How do we get Natural Gas ?
Millions of years ago, the tiny sea plants and animals had died and these remains were buried on the ocean floor. Over time, they were covered by layers of silt and sand. Over millions of years, the remains were buried deeper and deeper. The enormous pressure and heat changed these organic materials into coal, some into oil (petroleum) and some into natural gas-tiny bubbles of odourless gas. Today, we drill down through the layers of sand, silt and rock to reach the rock formations that contain oil and gas deposits.
Natural gas is used for cooking and heating in homes. In some power stations, gas is burnt to produce electricity. Natural gas can be converted to electricity in various applications, and it plays a crucial role in meeting global energy demands.
Natural gas is a fossil fuel that is primarily composed of methane, along with small amounts of other hydrocarbons, carbon dioxide, nitrogen, and traces of other elements. It is extracted from underground reservoirs and is considered a clean-burning fuel compared to coal and oil.
Following are the steps followed in the extraction and production of natural gas.
• Exploration : Geologists and geophysicists use various technologies, including seismic surveys and drilling, to identify and assess underground formations that may contain natural gas.
• Drilling : Once a potential reservoir is identified, a well is drilled into the ground to reach the gas-bearing rock formations.
• Extraction : Once the well reaches the natural gas reservoir, the gas is released from the rock formations and flows up the well to the surface. Techniques such as hydraulic fracturing or enhanced recovery are used to improve gas flow.
• Processing : The extracted natural gas often contains impurities such as water vapor, carbon dioxide, sulfur compounds, and other contaminants. Before it can be transported and used, the gas undergoes a processing stage to remove these impurities.
• Transportation : After processing, the natural gas is transported from the production site to end-users through pipelines, LNG (liquefied natural gas) carriers, or other means of transportation.
• Distribution and Storage : Once the natural gas reaches its destination, it is distributed to consumers through a network of pipelines. In some cases, natural gas is stored in underground storage facilities to meet fluctuations in demand.
Generating electricity from Natural Gas
Generating electricity from natural gas involves the combustion of the gas to produce heat, which is then used to generate steam or directly drive turbines connected to generators. The figure-2 below depicts combination of steam turbine and gas turbine cycles.
The following steps are followed to generate electricity from natural gas.
• Combustion : Natural gas is primarily composed of methane (CH4). When burned in the presence of oxygen, it undergoes combustion, resulting in the production of carbon dioxide (CO2), water (H2O) and heat.
• Heat Generation: The heat produced during combustion is harnessed to raise the temperature and pressure of a working fluid, which can be either water or a specialized heat-transfer fluid.
• Steam Generation : In many natural gas power plants, the working fluid is water. The heat generated is used to produce steam by boiling water. The high-pressure steam is then directed to a steam turbine.
• Steam Turbine (If applicable) : The high-pressure steam flows through a turbine, causing the turbine blades to rotate. The rotating turbine is connected to a generator, converting the mechanical energy into electrical energy. This process is similar to how a wind turbine works but instead of wind, steam is the driving force.
• Gas Turbine (If applicable) : In some power plants, natural gas is directly used to drive a gas turbine. The combustion of natural gas occurs in the turbine itself, and the hot gases produced spin the turbine blades directly. The turbine is connected to a generator to produce electricity.
• Combined Cycle : In a combined-cycle power plant, both gas and steam turbines are used to maximize efficiency.
• Electricity Generation : The rotating turbines, whether driven by steam or gas, generate mechanical energy. This mechanical energy is converted into electrical energy by the connected generators. The generators use the principles of electromagnetic induction to produce electric current.
• Transmission and Distribution : The generated electricity is then transmitted through a network of power lines and transformers to distribute it to homes, businesses, and industries for various uses.
Natural gas power plants are known for their flexibility and relatively lower greenhouse gas emissions compared to some other fossil fuels. However, they are not as carbon-neutral as renewable energy sources like wind or solar power. The choice of technology (combined cycle, simple cycle, etc.) depends on factors such as efficiency requirements, environmental considerations, and economic considerations.
Advantages of Natural Gas to Electricity Conversion
Following are about 5 to 10 benefits or advantages of Electricity generation from Natural Gas.
1. It is considered as cleaner burning fossil fuel compared to coal and oil.
2. Combustion of natural gas produces less carbon dioxide (CO2) compared to coal and oil. Hence it reduces greenhouse gas emissions.
3. Combined gas power plants which use both natural gas and steam turbines can achieve high overall thermal efficiency.
4. Natural gas power plants can start up quickly and respond rapidly to changes in electricity demand.
5. Natural gas power plants can provide a continuous and reliable power supply, which is crucial for maintaining a stable electrical grid.
6. Natural gas reserves are widely distributed around the world, making it a readily available and accessible energy source.
7. Infrastructure for natural gas extraction, transportation, and distribution is well-established in many regions which contribute to a reliable supply chain.
8. Natural gas power plants generally require less water for cooling compared to some other forms of electricity generation, such as coal-fired power plants. This can be advantageous in regions facing water scarcity or during drought conditions.
9. Natural gas prices have often been competitive, making it a cost-effective option for electricity generation.
10 Disadvantages of Natural Gas to Electricity Conversion
Following are 10 disadvantages of Natural Gas to electricity conversion.
1. While natural gas is considered cleaner than coal and oil, it still produces carbon dioxide (CO2) when burned.
2. During the extraction, production, and transportation of natural gas, methane can be released into the atmosphere. Methane is a potent greenhouse gas, and even small leaks can significantly impact the overall environmental footprint of natural gas.
3. Relying on natural gas for electricity generation can contribute to continued dependence on fossil fuels, hindering the transition to more sustainable and renewable energy sources. Overreliance on natural gas may delay efforts to decarbonize the energy sector.
4. Extracting natural gas involves depleting finite underground reservoirs. While natural gas reserves are currently abundant, over-extraction can lead to resource depletion and potential environmental consequences, such as land subsidence.
5. The extraction of natural gas, especially through hydraulic fracturing , can have environmental impacts.
6. Natural gas infrastructure, including pipelines and storage facilities, can be vulnerable to leaks and accidents. These incidents can pose safety risks and result in environmental damage.
7. Natural gas prices can be subject to volatility, influenced by factors such as geopolitical events, supply and demand fluctuations, and weather conditions.
8. Natural gas is a non-renewable resource. Hence it does not offer the long-term sustainability benefits associated with renewable energy sources like solar, wind, and hydroelectric power.
9. The extraction and transportation of natural gas often require significant land use. Infrastructure required for its use can impact ecosystems and local communities.
10. Natural gas is flammable, and accidents, such as explosions or leaks, can pose safety risks to nearby communities. Proper safety measures and monitoring are essential to mitigate these risks.
Conclusion : Balancing the benefits and disadvantages of natural gas for electricity generation is important, especially in the context of global efforts to transition to cleaner and more sustainable energy systems. Policymakers, energy providers, and society at large must consider a mix of energy sources to meet both current and future energy needs while minimizing environmental impacts.
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