Home Solar Panels How Does Sunlight Amount Affect Solar Panels?

How Does Sunlight Amount Affect Solar Panels?

by Know it All Solar Nerds

Solar power is a reliable, renewable energy source that provides clean power to your home. Renewable energy like solar is a sustainable alternative to fossil fuels because we don’t have to rely on finite resources to fuel our appliances. As long as the sun is shining, our solar panels will collect sunlight and turn it into electricity. 

It’s important to consider external, sunshine-related factors when installing a solar panel system because the amount of sunlight affects your solar panels’ performance. For example, a solar power system’s energy efficiency and production can shift when experiencing dappled light vs. direct sunlight or when the solar panels are tilted at different angles. In this article, we’ll take a more in-depth look at how the amount of sunlight influences your solar power system.

How Solar Panels Convert Sunlight into Energy

To better understand how solar panels interact with the sun, let’s discuss how solar panels convert sunlight into energy. The two most common types of solar panels on the market are photovoltaics (PV) and concentrating solar-thermal power (CSP).

Photovoltaic

Residential homes operating on solar power typically use PV cells. PV cells in these solar panels absorb energy from the sun. An internal electric field in the cell moves the energy that creates an electrical charge, and this causes a steady flow of electricity. 

Concentrating Solar-Thermal Power

Large power plants typically use CSP systems, which operate differently than PV cells by using mirrors to reflect sunlight and concentrate it into receivers that collect solar energy. The receivers convert the energy into heat, producing electricity that can be stored for later use. 

How much sunlight do solar panels need to be economical?

Generally, solar panels require an average of four peak sun hours daily to make a solar power system worthwhile. One peak sun hour equals 1,000 W/m2 of sunlight. Therefore, four peak hours equals 4,000 Watt-hours of solar radiation or sunlight throughout one day.

What are peak sun hours?

A peak sun hour refers to one hour of optimal sunlight that offers 1,000 W/m2 of sunlight or 1,000 watts of photovoltaic sunlight per square meter. Peak sun hours occur when the sun is the highest in the sky and generates the most intense sunlight. Different cities reach different average amounts of peak sun hours per day. 

Example of Peak Sun Hours in Australian Cities

City

Daily Hours of Sunshine Range

Average Daily Peak Sun Hours

Average Daily Energy Output

Melbourne

3-8

4.1

4,100 W/m2 

Sydney

6-8

4.5

4,500 W/m2 

Brisbane

7-8

5.1

5,100 W/m2 

Perth

5-11

5.5

5,500 W/m2 

Sunlight Factors that Affect Solar Panels

Now let’s consider the commonly asked question, “How does sunlight amount affect solar panels?” When installing solar power systems, several external variables like location, tilt, and common weather conditions should be strongly considered. The amount of solar power produced by your system depends on a slew of factors. Your system’s efficiency (and, in turn, your electricity bill) can shift as these variables change. Ensure that you’re aware of these factors before installing your solar power system to save energy, time, and money. Here are common factors that affect your solar panels.

Direct Sunlight, Indirect Sunlight, and Shade

Direct vs. Indirect

Solar panels don’t need direct sunlight to generate electricity; however, they benefit greatly from a direct hit of that brilliant light. While solar panels work most efficiently in direct sunlight, they can still generate electricity in indirect sunlight. Each form of sunlight carries photons that are converted into electric current by your solar panels.

If your solar panels are situated in indirect sunlight alone, they will still perform. However, your solar power system will not experience its peak performance. Since solar panels require 1,000 W/m2 of sunlight to reach their peak output, this amount can only be achieved when they are placed in direct sunlight.

Shade

Dappled lighting isn’t a solar panel’s best friend. Shade or shading elements can cause a significant reduction in your solar panel performance. Your energy generation output will lower if your roof-lining panels are blocked by shading elements like chimneys, scaffolding, or ventilators. Even if just a small section of your solar panel assembly is shaded, that portion will not have the opportunity to capture any sunlight for conversion into electricity. 

You’ll also need to consider how the sun’s angle casts shadows on your solar panels. If some aspects like towering trees in your yard or segments of your solar panel system are casting shadows on your panels, then your system will experience a drop in performance. 

Here are additional shading characteristics to consider:

  • The duration of the shading throughout the day impacts your solar panels. The longer your panels sit in the shade, the less optimal their performance will be.
  • Your inverter setup can determine how shade affects your system. If a central string inverter is used, for example, then shade on just one of your panels will reduce your entire system’s energy generation output. However, if you use microinverters or DC power optimizers, shade on just one panel will not affect the other panels’ performance.

While shade can negatively impact your solar panel’s electricity generation, your solar system can still operate in the shade! Note that more optimal conditions like direct or indirect sunlight will improve the electric current flow.

Orientation of the Azimuth Angle and Solar Panel Tilt

The orientation of the tilt of your solar panel installation will affect its performance. Generally, you’ll want to tilt them in the direction that captures the most sunlight. This means it’s important to know what time of day peak sun hours occur in your city.

The Azimuth angle is the direction from which the sunlight shines. This angle refers to the difference from the southern hemisphere, and it varies throughout the day, time of year, and your city’s latitude. Your solar power system is more efficient with a smaller Azimuth angle.

Weather

Weather conditions like clouds, fog, haze, rain, and snow all affect your solar system’s performance. Direct and indirect sunlight availability lessens as weather conditions change. The more particulates in the air, the less energy your system will be able to generate. Solar panels can still work on cloudy days, as they can still receive indirect sunlight. However, cloud cover will reduce your power output. Additionally, rain or snow can impact performance due to added cloud cover. The rain and snow itself will likely just clean your panels for you! But if it snows so much that your panels are completely covered, they’ll be temporarily blocked from the sun.

Temperature plays a role, as well. Cold weather improves the performance of your solar panels by preventing a loss of efficiency due to overheating. Conversely, hot weather above 35 degrees Celcius can slightly decline your system’s efficiency.

Pollution, clouds, dust, air molecules, water vapor, and wildfire smoke all cause absorption, reflection, and scattering of the sun’s rays. Diffuse solar radiation doesn’t reach Earth’s surface without being diffused. The radiation that does is called direct beam solar radiation. These atmospheric conditions can reduce direct beam radiation by 10% on dry, clear days and up to 100% on cloudy days with precipitation.

Geographic Location

The city’s location on our planet matters! The amount of direct beam solar radiation varies depending on many of the factors on this list. The Earth’s elliptical rotation around the sun causes the sunbeams to strike at different angles, between 0 and 90 degrees. When the sun’s rays are vertical, we receive maximum energy, but as they become more slanted, they become more scattered and diffused. 

The polar portions of the Earth never experience a high sun, which makes them less ideal places to use solar panels. The closer your city lies to the equator, the more direct sunlight your solar panels are able to receive. The sun’s rays are the most perpendicular to Earth at the equator. This means the number of peak hours will increase the closer your city is to the equator. 

Since Australia is located south of the equator, you won’t receive as much sunlight as certain South American and African cities that exist smack dab on the equator. However, Australia is a very sunny place relatively close to the equator. 

Time of Day and Year

The time of day determines the amount of solar energy that can be produced. Peak sun hours occur midday or in the afternoon depending on the time of year. Seasons significantly affect the sun’s location in the sky, which adjusts the daily hours of sunlight. For example, during a northern winter, the Southern Hemisphere receives more sunlight. During these summer months in Australia, sunlight is more direct, which causes an increase in solar power output.

Now that you’re well-versed in the factors that affect sunlight, you’re better equipped to install your solar panel systems most efficiently!

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