2. Renewable Energy Sources

Any energy source that is sustainable and can be used for a longer run without running out, is known as a renewable energy source. These sources get replenished at a rate higher than their consumption. With the growing threat of climate change due to excessive release of carbon emissions, many countries are looking to shift to cleaner energy alternatives to replace the traditional fossil fuels. Some of the popular renewable energy sources^[3] are briefly explained subsequently.

Wind Energy

The term ‘wind’ refers to the movement of air. The moving air (wind) has lots of energy, which can be converted to obtain electricity. The energy from the wind can be harnessed using the huge wind turbines. When the wind (heavy and fast) flows through the turbine, the blades of the fan spins and captures the energy. The captured energy is used to drive generators which then feed electricity into the National Grid. Although domestic or ‘off-grid’ generation systems are available, not every property is suitable for a domestic wind turbine.^[4]
The merits and demerits of wind enegry is given in the following figure-

Hydro Energy

Hydro power is one of the most commercially developed renewable energy. Here, the energy from the fast flowing water is captured and converted to electricity with the help of water turbines. To harness hydropower, a dam or a barrier is built across a river valley or flowing water source along with a large reservoir. This helps to create a controlled flow of water to drive the turbine and generate electricity. This energy source is more reliable than solar or wind power and also allows electricity to be stored for use.
The merits and demerits of hydro energy is given in the following figure-

Geothermal Energy

Geothermal energy is the energy that is produced from beneath the Earth's surface. The earth’s core is the hottest part of the planet. This is because of the continuous radioactive decay taking place in the core. This energy travels upwards and helps produce temperatures high enough to heat the water and produce steam. The steam is then captured to rotate the turbines that power the generators. It can be used by a residential unit or on a large scale by an industrial application.
The merits and demerits of geothermal energy is given in the following figure-

Solar Energy

Sunlight is one of our planet’s most abundant and freely available energy resources. The amount of solar energy that reaches the earth’s surface in one hour is more than the planet’s total energy requirements for a whole year. But, the solar radiation received is not uniform in distribution across the world. These solar radiations from the sun can be converted into electricity with the help of technology. The sunlight is transformed into electrical energy either through photovoltaic (PV) panels or through mirrors that concentrate solar radiation. The generated energy is either used to generate electricity or stored in batteries and thermal storage.
The merits and demerits of solar enegry is given in the following figure-^[5]

173,000, the approximate number of terawatts of solar energy that shine on the Earth each day—10,000 times the daily global energy use.^[6]

Hydrogen energy ^[6]

Hydrogen is a versatile energy carrier and can be a solution to various critical energy challenges. Hydrogen based energy can be extracted from a variety of resources such as natural gas, nuclear power, biomass and biogas. The most common methods of producing this energy are : water electrolysis and thermochemical processes using methane. The hydrogen energy aids in decarbonising a range of sectors (including long-haul transport, chemicals, and iron and steel), where it has proven difficult to reduce emissions. Hydrogen-powered vehicles help in the improvement of the air quality and promote energy security. Hydrogen can act as a source of fuel to power ships, vehicles, industries and rockets. Hydrogen is much lighter than air. Thus, it dissipates rapidly when it is released, allowing for relatively rapid dispersal of the fuel in case of a leak.
There are two types of hydrogen energy-

• Green Hydrogen- produced using renewable energy sources like solar and wind.
• Blue Hydrogen- produced using fossil fuels such as natural gas etc.

The merits and demerits of hydrogen energy is given in the figure below-

Tidal Wave Energy^[7]

Tidal Energy is a form of power that is generated by the natural rise of and fall of tides in the ocean water caused due to the gravitational interaction between the sun, earth and the moon. The suitable location for the energy generation is the area with significant tidal range, i.e., the difference between high tide and low tides. The kinetic energy between the low tide and high tide is used to rotate the turbine that is placed in a tidal stream. In order to capture sufficient power from the tidal energy potential, the altitude of high tide needs to be at least five meters (around 16 feet) greater than low tide. However, there are very few commercial tidal power plants in the world and are more prevalent in coastal areas.
The merits and demerits of tidal energy is given in the figure below-