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Non-Conventional Energy Sources

Alternative Or Non-Conventional Sources Of Energy

With the increasing concerns about the depletion of fossil fuel reserves and the severe environmental consequences of their use, there is a growing global emphasis on developing and utilising alternative or non-conventional sources of energy. These sources are generally renewable, cleaner, and offer a more sustainable path for meeting future energy demands compared to traditional fossil fuels.

Non-conventional energy sources are diverse, harnessing natural processes like sunlight, wind, biomass growth, geothermal heat, and the energy of oceans. While some, like large-scale hydropower, are often considered conventional due to their long history of use, the term "non-conventional" typically refers to sources whose widespread adoption and technological development are more recent compared to coal or oil.

Solar Energy

The Sun is the primary source of energy for almost all processes on Earth. The energy radiated by the Sun in the form of electromagnetic waves (primarily visible light, infrared, and ultraviolet radiation) is known as solar energy. It is a vast, inexhaustible, and clean resource.

Solar energy can be harnessed in two main ways:

Solar Thermal Energy

This involves converting solar radiation directly into heat energy. Devices used for this purpose include:

The efficiency of solar thermal systems in converting solar radiation to usable heat depends on factors like the type of collector, insulation, and temperature difference.

Solar Photovoltaic (PV) Energy

This involves converting solar radiation directly into electrical energy using photovoltaic cells, commonly known as solar cells. These cells are typically made of semiconductor materials like silicon.

Working Principle of a Solar Cell

A solar cell is essentially a p-n junction diode. When sunlight falls on the cell, photons with sufficient energy strike the semiconductor material. This energy breaks the bonds, creating electron-hole pairs. Due to the internal electric field at the p-n junction, electrons are driven towards the n-side, and holes are driven towards the p-side. This separation of charge creates a potential difference across the junction. When an external circuit is connected, the electrons flow through it from the n-side to the p-side, constituting an electric current. This flow of current can be used to power electrical devices.

Multiple solar cells are connected together to form a solar panel (or module), and several panels are combined to create solar arrays for larger power output.

Schematic diagram of a basic solar cell (p-n junction).

(Image Placeholder: A diagram showing a p-n junction with incident photons creating electron-hole pairs, charge separation across the junction, and external circuit connection showing current flow.)

Advantages of Solar Energy

Disadvantages of Solar Energy

India has abundant sunshine and has been aggressively promoting solar energy adoption through policies and subsidies, becoming one of the world leaders in solar power capacity.

Energy From The Sea

The oceans are vast reservoirs of energy, primarily derived from solar energy and gravitational forces. Several technologies exist to harness this marine energy:

Tidal Energy

This energy is derived from the rise and fall of tides, which are caused by the gravitational pull of the Moon and the Sun. The movement of large volumes of water during high and low tides can be used to generate electricity.

How Tidal Energy is Harnessed

One common method is using a tidal barrage, a dam-like structure built across a bay or estuary with a large tidal range. Sluice gates in the barrage allow water to flow into the basin during high tide and trap it. During low tide, when the water level outside the barrage is significantly lower than inside, the trapped water is released through turbines located in the barrage, generating electricity.

Another method uses tidal stream generators, which are like underwater wind turbines placed in areas with strong tidal currents. The flowing water turns the blades, generating electricity. This method does not require building barrages.

Schematic diagram of a tidal barrage power plant.

(Image Placeholder: A diagram showing a tidal barrage between the sea and a basin, with turbines embedded, illustrating water flowing through turbines during incoming or outgoing tides.)

Advantages of Tidal Energy

Disadvantages of Tidal Energy

India has potential for tidal energy in regions like the Gulf of Cambay and the Sunderbans, but large-scale projects have faced economic and environmental challenges.

Wave Energy

This energy is harnessed from the motion of ocean surface waves, which are primarily caused by wind blowing over the water surface. The energy is present in the form of kinetic and potential energy of the water.

How Wave Energy is Harnessed

Various technologies are being developed to capture wave energy, including:

Diagram of an Oscillating Water Column (OWC) wave energy converter.

(Image Placeholder: A diagram showing a partially submerged chamber open to the sea, with waves causing water level fluctuations that compress air above, driving a turbine at the top.)

Advantages of Wave Energy

Disadvantages of Wave Energy

India has a long coastline and potential for wave energy, but it is not yet exploited on a significant scale.

Ocean Thermal Energy Conversion (OTEC)

OTEC harnesses the temperature difference between warm surface water and cold deep ocean water to run a heat engine and generate electricity. The temperature difference required is typically around 20°C or more.

