today is Feb 02, 2023

The Sun can be considered the ultimate source of energy. Most forms of energy have the sun as their main source of origin.

The last few years were really progressive in the field of solar energy. Because of the desirable environmental and safety aspects, solar energy is becoming widely popular. It can undeniably be called the future of energy needs.

Solar energy is the energy derived from the sun and transformed into usable forms (such as thermal or electrical energy).

This transformed energy is then used in multiple ways like in transportation, water heating, electricity, cooking, in-room heating, and much more. Also, Solar energy is even used in airplanes and satellites.

To convert sun rays into a usable form of energy, there are primarily two methods of conversion to follow:

  • Direct / Active
  • Indirect / Passive

In this post, you will know everything about direct and indirect forms of solar energy, the difference between the two and also we will be discussing all the significant forms of indirect solar energy.

Forms of Solar Energy

Renewable energy technologies produce marketable energy by converting natural phenomena into useful forms of energy.  

These technologies use the sun’s energy and its direct and indirect effects on the earth. Some resources from which energy can be produced are due to solar radiation, wind, biomass, gravitational forces (tides), and heat on the earth’s core (geothermal).

Solar energy can be divided into direct and indirect categories. Most energy sources on the earth are forms of indirect solar energy, although we usually don’t think of them in that way.

Before jumping to the indirect forms of solar energy, we first have to understand indirect and direct solar energy. 

What is Indirect Solar Energy?

When one form of energy is converted to another useful energy source and we need more than one process for the conversion, then the energy obtained is called indirect energy.

Likewise, when the energy is obtained indirectly from the sun’s energy via other energy forms caused by sunlight, it is thus called indirect solar energy. 

For example, Solar radiation warms the oceans, thus the ocean water is then converted to vapors in the air which then condenses as rain to feed rivers, into which dams and turbines are located to convert that flow of water into hydropower.

Types of Indirect Solar Energy

Most of the electric plants are producing electricity using indirect energy conversion processes.

Some ways to utilize solar energy are:

  • Wind
  • Wave/Tidal 
  • Ocean Thermal
  • Hydro Energy
  • Geothermal Energy
  • Biomass

Before discussing these forms in detail, let’s first quickly have an understanding of what direct solar energy is?

What is Direct Solar Energy?

The energy obtained from a single conversion of sunlight using various technologies and resulting in a usable form of energy is called direct solar energy.

Direct solar energy can be used for sunlight, heating or for generating electricity.

Types of Direct Solar Energy

Direct solar energy can be obtained using any of the following methods:

  • Thermal 
  • Photovoltaic

Solar radiations can either be absorbed in solar collectors to provide hot water for washing and space heating or they can be converted directly into electricity using photovoltaic (PV) panels which are normally mounted on the roofs or as arrays in fields.

Solar panels are the array of photovoltaic cells that converts light into electricity using the photovoltaic effect.

“It is time for sustainable energy policy which puts consumers, the environment, human, health, and peace first.” -Dennis Kucinich Click To Tweet

Difference Between Direct and Indirect Solar Energy

Solar radiation is the main driving force behind natural processes taking place on the earth and is the indirect source of all renewable forms of energy.

Even the origins of fossil fuels, which were produced as a result of the decay of plants and animals millions of years ago, lie in solar energy.

As we have discussed in the above writing, both direct and indirect solar energy have some similarities and differences.

Indirect and Direct solar energy both have the sun as their ultimate source, primarily, the difference is because of their production processes and functions.

Indirect Forms of Solar Energy: Explained 

Now, it’s time to discuss all the significant forms of indirect solar energy. 

Let’s just dive right into it!

01. Wind Energy

When atmospheric air heats up by sun radiation, the air gets lifted up and the cold air takes its previous place, this circulation of air results in the flowing of wind.

Also, the rotation of the earth, mountains, water bodies, and vegetation all affect the wind flow patterns.

Wind turbines are used to convert wind energy into electricity. The flow of the wind produces kinetic energy that rotates turbine blades and thus, electricity is generated. 

Wind speed and air density are the factors that affect the amount of energy generated by a wind turbine.

According to a report, by the end of 2019, the overall capacity of all wind turbines installed worldwide had reached 650,8 Gigawatt and is still growing.

Benefits of Wind Energy

  • Wind energy is a clean renewable source of energy and produces no pollution.
  • It is sustainable, i.e. wind energy is replenishing the present energy needs without causing any long-term damage to the environment.
  • These turbines are highly efficient and can convert half of the wind hitting them into electricity.
  • Wind Energy performs best in coastal areas, on the top of round-shaped mountains and plains.
  • Wind turbines last for around 20-25 years.

02. Biomass Energy

Due to the process of photosynthesis, plants receive energy from the sun, and then they are used in the production of biomass.

Biomass includes plants, starch, manures, and food crops like corn and sugarcane, etc.

Biogas is a combustible gas mixture that is produced from the fermentation of biomass by bacteria.

Thus, Biomass energy is one form of indirect solar energy.

Biomass is used to produce steam (biogas) in a biomass power plant. 

This steam runs the turbine and makes electricity from waste. 

