Exergy: Kay

About....... exergy (James Kay)

This site points out that we do not have an energy crisis, since energy is conserved. However, energy declines in its ability to do useful work (exergy) as it is used - exergy is the resource that is in short supply. Kay states "Second law analysis gives a very different perspective on our resource consumption and the realities of our economy. Unfortunately the fundamental realities revealed by second law analysis have not been embraced by economics and hence this discipline is misguided." Note: many of the links on the page are broken - some have been corrected below.

Availability, Exergy, the Second Law and all that....... (1989)

This article written for high schools explores how we can better match energy sources to the work required. It compares a First Law energy analysis that only compares 'energy in' with 'energy out', rather than comparing actual work with theoretical work. A 1st Law analysis suggests 40% of the fuel's energy is lost up the chimney, while a 2nd Law analysis considers the degree to which energy is diffuse and unable to perform useful work. This analysis suggests losses of 30% in combustion and 35% in heat transfer, and only 25% up the chimney. This approach may explain why photosynthesis is very inefficient (only a small percentage of the solar energy is captured) while being effective (a large portion of the available exergy is captured). Photosynthesis: Efficiency and effectiveness looked intriguing.

A 2nd Law analysis takes into account not just the amount of energy, but the ability of that energy to flow across a gradient and do work. Thus "A second law efficiency is the ratio of the minimum amount of available work required to do a particular job to the amount of available work actually used to do the job." It is important to look at the environmental conditions as well as the nature of the work required. Burning fossil fuels at high temperatures for space or water heating wastes the high quality of fossil energy. 1st Law efficiency of baseboard heaters is about 90%, while 2nd Law efficiency is about 2.5%. Heat pumps deliver more heat with less electricity. Unfortunately, Table 1 in the article confuses the issue by showing a 350% increase in 1st Law efficiency of heat pumps compared to space heating furnaces, but only a 50% increase in 2nd Law efficiency.

Exergy analysis has policy implications. Aside from matching energy quality to the task required, it requires an extensive analysis of the environment in which the task occurs. If the goal is space heating, the minimum amount of energy required depends on a wide range of factors, from insulation and weather stripping to acceptable air temperatures at different times of the day. A presentation by Thomas Auer of TransSolar explained how placement of shading can dramatically reduce radiant temperatures inside buildings, allowing a high air temperature while maintaining comfortable conditions for the tenants. A 1st Law analysis argues for high efficiency electrical heaters driven by centralized power plants. A 2nd Law analysis argues for decentralized energy matching the task required (e.g. space heating and cooling) with local energy sources of appropriate quality (passive solar, waste heat, geothermal and night-time cooling). The challenge is the higher capital cost of tapping into exergy, especially given the low cost of energy in North America.

Life as a Manifestation of the Second Law of Thermodynamics (1992/1994)

This article tries to link ongoing research into the 2nd law of thermodynamics with ecosystems and the development of life itself. Kay and Schneider (who has gone on to write Into the Cool: Energy Flow, Thermodynamics and Life with Dorion Sagan) believe their "thermodynamic paradigm makes it possible for the study of ecosystems to be developed from a descriptive science to a predictive science founded on the most basic principles of physics."

The 1st law of thermodynamics states that energy cannot be created or destroyed, and the total energy within a closed system is constant. The quantity of energy is distinguished from the quality of energy, which Kay calls "free energy" or exergy". The second law of thermodynamics developed out of Carnot's finding that heat within a system could not be completed converted to work. Any chemical or physical process degrades the quality of energy. Most process are irreversible - work can be dissipated into heat, but that heat cannot be fully converted back to the work, returning the system to its original state. Clausius developed the concept of entropy, the quantitative measure of this irreversibility: real processes in closed systems proceed in the direction of entropy increase, such that the system becomes increasingly disordered or random.