How OTEC Works (Closed Cycle)

In a closed-cycle OTEC system, a working fluid with a low boiling point (like ammonia) is vaporised using the warm surface water. The high-pressure vapour drives a turbine connected to a generator. Cold water from the deep ocean is then used to condense the vapour back into a liquid, and the cycle repeats.

Schematic diagram of a closed-cycle OTEC system.

(Image Placeholder: A diagram showing a heat exchanger using warm surface water to vaporise a working fluid, a turbine driven by the vapour, a generator connected to the turbine, a condenser using cold deep water to liquefy the fluid, and pumps to circulate the fluid.)

Advantages of OTEC

Disadvantages of OTEC

India has conducted research and pilot projects on OTEC, particularly in the coastal regions with suitable temperature differences.

Geothermal Energy

Geothermal energy is heat energy derived from within the Earth. This heat originates from the formation of the planet (primordial heat) and the radioactive decay of minerals in the Earth's crust and mantle.

In certain regions, this heat is concentrated closer to the surface, making it accessible for various uses, including electricity generation and direct heating.

How Geothermal Energy is Harnessed (Electricity Generation)

Geothermal power plants typically tap into underground reservoirs of hot water or steam. Wells are drilled to bring this hot fluid to the surface. The hot fluid (or the steam produced from it) is used to drive a turbine, which powers a generator to produce electricity.

There are different types of geothermal power plants depending on the nature of the underground resource (dry steam, flash steam, binary cycle).

Schematic diagram of a geothermal power plant.

(Image Placeholder: A diagram showing wells drilled into the earth tapping into a hot reservoir, bringing steam or hot water to the surface to drive a turbine connected to a generator, and cooled fluid being reinjected underground.)

Advantages of Geothermal Energy

Disadvantages of Geothermal Energy

India has potential geothermal resources in several areas, such as Puga Valley (Ladakh) and Tatapani (Chhattisgarh), but large-scale development is still limited.

Nuclear Energy

Nuclear energy is released from the nucleus of atoms, typically through nuclear reactions like fission or fusion. While sometimes grouped with conventional sources due to its established technology and large-scale deployment in many countries, it is non-conventional in the sense that it doesn't involve combustion like fossil fuels and offers an alternative path to low-carbon energy generation.

Currently, almost all commercial nuclear power plants use nuclear fission.

Nuclear Fission

Nuclear fission is the process where a heavy atomic nucleus (like Uranium-235) is split into two or more lighter nuclei, releasing a tremendous amount of energy in the form of heat, along with neutrons and gamma rays. This fission is typically initiated by absorbing a neutron.

The energy released is significantly larger than that released during chemical reactions (like combustion) for the same mass of fuel, as described by Einstein's mass-energy equivalence ($E=mc^2$), where a small amount of mass is converted directly into energy.

How Nuclear Fission is Used for Electricity Generation

In a nuclear power plant, fission reactions are controlled in a device called a nuclear reactor. The reactor core contains nuclear fuel (usually enriched uranium) and a moderator (like water or graphite) to slow down neutrons and sustain a controlled chain reaction. Control rods (made of neutron-absorbing material like cadmium or boron) are used to regulate the rate of the fission chain reaction.

The heat generated by fission heats a coolant (usually water) circulating through the reactor core. This hot coolant is then used to produce steam (either directly or indirectly in a heat exchanger). The high-pressure steam drives a turbine connected to an electrical generator, producing electricity. The steam is then condensed back to water, similar to a thermal power plant.

Schematic diagram of a nuclear power plant.

(Image Placeholder: A diagram showing a reactor vessel where fission occurs generating heat, a heat exchanger or steam generator where the heat transfer produces steam, a turbine driven by steam, a generator connected to the turbine, and a condenser where steam is cooled by external water.)

Advantages of Nuclear Energy

Disadvantages of Nuclear Energy

India has a significant nuclear power program and is actively developing its capacity, focusing on a closed fuel cycle and breeder reactor technology to utilise its vast thorium reserves.

Nuclear Fusion

Nuclear fusion is the process where two light atomic nuclei (like isotopes of hydrogen, deuterium, and tritium) combine to form a heavier nucleus, releasing an even larger amount of energy than fission. This is the process that powers the Sun and other stars. Achieving controlled nuclear fusion on Earth for power generation is a major scientific and engineering challenge, requiring extremely high temperatures and pressures to overcome the electrostatic repulsion between the nuclei.

If successful, fusion could provide a nearly inexhaustible, clean, and safe energy source, as the fuel materials are abundant and the byproducts are less radioactive than fission waste. However, it is still in the experimental stage, with large international projects like ITER aiming to demonstrate its feasibility.