Physics of sustaianble energy 1

Evolution of energy converters

1. Human labour dominant before industrial revolution

2. Then animals and diffusion of winds and watermills

3. Then fuels

   1. fuel wood

   2. 1840 —> coal

   3. 1915: —> oil

   4. 1930 —> natural gas

   5. now: —> renewable energies

Transititon from one furl to another

• takes 50 - 75 years

• Develop production techniques

• develop distribution techiniques

• develop conversion techniques

Influential factors determininnng the pace of the transititon

• Infrastructural development

• Inertia to replace the embedded energy systems

Primary energy

Energy content of a fuel before it’s transformed

Energy

Capacity to do work

power

rate, enrgy per unit time

mechanical energy

Due to moving weights around (macroscopic forms of energy)

1. Potential energy: moved against gravity

2. Kinetic energy: when there’s movement

Thermal vs heat energy

Heat Energy: Energy transferred between two systems due to their temperature difference

Thermal Energy: Internal energy due to the microscopic potential and kinetic energy of the constituent particles such as atoms and molecules

Electrical energy

Energy associated with the movement of electric charges

Electric current

rate of flow of electric charges and is measured in amperes

1. Direct current

2. Alternating current varying periodically, at affixed frequency

Chemical energy

Energy possessed by substances due to their chemical composition and chemical structure. It’s the energy stored in the bonds of atoms and molecules

Enthalpy of formation

describes the energy balance of chemical reactions. it’s the measure of energy involved when a substance is formed from its constituent elements.

meanings of enthalpy signs

-ve:

• products have less enthalpy than the reactants

• heat released → exothermic reactions

• products stable

+ve:

• products have higher enthalpy than reactants

• heat obtained → endothermic reactions

• products unstable

Benefits of sustainable energies

• Sustainable energy would eventually eliminate dependence on fossil fuels,, which is responsible for huge greenhouse gas emissions

• Sustainable energy sources would never be depleted as they are produced naturally

• During energy production from sustainable energy sources, almost no GHGs are emitted, thus contributing to the environment and public health

• As the cost of sustainable energy production is decreasing rapidly, it will eventually be a more economic option for the global population

First law of thermodynamics

the internal energy of an isolated system is conserved under any thermodynamical change. A system is anything with an imaginary boundary around. Total energy in a closed system is neither lost or gained, it is only transformed.’

Secon law of thermodynamics

Entropy constantly increases in a closed system

Clean energy technologies

• Solar PV

• Wind

• Nuclear

• Electric vehicles

• Heat pumps

• Hydrogen

• Carbon capture Utilisation and storage (CCUS) → GHG removal

AM > 1

Sunlight travels through a greater thickness of the atmosphere as the sun is lower in the sky

AM = 1

Sun directly overhead

3 components of solar radiation

1. direct (B)

2. diffused (D)

3. reflected (R)

Photovoltaic devices

Solar cells are photovoltaic devices which can convert sunlight to electricity in a single step. Semiconductor materials are necessary for the photovoltaic effect to happen.

3 generations of photovolatic devices

Mono and ply cristalline Si

Thin film solar cells amorphous SI, CIGS, CdTe

Solution processable, QD, DSSC, Organic, Hybrid perovskites

3 processes of pjotovlatic cell

1. Absorption of the incident light

2. Generation of the electron hole pairs

3. Extraction of transport of these electrons and holes to constitute the electrical current

Off grid PV system

• PV systems is physically isolated from the main power grid

• Generally a battery is included to balance fluctuations in the mismatch between the PV generation and the electricity demand

On grid PV system

• System that can import and export electricity to the grid

• Systems that only export electricity to the grid

power to weight ratios

why does water have such a high Ce

This is due to their strong hydrogen bonding.

BTU

British Thermal Units (BTU) is the energy needed to raise 1 pound of water by 1 degree Fahrenheit

Calorie

Calorie is the quantity of heat needed to raise 1 gram of water by 1 degree Celsius

Earth’s energy budget

A balance between radiant energy reaching Earth from the sun, and energy that flows from earth back out to space. In order to meet this budget, energy released from Earth via evaporation, convection, and radiation must match the energy recieved. Basically radiative equilibrium - in order to keep the earth at a stable temperature

Ocean energy - what does it generate?

• Thermal energy from the usn

• Mechanical energy from tides and waves

Pros of ocean renewbale energy

• abundant, renewable

• no GHG

• tidal energy is predictable

• many cities have acces

• local resource for islands

Cons for ocean energy

• Site specific

• Harsh environment

• depends on weather (waves)

• Environmental concerns —> wild life

• competing uses (fishing, navigation…)

• Need a lot of investment to exploit fully

Environmental concerns for ocean energy

• Wildlife

• Changes to estuary

• Shoreline, and beac formation

• Human uses

What are tides caused by?

