Termodinâmica definições principais

Emergy & Complex Systems
Day 1, Lecture 2….
Energy, Emergy, Exergy
and Thermodynamics
Thermodynamics, Maximum power, Hierarchies,
and Material cycles

Energy….
The ability to cause work…
and WORK is defined as any
useful energy transformation
…in most kinds of work, one type of energy is transformed
into another with some going into a used form that no
longer has potential for further work

Energy
Transformation
Process

Two types of energy….
Potential and kinetic
1. Potential - energy that is capable
of driving a process with energy
transformation from one form to
another
Potential energy from outside energy sources provides
the means for keeping systems generating work.
Storages within systems have potential energy that can
drive work processes

2. Kinetic - the energy of
movement as in a spinning top or
traveling car
Kinetic energy can be converted to potential and back again, in
some systems without a loss of potential energy to heat..
The amount of kinetic energy that a body possesses is
dependent on the speed of its motion and its mass.
At the atomic scale, the kinetic energy of atoms and molecules
is sometimes referred to as heat energy.
Two types of energy….
Potential and kinetic

Energy = Heat
There are many types of energy and they can all be
quantitatively related by converting them into heat...
Since all energy can be converted into heat at 100%
efficiency
In practice energy is defined and
measured by the heat that is formed
when converted into heat!

Heat
- the collective motions of molecules,
whose average intensity is the
temperature which may be measured by
expansion of matter in a thermometer

Available energy (exergy)...
Potential energy capable of doing work and
being degraded in the process
As long as comparisons are made between energies of the same
type, we may say that available energy measures the ability to
do work

Efficiency...
The ratio of the useful energy delivered
by a dynamic system to the energy
supplied to it...
Time’s speed regulator- power in an energy transformation
depends on the workload. Maximum output power occurs with
an intermediate efficiency

.
Source
No flow
(a)
1
1
Source
1
0
(b)
100%
1
(c)
(e)
Power
Efficiency
Load
0 10050
Forces
Equal
Heat
Source 50%
50%
(d)
Falling
Lifting
0.5
No Useful
Power
Backforce
.
Source
No flow
(a)
1
1
Source
1
0
(b)
100%
1
(c)
(e)
Power
Efficiency
Load
0 10050
Forces
Equal
Heat
Source 50%
50%
(d)
Falling
Lifting
0.5
No Useful
Power
Backforce
The Atwood machine...
Demonstrating optimum
efficiency of 50%…
A) 100% efficient, no
work
B) 0% efficiency, all
energy goes into heat
C) 50% efficiency
maximizes useful work

Energy
Transformation
Process
100
90 (140)
10
50
1st law efficiency = 10/100 = 10%
2nd law efficiency = 10/150 = 6.67%
Efficiency of process
vs. efficiency of the
system….

Work:
Mechanical work - aforce operated against an
opposing force for a distance, the energy
transformed is the product of the force times
the distance.
Work.. A useful transformation - work means a
useful energy transformation where use can be
defines as contributing to the survival of the
system

Power:
Energy flow per unit time. Engineers restrict
the term to the rate of flow of energy in useful
work transformations

Energy Systems Theory….
Important principles and concepts
 1st Law of Thermodynamics
 2nd law of Thermodynamics
 3rd law of Thermodynamics
 Maximum Power Principle (4th law)
 Hierarchically organized systems (5th
law)

1st Law of Thermodynamics
Energy cannot be created or destroyed
Interaction = Energy Transformation
100 J
20 J
108 J
12 J
All energy is accounted for...
Used energy
X
Interaction = Energy Transformation
100 J
20 J
108 J
12 J
All energy is accounted for...
Used energy
X

2nd Law of Thermodynamics
In all real process (transformations), some
energy loses its ability to do work
100 J
100 J
4 J
1 J
97 J
3 J
St orage
Transformation
We sometimes speak loosely of
energy being “used up” whereas
what is really meant is that the
potential for driving work is
consumed, while the calories of
energy inflows and outflowing are
the same.

3rd Law…
Absolute Zero Exists
Entropy at absolute zero is zero….
As heat content approaches absolute zero molecules are
in crystalline states, and the entropy of the state is
defined as zero
(- 273o
C)

During self-organization, systems are guided by the
Maximum Empower Principle…
Self-organization tends to develop network
connections that use energies in feedback
actions to aid the process of getting more
resources or using them more efficiently...
4th Law...
Maximum Empower Principle

“In time, through the process of trial and
error, complex patterns of structure and
processes have evolved...the successful ones
surviving because they use materials and
energies well in their own maintenance, and
compete well with other patterns that
chance interposes.”
H.T. Odum
Maximum Empower Principle…

