droplets reflect the incident sunlight on the panel. So the amount of energy absorbed by the panel will be less.
These water droplets can cause rusting of the metal parts used in the construction of the panels. So this will decrease the lifetime of the solar panels as well.
We can simply define wind velocity as wind-flowing speed.
Wind velocity positively affects solar panel efficiency. That means output of the solar pane increases when the wind velocity is high.
These two are related to the surface temperature of the solar panel. When there is wind, the air around the solar panel refreshes. That means the air molecules surrounding the panel replace with the flowing air.
As the surrounding air is colder than the solar panel the heat transfers from the panel to the air. This increases the temperature of the air. Now because of the wind, the hot air is replaced by the air with lower temperatures. Again heat is transferred from the panel to the air.
When the wind velocity is high air surrounding the panels refreshes more quickly. So the heat transferring process becomes faster so this cools off the panel more quickly.
As we explained before the surface temperature is inversely proportional to the output voltage of the solar panel. So when the surface temperature decreases the output of the solar panel increases.
Light intensity is the amount of light or the power produced by a light source. In this case the sun. This is usually measured by the watt per unit area.
Light intensity is a very important factor when generating solar power.
Light intensity positively affects the output of the solar panel. When the light intensity is high the solar panels receive more energy. So the output also increases.
If there is not enough intensity your solar panels will not work properly and the generated power will not be adequate.
Altitude is the height above a certain level. Most of the time altitude will be taken from the sea level. If we considered two levels such as ground and rooftop, the rooftop has a higher altitude.
So as you can see higher the altitude it becomes closer to the sun.
So when you compared the panels set on the ground with the panels set on the rooftop and keep all the other factors as constant as possible, you can see that the panels on the roof give more output than the panels on the ground.
So that means panels produce more output at higher altitude level.
Atmospheric pressure is also called air pressure. It is the pressure formed by the weight of the air molecules present in the atmosphere.
So the air pressure will increase towards the surface of the earth. Because of the increased air pressure, the number of photons that fall from the solar radiation will be increased. This increases the light intensity.
As we said earlier when the light intensity increases the solar panel output also increases. So the atmospheric pressure positively affects the output.
Solar panels do not require much maintenance. They are designed in a way that the maintenance cost is less. Because they are fixed at an angle in the rainy season it allows self-cleaning.
But if there is not much rain you have to clean your panels more frequently. Also if the panels are not mounted in an angled position you have to clean the panels more frequently.
If the panels are not cleaned properly then debris such as fallen leaves and bird droppings will be collected on the glass.
This will block the sunlight and decreases the number of photons absorbed into the solar cells. So the incident energy will be less. This decreases the output of the panels. To know more about the maintenance of the panels read the article.
What can we do to increase the output of solar panels?
You can use the following tips to increase the output of your solar panels;
- First, before buying a solar system you have to make sure that your area gets enough sunlight throughout the year. Otherwise, this investment will fail. Not just the light intensity but you have to consider other factors such as humidity. You can always discuss these with solar system providers or with any other competent person.
- When installing the panels make sure there are not many tall trees or any other structures that can shade the panels. Also, fewer trees mean less cleaning to do.
- When selecting the location you have to care about the altitude and the air pressure. Locations like rooftops are the most suitable for solar panels.
- Regular maintenance and checkups on solar panels can increase both the output and the lifetime of the solar panels.
Many factors contribute to the output of solar panels. Most of them should be carefully assessed during the planning stage of the solar installation process. Even though we can select the solar panels according to our needs we cannot control the environmental factors.
So before going solar you have to make sure that your location is suitable for installing a solar system. You can always get help from solar system providers or any competent person. After the installation is completed proper maintenance also very important to get a good output. Even though solar panels do not need much maintenance this can be varied according to your location and the season.