# Understanding the solar constant

If you are thinking of installing solar cells บริษัทติดตั้งโซล่าเซลล์ Let me take you to know the solar constant. Since the Earth orbits the Sun in an ellipse, the distance between the Earth and the Sun at any time is not equal.

Variation of the intensity of sunlight that strikes the Earth above the atmosphere

The main reason why the solar intensity outside the earth’s atmosphere at different times is different is the distance between the earth and the sun is almost always changing. We can write the relationship between the incident sunlight intensity. The unit area above the Earth’s atmosphere G at the nth day of the year and the solar constant are given by the equation

Gon= Gon1+0.33cos360n365

Gon is the solar intensity outside the Earth’s atmosphere

Gon is the solar constant.

n is what day of the year (1 January n =1 31 December n = 365 )

The average distance between the Earth and the Sun is about 8 × 10 meters. The intensity of the incident solar radiation per unit above the Earth’s atmosphere at different times is therefore not equal, with an average radiation value between 1,350 – 1,440. watts per square meter The average light intensity is about 1,368 watts per square meter. This light intensity is called solar constant, but when it reaches the earth Some of the energy must be lost when passing through various layers of the earth’s atmosphere such as the ozone layer, water vapor layer, carbon dioxide layer. causing the light intensity to be reduced to about 1,000 watts square meters or about 10 percent)

## The average light intensity at noon is approximately 1,868 watts per square meter.

The electromagnetic waves emitted by the Sun have wavelengths ranging from more than 1000 micrometers continuous to less than 0.2 micrometers. Yellow light with a wavelength of 0.55 micrometers is the light wave with the highest intensity.

Electromagnetic waves emitted from the Sun come in all wavelengths. or all frequencies, but most of the electromagnetic radiation emitted from the Sun is about 44% light, about 44% ultraviolet radiation. 3%, and infrared radiation heat generated by sunlight caused by infrared radiation and light combined infrared rays is only part of the sunlight that cannot be seen with the naked eye But you can feel it from the heat.

The potential of electricity generation from solar energy in Thailand is quite high. With terrain near the equator Resulting in getting solar energy on average throughout the year higher than other regions of the world, which studies from satellite data and ground measurements of the Department of Alternative Energy Development and Efficiency. It was found that the areas with solar energy potential in Thailand which has an average annual solar radiation intensity of about 18.2 mega joules per square meter Most of them are in the northeastern region such as Roi Et, Si Sa Ket, Ubon Ratchathani and Udon Thani, and some are in the lower central region such as Saraburi, Lop Buri and Phra Nakhon Si Ayutthaya, etc., which results in Thailand’s potential to produce electricity from solar energy up to 10,000 megawatts.

from such potential The government has tried to encourage the private sector to build solar power plants. For example, with support in various fields such as tax measures and various privileges to create incentives to invest, such as exemption of import taxes on raw materials for solar panel production. or install solar cells บริษัทติดตั้งโซล่าเซลล์ as well as supporting capital borrowing and working capital through financial institutions, etc.

“Sunlight” is the largest source of natural energy. It is clean and ubiquitous energy. But the utilization of solar energy may still have some limitations because sunlight is only available during the day. and the intensity of the light is uncertain. depending on weather and season When sunlight reaches outside the Earth’s atmosphere will have an average light intensity of about 1,367 watts/square meter But when it reaches the earth’s intensity about 1,000 square meters, the energy from sunlight received in a particular area. It has maximum volume when the area is perpendicular to the sunlight. Therefore, if wanting an area to receive the most sunlight per day will have to adjust the receiving area according to the movement of the sun

## Types of solar radiation at the Earth’s surface

Direct radiation is radiation that comes directly from the sun. There is a definite direction the radiation can be included.

higher intensity

Diffuse radiation is the radiation of sunlight that scatters when it strikes particles in the atmosphere such as gas, dust and water vapor, etc.

Reflection radiation is the amount of sunlight reflected off objects.

The total radiation is the sum of the rays in items 1), 2) and 3).

## absorption of solar radiation of the atmosphere

When solar radiation travels through the atmosphere into the earth. The atmosphere absorbs almost all white wave radiation. causing all wavelengths of radiation to decrease in intensity

Since the sun’s rays have many wavelengths, each wavelength has different names and properties. Absorption of solar radiation at different wavelengths is caused by the absorption of different gasses as follows:

ultraviolet range (below 400 nm) is absorbed by nitrogen gasses, oxygen and ozone in the stratosphere.

the range of visible light (wavelength 400 – 700 nm) will be absorbed by oxygen gas, ozone and water.

infrared ray range (Wavelength greater than 700 nm) will be absorbed by Greenhouse gasses (carbon dioxide, methane), water vapor in the tropospheric atmosphere cause the surface temperature to be warm