Conventional Energy Sources

Conventional Sources Of Energy

Conventional energy sources are those that have been in widespread use for a long time and form the backbone of our current energy infrastructure. Historically, these sources have been dominant due to their availability, ease of extraction and processing, and established technologies for energy conversion. However, many of these sources are non-renewable and have significant environmental impacts.

The most prominent conventional energy sources are:

Fossil Fuels: Coal, Petroleum (Oil), and Natural Gas
Hydro Energy: Energy from flowing water, typically harnessed through dams
Nuclear Energy: Energy from the fission of heavy radioactive elements like Uranium (often considered conventional in developed energy economies, though sometimes grouped separately).

While hydro energy is renewable, it is often included in the 'conventional' category due to the long history of using hydropower technologies and large-scale dam constructions forming a traditional part of the energy mix.

Fossil Fuels

Fossil fuels are formed over millions of years from the remains of ancient plants and animals buried deep underground. Under immense pressure and heat, this organic matter transformed into energy-rich substances: coal, petroleum (crude oil), and natural gas.

They are called 'fossil' fuels because they originate from fossilised biological material. They are the primary source of energy for electricity generation, transportation, and heating globally, including in India.

Formation and Extraction

The process of formation takes millions of years, making them non-renewable resources. Coal is primarily extracted through mining (surface or underground). Petroleum and natural gas are extracted by drilling wells into underground reservoirs.

Types and Usage

Coal: A solid fossil fuel. It is the most abundant fossil fuel and is a primary source for thermal power generation in India. It is also used in industries (like steel production) and historically for heating. Burning coal produces significant air pollution and CO2 emissions.
Petroleum (Crude Oil): A liquid fossil fuel. It is refined into various products like petrol, diesel, kerosene, lubricants, and petrochemicals. Primarily used for transportation, heating, and as feedstock for the chemical industry.
Natural Gas: A gaseous fossil fuel, primarily methane ($CH_4$). Often found alongside petroleum deposits. It is considered a cleaner-burning fossil fuel than coal or oil, producing less air pollution and CO2 per unit of energy. Used for electricity generation, heating, and as fuel for vehicles (CNG).

Fossil fuels are popular due to their high energy density and relative ease of storage and transport (especially liquids and gases). However, their combustion releases greenhouse gases and other pollutants, contributing significantly to climate change and air quality issues. Their finite nature also means they will eventually be depleted.

Thermal Power Plant

A thermal power plant is a facility that converts heat energy into electrical energy. The heat is typically generated by burning a fuel, most commonly fossil fuels like coal, but also natural gas, oil, or biomass.

In India, coal-based thermal power plants account for a large majority of electricity generation.

Working Principle

The basic principle involves a heat engine. The steps are generally:

Fuel Combustion: The fuel (e.g., coal) is burned in a furnace or boiler. This process releases chemical energy as heat.
Water Heating: The heat produced is used to heat water, converting it into high-pressure, high-temperature steam.
Turbine: The high-pressure steam is directed onto the blades of a turbine, causing it to rotate. This converts the thermal energy of the steam into mechanical energy.
Generator: The turbine is connected to an electrical generator. As the turbine spins the generator's rotor, it produces electricity based on the principle of electromagnetic induction.
Condenser: After passing through the turbine, the steam is cooled in a condenser, usually by water from a nearby river, lake, or cooling tower, turning it back into liquid water. This water is then pumped back to the boiler, completing the cycle.

Some advanced thermal plants use natural gas in a "combined cycle," where a gas turbine (powered by burning gas) generates electricity, and the hot exhaust gases from the gas turbine are then used to produce steam for a steam turbine, increasing overall efficiency.

Schematic diagram of a thermal power plant.

(Image Placeholder: A diagram showing the flow: Boiler (fuel combustion heats water) -> Steam Turbine (steam rotates turbine) -> Generator (turbine drives generator) -> Condenser (steam cooled back to water) -> Pump (water returns to boiler). Smoke stack showing emissions.)

Efficiency and Environmental Impact

The efficiency of thermal power plants (the ratio of electrical energy output to fuel energy input) is limited by the laws of thermodynamics, typically ranging from 30% to 45%. The remaining energy is lost as waste heat.

Environmental impacts include air pollution (SOx, NOx, PM, CO2) from combustion, thermal pollution of water bodies used for cooling, and production of large amounts of solid waste (ash).

Hydro Power Plants

A hydroelectric power plant (hydro power plant) generates electricity using the energy of falling or flowing water. It is a clean and renewable source of energy during operation, as it does not burn fuel or produce air pollutants.

