3.2 - Greenhouse Gas Emissions Flashcards
(34 cards)
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
