Did you know, the chemical energy stored in fossil fuels originally came from the Sun. Ancient plants like their contemporary cousins converted solar energy into chemical energy with the help of photosynthesis. Through millions of years, the remains of those plants and the animals who ate them turned into fossil fuels. Fast forward today, fossil fuels meet eighty percent of the world’s energy needs, polluting our air and water, and causing climate change. This tiny factoid reminds us how pervasive solar power is in our lives and the urgent need to use this abundant source of power directly from the sun. But we want to know how the sun and solar power came into existence. And how solar panel makes it possible to convert them into a more usable form of energy for us.
Big Bang and the Nuclear Fusion
Hydrogen and Helium were among the first elements created during when the universe began expanding. 4.6 billion years ago, one such giant molecular cloud of these two gases collapsed under the weight of its gravity. Gravitational forces and pressure within the core of the cloud produced a lot of heat. The extreme heat generated subsequently triggered nuclear fusion between hydrogen and helium atoms, giving birth to many stars including the sun of our solar system.
What is Nuclear Fusion?
A stable atom consists of a nucleus of photon and neutrons, with electrons revolving around the nucleus. When two light nuclei join together to make a single heavy nucleus, these atoms lose some of the pre-fusion mass in the form of energy. This process is called nuclear fusion. At the core of the sun, hydrogen atoms fuse together to form helium. This nuclear reaction is what essentially generates the solar power.
Journey to the Earth
The photons generated during the nuclear reaction at sun’s core travel through the thick layers of the Sun with repeated collisions, absorption and re-emission by atoms in the Sun’s plasma. Due to this ‘Photon Random Walk’, it takes between 10,000 to 1,70,000 years for photons to reach the surface of the Sun. Once escaped from the Sun’s atmosphere, the photon travels 150 million kilometres to the Earth at the speed of light. It takes 8 minutes 20 seconds for sunlight to reach the earth's surface.
Atmospheric particles, clouds, ice and snow reflects about 29 percent of the total amount of Solar energy that reaches earth, back into space. About 23 percent of incoming solar energy is absorbed in the atmosphere by water vapour, dust, and ozone. And 48 percent passes through the atmosphere and is absorbed by the surface.
Solar Panels- Turning Solar Power into Electric Current
Solar panels make it possible to convert solar power that manages to reach earth surface into electrical power. A solar panel is made of smaller units called solar cells. A solar cell uses two different layers of crystalline silicon. An n-type silicon has extra electrons and p-type silicon has extra spaces of electrons called holes. A p-n junction is where the two types of silicon meet. Electrons can wander across the junction, leaving a positive charge on one side and creating a negative charge on the other.
When a photon strikes the silicon cell with enough energy, it can knock out an electron from its bond, leaving a hole. Due to the electrical field at the junction, the electron is drawn to the n side and the hole is drawn to the p side. A thin conductor at the top of the cell collects the mobile electrons which then flows through an external circuit, doing electrical work before returning through the conductive pane on the back. This electrical energy generated from solar panels can power households, industries and entire cities.
A nuclear reaction triggered over 4 billion years ago. And the human invention called solar panel that uses Silicon, the second most abundant element on the earth to transform Solar power into electricity. The saga of human travail to create a prosperous but self-sustainable society with the help of solar is still unfolding.