# Energy and Power: Production, Distribution, and Society/Solar

Energy is the ability to do work. We eat, travel, do our job, socialize with people, none of these things can happen without energy. Most of the energy use today are direct or indirect forms of solar energy.
The food we eat comes from plants or animals. Plants convert light from the sun into carbohydrates and tissue. We eat plants (rice, wheat, corn, potatoes) which are foods from plants. Animals we eat such as chicken, goat, fish get their energy by eating plants. So its safe to say all food we eat is produced from solar energy.
We fill our tanks with gas, most of our power stations runs on coal. Petroleum is nothing but remains of dead animals that once existed millions of years ago. Coal is remains of trees and forest that once flourished under sunshine. So the power we get from gas and coal is nothing but a stored solar energy.
Solar energy was harvested and used by our ancestors for a long time. For example, we dry clothes outdoors. The sun shines on it, heats it up and quickens the pace at which water evaporates from the clothes. Mayans started fires using parabolic mirrors to concentrate the Sun's rays into a tiny spot on tinder. The tinder will get hot enough and burn, thus it could be used to start fire. Glass houses are being used in cold climatic region to keep crops from freezing by trapping warmth giving the sun inside a glass structure.

## How does the Sun produce power?

The heat of the Sun is generated by nuclear fusion.

## Potential of solar energy

On the surface of the sun, the intensity of solar radiation is estimated as 73 MW per squared meter surface. But, on the surface of the earth, it is reduced to maximum of 1000W per squared meter at air-mass of 1.5 and 25 degree Celsius.

## History of solar energy

The history of solar energy is fascinating and awe inspiring. We humans have taken the Sun as granted. We have used solar energy even before we realized we were using it. But even before us animals and plants have been using the energy of the Sun for millions and millions of years.

### Life depends on solar energy

Almost all life on Earth is directly or indirectly dependent on solar energy. The abundance of sunlight has made rain forests flourish, has made the winds blow, rains to occur, rivers and streams to flow.
So which life first used the power of the Sun? The answer probably is plants. Plants use a unique chemical process called photosynthesis. They take in carbon dioxide and water, use solar energy to convert it to carbohydrates and oxygen. The oxygen is released as a byproduct into the atmosphere. In other words plants convert light energy into chemical energy which is used for it to function like creating more leafs, wood, bark, fruits, seeds and so on.
Animals use solar energy. Animal skin uses sunlight to produce vitamin D which is essential to develop and maintain the skeleton. The most visible use of solar energy or light is for vision. Many animals can see with eyes which are sensitive to light.
Ants use the position of the Sun as a compass and they navigate accordingly. The Sun does not stay in the same spot in the sky, but ants somehow are able to use the position of the Sun to navigate.
Cold blooded animals like crocodiles bask. This enables then to quickly raise their body temperature which enables them to be active. Even warm blooded animals position themselves to receive maximum sunlight at dawn for their body to warm up a bit.

### Humans use solar energy

Humans were quick to adopt the use of solar energy. Perhaps the first application was for drying. It could have been drying meat, fish, washed clothes or perhaps to dry themselves when they are wet.
Humans really started harvesting solar energy when they started to grow crops. Many civilizations realized sunlight is a vital component for crop growth. For example farmers in the state of Andhra Pradesh India celebrate a festival called Pongal on January 14 of every year. Pongal is a way of thanking the sun for aiding the farmers in agriculture and on their quest for a good harvest.
Egyptians worshiped the Sun as a god who they named Ra. Mayans respect the Sun and have gone to the extent of sacrificing humans so that the Sun would rise everyday without fail. Mayans were the first to use solar concentrator. They used a highly polished parabola to concentrate sunlight into a tiny spot so that it could light a tinder to make a fire.
Many cultures feared eclipses as they thought the Sun was failing and may not return. The Sun was clearly important to ancient civilizations. Though they never understood what the Sun was, they knew it was important and they could be doomed if the Sun was doomed.

## Successful solar energy projects

Solar energy today is recognized as a important means of renewable energy and there are different types of extracting the energy. they are
* Direct Heating mode- Used in water heaters /solar thermal systems
* Solar PV model - This method is used for creating photovoltaic signals and thereby power to charge a battery.
Solar PV modules comes in three types:
* Solar crystal module
* Thin Flim technology
* Nano film technology
Today the solar energy is convertible for use in real life with moderate investment