Working Principle

Hydroelectric power generation typically relies on harnessing the potential energy of water stored at a height. The process is as follows:

Dam and Reservoir: A dam is built across a river to create a large reservoir of water upstream. This stores a large volume of water at a significant height, giving it gravitational potential energy. Run-of-river hydro plants exist that don't use large reservoirs but divert a portion of the river flow through turbines.
Penstock: Water from the reservoir is channelled through large pipes called penstocks, which lead downhill to the power plant.
Turbine: As the water flows down the penstock, its potential energy is converted into kinetic energy. This high-speed water hits the blades of a turbine (e.g., Francis, Kaplan, Pelton turbine), causing it to rotate. This converts the kinetic energy of the water into mechanical energy.
Generator: The turbine is connected to an electrical generator, which converts the mechanical energy from the rotating turbine into electrical energy using electromagnetic induction.
Tailrace: After passing through the turbine, the water is discharged back into the river downstream of the dam.

Schematic diagram of a hydroelectric power plant with a dam and reservoir.

(Image Placeholder: A diagram showing a dam holding back a reservoir, a penstock leading down to a power house at a lower level with a turbine and generator, and water exiting into a river downstream.)

Advantages and Disadvantages

Advantages:

Renewable energy source.
No greenhouse gas emissions during operation.
Low operating costs once built.
Reservoirs can also provide benefits like irrigation, flood control, and water supply.
Hydro plants can be quickly started or stopped, making them useful for balancing grid load.

Disadvantages:

High initial construction costs.
Requires specific geographical locations (suitable rivers and topography).
Environmental impacts of dam construction: flooding land, changing river ecosystems, affecting fish migration, displacing communities.
Vulnerability to droughts, which can reduce water availability and power generation.
Sediment build-up behind the dam over time.

Despite the environmental and social challenges associated with large dams, hydro power remains a significant source of clean electricity in many countries, including India.

Improvements In The Technology For Using Conventional Sources Of Energy

While there is a global push towards renewable energy, conventional sources, particularly fossil fuels and hydro, continue to play a major role in the energy mix. Significant efforts are being made to improve the efficiency of these technologies and mitigate their environmental impact.

Fossil Fuel Technologies

Improvements in thermal power plants include:

Increasing Efficiency: Developing supercritical and ultra-supercritical boilers that operate at much higher temperatures and pressures, leading to higher thermal efficiency (up to 45-48% for ultra-supercritical coal plants) and thus burning less fuel per unit of electricity generated, reducing emissions. Combined Cycle Gas Turbines (CCGT) achieve efficiencies over 60%.
Reducing Air Pollution: Installing technologies like Flue Gas Desulfurization (FGD) to remove SO2, Selective Catalytic Reduction (SCR) or Selective Non-Catalytic Reduction (SNCR) to reduce NOx emissions, and advanced particulate filters (like electrostatic precipitators) to capture ash particles.
Carbon Capture, Utilisation, and Storage (CCUS): Technologies to capture CO2 emissions from power plant flue gases, potentially utilising them for other purposes or storing them underground. This technology is still under development and is expensive but holds potential for reducing greenhouse gas emissions from large point sources.
Cleaner Fuels: Promoting the use of natural gas over coal where feasible, as it is a cleaner-burning fuel.

Hydro Power Technologies

Improvements in hydro power focus on reducing environmental impact and increasing efficiency:

Fish Ladders/Passages: Designing structures to help fish migrate past dams.
Minimum Environmental Flows: Ensuring a minimum amount of water is released downstream to maintain the river ecosystem.
Improved Turbine Designs: Developing turbines that are more efficient across a wider range of flow rates and potentially more environmentally friendly (e.g., less harmful to aquatic life).
Pumped Storage Hydro: While not a primary energy source, these facilities use excess electricity (often from intermittent renewables) to pump water to an upper reservoir, storing energy as potential energy, and releasing it to generate power when needed. This enhances grid stability.

Nuclear Power Technologies

Developments in nuclear technology aim at improving safety, reducing waste, and potentially using different fuels:

Advanced Reactor Designs (Generation IV): These concepts promise improved safety, higher efficiency, reduced waste generation, and the ability to use different fuel cycles, including potentially burning existing nuclear waste.
Small Modular Reactors (SMRs): Smaller, factory-built reactors that could offer more flexibility and potentially lower costs.
Improved Waste Management: Research into reprocessing techniques and long-term geological storage solutions for nuclear waste.

These technological advancements aim to make conventional energy sources more sustainable and less environmentally damaging, although the fundamental challenges of resource depletion (for fossil fuels and uranium) and significant environmental trade-offs (for large hydro and nuclear waste) remain.