Systems maximize power by: 1) developing storages of high-quality energy, 2) feeding
back work from storages to increase inflows, 3) recycling materials as needed, 4)
organizing control mechanisms that keep the system adapted and stable, 5) setting up
exchanges for needed materials, 6) Contributing work to the next larger system
Maximum EmpowerMaximum Empower

5th Law…
All systems are organized hierarchically
Energy flows of the universe are organized in
energy transformation hierarchies. Position in the
energy hierarchy can be measured by the amount of
energy required to produce something

Energy Transformation Hierarchy
Spatial view of units and their
territories
Energy networks including
transformation and feedbacks
Aggregation of enerrgy network
into an energy chain
Bar graph of the energy flows for
the levels in the energy hierarchy
Bar graph of solar transformities

Heat and Entropy…
If there is a difference in temperature within
a system, the difference can drive other
transformations.
The useable heat in any system is the difference between the
inflowing temperature and the outflowing temperature
T1
T2
T1 - T2 = ∆T
Efficiency = T2 - T1 = ∆T
T2 T2

Heat and Entropy…(continued)
The Carnot Ratio ( ∆T/T ) is called a
thermodynamic force since it indicates the
intensity of delivery of a potential energy flow
from a storage of heat relative to one at a
lower temperature.

Heat Capacity - of a substance is the ratio of the amount of heat
energy absorbed by that substance to its corresponding
temperature rise.
Specific Heat - is the heat capacity of a unit mass of a substance
or heat needed to raise the temperature of 1 gram (g) of a
substance 1 degree Celsius.
Sensible Heat - is heat that can be measured by a thermometer,
and thus sensed by humans. Several different scales of
measurement exist for measuring sensible heat. The most common
are: Celsius scale, Fahrenheit scale, and the Kelvin scale.
Latent Heat - is the energy required to change a substance to a
higher state of matter. This same energy is released from the
substance when the change of state is reversed. The diagram below
describes the various exchanges of heat involved with 1 gram of
water.

Latent heat exchanges of energy involved with the
phase changes of water….
1 gram of water…

Net absorption and release of latent heat
energy for the Earth's surface. High
temperatures and a plentiful supply of
water encourage the evaporation of water.
Negative values of latent heat flux
indicate a net release of latent energy
back into the environment because of the
condensation or freezing of water. Values
of latent heat flux are generally low over
landmasses because of a limited supply of
water at the ground surface.

Entropy Change…
S = entropy
In an energy transformation, the change in
heat divided by the absolute temperature at
which the heat chnge occurs is defined as the
entropy change
When heat is added to a storage entropy increases, when heat
is subtracted, entropy decreases.

Energy Storage…
Generation of new potential energy
concentrations… these are capable of driving
other pathways.
Potential energy per unit of matter stored that carries the
energy. Thus there are water potentials, potential in
electrical charge storage, and chemical potential.

Reversible and Irreversible
Processes…
Reversible processes are those where no
energies are made unavailable. ie pendulum,
population of molecules…
However most processes in the biosphere
are Irreversible, requiring new potential
energies to maintain them

Chemical Potential Energy…
∆Hrev = reversible heat change of state…
In most chemical reactions there are changes of physical state. A
portion of the reaction may be reversible and this this energy is
not available to drive the process spontaneously.
For a spontaneous reaction there must be potential energy in the
reaction over and beyond that necessary for the reversible heat
changes in involved in the change of state.
Thus the total heat change of a reaction is the sum of the two
heat changes… the ∆Hrev and ∆F (free energy)

Chemical Potential Energy… (continued)
The total heat change in a chemical reaction
is called enthalpy…
∆Htotal = ∆F + ∆Hrev
Enthaply
Free energy
Reversible heat

Sign convention…
If heat is released and temperature rises as as heat
flows out to the environment… ∆H tot is MINUS
If there is potential energy to drive the reaction
over and above the reversible energy… ∆F is Minus
If heat is released as part of the reversible heat
change…∆Hrev is MINUS
If heat is absorbed as part of the reversible heat
change … ∆Hrev is PLUS

Gibbs Free Energy - free energy of a chemical
reaction where pressure is held constant during
the change.
Helmholtz Free Energy - free energy where
volume is held constant during the change.

Material Cycles...
Matter is conserved…when chemical reactions
take place, matter is neither created or
destroyed
Matter going into a system is either stored within the
system or flows out…

Water CycleWater Cycle Nitrogen CycleNitrogen Cycle
Carbon CycleCarbon Cycle
Phosphorus CyclePhosphorus Cycle

Mass Balance of
materials in an
ecosystem...
Mass Balance of
materials in an
ecosystem...

When self organization converges and
concentrates high quality energy in centers,
materials are also concentrated by the
production functions.
Because available energy has to be used up to
concentrate materials, the quantity of material
flow also has to decrease in each successive step
in a series of energy transformations.
Material Cycles and Energy
Hierarchy...

