Week 1 - lecture: Introduction to Energy Systems
What is energy?
Energy = the capacuty to do work
Work = applying a force over a distane
1 joule = 1 newton over 1 meter
Force = an in uence that can cause an object to change velocity
Power = rate of energy transfer
1 watt = 1 joule per second
Forms of energy (kinetic and potential)
E = 1/2 mv2 (kinetic) + V (x) (potential)
Kinetic energy is about motion, moving electrons/molecules including light, thermal, motion,
sound and electrical.
Potential energy is stored energy, including chemical bonds, magnetic elds, nuclear forces and
gravitational potential.
Every energy system involves transformations between these forms. e.g., burning fuel (chemical →
thermal), turning a turbine (thermal → mechanical), and generating electricity (mechanical →
electrical).
Thermodynamic limits and perpetual motion
Can we build a perpetual motion machine? (something that does work forever without input)
No, because of laws of thermodynamics.
First law: energy can not be created or destroyed, only transformed (so work without input of
external energy is not possible)
Qi = W + Qo
Qi = amount of heat supplied to the system
W = amount of work done by the system
Qo = amount of heat generated by the system
Second law (Entropy): heat goes from hot to cold unless energy is supplied to reverse it.
Entropy always increases in an isolated system.
ΔS = QC/TC −QH/TH ≥0
C = cold object
H = hot object
S = change in entropy of the system
Q = quantity of heat owing
T = thermodynamic temperature
Perpetual motion machines (work from single heat source) can not exist.
Entropy is a measure of energy dispersal or disorder, and it’s the only physical quantity that
gives direction to time. This is why energy conversions always involve losses. Entropy always
increases.
fl fl fi
, The Carnot cycle
The carnot cycle is the most ef cient heat engine. It operates between a hot and cold resevoir with
no change in entropy. No real machine can achieve this, all processes have some entropy (unusable
heat).
Heat pumps: input work → move heat from cold to hot
Energy carriers
An energy carrier is a substance used to produce work or heat. Different fuels have different
amounts of energy per unit mass (calori c values).
Energy ef ciency
Energy ef ciency is the amount of useful energy obtained from a system.
η = Useful energy output / Energy input
Electric heater: 100% → almost all electricity is converted to heat
Every conversion loses some energy: minimizing unnecessary conversion and improved ef ciency
is crucial.
Global energy system:
Primary resources → Energy carriers → Energy forms → Final energy → Energy services (e.g.
heating, lighting, mobility).
First-law versus second-law ef ciency
First law ef ciency = ratio of the desired energy to the energy input ( rst law of thermodynamics)
Second law of ef ciency = ratio of actual energy use to the theoretical minimum required for a task
(second law of thermodynamics)
Example: a domestic boiler heating air from 5 °C to 20 °C. First-law ef ciency might be 90%, but
second-law ef ciency is lower because the theoretical minimum energy needed to achieve that
temperature difference is much less than the input.
Energy resources:
- fossil (dominates)
- Nuclear (dense but dangerous)
- Renewable (essential but variable)
Fossil fuels are nite and emit co2. Decarbonization also makes long-term economic sense, as
renewable technologies become cheaper and carbon costs rise.
So…
- Energy is conserved but always degrades in quality through entropy.
- There are strict physical limits to ef ciency (Carnot).
- The global energy system involves many conversion steps, each with losses.
- Fossil fuels are energy-dense but unsustainable; renewables are sustainable but variable.
- Improving energy ef ciency and decarbonizing supply are central to sustainable energy
transitions.
fifi fi fi fi fi fi fifi fi fi fifi fi
,Week 2 - lecture: Energy supply, fossil fuels and carbon sequestration
Energy supply structure
The energy supply chain has two main stages:
Upstream (primary): obtaining raw resources as they occur in nature (coal, oil, wind)
Downstream (secondary): transforming primary resources into usable energy carriers (electricity,
fuel, etc.) that can be distributed and consumed.
Two types of energy sources:
Work sources: wind, rivers, tides → directly drive turbines
Heat sources: geothermal, solar, nuclear → produce heat to power turbines through thermal cycles
Turbines and generators convert these ows into electricity, which becomes the main secondary
energy carrier in modern economies.
Current global energy supply
Fossil fuels still dominate global energy supply and it is impossible to stop all fossil fuels at once.
60% fossil fuels for electricity and 75% for heat. There is not enough good technology to change
this yet. Renewables are increasing their share mainly in the electricity sector, but fossil fuels
remain strong in transport and industry.
- Renewables (wind, solar, hydro, bioenergy) are growing fast but start from a small base
- Investment is increasing in renewable electricity, but fossil fuel infrastructure continues to
receive signi cant funding, locking in emissions for decades.
- Non-electric sectors (e.g. transport fuels, industrial heat) remain largely fossil-based.