Benefits of Biomass Energy

  • Biomass energy is eco-friendly and green.
  • It reduces soil and water pollution and also helps in the reduction of the greenhouse effect.
  • The gas generated through bio-digestion is non-polluting.
  • Setting up a Biogas power plant requires less initial investment. 

03. Ocean Thermal Energy

When sun radiations fall on the surface of the ocean, the temperature of the water on the surface of the ocean increases while the temperature deep into the ocean remains cold. 

This results in temperature differences in the ocean layers and the differences are used in generating electricity.

A plant is set up between these warm and cold layers of the ocean. This plant uses a fluid that vaporizes at a low temperature.

When the fluid reaches the surface of the region, it gets vaporized. This vapor is used to turn a turbine to make electricity.

The fluid is condensed using a condenser which uses cold water from the bottom of the ocean.

Image Source:

Benefits of Ocean Thermal Energy

  • It is marine renewable energy technology.
  • This method can bring nutrients to the surface and cool the surface.
  • The bigger the temperature difference between layers, the higher will be the efficiency. 

04. Hydro Energy

When rainwater gets vaporized by solar heat and gets condensed in the form of clouds which then turn out as rain or snow over the mountains. 

This water runs down with potential energy and converts into hydropower in the hydel power plant.

The accelerated water is used to spin the blades of the turbine. These turbines then convert mechanical energy into electricity.

In this process, the sun heats up the water bodies,as a result of which vapor rises in the atmosphere( evaporation happens) which then condenses into water droplets which causes rain. Thus, hydropower is an indirect form of Solar Energy.

Benefits of Hydro Energy

  • It is renewable energy and creates no pollution.
  • Hydro Energy is highly efficient and sustainable.
  • It plays a major role in economic development. Also, Industrial countries produce nearly 80% of electricity from hydropower.

05. Tidal Energy

When the sun or moon is overhead of the ocean, the water is attracted towards them due to the gravitational force and thus causing a temporary increase in sea level.

When the moon or sun comes underfoot, the situation is still similar. 

The overhead and underfoot conditions resulting in high tides while the Earth’s rotational and gravitational force pulls water downwards, thus resulting in low tides.

Due to these gravitational pulls, there are generally two high tides and two low tides per day, because of the rotation of the earth.

**The distance between the moon and the earth is much closer than between the sun and earth, so, the gravitational effect of the moon is much more than that of the sun on earth.

Sihwa Lake Tidal Power Station, located in Gyeonggi Province, South Korea, is the world’s largest tidal power installation, with a total power output capacity of 254 MW (Image Source: Wikipedia)

The intensity of the water from the rise and fall of tides is a form of kinetic energy. The movement of water is used to push a turbine using certain methods resulting in the generation of electricity. 

Benefits of Tidal Energy

  • Tidal Energy is also a form of renewable energy having no harmful emissions.
  • In the case of tidal power, there is predictable energy output because tides are predictable and constant because of gravitational forces. 
  • It also protects coastal flooding due to the tidal lagoons.
  • Tidal power can last longer and be more cost-effective than other renewable technologies. 

06. Geothermal Energy

Geothermal energy is heat inside the core of the earth. It is the underground heat leftover from the molten rocks and the radioactive decay of materials that formed earth billions of years ago.

International Geothermal Association says

“10,715 megawatts (MW) of geothermal power in 24 countries is online, which is expected to generate 67,246 GWh of electricity.”

Geothermal Energy can be harnessed using any of the three methods:

  • Using HydroThermal Reservoir
  • Using Hot or Dry Rock
  • Using Heat Pump

It is used for cooking, bathing, space heating, electrical power generation, and other uses.

Benefits of Geothermal Energy

  • These power plants produce electricity consistently irrespective of the weather conditions.
  • Since there is no requirement for combustion, geothermal energy is environmentally friendly.
  • It is reliable, sustainable and highly efficient.



What is Indirect Solar energy?

When the energy is obtained indirectly from the sun’s energy via other energy forms caused by sunlight, it is thus called indirect solar energy. 

For example, variation in the atmospheric pressure caused by the sun results in the flow of wind, it is thus called an indirect form of solar energy.

Is Geothermal Energy an indirect form of solar energy?

Yes! It is. Geothermal energy is heat inside the core of the earth. It is the underground heat leftover from the molten rocks and the radioactive decay of materials that formed earth billions of years ago.

What is an example of direct solar energy?

The energy obtained from a single conversion of sunlight using various technologies and resulting in a usable form of energy is called direct solar energy. Electricity collected using Solar panels is one example of direct solar energy.

What energy sources depend directly or indirectly on solar energy?

Almost all life on Earth depends directly or indirectly on solar energy either for food, electricity, or power. The Sun can be considered as the ultimate source of energy. Most forms of energy have the sun as their main source of origin.

What is the difference between direct solar energy indirect solar energy?

When we need multiple transformations of sunlight involving some technologies or effects to convert the sun radiations into a usable form of energy, then the energy produced is called Indirect solar energy. On the other hand, when we directly convert sunlight into electricity or any other usable form of energy then, it is called direct solar energy. For example, solar energy converted into electricity using solar panels will be considered direct solar energy. While wind energy which is caused by uneven heating of the atmosphere will be considered as indirect solar energy.