Solar Energy - Introduction

Solar energy is the energy obtained by capturing heat and light from the Sun. Energy from the Sun is referred to as solar energy. Technology has provided a number of ways to utilize this abundant resource. It is considered a green technology because it does not emit greenhouse gases. Solar energy is abundantly available and has been utilized since long both as electricity and as a source of heat.

Solar technology can be broadly classified as −

• Active Solar − Active solar techniques include the use of photovoltaic systems, concentrated solar power and solar water heating to harness the energy. Active solar is directly consumed in activities such as drying clothes and warming of air.

• Passive Solar − Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light-dispersing properties, and designing spaces that naturally circulate air.

Conversion of Solar Energy

The solar energy is the energy obtained by capturing heat and light from the Sun. The method of obtaining electricity from sunlight is referred to as the Photovoltaic method. This is achieved using a semiconductor material.

The other form of obtaining solar energy is through thermal technologies, which give two forms of energy tapping methods.

• The first is solar concentration, which focuses solar energy to drive thermal turbines.

• The second method is heating and cooling systems used in solar water heating and air conditioning respectively.

The process of converting solar energy into electricity so as to utilize its energy in day-to-day activities is given below −

• Absorption of energy carrying particles in Sun’s rays called photons.

• Photovoltaic conversion, inside the solar cells.

• Combination of current from several cells. This step is necessary since a single cell has a voltage of less than 0.5 V.

• Conversion of the resultant DC to AC.

In the next chapter, we will learn the Photovoltaic method of converting solar energy into electricity.

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Is solar power a clean energy source?

Yes, solar power is a renewable and infinite energy source that creates no harmful greenhouse gas emissions – as long as the sun continues to shine, energy will be released.

The carbon footprint of solar panels is already quite small, as they last for over 25 years. Plus, the materials used in the panels are increasingly recycled, so the carbon footprint will continue to shrink.
 

When was solar power discovered?

Solar energy was used by humans as early as the 7th century B.C. when humans used sunlight to light fires by reflecting the sun’s rays onto shiny objects. Later, in 3rd century B.C., the Greeks and Romans harnessed solar power with mirrors to light torches for religious ceremonies.

In 1839 and at the age of just 19, French physicist Edmond Becquerel discovered the photovoltaic (PV) effect while experimenting with a cell made of metal electrodes in a conducting solution. He noted that the cell produced more electricity when it was exposed to light – it was a photovoltaic cell.

In 1954 PV technology was born when Daryl Chapin, Calvin Fuller and Gerald Pearson developed the silicon PV cell at Bell Labs in 1954 – the first solar cell capable of absorbing and converting enough of the sun's energy into power to run everyday electrical equipment.

Today satellites, spacecraft orbiting Earth, are powered by solar energy.
 

How exactly is electricity from solar energy produced?

Solar panels are usually made from silicon, or another semiconductor material installed in a metal panel frame with a glass casing. When this material is exposed to photons of sunlight (very small packets of energy) it releases electrons and produces an electric charge.

This PV charge creates an electric current (specifically, direct current or DC), which is captured by the wiring in solar panels. This DC electricity is then converted to alternating current (AC) by an inverter. AC is the type of electrical current used when you plug appliances into normal wall sockets.

 

What’s the difference between solar PV panels and solar thermal panels?

Solar PV panels generate electricity, as described above, while solar thermal panels generate heat. While the energy source is the same – the sun – the technology in each system is different.

Solar PV is based on the photovoltaic effect, by which a photon (the basic unit of light) impacts a semi-conductor surface like silicon and generates the release of an electron. Solar thermal is less sophisticated and simply the direct heating of water (or other fluids) by sunlight. For domestic use, solar thermal panels are also installed on a roof facing the sun, heating water stored in a hot water cylinder and so providing hot water and heating. On a larger scale, solar thermal can also be used in power stations.
 

What are solar farms?

Solar farms, also known as solar parks or solar fields, are large areas of land containing interconnected solar panels positioned together over many acres, to harvest large amounts of solar energy at the same time. Solar farms are designed for large-scale solar energy generation that feed directly into the grid, as opposed to individual solar panels that usually power a single home or building.
 

Can solar power be generated on a cloudy day?

Yes, it can – solar power only requires some level of daylight in order to harness the sun’s energy. That said, the rate at which solar panels generate electricity does vary depending on the amount of direct sunlight and the quality, size, number and location of panels in use.
 

Who are the largest producers of solar power worldwide?

As of 2022, China is the largest producer of solar powered electricity generation in the world. The US comes in second, followed by Japan, Germany and India.1