Another class of systems are those which are open to flows of energy and materials, moving and maintaining the system away from a state of equilibrium. By continually dissipating energy, these systems can build structure and coherent behavior (and thereby locally reducing entropy) by increasing entropy in the encompassing system that provides the flow of resources. Various re-statements and corollaries of the second law measure the distance from equilibrium through the gradients imposed on the system and that systems "will utilize all avenues available to counter the applied gradients. As the applied gradients increase, so does the system's ability to oppose further movement from equilibrium." By focusing on gradient destruction sidesteps issues of entropy in non-equilibrium systems, and allows the methods of network thermodynamics to be applied.

The article describes in detail the formation of Benard cells in a fluid between a heat source and a cold sink. Initially, energy is dissipated by conduction, a relatively inefficient mechanism that causes a temperature gradient to form. As the heat increases, the gradient increases until at a critical value, convection (Benard) cells form, dramatically increasing energy dissipation and eliminating the temperature gradient outside of the fluid boundary layers. With additional heating, the boundary layers shrink leading to more dissipation. Graphs show that the increasing temperature gradient is associated with increased heat dissipation, entropy production, and the amount of work required to maintain the gradient. The latter two relationships appear to be non-linear, suggesting greater efficiency on the part of the system to degrade the gradient as the energy flow increases, through the formation of new structures within the system. When the energy flow reaches a critical high threshold, the system becomes chaotic.

Another example is the "Tornado Tube" sold by Edmund Scientifics. A tube with a constriction connects two soda bottles. Water in the top bottle normally drains into the bottom bottle in about 6 minutes. However, imparting a slight rotation causes a vortex to form, draining the upper bottle in 11 seconds. This vortex, the same that emerges as water drains from a bathtub, is an organized structure that dissipates the energy gradient than the original flow pattern. It appears that due to the specific energy gradient and configuration, structure normally does not emerge spontaneously in the "Tornado Tube", but can be easily initiated through a slight rotation of the bottles.

Kay distinguishes between energy dissipation (the movement of energy through the system, which may or may not result in gradient destruction) and energy degradation (the destruction of the ability of energy to create gradients). The context determines whether energy has the ability to create gradients that do work, as measured by exergy.

Kay provides various physical and chemical systems that dissipate energy and display structure, such as weather systems, autocatalytic reactions and the Belousov-Zhabotinsky reactions described by Gribbin. Kay proposes that life is a product of dissipative systems and one of the key means by which solar energy is degraded. Boltzmann argued in 1886 that the struggle for existence is not over raw materials, but rather over entropy (available energy). In What is Life? (1944), Schroedinger noted that it is based on two fundamental processes: "order from order" (DNA) and "order from disorder" (complex organic and ecological structures arising in spite of the 2nd law of thermodynamics). Although physical systems degrade much of the 1580 watts/square meter of solar radiation, a significant proportion is dissipated through evaporation, transpiration and photosynthesis. Kay believes the (re-stated) 2nd law is a necessary but not sufficient condition for the origin of life, as well as the evolution of increasingly complex organisms and ecosystems. His thermodynamic analysis of ecosystems is further explored in Characteristics of SOHO Systems.

Kay includes an analysis of marsh ecosystems, showing that stress "resulted in the ecosystem shrinking in size, in terms of biomass, its consumption of resources, and its ability to degrade and dissipate incoming energy." The stress system was "leaky", allowing resources to escape. Although the complexity of the food chain is not affected, the number of cycles is cut in half. He also showed work on the surface temperature of ecosystems at different levels of succession or stress. In general, mature ecosystems re-radiate less of the incident solar energy back into space, reducing the temperature gradient between the earth's surface and outer space by as much as 25 degrees Celsius. Disruptions to the ecosystems increased temperatures, through reduced complexity and resulting ability to dissipate energy.

Kay relates processes driven by the second law to evolution of organisms, succession and the biosphere. This approach is intended to complement Darwinian genetic processes (p. 15), balancing survival and the imperative of the 2nd law across a wide continuum of scale.

