Definition of Solar Radiation
The energy emitted by the Sun as an electromagnetic wave is called Solar radiation.
This energy influences atmospheric and climatological processes and phenomena like photosynthesis. Moreover, it is responsible for keeping the planet's temperature compatible with life and wind formation.
It is an energy source that can be measured, used to heat buildings and objects, and collected by photovoltaic cells. It comes in several different forms, including ultraviolet rays, visible light rays, infrared waves, and other forms of energy.
Moreover, this energy varies over time depending on weather conditions, locations, and other factors.
Basic Principles
How much solar radiation enters the Earth's surface is influenced by several factors, including the time of the day, the season, geographical location, local weather, and landscape.
Earth's Shape
The Sun hits the Earth at varying angles because it is round. It ranges from 0° (above the horizon) to 90° (directly overhead).
The Sun's rays become scattered and diffuse when they enter the Earth because the rays are slanted, and they travel in the atmosphere for longer. But when the Sun's rays are vertical, the Earth's surface gets all the energy.
The polar regions do not receive energy from the Sun because of the tilted axis of rotation.
Earth's Revolution
Because of the Earth's revolution around the Sun, there is part of the year where a section of the Earth is closer. When this happens, more solar energy is received by the area directly hit by the Sun's rays.
Earth's Tilting
A more significant factor determining how much sunlight strikes the Earth is the 23.5° tilt in the Earth's axis of rotation.
This factor results in longer days in the northern hemisphere from spring to the fall equinox. The Earth's southern hemisphere, on the other hand, experiences longer days during the remaining six months.
Earth's Rotation
Likewise, the Earth's rotation also influences the hourly variation of the amount of sunlight that reaches the ground. The peak time for solar energy to enter the Earth is around noon each day.
Measuring Solar Radiation
It is measured through wavelengths or frequency. Several instruments can be used to measure solar radiation.
- A pyranometer measures global horizontal and direct (beam) solar radiation fluxes, but it does not measure diffuse components. There are three common types of pyranometers: Solar Radiation Detector (SD), Solar Radiation Sensor (SRS), and Solar and Global Horizontal Irradiance Sensor (SG&HIS).
- Solar radiation is also measured by a Solarimeter, a non-contact instrument that measures the intensity of the solar radiation.
- A Pyrheliometer, also known as Solar Radiation Sensor, is used to measure solar radiation in the Solar Spectrum.
Solarimeters and Pyrheliometers both use a sensor that detects solar radiation and a camera captures light for the eye.
Types of Solar Radiation Depending on Its Form As It Reaches the Earth
There are three major types of solar radiation, depending on its form that enters the surface of the Earth.
Direct Solar Radiation
This Solar radiation penetrates the atmosphere and reaches the surface without dispersing all the way.
Direct solar radiation, also known as global solar radiation, is measured at Earth's surface by a pyranometer or Solarimeter. It measures the strength of solar radiation from the Sun's rays as it falls perpendicular to a surface.
Diffuse Solar Radiation
Diffuse solar radiation, also known as diffuse sky radiation, is the radiation that reaches the Earth's surface after being scattered in the atmosphere.
The high level of atmosphere transparency in some regions results in low levels of diffuse solar radiation.
Diffuse solar radiation is measured by a Solarimeter, Solarimeter, and Pyrheliometer. The two components of diffuse solar radiation are Global Diffuse Irradiance and Diffuse Horizontal Irradiance (DHI).
Reflected Solar Radiation
The Albedo effect is a phenomenon where the Earth's surface reflects solar radiation.
The Solar radiation reflects off objects such as cars, buildings, or any other solar panel reflector.
Types of Solar Radiation Depending on the Types of Light
Three types of light reach the Earth's surface.
Infrared Rays
This type of light has a longer wavelength than visible light, reflecting more than UV and Visible Light.
This has a wavelength of less than 700 and provides 49.4% of solar energy, and can be easily absorbed by water and carbon dioxide molecules and converted to heat energy.
Visible Rays
Visible solar radiation or visible light includes light colors visible to the human eye.
Ultraviolet Rays
Ultraviolet solar radiation or Ultraviolet Light has shorter wavelengths than visible light and can be harmful to humans and other living things if exposed for a long time.
It can be separated into three types based on its wavelength ranges:
- UV-A can pass through the Earth's surface quickly. It has a wavelength of 320-400 nanometer (nm). This is also known as backlight, which causes fluorescence in some objects.
- UV-B cannot penetrate the atmosphere easily but still reaches the Earth's surface and is responsible for skin damage and impairment of photosynthesis in many plants. It has a wavelength of 280-320 nm.
- UV-C cannot get through the atmosphere since the Earth's Ozone Layer absorbs it. It has wavelengths ranging between 100 and 280 nm.
Importance of Solar Radiation
Solar Radiation is very important for the following reasons:
- It provides light.
- It balances the temperature of the Earth, providing its heat.
- It gives out energy that can be stored and converted into electricity.
- It is needed for photosynthesis.
Drawbacks of Solar Radiation
There are several drawbacks that Solar Radiation causes:
- Solar radiation can be harmful to human skin, especially when exposed for too long.
- It is found to alter the immune response.
- It causes eye problems.
- It is detrimental to microscopic life.
Final Thoughts
Solar radiation is very important in our daily lives by providing light, electricity, and heat for many purposes. Solar panels are used to harness solar radiation into electricity.
It supports living organisms on the Earth, but it can also be harmful if exposed for too long.
FAQS
1. What is solar radiation?
Solar radiation is the electromagnetic radiation emitted by the Sun.
2. How do solar panels work?
Solar panels are designed to absorb as much solar radiation as possible, incorporating materials that can convert sunlight into electricity. The absorbed energy is transformed into the usable direct current (DC) electricity.
3. What is the importance of solar radiation?
Solar radiation provides light, electricity, and heat that supports living organisms.
4. What are the drawbacks of solar radiation?
Solar radiation is harmful to humans if exposed too long. It can also damage human skin, among others.
5. What are the types of solar radiation depending on its form?
There are three types of solar radiation: diffuse solar radiation, direct solar radiation, and reflected solar radiation.
