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Solar Energy Definition

concentrated solar

Solar power can be defined as the most important source of clean and renewable energy available for us in this corner of the universe provided by the Sun.

The Sun was formed before the birth of our planet and will be here to send us light and heat for at least another 5 billion years, which means that the power of the Sun can be considered a major source of renewable and free energy for mankind.

The Sun is not producing energy only through solar panels, the Sun is also responsible for the energy produced by wind, water (water cycle) and fossil fuels.

The sunlight helped plants, trees and animals to grow and after dying, they have become the coal, the oil and the gas used today.

Solar Energy Definition

Solar energy represents the most important source of clean, renewable and free energy available for us on the planet that can be used to replace the energy produced by fossil fuels to eliminate pollution and avoid a catastrophic shift of the climate conditions.

To produce the tremendous amount of power sent to Earth, the Sun burns every second 600 million tons of hydrogen in the nuclear fusion reaction that takes place in its core.

The fusion reaction is produced in the Sun’s core at a temperature of 15 million Kelvin (27 million Fahrenheit) and turns hydrogen into helium with the release of energy.

The energy produced during the nuclear fusion reaction is received here on the planet under the form of light and heat.

In addition, the Sun also releases particles continuously in the solar wind, which increases during solar activity.

The power of the Sun is used in two different ways on our planet: passive and active.

Passive Solar

Passive solar heating takes advantage of the heat produced by the Sun to heat living spaces for free.

Passive solar heating is usually used by passive homes to reduce energy bills and improve comfort.

To use the free heat provided by the Sun in a passive and efficient way, the house must be positioned in a way to allow the Sun’s heat to naturally enter the house during the winter and be rejected during the summer months.

Positioning the house could vary due to local climate conditions, but in the Northern hemisphere a passive home will use south facing windows to capture the Sun’s rays.

Passive homes are very efficient

During the winter, when the Sun is positioned low in the sky, the south facing windows will allow the sunlight to enter the rooms and heat the home.

In the summer months, when the Sun is positioned high in the sky, the passive home will use a large overhang for shade, to prevent the Sun’s rays from entering the rooms and keep the home cool.

Besides positioning correctly the house in relation to the Sun, the materials used to build the house must have a high thermal mass.

Thermal mass can be defined as the ability of a material to absorb, store and release heat.

During the winter, when the Sun’s rays enter the house through the south facing windows, the heat energy is absorbed by the materials inside the building that have a high thermal mass.

We can include here materials that are dense such as: stone, brick, concrete, ceramic tiles, etc.

These materials absorb and hold on heat when the Sun is shining, and slowly release the heat during the night keeping the home warm.

Using the natural heat provided by the Sun during the winter will reduce the energy consumption in the house for heating, which will reduce the energy bills.

Blocking the sunlight from entering the house during the summer will reduce the electricity consumption to cool the house, which will again reduce the energy bills.

Active Solar

Active solar uses mechanical and electrical equipment to convert the sunlight into heat and electricity.
Compared to passive solar, active solar generates much more energy.

To heat water or generate electricity using active solar systems we use solar water heaters, solar panels and concave mirrors.

There are several types of solar water heaters used today to produce warm water using only the sunlight.

1. Solar Batch Collectors (Integrated Collector-Storage or ICS)

Water is heated by the Sun in dark tanks or tubes within an insulated box.

The warm water is stored and used in the house when needed

Solar batch collectors are incompatible with closed-loop circulation systems, and generally not recommended in cold climates.

2. Solar Flat-Plate Collectors

These collectors usually use copper tubes fitted to flat absorber plates.

The system uses a series of parallel tubes that are connected at each end of the tube by two pipes, the inlet and outlet manifolds.

The flat absorber plate is mounted in an insulated box, which is covered by tempered glass.

These flat collectors usually hold about 40 gallons of hot water, which means that to ensure the demand of hot water for a family of four, you need to install about four of them.

3. Evacuated Tube Collectors

Each evacuated tube in the system works like a thermos tube (in principle). A glass or metal tube that contains the water or a heat transfer fluid is surrounded by a larger glass tube. The space between the tubes is a vacuum, which means that almost no heat is lost from the fluid.

These solar heaters work well even during the winter because they support temperatures as low as -40°F (-40°C).

To generate electricity using the sunlight, we are using solar panels covered by solar cells and concave mirrors that are concentrating the sunlight into a focal point located in a tube or at the top of a tall tower where an agent (molten salt) is heated to generate steam, which will spin a turbine to produce clean electricity using a large generator.

How Does a Solar Power Plant Work?

Today we are generating clean electricity using large solar farms containing a very large amount of photovoltaic (PV) solar panels.

These solar farms are located in areas receiving a good amount of sunlight during the year and could cover areas of tens of square of kilometers to ensure an output of more than 1 GW (1,000 MW).

The very large number of solar panels used by the power plant to generate electricity are facing south in the Northern hemisphere and north in the Southern hemisphere to ensure the maximum production of clean electricity possible.

The photovoltaic solar cells are built from silicon and are converting the sunlight into electrical energy using the photovoltaic effect.

The amount of electrical power produced form photovoltaic solar cells is increasing year after year because the demand for renewable energy increases and the price of the technology decreases.

How Does a Solar Thermal Power Plant Work?

Solar Thermal Power Plants also called Concentrated Solar Power (CSP) use a big number of large concave mirrors that are concentrating the sunlight towards a central tower called central collector.

Inside the collector we can find an agent (usually molten salt), which is heated at high temperatures to generate steam that will spin a turbine to drive a generator and produce clean electricity.

CSP (Concentrated Solar Power) systems are usually located in desert locations where space and sunlight are abundant.

In contrast to a solar power plant, a solar thermal power plant (CSP) can generate clean electricity even during the night or in the cloudy days because the agent heated by the sunlight can be stored for later use.


Solar energy has a very tiny share in the world’s energy mix today, but because the technology becomes more affordable year after year, and the investments in the field continue to increase the generation capacity for solar power on the planet, solar energy will become a major source of clean power of the future.

Article written by:

I am a writer and reporter for the clean energy sector, I cover climate change issues, new clean technologies, sustainability and green cars. Danny Ovy

1 Comment

  1. Muhammad Ahmar

    Great Explained
    Thank u guy!

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