Sunday, July 8, 2012

Axes of Resiliency

Response, recovery, regeneration

We continue here our discussion on "resiliency" and how it relates to green and sustainable manufacturing. Recall that we started with a standard dictionary definition of resiliency as the capability of a body under strain to recover its original size and shape after some external disturbance or deformation. It also listed the ability to recover from or "adjust to misfortune or change."

Engineers think of the first definition in terms of a "rubber band" which can be stretched and then, when released, returns to its original shape. This is certainly a recovery from change as well. I also believe this includes "inoculation" to disruption and risk - the rubber band is designed to recover.

In the last posting we ventured into the muddy waters of "equilibrium state" of a manufacturing process or system.  The idea was that resilience refers to the ability of an engineering system to return to equilibrium. But, I don't want to confuse equilibrium in the sense of mechanical equilibrium we learned in our early physics course. There we said that equilibrium was the state in which the sum of the forces, and torque, on each particle or element of the system is zero or thermal equilibrium wherein there is no exchange of energy between an object and the surrounds - meaning everything is at the same temperature.

I inferred that, here, equilibrium was essentially a stable operable state that the system returns to following a disruption that would tend to move the system into another state of operation - presumably less stable, or less profitable, or less environmentally benign.

So, what are the various dimensions (or axes) of resiliency?

We can think about measures of responsiveness, recovery and regeneration for starters. Returning to the information from NIST on resilience (specifically National Institute of Standards and Technology (NIST), 2008, “Strategic Plan for the National Earthquake Hazards Reduction Program: Fiscal Years 2009-2013”) one might argue that resilience entails three interrelated dimensions: reduced failure probabilities; reduced negative consequences when failure does occur; and reduced time required to recover.

So, how do these relate to green or sustainable manufacturing? To what extent can elements of manufacturing, as practiced, be implemented to reduce the likelihood of failure, minimize negative consequences when some disruption or failure occurs and, finally, minimize the time to recover (that is, get back to "equilibrium")?

These are normally topics covered in more conventional manufacturing business practices and system management - mean time to failure and mean time to repair, redundancy, etc.

One might start out with the three elements of sustainable manufacturing - materials, energy and technology. We've described in earlier postings the basics of green at a process level (see for example the diving deeper discussions)  but we can also think about the interplay of these three "elements".

The figure below, from a presentation in our lab in 2009 by Professor Chris Yingchun Yuan of UW-Milwaukee (he was a student back in in LMAS then and this was part of the research going into his

PhD thesis) illustrates this interplay well. It shows how the reduction of consumption of either materials or energy or the improvement of efficiency of converting or using materials, or cleaner energy sources or alternative materials or processing technology all work towards greening manufacturing (any one of these trajectories would be a worthy "technology wedge" as we've used it here.) Better use of lower impact materials with no deleterious side effects converted with optimal yield into a product with minimal energy use and that from renewable sources all done in a cost-effective manner - that's the ticket!

Ok, that's not so simple - but that is not our point here. The point is to add on the aspect of resilience to this picture.

If we look at the drivers for resilience, for example:

  - risk and risk reduction
  - time and schedules/availability
  - cost
  - responsiveness
  - competitiveness
  - consumer reaction/acceptance
  - responsiveness to markets and suppliers
  - regulatory compliance
  - etc.

it is an impressive list. In fact, it includes most of what we listed when the blog was started in the posting on "Why Green Manufacturing?" Missing in that list (except for a maintaining competitiveness angle) was the time factor. Resilience includes time.

So, take these three elements from the triangle and ask - "how do the drivers listed above affect these?"

We are not going to go through all the combinations but a few obvious ones come to mind. For example, cost. Maintaining the ability to control costs in the face of uncertainty is a fundamental tenet of manufacturing. It can be accomplished by being able to boost productivity (output per unit of labor) so that wild swings in exchange rates don't drive you out of the market because of prices. Consider Japanese manufacturers who were, at one time, manufacturing products with the Yen at 120 to the Dollar. Now it is closer to 80 Yen to the Dollar. That means my costs (in dollars) for the same product are increased by 50% with no appreciable change in the product. That means I have to be able to be that much more productive just to stay even. The Japanese have excelled at creating production systems that can increase productivity to accommodate swings in exchange rate. That's resilience!

Now think about energy and the "cost" in terms of energy needed to produce a product. You can track energy pries like exchange rates. This gives you the required improvement in "energy productivity" required for making a product to keep ahead of that variation. That's another form of resilience.

Risk is a bit trickier but follows the same general thread of logic. Reducing risk (and hence enhancing resilience) can be done by using less (and hence reducing demand) by redesign of process or improvement of yield  in material conversion, finding alternatives (materials or technology) or, less effective, redundant supplies.

This strategy certainly leads to reduced failure probabilities; reduced negative consequences when failure does occur; and reduced time required to recover. Mostly by "inoculating" the system against failures.

Once we start looking into less technical aspects like consumer response/acceptance we get into the more esoteric aspects of green and sustainable. This is a great segue (note: that's "seg-way" … but not the two wheeled scooter!) into our next topic - societal dimensions of sustainable design and manufacturing.

To the extent that larger civil systems are involved in manufacturing supply chains or labor responsiveness, enhancing manufacturing resilience to disruptions and disasters is not a purely technical problem, but involves societal dimensions.

We'll pick that up next time.

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