The Second Law and Self-organization revisited (1996)

This one-page article argues that "emergence of self-organizing structures provides an avenue for dissipation that otherwise would not exist. ... In fact the emergence of life hastens the progression to equilibrium." More exergy increases the likelihood that self-organizing structures will emerge, which in turn dissipate that exergy. The paradox is that these systems seem to be very efficient at using energy (exergy?), which would seem to be at cross-purposes with the movement to equilibrium. Further confusing the issue is the context - are we dealing with the local system where entropy is reduced, or the encompassing system that provides the flow of energy and where entropy is increased?

Ecosystems as Self-organizing Holarchic Open Systems: Narratives and the Second Law of Thermodynamics (2000)

The article re-caps Life as a Manifestation of the Second Law of Thermodynamics, covering the history of thermodynamics and the re-stated 2nd law as applied to non-equilibrium open systems:

• "As systems are moved away from equilibrium, they will utilize all available avenues to counter the applied gradients."
• "... attractors, for (thermodynamic) nonequilibrium organizational steady states, will emerge that allow the system to be organized in a way that reduces or degrades the applied gradients."
• "... as the applied gradients increase, so does the system's ability to oppose further movement from equilibrium." (through the emergence of increasingly sophisticated processes)
• "If environmental conditions permit, self organization processes are to be expected."
• "The building of organizational structure and associated processes is such that it degrades the imposed gradient more effectively than if the dynamic and kinetic pathways for those structures were not available."

Kay defines exergy as the "quality or capacity [of energy] to do useful work." Exergy:

• "... is a function of the gradients between a system and its environment... it measures how far a system is from thermodynamic equilibrium with its environment."
• ... is a summation of the free energies in a situation."
• ... is not a useful concept for discussing equilibrium situations ... but is a very powerful tool for nonequilibrium situations."

Kay expands on previous discussions about the 2nd law and life:

• "Living systems are essentially dynamic dissipative processes [Schroeder's 'order from disorder'] with encoded memories [Schroeder's 'order from order']."
  • --Norbert 22:32, 22 January 2008 (EST) fixed 2008/01/22 --Martha This last one should be "order from order", right?.
• "Species which survive in ecosystems are those that funnel energy into their own production and reproduction and contribute to autocatalytic processes with increase the total exergy degradation of the ecosystem."
• "... survival [is] an imperative which may not be consistent with maximum exergy degradation." (this point is not explained)

User:Martha This point intrigues me and I attempted to integrate it with other things I've been reading and thinking about. I'm not sure if what I put here will accurately reflect what Kay really meant by his comment. A lot of the concepts we've been discussing are also mentioned in an article, "A general theory of evolution based on energy efficiency: its implications for diseases" by A.J. Yun, et al in Medical Hypotheses(2006) Vol. 66:664-670. (I don't have permission to submit this work here right now but I could share it with those interested.) I have created a figure (which I will share if I can get these uploading and linking things to work, something I've had trouble with on this wiki) that uses Hollings 4-box modeling. The latter has helped me put humans in a succession scheme, where the concept of facilitation is very important. (Facilitation happens when one community in an early stage of succession prepares the environment -- usually unwittingly, since most such organisms don't have consciousness anyway -- for the emergence of species that will form the next community in succession. For example, a particular plant might acidify the soil and thereby make it possible for an acid-loving plant to grow, and the latter might end up shading out the former.) In a similar way, perhaps humans are preparing the environment for the emergence of...something else. Maybe the life of memes, which will be subject to natural selection. Genes and memes might sometimes, but not always, be in competition. Perhaps one or the other will be a better exergy user. For example, I could decide to have a family and thereby become an evolutionary "success." (Fortunately, I have an identical twin and I might achieve success through her efforts -- sometimes it's great having clone.) Or I could decide that I want to devote as much time and energy as possible to the meme, biomimicry. All investments carry some risks. The meme I invest in might die. In a sense, there will be an ecosystem of memes and succession and facilitation will be in play there, too. My survival or even the survival of humans might not be necessary for the lives of memes (if we contribute to the emergence of artifical intelligence which might be selected for if it's a better exergy user than we are). Or, in a not-quite-so-science-fiction-like scenario, Yun, et al suggest that the best return on energy (ROE they call it) might be humans leading longer lives of creative input and breaking a little freer of the familiar life-death cycling. Memes would be served by this.