Caused by the gravitational frorces from the moon and the usn and the centrifugal forces on the rotating earth

what is Tidal energy

The motion of large bodies of water can be used to turn mechanical devices to produce electricity. Tidal energy exploits the natural ebb and flow coastal tidal waters 

What are the categories of tidal power?

• Tidal stream genrators - kinetic enrgy of mocing water

• Tidal lagoon/barrage - potential energy in differnce of heigh in tides

• Dynamic tidal power - both

How is the tidal energy turned into electricty?

roatating blades around a rotor —> rotor turns the drive shaft —> turns an electric genrator

Contributions of ocean wave energy ?

• potenital due to the displacement

• knitic dut to water molecules in motion

Attenuators - wave energy

• capture E form wave movement

• movement —> hydraulic pums —> energy

Osciallatin water columns - wave enrgy

• Columns partially submerged

• top of structure (above water) → filled with air → forcing incoming waves to be funneled into the bottom

• Flow causes the column to rise and fall with each wave → air in the top of the structure to pressurize and depressurize → connected air turbine converts air movement into electricity

Overtopping reservoir - wave energy

• wave lift over a barrier wich fills a reservoir with incoming water from waves that pass over the barrier

• water drained through a hydro turbine

Inverted pendulum - wave enregy

• Motion of waves to move a paddle back and forth

• motion of paddle → drives hydraulic pumps → electric generators

Challenges of wave enrgy converters

• cost

• not v efficient

• need to be precisly tuned

• need investment that we dont have

Ocean thermal energy converters (OTEC)

Exploits the temp differnce between war seawater and the surface and cold seawater in deeper parts to produce electricity

Components of OTEC

• Working fluid: water

• evaporator. increase vapor pressure

• condenser

• tubine

Carnot’s efficiency:

States that no heat engine can be more efficient than a carnot engine operating between the same two heat reservoirs.

Fission

Nuclear fission in the splitting of an atom after it is hit with a neutron

How does a nuclear power plant work

Nuclear power plants are similar in design to fossil fuel plants, except that nuclear fission replaces to combustion as a heat source

the heat from fission boils water and creates steam to turn a turbine

as the turbine spins,, the generator turns and produces electricity

COmponents of nuclear power plant

• moderaotr: slows down the neutrons

• control rods: neutron absorption material

• coolant

• pressure vessel

• steam generator

• cantainment

• reator

Generation 1 nuclear pp

proof of concept, dont run anymore

Generator 2 npp

• comercial reactors that are economical and relaible

• Traditional active safety features

• PWR, CANDU BWR AGR

Generation 3 npp

Like gen 2 but with evolutionary state of the art design improvemnts, aim for a longer operational life

Gen III + npp

Advanced gen 3, passive safety feature

Generation IV npp

Have as objectives sutainability , safety, reliability, economics and Proliferation resistance and physical protection *no stealing for weaposns)

Nuclear fusion

Occurs when 2 nuclei combine to form single nucleus, releasing massive amounts of heat with no long-lived radioactive waste

Advantages of nuclear energy

• No GHG production

• Efficient

• Relaible

• Low cost

Dsivantages of nuclear energy

• Radiocative waste

• Risk of nuclear accident

• Nuclear proliferation concerns

• Difficult to decommission

Moder wind turbines: lift trubines

• Lift blades can generate more force than drag turbines

• Extract more of wind’s energy

• Much cheaper since need fewer blades

Horizontal wind tubines

• most popular

• Horizontal designs use blades similar to wings of planes 

• Lift is used to drive the rotor 

• The rotor is connected to a generator through a shaft & gears which will convert the aerodynamic force into electricity

Vertical axis wind turbines

• Advantages: works with any wind direction, mechanics in the base for easy access, less stress on the tower since stabilizing wires can be used to hold the top. 

• Disadvantages: not self-starting, cannot be turned out of the wind for protection, high centrifugal stresses in the wings, resonant phenomena can occur and certain rotational speeds need to be avoided. Less cost effective

Suitable locations for onshore wind farms

High-altitude plains, exposed ridges, open lands, and coastal areas

Advantages of offshore farms

• higher winds speeds

• higher capacity factos

• less turbulance

• less obstrusive

• more sites and bigger

Disadvantages of offshore farms

• hogher contruction and mainatnace costs

• more expensive to connect to grid

Types of waste

• municipal solid wates

• bio medical waste

• industrial waste

• agricultural waste

• radioactive waste

• E-waste

Impact of landfills

• waste dumped in landfills does not genreate any added value

• soli and water fcontamination ´microplastics blown into water

• production of methane

Advantages of waste to energy

• help to reduce dependence on fossil fuels imports

• save millions of tonnes of CO2

• contributes to security of energy supply

• provides sustainable, local, low carbon, cost-effective and reliable energy

Thermal processing technologies for wate to energy

1. Incineration

2. Pyrolysis: thermochemical decomposition

3. Gasification: conversion od the carbon into a synthetic gas

Electrodes

• cathode +

• anode -

working of a battery

Anode oxidises → provides anode with negative charge (excess e-)

Reduction at cathode → gives it positive charge 

excess e- from anode → → cathode 

But for it to be complete theatre needs to be charge transport must also happen through the electrolyte. 

