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Where Does the Largest Input of Solar Energy Occur?

Tim Carter
Written by Tim Carter Last Updated: August 7, 2022

Nearly 300,000 kilometers per second is the speed of sunlight (186,000 miles per second) that reaches the Earth. Most sunlight that reaches our planet either reflects or gets absorbed. While absorbed light is the source of energy that powers processes in the atmosphere, hydrosphere, and biosphere, reflected light bounces back into space. So where does the largest input of solar energy occur on our planet?

Because of the sphere-like nature of the Earth, the planet receives different quantities of solar energy. The equator receives and absorbs more solar radiation compared to the poles.

The rays hit our planet most directly close to the equator whereas, near the poles, they reach the surface at a sharp angle.

Depending on the makeup of Earth’s surface and atmosphere, variations in the percentage of solar heat that is reflected rather than absorbed can change the planet’s temperature and ecosystems.

Table of Contents

How is the Atmosphere Heated?

The sun is the primary source of energy for the atmosphere. Solar radiation enters the atmosphere and is reflected or absorbed by the earth’s surface.

The earth’s surface then radiates heat upward, which warms the atmosphere. This process is known as convection.

Additionally, the earth’s rotation causes air to circulate in a pattern called Hadley cells.

This circulation helps to disperse heat around the globe. Finally, latent heat released by water vapor condensation also contributes to heating the atmosphere.

How Does the Earth Get All of its Energy?

The Earth gets its energy from a variety of sources, including the sun, the planets in the solar system, and even other galaxies.

The sun is by far the largest source of energy for the Earth, providing over 99% of the planet’s total power.

Solar radiation comes to the Earth as electromagnetic waves, which are then converted into heat and light by the atmosphere.

This heat and light provide energy for all life on Earth, but the global warming we experience nowadays affects us all. We emit greenhouse gases that contribute to high temperatures around the globe.

That is why turning to renewable energy sources should be a priority for all.

Other sources of energy include geothermal energy (from within the Earth), nuclear energy (from radioactive decay), and tidal energy (from the ocean’s tides).

These sources are much smaller than solar radiation, but they still play an important role in powering the Earth.

The heat of the Earth’s molten core creates geothermal energy.

This heat is transferred to the surface of the Earth through convection, which drives plate tectonics and creates volcanoes.

We can harness this heat to generate electricity or to heat homes and businesses.

Nuclear energy comes from the radioactive decay of atoms.

This energy can generate electricity, but it must be carefully controlled to avoid accidents.

Tidal energy comes from the gravitational pull of the moon and sun on the oceans.

This gravitational pull creates tides, which can be harnessed to generate electricity. Tidal energy is a renewable resource, but it is not yet widely used.

How Much Solar Radiation Is Absorbed by the Atmosphere?

The sun emits a tremendous amount of radiation. Most solar energy is visible light and infrared radiation. A small amount of this radiation is ultraviolet (UV) radiation.

This UV radiation gives us our tans and sunburns, and it’s harmful to our health if we’re exposed to too much of it.

When UV radiation reaches the Earth’s atmosphere, some of it is scattered back into space while some of it is absorbed by the atmosphere.

The atmosphere absorbs how much UV radiation depends on several factors, including the altitude of the sun in the sky and the amount of cloud cover.

The higher the sun is in the sky, the more UV radiation will reach the Earth’s surface. This is because there is less atmosphere between us and the sun when the sun is high in the sky.

Similarly, if there are more clouds in the sky, more UV radiation will be absorbed and scattered by these clouds, and less will reach the ground.

So, how much solar radiation is actually absorbed by the atmosphere?

Estimates vary, but it’s thought that between 60% and 80% of UV radiation is absorbed by the atmosphere before it reaches us. This means that a large part of the harmful UV radiation from the sun never even makes it to the ground!

In What Region of the Sun Is Solar Energy Generated?

Solar energy is generated in the photosphere, which is the outermost layer of the sun.

The photosphere is where sunlight comes from. In this region, the sun’s energy is converted into the sunlight.

This sunlight then travels through space and eventually reaches Earth. Solar panels on Earth capture this sunlight and convert it into electricity.

Where Does the Largest Input of Solar Energy Occur?

The amount of solar energy that reaches the surface depends on several factors, including the time of day, the season, and the weather.

