Sunlight is the primary source of renewable energy. The other is the geothermal energy. All other forms of renewable energy are the manifestation of solar and geothermal energy. For instance, initially the Earth’s atmosphere had only Hydrogen received from the nebula of the Sun with some amount of water, Methane and Ammonia. Later, bombardment of asteroids and outgassing of volcanoes inside the body of the Earth, built up Carbon dioxide and Nitrogen. An incessant rain for thousand of years dissolved most of the carbon dioxide floating in the atmosphere.
All other forms of renewable energy, namely wind, tidal, chemical, and water have their seeds in these two resources. Even geothermal energy may be attributed to the Sun. It is built up during the formation of the Earth and subsequent radioactive decay of minerals inside the crust of the Earth.
The Earth’s surface receives only 70% of the solar energy that falls on it. 30% is reflected back. The ocean, land and atmosphere absorb the received solar radiation in the form of heat and light. Only afterwards, we have wind, rains, tidal waves, photosynthesis and endogenous synthesis (vitamin D).
The total solar energy received by ocean, land masses and the atmosphere of the Earth is around 4 million exajoules per year. According to one estimate, the world’s consumption of total energy is equal to one hour of such solar energy.
We have been utilizing passive solar energy since the primitive age. Location of the caves and huts with naturally circulating air and use of light dispersing thermal mass are examples. We are now building houses which are well-lit and have a comfortable temperature gradient inside.
Use of active solar energy has no bounds. We have solar photovoltaic, solar heating, solar thermal electricity.Wherever, there was a need of either electricity or heat, solar-powered products and appliances are taking over.
The most significant innovations are being seen in the architecture. Both active and passive solar technologies are being scientifically exploited.
There is a kind of revolution in gadgets that receive their energy need from the Sun. To name a few, we have solar powered air conditioning, car, boat, backpack, compacting trash can, fan, golf cart, computer keyboard, lamp, calculator, pump, radio, notebook, refrigerator, watch and cell phone chargers.
These solar-powered gadgets and appliances are energy-efficient and environment friendly. These days where conventional electricity generation is in plenty, people still use solar panels as a standby.