Month: August 2013

Fracking

The British Prime Minister, David Cameron has argued in an article in the Sunday Telegraph (on August 11th, 2013) that if we don’t back fracking technology then the country will miss an opportunity to help families with their bills and make the country more competitive.  In his article the Prime Minister only makes the economic case in favour of using fracking to extract shale gas.  He completely ignores the environmental costs of these economic gains, which will always be present as in any industrial process – the second law of thermodynamics tells us to expect these costs – a form of increased entropy.  The environmental costs of fracking are still disputed.  Companies and politicians with something to gain from its successful implementation argue that the costs are very low or insignificant.  However, recent research has concluded that more than 100 earthquakes were triggered in a single year in Ohio due to fracking-related activities (J. Geophysical Research: Solid Earth, doi.org/nh5).  The largest of these quakes was of magnitude 3.9 and was caused by pumping pressurised waste water into a deep well.  There are also concerns that waste water from fracking might contaminate groundwater.

A joint report of the Royal Society and the Royal Academy of Engineering has concluded that the fracking process can be successfully managed without significant risks to the environment or society.  However, in France fracking has been banned.  So, the arguments flow in both directions.  As a society we are addicted to energy, and fossil fuels in particular, and hence we need sources of oil and gas.  The risks involved in extracting shale gas by fracking are probably no greater than those associated with oil or natural gas; its just that they tend to occur closer to people’s backyard, which makes people more sensitive to them.  Actually, the technology has been around and used for a long time; see John Kemp’s column at Reuters for an explanation of the process and its history.  However, if we intend to use it on a larger scale then we need to guard against unexpected consequences and be ready to deal with the mess when things go wrong.  When engineers succeed in these two goals then no one will notice but when they fail the public and many politicians will be quick to attribute blame to them, whereas it likely will be our addiction to fossil fuel that is to blame.

Detroit

978000655083970256Last week we drove from the south through downtown Detroit on Interstate 75.  Approaching from a distance along the shore of Lake Erie and the banks of the Detroit river, the city looks like many others in the US with glass-clad towers clustered together and stretching towards the clear blue sky.  Close-up and beyond the glass skyscrapers, Detroit offers a different view of derelict apartment blocks, factory buildings and offices covered in graffiti with weeds growing out of them.  These are not isolated buildings but whole city blocks.  It is reminiscent of Hadron in Doris Lessing’s book ‘Mara and Dann’, in which twenty-five towers built for city administrators are left abandoned in preference for fine houses in large gardens.  The mental picture that our drive brought to mind was from Lessing’s book; however, in searching out the book at home I remembered a similar image drawn by JG Ballard in ‘High Rise’ in which civilised life in a 42-storey degenerates as residents abandon all moral and social conventions and a hunter/gatherer culture of competing gangs developed.

Of course Detroit is infamous for having recently become the largest municipal bankruptcy when it filled for Chapter 9 Bankruptcy on July 18th, 2013.  However, not all is doom and gloom in Detroit; it might be suffering from entropic decay but they know how to conserve energy (available energy).  At Detroit  Metropolitan Airport they are replacing more than 6000 light fixtures with LED (light emitting diodes) lights in the parking structures (multi-storey car parks) as well as adding an extra thousand for a total cost of $6.2 million (£4M).  It is anticipated that the resultant reduction in energy consumption will be 7,345,000 kilowatt hours (kWh) worth about $1.2 million per year (£0.77M).  According to Ali Dib, Director of Infrastructure & Engineering for Wayne County Airport Authority, the energy saved by the light replacements will be “equivalent to powering 880 U.S. households for one year, and the reduction of 7,000 metric tons of CO2 per year is equal to taking 1,350 passenger vehicles off the road.” Not something they would be very happy about you doing in the ‘Motor Capital of the World’.  So the other way of looking at the CO2 production saved is that it is equivalent to  25,400,000 passenger air miles not flown or a thousand round-the-world flights.

Oh, and the LEDs will only need changing every ten years instead of every thirteen months for the current light bulbs.

