Energy Resources and Electricity Generation » Fossil Fuels for Electricity Generation

What you'll learn this session

Study time: 30 minutes

The main types of fossil fuels used for electricity generation
How fossil fuel power stations work
Environmental impacts of fossil fuel electricity generation
Advantages and disadvantages of different fossil fuels
Case studies of fossil fuel power generation
Current trends and future outlook for fossil fuels in electricity generation

Introduction to Fossil Fuels for Electricity Generation

Fossil fuels have powered our world for over a century and still generate about 63% of the world's electricity. These fuels formed millions of years ago from the remains of plants and animals that were buried and subjected to heat and pressure over time.

Key Definitions:

Fossil fuels: Natural fuels formed in the geological past from the remains of living organisms.
Thermal power plant: A power station that converts heat energy from burning fuel into electrical energy.
Combustion: The process of burning a fuel in the presence of oxygen to release heat energy.
Carbon intensity: The amount of carbon dioxide emitted per unit of electricity generated.

🔥 Types of Fossil Fuels

Coal: A black sedimentary rock made mostly of carbon. It's the most abundant fossil fuel but also the most polluting.

Natural Gas: Primarily methane (CH₄), it burns cleaner than coal and oil.

Oil (Petroleum): Less commonly used for electricity generation, but still important in some regions.

📈 Global Electricity Mix

As of 2022, fossil fuels account for:

Coal: ~36% of global electricity
Natural gas: ~23% of global electricity
Oil: ~4% of global electricity

The remaining 37% comes from nuclear and renewable sources.

How Fossil Fuel Power Stations Work

Most fossil fuel power stations operate on the same basic principle: burning fuel to heat water into steam, which drives a turbine connected to a generator that produces electricity.

The Electricity Generation Process

🔧 Step 1: Combustion

Fossil fuel is burned in a furnace or combustion chamber, releasing heat energy.

⚡ Step 2: Steam Generation

Heat boils water in pipes to create high-pressure steam that spins turbines.

💡 Step 3: Electricity Production

Turbines drive generators that convert mechanical energy into electrical energy.

Coal-Fired Power Stations

Coal power stations are the most common type of fossil fuel power plant worldwide. Coal is pulverised into a fine powder before being burned in the boiler.

The efficiency of coal power stations has improved over time:

Subcritical plants: 33-35% efficient
Supercritical plants: 38-40% efficient
Ultra-supercritical plants: Up to 45% efficient

Natural Gas Power Stations

Natural gas power stations come in two main types:

💪 Combined Cycle Gas Turbines (CCGT)

These plants use both a gas turbine and a steam turbine together. The hot exhaust gases from the gas turbine are used to generate steam for a second turbine, increasing efficiency to around 50-60%.

⏱ Open Cycle Gas Turbines (OCGT)

Simpler but less efficient (35-40%), these plants can start up quickly and are often used to meet peak demand or provide backup power.

Environmental Impacts of Fossil Fuel Electricity Generation

🌫 Air Pollution

Burning fossil fuels releases:

Carbon dioxide (CO₂) - greenhouse gas
Sulphur dioxide (SO₂) - causes acid rain
Nitrogen oxides (NOₓ) - smog formation
Particulate matter - respiratory problems

💧 Water Impacts

Fossil fuel power stations:

Use large amounts of cooling water
Can cause thermal pollution in water bodies
Risk of water contamination from coal ash
Potential groundwater pollution from fracking

🏠 Land Impacts

Environmental consequences include:

Land disturbance from mining
Ash disposal problems
Habitat destruction
Land subsidence from extraction

Carbon Intensity Comparison

The amount of CO₂ emitted per kWh of electricity generated varies significantly between fossil fuels:

Coal: 820-950 g CO₂/kWh
Oil: 650-750 g CO₂/kWh
Natural gas: 350-450 g CO₂/kWh

Case Study Focus: Drax Power Station, UK

Drax was once the UK's largest coal-fired power station, producing about 7% of the country's electricity. In recent years, it has undergone a remarkable transformation:

Four of its six generating units have been converted from coal to biomass
Carbon emissions have been reduced by over 80% since 2012
The station has installed carbon capture technology on one biomass unit
The remaining coal units are scheduled to close by 2025

This case study demonstrates how even large fossil fuel power stations can adapt to reduce their environmental impact.

Advantages and Disadvantages of Fossil Fuels

👍 Advantages

Reliability: Can generate electricity 24/7 regardless of weather
Cost-effective: Generally cheaper than alternatives in the short term
High energy density: Small amount of fuel produces large amount of energy
Established infrastructure: Well-developed supply chains and technology
Dispatchable: Output can be adjusted to meet demand

👎 Disadvantages

Environmental pollution: Air, water and land pollution
Climate change: Major source of greenhouse gas emissions
Non-renewable: Limited supplies that will eventually run out
Health impacts: Air pollution causes respiratory diseases
Extraction impacts: Mining and drilling damage ecosystems

Mitigation Technologies

Several technologies are being developed to reduce the environmental impact of fossil fuel power stations:

🔍 Carbon Capture and Storage (CCS)

Technology that captures CO₂ emissions from power plants and stores them underground. Can reduce emissions by 85-90% but increases costs and reduces efficiency.

🔋 Flue Gas Desulphurisation (FGD)

Removes sulphur dioxide from exhaust gases using limestone slurry, reducing acid rain. Now standard in modern coal plants.

🛠 Selective Catalytic Reduction (SCR)

Reduces nitrogen oxide emissions using ammonia and catalysts, cutting smog formation and respiratory problems.

Future Outlook for Fossil Fuels in Electricity Generation

The role of fossil fuels in electricity generation is changing due to climate concerns and the falling cost of renewables:

Coal phase-out: Many countries have committed to phasing out coal power, with the UK aiming to end coal use by 2024.
Natural gas as a "bridge fuel": Some see natural gas as a transition fuel between coal and renewables due to its lower emissions.
Policy changes: Carbon taxes and emissions trading schemes are making fossil fuel generation more expensive.
Investment shifts: Many financial institutions are reducing funding for new fossil fuel projects.

Case Study: Germany's Energiewende

Germany's energy transition (Energiewende) aims to phase out both nuclear and fossil fuels:

Coal phase-out planned by 2038 (with discussions to bring forward to 2030)
Renewable energy has grown from 6% in 2000 to over 45% in 2020
Natural gas still plays a significant role as a transition fuel
Challenges include grid stability and electricity prices

This case study shows both the possibilities and challenges of moving away from fossil fuel electricity generation.

Key Takeaways

Fossil fuels remain crucial for global electricity generation, but their role is changing:

Coal use is declining in developed countries but still growing in some developing nations
Natural gas is increasing as a cleaner alternative to coal
Technologies to reduce emissions from fossil fuels are improving
The long-term trend is towards renewable energy sources
The transition away from fossil fuels must balance environmental concerns with energy security and affordability

🧠 Test Your Knowledge!