Concepts

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This page is intended as an anchor for concepts that are useful in exploring Patterns from Nature.


Non-Equilibrium Thermodynamics

Martha introduce the concept in her exploration of the idea that Nature Abhors a Gradient. I think this line of research is central to a deeper understanding of the Conducive to Life pattern.


I have been reading Deep Simplicity by John Gribbin on how complexity can come out of simple components that interact in simple ways. Gribbin claims non-equilibrium thermodynamics, complexity theory and self-organizing systems can explain life itself: how it started, how it evolved, and how it maintains a degree of stability (paradoxically, by staying 'near the edge of chaos').


Self-Organizing Hierarchical Open (SOHO) Systems

Gribbin's Deep Simplicity discusses how non-equilibrium thermodynamics can explain the how systems can self-organize far from a state of equilibrium. James Kay expands on this idea with his analysis of SOHO Systems and their implications on the design process. To close the circle, Martha mentioned a paper by Kay and Schneider (still on my 'to read' list).


Exergy

In Using hot asphalt to heat buildings, Fil suggested that:

"If we define the system as the roads, the buildings, the piping under the roads, and the sun, then it's the inefficiency of the system components that gives rise to a greater system efficiency. The effectiveness of the system increased when they found they could use the excess energy to heat buildings.
What I'm not sure about is: if the system components are inefficient (per the argument above), then does this mean the components are effective? (I see efficiency and effectiveness as working somewhat at cross-purposes.) If so, then how are they effective? Understanding this could help us understand how to balance efficiency and effectiveness."


That led me to read up on exergy, which Kay uses as a measure of effectiveness(vs. efficiency) or quality (vs. quantity). I posted the following reply on Fil's blog:

"Fil, I decided I better read up on Exergy, and posted a review of some articles at http://sinet.ca/patterns/index.php?title=Exergy. James Kay seemed to have the best description and also touched on the policy implications of considering effectiveness over efficiency. Key points:
  • the quantity of energy needs to be considered in context - energy needs to flow across a gradient to do useful work
  • the quality of energy is a critical factor - it cannot do useful work if it is diffuse, and the quality is wasted if it is too high compared to the task
  • exergy efficiency (effectiveness) is related to the minimum energy required to complete a task compared to the actual energy used
  • the environment surrounding the task has a significant impact on the minimum energy required for that task (there may be many ways to 'skin the cat')


Kay argues that exergy (or 2nd Law) analysis forces us to ask how the task can best be accomplished, rather than how efficient an individual component is. System efficiency/effectiveness are not necessarily related to component inefficiency, although the inverse may be true (an over-emphasis on component efficiency may blind us to what is happening at the system level). This suggests a few 'rules of thumb':
  • use local sources of energy
  • match energy quality to the task
  • search for existing energy gradients (day/night, summer/winter, air/ground)


What would be ideal is a simple yet reliable way of estimating the minimum energy required to execute a task, taking into account the system in which the task is executed. That could become a 'reference point' for designers, much like Mazria's 2030 challenge for architects."


Recent Nature Articles

Ecology: Forest air conditioning p422

During the growing season, with photosynthesis at its peak, leaf temperatures remain constant over a wide latitudinal range. This is a finding that overturns a common assumption and has various ramifications.

F. I. Woodward doi:10.1038/454422a

Full Text | PDF


Subtropical to boreal convergence of tree-leaf temperatures p511

This paper reveals why climate doesn't have as great an impact on leaf morphology and physiology as one might think. During periods in which plants assimilate carbon, temperatures within leaves remain at around 21.4°C, whether the leaf is in the subtropics or the polar regions, a range of 50° of latitude. This goes against the received wisdom that the temperature and relative humidity in an actively photosynthesizing leaf is the same as that of the surrounding air.

Brent R. Helliker & Suzanna L. Richter doi:10.1038/nature07031

First paragraph | Full Text | PDF See also: Editor's summary | News and Views by Woodward