For ‘Mara and Dann’ see: http://www.dorislessing.org/maraand.html And for reviews: http://www.nytimes.com/books/99/01/10/reviews/990110.10upch.html or http://www.theguardian.com/books/1999/may/29/books.guardianreview27

For ‘High Rise’ see: http://www.jgballard.ca/criticism/highrise.html

Information on changing light fixtures from The Metropolitan dEtroit, August 2013 (p.11) and http://www.themetropolitandetroit.com/

Passenger air miles CO2 production from http://www.transportdirect.info/Web2/JourneyPlanning/JourneyEmissionsCompare.aspx

I and the village

'I and the village' by Chagall

‘I and the village’ by Chagall

Last week’s post ended up a bit heavier, both in size and content, than I intend most posts to be so I thought this week’s should be short.

Recently, I visited the exhibition of Marc Chagall’s paintings at the Tate Liverpool and was particular inspired by ‘I and the Village’, which was painted in Paris in 1911 although Chagall was born in a small village in Belarus.  Apparently, the painting signifies the interconnectivity of human life and the surrounding natural world – notice the fine line connecting the eyes of the peasant and the animal also the peasant holding a sprig of a tree.  The orbits of the earth and moon are suggested by the circular shapes in the painting, which perhaps also represent the cyclical nature of life.

As you might guess from my posts over the last year, these ideas resonant with my own approach to our interaction with the earth and the natural resources available to us.  I like the layers of connections and interacting activities illustrated in the painting, including many that are not immediately obvious, just as in life.

The painting is part of the collection of the MoMA in New York [http://www.moma.org/collection/object.php?object_id=78984] but is part of the Chagall: Modern Master Exhibition at the Tate Liverpool until October 6th, 2013 [http://www.tate.org.uk/whats-on/tate-liverpool/exhibition/chagall-modern-master] for which it is their poster picture.  Either website will give you a better picture than the thumbnail above, or you could go and see it in person…

Wind power

Winds are generated by uneven heating of the earth’s atmosphere by the sun, which causes hotter, less dense air to rise and more dense, colder air to be pulled into replace it.  Of course, land masses, water evaporation over oceans, and the rotation of the earth amongst other things added to the complexity of weather systems.  However, essentially weather systems are driven by natural convection, a form of heat or energy transfer, as I hinted in my recent post entitled ‘On the beach’ [24th July, 2013].

If you are thinking of building a wind turbine to extract some of the energy present in the wind, then you would be well-advised to conduct some surveys of the site to assess the potential power output.  The power output of a wind turbine [P] can be defined as a half of the product of the air density [d] multiplied by the area swept by the blades [A] multiplied by the cube of the velocity [v].  So the wind velocity dominates this relationship [P = ½dAv3] and it is important that a site survey assesses the wind velocity.  But the wind velocity is constantly changing so how can this be done meaningfully?

Engineers might tackle this problem by measuring the wind speed for ten minute intervals, or some other relatively short time period, and calculating the average speed for the period.  This process would be repeated over a long period of time, perhaps weeks or months and the results plotted as frequency distribution, i.e. the results would be assigned to ‘bins’ labelled for instance 0.0 to 1.9 m/s, 2.0 to 3.9 m/s, 4.0 to 5.9 m/s etc and then the number of results in each bin plotted to create a bar chart.  The number of results in a bin divided by the total number of results provides the probability that a measurement taken at any random moment would yield a wind speed that would be assigned to that bin.  Consequently, the mathematical function used to describe such a bar chart is called a probability density function.  Now returning to the original relationship, P = ½dAv3 and using the probability density function instead of the wind velocity yields a power density function that can be used to predict the annual output of the turbine taking account of the constantly changing wind velocity.

If you struggled with my very short explanation of probability density functions, then you might try the Khan Academy video on the topic found on Youtube at http://www.youtube.com/watch?v=Fvi9A_tEmXQ

Engineers use probability density functions to process information about lots of random or stochastic events such as forces ocean waves interacting with ships and oil-rigs, flutter in aircraft wings, the forces experienced by a car as its wheels bounce along a road or the motion of an artificial heart valve.  These are all activities for which the underlying mechanics are understood but there is an element of randomness in their behaviour, with respect to time, that means we cannot predict precisely what will be happening at an instant in time; and yet engineers are expected to achieve reliable performance in designs which will encounter stochastic events.  Frequency distributions and probability density functions are one popular approach used by engineers.  Traditionally engineers have studied applied mathematics that was equated to mechanics in high school but increasing they need to understand statistics.