Photon Number Hitting Solar Panel

For more or less power multiply by the number of watts.

Photon number hitting solar panel.

Enough energy from the sun hits the earth every hour to power the planet for a year sunlight is made up of tiny packets of energy called photons these photons radiate out from the sun and about 93 million miles later they collide with a semiconductor on a solar panel here on earth. In order to collect energy more efficiently solar panels should be angled to face as close to the sun as possible. What happens when the photons hit the solar panels. Looking at the big picture conservation of momentum implies that the momentum of the photon ultimately contributes to the momentum of earth.

We won t be pushed out of orbit as when we are pushed out to a larger orbit from the sun our angular velocity will be lowered increasing our acceleration back towards the sun. It all happens at the speed of light. That would suggest by dividing power by energy per photon that there would be about 3 x 10 18 photons per second. Photovoltaics produce power when the angle at which the sun s rays hit the panel surface the angle of incidence is small or when light strikes the panel as close to perpendicular as possible.

The average visible light photon has about 3 3 x 10 19 joules of energy. A spectral response curve is shown below. The spectral response is conceptually similar to the quantum efficiency. If we are interested in knowing how much power we can generate from a solar panel we need to determine the amount of photons that are hitting the surface of our panels at any given time flux is just a technical term that denotes a quantity passing through a given surface area.

The quantum efficiency gives the number of electrons output by the solar cell compared to the number of photons incident on the device while the spectral response is the ratio of the current generated by the solar cell to the power incident on the solar cell. When a photon hits an electron the photon is absorbed by the electron. A watt is a joule per second. Due to their special structure and the materials in solar cells the electrons are only allowed to move in a single direction.

Photon flux is an important concept in solar energy. Electrons negatively charged are knocked loose from their atoms as they are excited. As the next diagram shows panels like everything else are made up of atoms and atoms contain electrons.