Energy Concentration and
Emergy per Unit Mass
Natural Depreciation
(Second Law)
(a) Concentration
Gradient
Materials
Energy Required
(b) Process of
Concentrating
Materials
(c) Emergy
per Mass
(d) Emergy and Materials into Production
Production
Process
Energy &
Emergy
Dispersed
Material
Storages
Recycle
Energy Concentration and
Emergy per Unit Mass
Natural Depreciation
(Second Law)
(a) Concentration
Gradient
Materials
Energy Required
(b) Process of
Concentrating
Materials
(c) Emergy
per Mass
(d) Emergy and Materials into Production
Production
Process
Energy &
Emergy
Dispersed
Material
Storages
Recycle
(a) Concentration of materials
indicated by density of dots;
(b) use of available energy to
increase concentration and energy
storage;
(c) emergy per mass increases with
concentration;
(d) autocatalytic production process
utilizing available energy to
concentrate dispersed materials.
Dotted lines = energy flow only;
solid lines = material flow.
Consumption of available energy
is necessary to increase
material concentration
Consumption of available energy
is necessary to increase
material concentration

On the left there is
non-specific
transport of trace
concentrations by a
carrier material. On
the right there is a
specific use of the
trace material in an
autocatalytic
production process
that accelerates
energy use and
material
concentration.
Coupling of a trace material to energy flow
and transformations...showing two stages.
Coupling of a trace material to energy flow
and transformations...showing two stages.

(a) Materials and
energy transformation
hierarchy on an energy
systems diagram;
(b) spatial pattern of
material circulation.
Spatial convergence of
materials to centers
because of their
coupling to the
convergence of energy.
Spatial convergence of
materials to centers
because of their
coupling to the
convergence of energy.

(a) Inverse plot of rate of
material concentration and
emergy per mass where
emergy flow is constant;
(b) systems diagram of the
circulation of material (dark
shading driven by a flow of
empower Jemp;
(c) rate of materials
concentration as a function
of emergy per mass on double
logarithmic coordinates.
Inverse relation of material
flow and emergy per mass.
Inverse relation of material
flow and emergy per mass.

The coupling of biogeochemical cycles to the
energy transformation hierarchy explains
the skewed distribution of materials with
concentration.
Material Cycles and Energy
Hierarchy...

.
Feedback Control Loops
104 103
103 102 10
10105
104
106
Degraded Energy
102
1
(a)
(b)
LogEnergyFlow
Transformity
10 102 103 1051041
1
(c)
Source
Increasing Unit Size and Size of Territory
Increasing Period and Pulse Amplitude
(d)
(e)
.
Feedback Control Loops
104 103
103 102 10
10105
104
106
Degraded Energy
102
1
(a)
(b)
LogEnergyFlow
Transformity
10 102 103 1051041
1
(c)
Source
Increasing Unit Size and Size of Territory
Increasing Period and Pulse Amplitude
(d)
(e)
(a) Web of energy transformation
processes (rectangles) arranged in
series with energy decreasing from
left to right;
(b) energy system diagram of
energy webs aggregated into a
linear chain.
(c) energy spectrum: energy flow
plotted as a function of
transformity on logarithmic scales
increasing from left to right
(d) sizes of unit centers and
territories increasing with scale
from left to right;
(e) periods and intensities of
energy accumulation, pulsing, and
turnover time increasing from left
to right.
Energy hierarchy conceptsEnergy hierarchy concepts

.
P arts P er M illion Lead
0 50 80
NumberperInterval
15
10
5
5 ppm interval
0
Ahrens 1954
15
10
5
0
-1.2 0.0 0.5 1.6 2.4 3.2
Log ppm Lead
NumberperInterval
Log N orm al
(a) Lead D istribution in G ranites
(b)
.
P arts P er M illion Lead
0 50 80
NumberperInterval
15
10
5
5 ppm interval
0
Ahrens 1954
15
10
5
0
-1.2 0.0 0.5 1.6 2.4 3.2
Log ppm Lead
NumberperInterval
Log N orm al
(a) Lead D istribution in G ranites
(b)
Example: Distribution of lead
in granites as a function of
concentrations from Ahrens
(1954). (a) Linear plot;
(b) log normal plot.
Distribution of materials in
the biosphere follows a log
normal distribution
Distribution of materials in
the biosphere follows a log
normal distribution

(a)Energy hierarchical
spectrum showing the
cycles of different
materials in different
zones;
(b) log-log plot of mass
flow as a function of
emergy per mass.
Zones of material
cycles in the
hierarchical energy
spectrum.
Zones of material
cycles in the
hierarchical energy
spectrum.

The principle of universal material distribution
and processing was proposed by H.T. Odum as
a 6th energy law.
“Materials of biogeochemical cycles are
hierarchically organized because of the
necessary coupling of matter to the
universal energy transformation hierarchy.”

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