Energy, Emergy, Exergy and Thermodynamics

1. Energy, Emergy, Exergy and Thermodynamics Thermodynamics, Maximum power, Hierarchies, and Material cycles

2. 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

3. Energy Transformation Process

4. 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

5. Two types of energy…. Potential and kinetic 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.

6. Energy = Heat In practice energy is defined and measured by the heat that is formed when converted into 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

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

8. 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

9. 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

10. 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

11. 50 Efficiency of process vs. efficiency of the system…. 100 10 Energy Transformation Process 90 (140) 1st law efficiency = 10/100 = 10% 2nd law efficiency = 10/150 = 6.67%

12. 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

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

14. 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)

15. 1st Law of Thermodynamics Energy cannot be created or destroyed

16. 2nd Law of Thermodynamics In all real process (transformations), some energy loses its ability to do work 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.

17. 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)

18. 4th Law... Maximum Empower Principle • 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...

19. 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

20. Maximum Empower 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

21. 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

22. 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

23. 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 T1 - T2 = DT T2 Efficiency = T2 - T1 = DT T2 T2

24. Heat and Entropy…(continued) The Carnot Ratio (DT/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.

25. 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.

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

27. 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.

28. 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.

29. 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.

30. 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

31. Chemical Potential Energy… DHrev = 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 DHrev andDF (free energy)

32. Chemical Potential Energy… (continued) The total heat change in a chemical reaction is called enthalpy… DHtotal = DF + DHrev Enthaply Reversible heat Free energy

33. Chemical Potential Energy… (continued) Sign convention… If heat is released and temperature rises as as heat flows out to the environment… DH tot is MINUS If there is potential energy to drive the reaction over and above the reversible energy… DF is Minus If heat is released as part of the reversible heat change…DHrev is MINUS If heat is absorbed as part of the reversible heat change … DHrev is PLUS

34. Chemical Potential Energy… (continued) 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.

35. 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…

36. Nitrogen Cycle Water Cycle Phosphorus Cycle Carbon Cycle

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

38. Material Cycles and Energy Hierarchy... 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.

39. Consumption of available energy is necessary to increase material concentration (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.

40. Coupling of a trace material to energy flow and transformations...showing two stages. 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.

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

42. Inverse relation of material flow and emergy per mass. (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.

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

44. Energy hierarchy concepts (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.

45. Distribution of materials in the biosphere follows a log normal distribution Example: Distribution of lead in granites as a function of concentrations from Ahrens (1954). (a) Linear plot; (b) log normal plot.

46. Zones of material cycles in the hierarchical energy spectrum. • (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.

47. 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.”