Download The Physics of Energy sources Introduction

The Physics of Energy sources
B. Maffei
School of Physics and Astronomy
[email protected]
Turing Building room 3.125
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Practicalities
!   PowerPoint presentations will be on Blackboard
!   The material will also be available on the web:
•  http://www.jb.man.ac.uk/~bm/Teaching/en_sources/index.html
!   Lectures are the basis of the course
!   Will need further readings and work
•  Boyle, Everett and Ramage, Energy Systems and Sustainability (2003)
–  From which many pictures have been taken * ref 1
•  Lilley, J. Nuclear Physics Principles and Applications (Wiley 2006)
•  Krane, K.S. Introductory Nuclear Physics (Wiley 1998)
•  Twidell, J.W. & Weir, A.D. Renewable energy resources, (Spon 1986)
!   Do not hesitate to ask questions
!   Exam: 1:30 in May/June
!   Answer all questions of part 1 AND 2 sets of questions out of 3
!   No notes allowed. Necessary constants will be given.
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Foreword
!   This is an option for 1st and 2nd year
!   We will see a wide range of Physics concepts
!   But sometimes not in depth
!   It is your task to go further than the lecture notes
!   This course will need/develop basic knowledge on various topics:
!   General physics concepts: electricity, dynamics, nuclear….
!   Chemistry (not much!)
!   Geo-politics (just a bit...)
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The Physics of Energy sources
Introduction
- What will you learn?
- Back to basics
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What will you learn?
!   Introduction
!   Geopolitical context
!   Human needs: Before, now and for the future
!   Where does our energy come from ?
!   Government policies
!   Pre-Nuclear energies
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J. Dalton
E. Rutherford
The atom – Nuclear physics
E. Schrödinger
N. Bohr
Fusion - Theory
Radioactive decays
A. Einstein
E. Fermi
Fission - Theory
M. Curie
H. Becquerel
Fission applications
Nuclear power plants
Radiation effects
Fusion
Current
research
Nuclear waste
Spherical Tokamak
Culham (UK)
Greenpeace
Laser Megajoule - CEA
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Mechanical
• Hydroelectric
• Tidal
• Wind
• Wave
Wind turbines near Copenhagen
The future of clean
renewable energy
Other fuels
• Bio-fuels
• Biomass
Courtesy of middlebury college-USA
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Geothermal
Use of heat from
geothermal activity
Production and storage
Hydrogen cells
Solar
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Definitions – a bit of history
Oxford
dictionary
Exact, but what does it mean ?
17th – 18th century thinking:
!   Force
!   Newton: Motion of an object is changed by forces

•  A force is needed to produce an acceleration a of an object of
mass m


F = m.a
!   Work

! Rankine: work done by a force to move a mass m over a distance d

Work = F.d
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Kinetic and Potential energies
 
v=0
Free falling object


F = m.g
d

F2


F = m.g
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d

F2 Is the force applied against the gravity

KE = 0 ; PE = m.g.h
1
KE = .m.v 2
2
h
 
v=0
 1
Kinetic energy = m.g.d = .m.v f2
2
 
v = vf
More general: throwing an object in the air
 
v=0
Energy gained by object =
work done by gravitation force

PE = m.g.d
KE = 0 ; PE = 0
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Various forms of Energy
!   From the 18th century explanation of other forms of energies
!
!
!
!
!
!
 
 
 
 
 
 
Heat  thermodynamics
Chemical: exothermic and endothermic reactions
Electrical: electric charges with creation of currents and potential differences
Electromagnetic radiation: photons – EM fields
Nuclear: nuclear forces – fission ….
Mass: conversion between mass and energy
!   For an isolated system, we can have conversion of energy
(transformation) but the overall energy remains constant !
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Units
Various units for the same quantity: we will try to stick to S.I. Units: [m], [Kg], [s], [A]
!   Force: newton (N) – [N] = [kg].[m].[s-2]
!   Force needed to accelerate 1kg of mass by 1m.s-2
!   Energy: joule (J) – [J]=[N].[m] ; [J]=[C].[V]
!   Energy corresponding to a force of 1N moving an object over a distance of
1m along direction of force
!   Work to move a charge of 1 coulomb through a potential diff of 1 volt
!   Other units
•  1J = 6.2415x1018 eV (electron-Volt)
•  1J = 107 ergs
1J = 0.2388 cal (calories)
cal ≠ Cal
•  2.7778x10-4 watt.h strange unit but widely used: electricity bill
!   Power: watt (W) – [W]=[J].[s-1] ; [W]=[V].[A]
!   Energy of 1J dissipated during 1s – P diss. in a resistor with 1A under 1V
!   Photometry
!   Power per unit of surface W.m-2
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Angle definitions
circumference of circle of radius unity = 2π
c
l
θ
r
!
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l
sin(" ) =
c
r
cos(θ ) =
c
l
tg(" ) = ~ " for small angle
r
here s ~ l
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Solid angle
Surface of the sphere
4πr2
For total sphere
Ω=4π steradian
For small angles
r~c
θ
c
r
b
S~πb2
Ω~πb2/r2=πθ2
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Photometry – Energy from EM radiation (1)
!   Electromagnetic radiation has an associated energy:
!   Energy in EM field  Poynting vector
!   Energy of photon (particle)
E = hν with h = 6.626 ×10 −34 J.s (Planck constant) andν being the frequency
P=power that a source will emit over 4π steradian and across the whole EM spectrum:
Power (a.k.a. radiant flux, luminosity or flux in Astronomy) in Watts
Ex: Solar Luminosity = 3.827 . 1026 W
For a surface element dS of the source: emittance = dP/dS in W/m2
Or power received from the source by an element dS: irradiance=dP/dS in W/m2
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Photometry – Energy from EM radiation (2)
If we consider only a portion dν of the EM spectrum:
spectral power (or spectral radiance – to be avoided) = dP/dν in W/Hz
Power (emitted by a source) contained in a solid angle element dΩ:
radiant intensity = dP/dΩ in W/sr
dν
dΩ
Spectral radiance: in W.sr-1.m-2.Hz-1
Spectral irradiance: in W.m-2.Hz-1
In Astronomy 1Jansky (Jy)=10-26 W.m-2.Hz-1
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A few basic examples of energy / power consumption
!   Climbing stairs
Mass.Gravity.height 75kg.10m.s-2 .0.5m
Power =
=
= 375W
unit of time
1sec
!   Human body requirement
Average of 2400 kcal per day à ~10000 kJ per day
Power needs: ~ 115W
!   Electrical appliances
From 1-2W (elec. clock) to 10kW (large oven)
!   Nuclear power plant
Typical power output few GW
!   Astrophysics: 1 Solar Luminosity
L = 3.827 . 1026 W=382.7YW
Stanby power ?
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