Tag Archives: sustainability

Small is beautiful

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In the context of using algae to produce aviation fuel (see my previous post), ‘small is beautiful’ to cite the title of the famous book by E.F. Schumacher.  As a society we have tended towards achieving perceived economies of scale that lead to a uniformity of approach and a lack of diversity. ‘Perceived’ because often the boundary for the economic calculation is defined in a way that excludes the entropy demanded by the second law of thermodynamics and which should be included on the deficit side of the calculation.  Engineers learn about drawing appropriate boundaries for systems and looking for the source of entropy creation.  Sometimes, perhaps as in the case of the algae-based biofuels, we are unaware of the form and magnitude of the entropy being generated and hence there is a considerable risk that we will be surprised when we find out about it.  The entropy might take the form of heat, disorder, pollution, climatic disruption or combinations of these phenomena. So, pursuing a diverse set of approaches at a modest level, reduces the risk of an unpleasant surprise with substantial ecological and, or financial consequences.

More material

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In previous posts I have mentioned the need for ‘more material’ in order to reduce the probability of failure.  This is a little sloppy, since there are, at least, two options buried in these statements.  Namely, the simple one, which is to add a greater mass of material; and the alternative, which is to use a stronger but lighter material, i.e. a more sophisticated material, e.g. a composite.  These are usually also more expensive but can also provide opportunities to incorporate sustainability via bio-based recyclability [for information on bio-based composites see http://www.ag.ndsu.edu/bioepic/documents/symposium/NDS%20Bio-BasedMaterials-DRZAL-10-07-final.pdf%5D.

Model validation

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Front cover of ASME V&V 10-2006, Guide for verification and validation in computational solid mechanics, American Society of Mechanical Engineers, New York, 2006.

Why is validation important?  Validation of computational mechanics models is defined as ‘determining the degree to which a model is an accurate representation of the real world from the perspective of the intended uses of the model’, according to  ASME V&V 10-2006.  So, the validation of models of structural integrity for engineering design provides information about the degree to which the simulation results from the model can be believed.  This in turn helps in making decisions about how little material, and in what configuration, should be used to create elegant, sustainable designs that are unlikely to fail. So validation of computational mechanics models is an essential step in solving the ‘two earths’ dilemma (see post on August 13th, 2012).

Population crunch

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The current growth trends suggest that the global population will increase by a billion in the next few decades, with perhaps 500 million additional people in Africa and the same number in Asia [see http://www.un.org/esa/population/publications/longrange2/WorldPop2300final.pdf%5D.  Another observable trend is urbanisation.  Thus, taking these together it is not unreasonable to expect most of the population growth to occur in cities.  The typical size of cities in Africa is 0.5 million people and so we might expect to see 1000 new cities in Africa and perhaps around 500 in Asia where the average size is 1 million.

The challenge for engineers is to provide an acceptable quality of life in these cities.  This involves providing a built environment, food, energy, transport and health care using scientific advances in novel materials, information communication technology, biosciences, electronics and photonics.

Can it be done? Probably, but it will require a higher level of innovation than is the norm at the moment, otherwise the population crunch might take many forms.