Heat transfer mechanism

• condution: Fourier’s law of heat conduction

• convection: Newton’s law of cooling

• Radiation: Stefan boltzman Law

Steady state heat transfer

In steady-state heat transfer, the rate of heat flow remains constant through different layers of material and different modes of heat transfer

Stack driven iniltration

• due to differnce to indoor to indoor temperatures

• near ceilings and floors

Wind driven infilitration

• Due to pressure diferences caused by wind blowing against side of the house

• near walls

BEVs electric cars

• Battery electric

• Pure electric

• No secondary energy storage

• Charged from external source

• 100 - 400 miles

PHEVs electric cars

• Plug in hybrids

• Sub clas of HEV

• Charged form external source

• 20 - 50 miles on electricity alone

• also rely on gasoline or diesel

FCEVs electric cars

• fuel cell electric

• Powered by hydrogen

• only meit water vapor and warm air

• can fuel in about 5 min

• more than 300 miles

EVs electruc cars

BEVs + PHEVs

HEVs electric cars

• Internal combustion engine with an electric drivetrain

• 400 - 600 miles

• Electric generator that recharges the battery or provides additional power to the electric motor

Powert train of vehicles

Level 1 recharging of EVs stations

• Standard outlet - 120V 

• 1.4-1.9 Kw charging power 

• 3-5 miles/h charging

Level 2 Recharging EV station

• Public servie stations or installed purposely at home - 240 V

• 3,3 - 19.2 kw charging power 

• 20 - 60 miles/ h charging

LEvel 3 recharging EV station

• Fast charging - 400 - 800 V

• 50 - 350 kw charging power 

• 60 - 200 miles in 30 minutes

Energy policy

It refers to the actions taken by a government to regulate and shape the energy sector. This include laws, regulations, and programs that affect energy production, consumption and distribution

Effects of policies

• Trade offs: compormise that involves giving something up in returnt for getting smth else 

• Synergies: Coordination in the design of multiple policy elements to improve efficency in their implementation and achieve optimal outcomes 

• Unintended consequences: Unexpected side effect → negativ effect on th e problem trying to be solved 

What are the differences between coal, oil, and natural gas? Compare their primary energy content.

• Coal is in the solid state, oil is in liquid form and natural gas is in the gaseous form.

• coal contains long and complex hydrocarbons, oil contains a mixture of medium-sized hydrocarbon chains and natural gas mainly contains small hydrocarbon gas molecules like methane.

• Coal i formed from dead plants ) in swampy areas buried under high pressure and temperature. Oil and Natural gas are mainly formed from microscopic marine organisms buried under the seabed in high-pressure and temperature conditions.

• The primary energy content of coal is relatively lower than that of oil and natural gas

• coal emits more co2

Primary content of gas

55 Mj/kg

Primary content of coal

24 MJ/kg

Primary content of oil

44Mj/kg

Compare the UK’s (2) primary energy with the World’s primary energy (1)

What are the three main primary energy-consuming sectors

• industry

• transport

• residential

Is the UK now a net energy exporter or importer?

importer

Water has a relatively high specific heat capacity. How is this helpful in climate regulation and thermal energy storage?

It can be seen that water has high volumetric heat capacity and that is one reason why water is used as a thermal storage medium. Water can pack more amount (almost double) of heat than concrete for a similar volume.

co2 and methane

The amount of CO₂ emitted per MJ of heat energy while burning CH₄ is 49.4 g of CO₂/MJ

What is meant by Earth’s energy budget?

The balance between the radiant energy that reaches Earth from the sun and the energy that flows from Earth back out to space i

natural vs anthropogenic greenhaouse effect

Net zero 2050 emission goal

Achieve a balance between the greenhouse gases emitted and the greenhouse gases removed from the atmosphere, effectively reaching "net zero" emissions by the year 2050

3 solar energy conversion technologies

•Photovoltaic devices (solar cells)

•Concentrated Solar Power (CSP)

•Solar thermal collectors

Max efficiency of soalr cell

The maximum theoretical efficiency of a single-junction solar cell is 33.7 % known as the Shockley-Queisser limit. The ideal bandgap for maximising the efficiency is 1.4 eV

Shading effect on J V curve