It may not be as clear in my diagram that the movement is in a figure-8 pattern and not two rotating circles side by side. I got lazy in my graphic design. Coincidentally, the competition between genes and memes makes it clear why it is mainly males that show up in the history of ideas. Males are required to invest only ___ number of minutes to the propagation of the species (not counting all the time it took them to convince the female -- but they can do this convincing partly by working on their ideas that will give them power or status or some evidence that will essentially tell the female "I have genes for intelligence"). It's good if they stick around to help raise the demanding being but biology does not require it. Females' investments in passing on their genes is many times larger. That's all for my meandering, right now. I've broken up the original flow quite a bit. Maybe this needs to be moved?

He presents a conceptual model for self-organizing systems based on dissipative structures (figure 3):

• high quality energy above a critical value allows self-organizing dissipative processes to emerge
• these processes restructure available resources to dissipate exergy
• the information available and environmental constraints define the context, promoting some processes over others
• dissipative processes manifest themselves as a structure, which provide a new context allowing new processes to emerge in a nested structure

Kay goes on to look at ways of making sense of complex systems. Approaches include:

• cybernetics and general systems theory: limited to systems where negative feedback led to homeostasis
• Koestler's analysis of self-organizing, holarchic (hierarchies with reciprocal power relationships between levels) and open (SOHO) systems
• Ulanowicz's development of Popper's 'propensity' proposal, where "a mutual-causal kind of autocatalysis plays a self-organizing role"

Kay promotes using narratives as a tool for analyzing SOHO systems such as ecosystems, different from traditional approaches that may be interdisciplinary, but "focus on forecasting and a single type of entity such as a watershed or a forest community." Steps include:

• defining the holons, the "self-organizing entities of interest", looking at multiple types (holarchies) and scales (levels of holons)
• identifying the processes within and between holons
• context of each holon, which constrains what behaviors and structures can emerge
• the system's array of behaviors (attractors), their limits (which when exceeded may cause the system to flip to another attractor)
• the "underlying morphogenetic causal structure" which maintain the attractors through positive and negative feedback loops
• a qualitative, multi-threaded story of how the system may evolve

Kay goes on to explore the Lake Erie environment through an analysis of pelagic and benthic attractors (note: page 20-21 seems to flip the definitions). In the benthic state, the water column is clear, allowing vegetation at the bottom to flourish and suppressing free phosphorus. In the pelagic state, phytoplankton in the water column capture and dissipate solar energy, shading the benthic regions. Low phosphorus levels limit the emergence of pelagic dissipative processes - although sunlight hits the water column, it has no exergy since the solar energy cannot be tapped. The degree of runoff from human activity can cause the system to flip between states.

Kay also links dissipative processes and narratives to the Holling's four-box model of ecosystem dynamics.

• exploitation: dissipative processes emerge, increasing the rate of solar exergy degradation and building up stored exergy in biomass (first thermodynamic pathway, based on solar exergy)
• conservation: combines maximum thermodynamic organization (exergy degradation) with maximum thermodynamic risk that dissipative processes emerge to utilize the stored exergy
• release: stored exergy in biomass made available to system (second thermodynamic pathway, based on stored exergy)
• reorganization: exergy from biomass exhausted, but other raw materials released in previous phase allow progression to exploitation

Kay closes the article with a discussion of causal loops, using as examples forestation of dry mountains, vegetation of southeastern Australia, acidification of lakes, and the Lake Erie system. Although many processes are involved, some are key in stabilizing the system around its current attractor, or conversely, causing the system to flip to a new attractor when pressures exceed the limits of system stability.