3.2 - Greenhouse Gas Emissions Flashcards
What are the components of the Kaya Identity that can be mitigated?
Carbon intensity, energy intensity, GDP per capita, population
Carbon intensity refers to the amount of CO2 emissions per unit of energy produced. Energy intensity refers to the amount of energy consumed per unit of GDP. GDP per capita is a measure of economic output that accounts for population size.
What are some methods to reduce carbon intensity?
- Fuel-switching
- CO2 capture and sequestration
- Renewable energies
- Nuclear energy
- Enhancements of CO2 sinks
Fuel-switching involves changing the type of fuel used for energy generation to cleaner alternatives.
List three strategies to improve energy intensity.
- Efficiency improvement
- Structural change
- Behavioral change
Efficiency improvement can lead to reduced energy consumption without sacrificing output.
What does ‘sufficiency’ refer to in the context of GDP per capita?
The concept of ensuring that economic growth does not exceed the ecological limits
Sufficiency emphasizes reducing consumption and focusing on quality of life rather than quantity of consumption.
What are the key strategies for efficiency improvement?
Reducing end-use energy demand, increasing conversion efficiencies through enhance power plant efficiencies, Heat supply improvements via condensing boilers and heat pumps, Cogeneration systems (heat and power), waste heat recovery of industrial process
This can be achieved through better thermal insulation in buildings, improved industrial processes, and reduced vehicle resistance.
Power plant efficiency can be done through Combined cycle gas-turbine power plants (CCGT), integrated gasification Combined Cycle (IGCC), fuel cells
What is the overall efficiency of traditional steam power plants?
45%
This refers to the ratio of useful energy output to the energy input.
What are the main components of a steam power plant?
- Boiler/Steam Generator
- Steam Turbine
- Generator
- Condenser
- Pump/Feed Water System
These components work together to convert thermal energy into mechanical and then electrical energy.
What are steam power plants?
Traditional method of energy generation using turbines and generators
Power plant efficiency equation
η = (Energy Output / Energy Input) × 100%
- Energy Output = Useful work/energy produced (electricity, heat)
- Energy Input = Total fuel energy consumed
- Higher η indicates better fuel utilization and lower waste heat
Gas Turbine efficiency
Electrical efficiency up to 36%
A gas turbine consists of these main components:
- Intake: where air comes in
- Compressor: Compresses incoming air to high pressure
- Combustion Chamber: Where fuel is mixed with compressed air and burned
- Turbine: Extracts energy from the hot gases to generate power
- Generator: Converts mechanical energy to electrical energy
- Exhaust: where the exhaust gases leave
- Exhaust gases include carbon dioxide (CO2), water (H2O), nitrogen, oxygen, nitrogen oxides
What distinguishes a Combined Cycle Gas Turbine (CCGT) from a regular gas turbine?
The reuse of exhaust heat
CCGT systems can achieve up to 60% efficiency by capturing hot exhaust gases to generate additional steam.
What is a Nuclear Power Plant?
Uses pressurized water reactors; water is heated using nuclear energy
What are the key components of a nuclear power plant?
- Reactor Core
- Control Rods
- Primary Cooling System
- Steam Generator
- Turbine
- Generator
- Containment Structure
- Cooling Towers
- Transformer
These components are essential for managing nuclear fission and generating electricity.
What safety concerns were highlighted by the Fukushima and Chernobyl accidents?
- Grid failure and tsunami damage (Fukushima)
- Core meltdown and radioactive release (Chernobyl)
These incidents raised awareness about the potential risks associated with nuclear energy.
What is a European Pressurized Reactor?
- 1600 MW output, 36-37% efficiency, service lifetime: 60 years
- Remedies the core melting issue → built-in core catcher that will cool any molten core that escapes from the reactor vessel
- Reduces need to evacuate populations
What is the current status of nuclear energy globally?
- Most of the nuclear reactors in operation today in advanced economies were built before 1990
- Not very economically viable at the moment → the risk of constructing and operating new plants has been too significant to attract investments
What are some renewable energy sources for power supply?
- Hydro power plants
- Wind energy converters
- Photovoltaic cells
- Solar thermal power plants
- Biomass fired power plants
- Geothermal power plants
These sources are considered cleaner alternatives to fossil fuels.
How does hydro power generate electricity?
By exploiting the kinetic energy of a river or dam to run turbines
It often involves the use of dams and reservoirs to manage water flow.
How do wind energy convertors generate electricity?