A heat pump does not work very well if its cold outside.
Russia is cold and poor and has oil → chances are low that they will change their way of heating.
Oil is a safe investment → banks keep on investing.
Countries dont want to commit to something that will make them poor → COP does not work, for
poor countires green energy is not a priority.
Fossil fuels - non renewable energy sources
1. Coal - abundant (140 years of reserves), used for power generation, burned directly
2. Petroleum (oil) - limited (60 years), must be re ned, dominant in transport
3. Natural gas - limited (50 years), versatile, good for heating and electricity
4. Uranium - technicaly non-renewable but very energy-dense
fi fl fi
, Despite nite reserves and emissions these fuels have been favored because of their high energy
density, dispatchability and established infrastructure.
Thermal power generation cycles
How fossil fuels are actually used to produce electricity. Four main thermodynamic cycles.
1. Rankine cycle (steam/vapor)
Used in coal, biomass, nuclear, and some solar thermal
plants.
1. Pump compresses uid →
2. Boiler heats it, turning water to steam →
3. Turbine expands the steam to produce work →
4. Condenser cools steam back to water → cycle
repeats.
Ef ciency is typically 30–40% for coal plants.
2. Brayton cycle (gas)
Used in natural gas plants and jet engines.
1. Air from atmosphere is compressed.
2. Fuel is injected and combusted at constant pressure,
heating it to system max temperature.
3. Hot gases expand through turbine to generate
power. The combustion products are expanded
through a turbine, creating the work output in the
form of the spinning turbine shaft.
Faster start-up, good for peak loads, but typically less
ef cient than steam alone.
3. Combined cycle
Modern gas plants often combine Brayton + Rankine for higher
ef ciency.
1. Gas-air mixture is combusted and expanded through a turbine,
as in the conventional Brayton cycle. (Brayton).
2. The exhaust is transferred to a heat exchanger where
pressurized, unheated water is introduced at the other end.
Heat is transferred from the gas to the water at constant
pressure so that the water reaches the desired temperature for
the vapor cycle (Rankine).
3. Steam exits the heat exchanger to a steam turbine, and gas
exits the heat exchanger to the atmosphere.
4. Steam is expanded through the turbine and returned to a
condenser and pump, to be returned to the heat exchanger at
high pressure.
This can push overall plant ef ciency to ~60%, making combined-
cycle gas plants among the most ef cient fossil systems today.
fifi
fi fl fi fi
What is energy?
Energy = the capacuty to do work
Work = applying a force over a distane
1 joule = 1 newton over 1 meter
Force = an in uence that can cause an object to change velocity
Power = rate of energy transfer
1 watt = 1 joule per second
Forms of energy (kinetic and potential)
E = 1/2 mv2 (kinetic) + V (x) (potential)
Kinetic energy is about motion, moving electrons/molecules including light, thermal, motion,
sound and electrical.
Potential energy is stored energy, including chemical bonds, magnetic elds, nuclear forces and
gravitational potential.
Every energy system involves transformations between these forms. e.g., burning fuel (chemical →
thermal), turning a turbine (thermal → mechanical), and generating electricity (mechanical →
electrical).
Thermodynamic limits and perpetual motion
Can we build a perpetual motion machine? (something that does work forever without input)
No, because of laws of thermodynamics.
First law: energy can not be created or destroyed, only transformed (so work without input of
external energy is not possible)
Qi = W + Qo
Qi = amount of heat supplied to the system
W = amount of work done by the system
Qo = amount of heat generated by the system
Second law (Entropy): heat goes from hot to cold unless energy is supplied to reverse it.
Entropy always increases in an isolated system.
ΔS = QC/TC −QH/TH ≥0
C = cold object
H = hot object
S = change in entropy of the system
Q = quantity of heat owing
T = thermodynamic temperature
Perpetual motion machines (work from single heat source) can not exist.
Entropy is a measure of energy dispersal or disorder, and it’s the only physical quantity that
gives direction to time. This is why energy conversions always involve losses. Entropy always
increases.
fl fl fi
, The Carnot cycle
The carnot cycle is the most ef cient heat engine. It operates between a hot and cold resevoir with
no change in entropy. No real machine can achieve this, all processes have some entropy (unusable
heat).
Heat pumps: input work → move heat from cold to hot
Energy carriers
An energy carrier is a substance used to produce work or heat. Different fuels have different
amounts of energy per unit mass (calori c values).
Energy ef ciency
Energy ef ciency is the amount of useful energy obtained from a system.
η = Useful energy output / Energy input
Electric heater: 100% → almost all electricity is converted to heat
Every conversion loses some energy: minimizing unnecessary conversion and improved ef ciency
is crucial.
Global energy system:
Primary resources → Energy carriers → Energy forms → Final energy → Energy services (e.g.
heating, lighting, mobility).
