Since Thomas Edison invented the light bulb, man has sought to effectively harness the boundless energy of the Sun and convert it to electricity. Sound simple? Well, it’s not! Let’s look at the basics.
Energy is electromagnetic radiation (EMR)—photons. Photons are discrete subatomic particles that have no mass, no weight and no electrical charge. These bundles of energy travel through a vacuum at a speed of 186,282 miles per second and have an indefinite life expectancy. There travel is not a direct path but in waves. No matter what the wavelength, the speed remains the same. Yet, the shorter the wavelength, the more energy produced.
Gamma rays are the shortest EMR wavelengths, highest energy form in the universe. The wavelength size is 10-12 meters, the size of an atomic nucleus. At the other end of the spectrum is radio waves with a wavelength up to 1,000 meters, the size of a building. Visible light is in the center of the spectrum and has a range 4 to 7 x 10-7 meters, the size of protozoan.
Although the Sun emits all forms of energy, about 50 percent of solar radiation that reaches Earth is visible light. A chunk of the remaining energy is near-infrared with some ultraviolet radiation.
The ultraviolet radiation (UV) which is not absorbed by Earth’s atmosphere is the invisible energy that produces suntans and sunburn and contributes to the man’s formation of Vitamin D. [Photo (below) shows UV radiation emitted as solar flares from the surface of the sun.] As for solar contributions, UV radiation takes the back seat of infrared and visible light. And it does not contribute to solar power!
The surface of the sun emits about 63,000,000 watts/m2 of visible light. Of amount of energy emitted from the sun, only about 1,370 watts/m2 reaches the outer atmosphere of the Earth. By the time the visible light has penetrated Earth’s atmosphere, an “average” 40 percent of the solar visible light emissions reach the sunny side of the surface —547 watts/m2. The average is based on light that hits the round surface of the Earth.
Unfiltered light on a clear day is capable of delivering 1,000 watts/m2 when the light hits the surface directly. When light hits Earth’s surface at an angle and at a greater distance from the direct impact, light is refracted—bounces off at an angle. The energy delivery is progressively less than 1,000 watts/m2 as the angle and distance from the Sun increase. Think about a ball. Shine a flashlight over the surface of the ball. Observe the light intensity throughout the surface of the ball. Does it bleed off along the edges? The further the light from the round surface the less light is delivered. Now, replace, in your mind, the flashlight with the Sun.
If the earth were flat, solar energy delivery would be much more consistent. If the earth did not rotate to and away from the Sun, solar energy delivery would be much more consistent. If it were not for weather, solar energy delivery would be much more consistent. “If” is not a reality. Solar energy distribution and delivery is inconsistent on planet Earth.
Infrared radiation (IR) is heat energy is not seen but experienced. IR energy delivery is second only to visible light. It is abundant and is used by thermal power plants. Wait. What is this thermal power? It is similar in operation to that of fossil fuel power plants.
IR is visible only by its impact of air movement. For example, you have likely observed heat rising from a hot road surface
Heat is typically greatest in desserts, areas closest to the Equator. The Sahara Dessert in Africa is the largest dessert in the world. In the United States, Arizona has considerable dessert lands. Southeastern California and western Texas have dessert land as well.