Leverages wind speed for power generation
Explain how Photovoltaic cells work
- Convert sunlight directly into electricity using semiconductor materials
- Key components and process:
- Silicon-based cells with two layers - n-type and p-type semiconductors
- When sunlight hits the cell, photons are absorbed, creating electron-hole pairs
- Built-in electric field separates electrons and holes
- Electrons flow through external circuit creating electrical current
- Can also work by concentrating solar power → central receivers, reflectors
- Work best in areas with lots of direct sunlight
Explain how solar thermal power plants work
- Uses mirrors/reflectors to concentrate sunlight onto a central point (solar trough field)
- The concentrated solar energy heats a fluid (often molten salt) to very high temperatures
- The heated fluid is used to:
- Generate steam to drive turbines
- Store thermal energy for later use (thermal storage)
- Power conventional steam generators for electricity production
Explain how solar thermal collectors for heat generation work
- Components
- Solar collector/plate where the solar energy is concentrated
- Controller to monitor temperature sensors in collector and storage tank and control pump operations
- Water is pumped when there is sufficient solar power to hear water; boiler generally exists to supply hot water when there is insufficient solar power
Explain how geothermal energy works
- Getting heat from underground (hot water reservoirs)
- For heating
- Gas separator → removes dissolved gases (like CO2 and H2S) from geothermal water to prevent scaling and corrosion in pipes and equipment
- Heat exchanger → heat water
- Backup boiler in case geothermal power is not enough
- For power
- Heat exchangers transfer thermal energy from geothermal fluids to a secondary working fluid (usually water/steam) without mixing them
- Allows geothermal fluid to be reinjected back to the reservoir
- Creates clean steam to drive turbines (geothermal fluids can be corrosive)
- Cooling tower to cool down steam after heating process
- Heat exchangers transfer thermal energy from geothermal fluids to a secondary working fluid (usually water/steam) without mixing them
Explain the different biomass that can be used for heat, power & fuels
- Feedstock can include
- oil crops (rape, sunflower, etc., waste oils, animal fats)
- Can be combusted for heat and/or power
- Can go through transesterification or hydrogenation to form bio fuels or renewable diesel
- sugar and starch crops
- Can go through hydrolysis and fermentation to form ethanol
- Can go through anaerobic digestion to form heat and/or power OR biomethane (renewable natural has which can be used to form heat or power)
- Lignocellulosic biomass (e.g. wood, straw, energy crops)
- Can go through combustion to form heat and/or power
- Can go through pyrolysis (a thermal decomposition process) to form heat and/or power
- Can go through anaerobic digestion for heat and/or power or to produce biomethane
- Biodegradable municipal solid waste (MSW) (e.g. sewage sludge, manure)
- Can go through pyrolysis for heat and/or power
- Can go through anaerobic digestion for heat and/or power or to produce biomethane
- oil crops (rape, sunflower, etc., waste oils, animal fats)
What is the process of Carbon Capture and Sequestration (CCS)?
- Capture: CO2 is separated from other gases produced during industrial and energy-related processes
- Transport: The captured CO2 is compressed and transported via pipelines, ships, or trucks to storage locations
- Storage (Sequestration): CO2 is injected into deep underground geological formations for long-term storage
CCS aims to prevent CO2 emissions from entering the atmosphere by capturing, transporting, and storing it underground.
What is Carbon Capture and Sequestration (CCS)?
Carbon Capture and Sequestration (CCS) is a technology designed to prevent large amounts of CO2 from entering the atmosphere by capturing carbon dioxide emissions from large point sources like power plants or industrial facilities
Explain post-combustion CO2 capture
- 80-90% cleaning degree (captured quantity)
- 9-14% efficiency loss
- CO2 is captured after energy generation → nitrogen, oxygen and water released to atmosphere
- Collected CO2 is stored in the ground eventually (not directly though)
- Can be a bit inefficient as CO2 concentration in exhaust gas is not that high
- Gas and steam power stations - 4%
- Conventional coal power plant - 14%
- integrated gasification combined cycle plants (use mixed gas) - 9%
Explain pre-combustion CO2 capture
- Pre-combustion CO2 capture
- 35-40% CO2 content in fuel gas
- Higher CO2 concentrations means process is easier and more efficient
- Efficiency loss - less than 12%
- Process involves putting coal through a gasifier to remove sulfur and to capture CO2
- Clean hydrogen is then used to fuel the turbine For power generation
- 35-40% CO2 content in fuel gas
What are some storage options for captured CO2?
- Saline aquifers
- Depleted oil and gas fields
- Unminable coal beds
- Ocean storage
Each option has different capacities for CO2 storage and varying ecological impacts.
What issues arise with CO2 storage?
- Transport issues
- Pipeline or tanker transport needed for liquefied CO2
- Health risks (CO2 release in sinks)
- Efficiency loss of 2-3%
- Possible concerns
- Storage reliability
- Ecological effects
- Health risks
- Conflicting usage goals
- Cost (small compared to capture and transport processes though)
What are nature-based solutions for emissions mitigation?
- Reforestation & Afforestation
- Planting additional trees to capture CO2 from atmosphere as they grow
- CO2 is stored in the living biomass
- Bioenergy with carbon capture and sequestration (BECCS)
- Plants turn CO2 into biomass, which is combusted in power plants → CO2 neutral process
- CCS can then be applied in addition to remove the CO2 from atmosphere
- Biochar and soil carbon sequestration (SCS)
- Biochar is created via the pyrolysis of biomass, making it resistant to decomposition
- Added to soil to store the embedded CO2
- SCS enhances soil carbon by increasing inputs or reducing losses
- Direct air capture (DAC)
- Chemicals are used to absorb CO2 directly from the atmosphere, which is then stored in geological reservoirs
These solutions leverage natural processes to capture and store carbon.
What is enhanced oil recovery?
- Popular in the US
- Uses CO2 injection into the ground to extract remaining oil reserves
True or False: Solar energy has the highest global technical potential as primary energy.
True
This indicates that solar energy could technically meet future energy demands even with increases in consumption.