First-law versus second-law ef ciency
First law ef ciency = ratio of the desired energy to the energy input ( rst law of thermodynamics)
Second law of ef ciency = ratio of actual energy use to the theoretical minimum required for a task
(second law of thermodynamics)
Example: a domestic boiler heating air from 5 °C to 20 °C. First-law ef ciency might be 90%, but
second-law ef ciency is lower because the theoretical minimum energy needed to achieve that
temperature difference is much less than the input.
Energy resources:
- fossil (dominates)
- Nuclear (dense but dangerous)
- Renewable (essential but variable)
Fossil fuels are nite and emit co2. Decarbonization also makes long-term economic sense, as
renewable technologies become cheaper and carbon costs rise.
So…
- Energy is conserved but always degrades in quality through entropy.
- There are strict physical limits to ef ciency (Carnot).
- The global energy system involves many conversion steps, each with losses.
- Fossil fuels are energy-dense but unsustainable; renewables are sustainable but variable.
- Improving energy ef ciency and decarbonizing supply are central to sustainable energy
transitions.
fifi fi fi fi fi fi fifi fi fi fifi fi
,Week 2 - lecture: Energy supply, fossil fuels and carbon sequestration
Energy supply structure
The energy supply chain has two main stages:
Upstream (primary): obtaining raw resources as they occur in nature (coal, oil, wind)
Downstream (secondary): transforming primary resources into usable energy carriers (electricity,
fuel, etc.) that can be distributed and consumed.
Two types of energy sources:
Work sources: wind, rivers, tides → directly drive turbines
Heat sources: geothermal, solar, nuclear → produce heat to power turbines through thermal cycles
Turbines and generators convert these ows into electricity, which becomes the main secondary
energy carrier in modern economies.
Current global energy supply
Fossil fuels still dominate global energy supply and it is impossible to stop all fossil fuels at once.
60% fossil fuels for electricity and 75% for heat. There is not enough good technology to change
this yet. Renewables are increasing their share mainly in the electricity sector, but fossil fuels
remain strong in transport and industry.
- Renewables (wind, solar, hydro, bioenergy) are growing fast but start from a small base
- Investment is increasing in renewable electricity, but fossil fuel infrastructure continues to
receive signi cant funding, locking in emissions for decades.
- Non-electric sectors (e.g. transport fuels, industrial heat) remain largely fossil-based.
A heat pump does not work very well if its cold outside.
Russia is cold and poor and has oil → chances are low that they will change their way of heating.
Oil is a safe investment → banks keep on investing.
Countries dont want to commit to something that will make them poor → COP does not work, for
poor countires green energy is not a priority.
Fossil fuels - non renewable energy sources
1. Coal - abundant (140 years of reserves), used for power generation, burned directly
2. Petroleum (oil) - limited (60 years), must be re ned, dominant in transport
3. Natural gas - limited (50 years), versatile, good for heating and electricity
4. Uranium - technicaly non-renewable but very energy-dense
fi fl fi
, Despite nite reserves and emissions these fuels have been favored because of their high energy
density, dispatchability and established infrastructure.
Thermal power generation cycles
How fossil fuels are actually used to produce electricity. Four main thermodynamic cycles.
1. Rankine cycle (steam/vapor)
Used in coal, biomass, nuclear, and some solar thermal
plants.
1. Pump compresses uid →
2. Boiler heats it, turning water to steam →
3. Turbine expands the steam to produce work →
4. Condenser cools steam back to water → cycle
repeats.
Ef ciency is typically 30–40% for coal plants.
2. Brayton cycle (gas)
Used in natural gas plants and jet engines.
1. Air from atmosphere is compressed.
2. Fuel is injected and combusted at constant pressure,
heating it to system max temperature.
3. Hot gases expand through turbine to generate
power. The combustion products are expanded
through a turbine, creating the work output in the
form of the spinning turbine shaft.
Faster start-up, good for peak loads, but typically less
ef cient than steam alone.
3. Combined cycle
Modern gas plants often combine Brayton + Rankine for higher
ef ciency.
1. Gas-air mixture is combusted and expanded through a turbine,
as in the conventional Brayton cycle. (Brayton).
2. The exhaust is transferred to a heat exchanger where
pressurized, unheated water is introduced at the other end.
Heat is transferred from the gas to the water at constant
pressure so that the water reaches the desired temperature for
the vapor cycle (Rankine).
3. Steam exits the heat exchanger to a steam turbine, and gas
exits the heat exchanger to the atmosphere.
4. Steam is expanded through the turbine and returned to a
condenser and pump, to be returned to the heat exchanger at
high pressure.
This can push overall plant ef ciency to ~60%, making combined-
cycle gas plants among the most ef cient fossil systems today.
fifi
fi fl fi fi