There are many factors that contribute to how much solar energy an area on earth receives.

These include latitude, temperature, cloud cover, and elevation.

We typically find the highest concentration of solar energy near the equator, where the sun’s rays are most direct.

The sun strikes the surface of our spherical planet at a variety of angles, from 0° (just above the horizon) to 90° (directly overhead).

The Earth’s surface receives all the energy when the sun’s rays are vertical.

The longer the sun’s rays travel through the atmosphere, becoming more diffuse and dispersed, the more tilted they are.

The cold pole regions never see a high sun since the Earth is spherical, and because of the tilted axis of rotation, they occasionally receive no sun at all.

The Earth’s axis of rotation’s 23.5° tilt plays a larger role in influencing how much sunlight hits the planet at any spot.

Light absorption on Earth

From the vernal equinox in the spring to the autumnal equinox, tilting causes longer days in the northern hemisphere, and during the next six months, longer days in the southern hemisphere.

The equinoxes, which fall on or about March 23 and September 22 of each year, have exactly 12-hour days and nights.

The rotation of the Earth also caused the hourly changes in the sunshine: the sun is low in the sky in the early morning and late in the day.

We talk about diffuse radiation when some of the sunlight is absorbed, dispersed, and reflected as it travels through the atmosphere by air particles, dust and pollutants, clouds, water vapor, fires, and volcanoes.

In contrast, direct beam solar radiation is the type of solar heat that directly reaches the surface of the Earth.

On the other hand, the incoming solar radiation is the total of both diffuse and direct sun radiation.

Atmospheric conditions can reduce direct beam radiation by 10% on clear days and by 100% on gloomy days.

At various periods of the year, scientists measure the amount of sunshine that strikes particular regions.

The amount of sunshine that strikes areas with comparable climates and latitudes is then estimated.

Total radiation on a horizontal surface or total radiation on a surface that tracks the sun are the two common ways that solar energy is measured.

Kilowatt-hours per square meter (kWh/m2) express radiation statistics for solar electric (photovoltaic) systems.

Watts per square meter (W/m2) can also indicate direct estimations of solar energy.

British thermal units per square foot (Btu/ft2) are the standard unit of measurement for radiation data for solar water heating and space heating systems.

Now let’s check out the following maps.

This map shows the annual average of global horizontal solar irradiance in the United States in 2018.

solar annual global horizontal irradiance USA

The following map represents global horizontal solar irradiance in the United States in June.

global horizontal irradiance for June

The following three maps show the situation in September, October, and December. You can see how the situation changes until the end of the year, and how the amount of sunshine that strikes particular regions slowly decreases until it is at its minimum.

Yet, that doesn’t mean that photovoltaic panels don’t function during the winter months. Remember diffuse radiation? It plays an important part in electricity generation via solar panel systems.

global horizontal irradiance for September
global horizontal irradiance for October
global horizontal irradiance for December

Source: Sengupta, M., Y. Xie, A. Lopez, A. Habte, G. Maclaurin, and J. Shelby. 2018. “The National Solar Radiation Data Base (NSRDB).” Renewable and Sustainable Energy Reviews 89 (June): 51-60.

What Is the Earth’s Average Surface Temperature?

The average surface temperature of the planet is 15 degrees Celsius or 59 degrees Fahrenheit.

However, climate change indeed changes things. Today, we speak of global warming that affects all life on Earth.

With 0.87°C (1.57°F) above the average for the 20th century, the worldwide surface temperature for June 2022 was the sixth-highest in the 143-year record.

Additionally, this month was 0.08°C (0.14°F) colder than the 2019 record-breaking June.

The ten hottest Junes all took place after 2010. In addition, June 2022 was the 46th successive June and the 450th consecutive month with temperatures that were nominally above the norm for the 20th century.

You can check some of the significant climate anomalies and events (and much more) here.

Final Thoughts

The sun heats the atmosphere and warms the earth’s surface, which then radiates heat upward. This process is known as convection.

This sunlight then travels through space and eventually reaches Earth. Solar panels on Earth capture this sunlight and convert it into electricity.

The earth’s rotation causes air to circulate in a pattern called Hadley cells, which also helps to disperse heat around the globe.

However, not all areas of the earth receive the same input of solar energy because of the position of Earth relative to the Sun and our planet’s oval shape.


Tim Carter
Tim Carter

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