Tag Archives: entropy

Year of Air: 2013

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I mentioned some time ago (Noise Transfer on 3rd April, 2013) that we are privileged to have magnificent views of the river and hills beyond from our city centre house.  From the back bedroom window you can just about see the sea and we are certainly aware of it in most days due to the almost constant sea breeze (or gale).  So despite living in a city centre we are not amongst the 95 percent of EU city dwellers who are exposed to fine particles levels that exceed WHO guidelines.  However, the EU levels are well below those in Beijing that are 300 times the guidelines and probably comparable to those in London during the Great Smog of 1952 that caused cows to choke to death and contributed to the death of about 3000 people.  London has come a long way in the intervening 60 years with current levels of fine particles at about half the WHO guideline, which is 25 micrograms per cubic metre, whereas Beijing has recorded levels of 400. it has been estimated that 13,000 people die prematurely in the UK due to combustion related pollution compared to 1.2 million in China

In my post entitled ‘Extraordinary Technical Intelligence’ on 10th April, 2013 I wrote about the process of urbanisation and industrialisation that has been seen repeatedly across the world.  The progress of this process in a region can also be measured in the levels and type of pollution being generated.  The West has been where China is now, and where India and Africa are likely to go next.  Air pollution on this scale effects the neighbours of the polluter so we have an incentive to help alleviate the problem.  We should also feel a moral obligation because much of the pollution is associated with factories producing goods that we buy and probably don’t repair or recycle at the end their useful life [see ‘Old is Beautiful’ posted on May 1st, 2013] .  If we drew the system boundaries more appropriately then the pollution generated during the manufacture of these goods is as much our responsibility as the manufacturer’s [see my post on 19th December, 2012 about ‘Drawing Boundaries’].

This is the Year of Air, maybe it should have been called the Year of Clean Air to make it absolutely clear what it is all about, i.e. giving everyone on the planet the chance to live and breathe clean air!

BTW, a fine particle is one of diameter less than 2.5 microns or 1/30th diameter of one of your hairs.  One my PhD students is working on tracking nano-particles about a hundred times smaller as they interact with biological structures such as human cells, but that’s another story [see last week’s post].

Sources:

‘Under a Cloud’ by Pilita Clark in the Financial Times, July 13/14, 2013 [ http://www.ft.com/cms/s/0/83ef4b78-eae5-11e2-9fcc-00144feabdc0.html#axzz2cgRhFXMs ].

Yim SHL and Barrett SRH. Public Health Impacts of Combustion Emissions in the United Kingdom. Environmental Science and Technology, 2012, 46 (8), pp 4291–4296.

‘Air Pollution Linked to 1.2 Million Premature Deaths in China’ by Edward Wong in the New York Times on April 1, 2013 http://www.nytimes.com/2013/04/02/world/asia/air-pollution-linked-to-1-2-million-deaths-in-china.html?_r=0

Silva, R.A., et al., 2013, Global premature mortality due to anthropogenic outdoor air pollution and the contribution of past climate change, Environmental Research Letters, 8:034005. http://iopscience.iop.org/1748-9326/8/3/034005/pdf/1748-9326_8_3_034005.pdf

Fracking

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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.

Impossible perfection

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Carnot's equation for ideal efficiency of a cyclic device converting heat to work and operating between two temperatures specified on the Kelvin scale

Carnot’s equation for ideal efficiency of a cyclic device converting heat to work and operating between two temperatures specified on the Kelvin scale

In my last post [National efficiency on 29th May, 2013] I calculated the efficiency of the nationwide process of electricity generation in the UK [35.8%] and made no comment on the relatively low value.  It will be similarly in all industrialised countries as a consequence of the second law of thermodynamics and the requirement for all real processes to increase entropy.  A French engineer / scientist, Sadi Carnot [1796-1832] demonstrated from the second law, that the maximum efficiency achievable in ideal conditions by a process operating in a cycle to convert heat into work is a ratio of the temperatures of the heat source and cold sink to which excess heat is dumped.  In a power station the heat source might be a fossil-fuelled furnace, a nuclear reactor or a solar concentrator.  The cold sink is usually the environment, perhaps in the form of river or sea water.  So both source and sink temperatures are limited.  The sink by the local climate and the source by the temperatures that modern materials can withstand.

The very best efficiency based on Carnot’s expression for a maximum material temperature of 350 degrees Centigrade [=623 Kelvin] and environment temperature of 5 degrees Centigrade [278 Kelvin] is 55%.  Of course a real power station will never operate at this level because ideal conditions are not achievable – perfection is impossible.

The ideal efficiency improves as the operating temperatures of the heat source and sink are moved further apart and this quest to raise this temperature difference drives a substantial proportion of materials research.  However, even operating with a heat source at 800 degrees Centigrade, using expensive, high temperature alloys, such as Hastelloy N  [a nickel-chromium alloy], on a winter day in the Canadian capital, Ottawa where the average January daytime temperature is -7 degrees Centigrade, the Carnot efficiency of a power station would be only 75%  [=1-(266/1073)].

National efficiency

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Thermodynamics, especially the first and second laws, are usually perceived as boring and perhaps mysterious by most people, including many engineers, as well as irrelevant by many non-engineers.  However, thermodynamics is fundamental to how engineers deliver products and services to society.  The name ‘thermodynamics’ does not help much, perhaps it would be better to call it ‘energy science’, since it is about energy transfers, conversions and flows.

The national energy flow charts mentioned in my post about ‘Energy Blending’ on 22 May 2013 illustrate nicely the first and second laws of thermodynamics (or energy science).  The underlying basis of the flowcharts is to treat the nation as a system and to account for the energy flows in and out across the system boundaries.  The first law, which is about conservation of energy, demands that the inflow and outflow balance one another, so for the UK and USA the annual inflows were 12.5 and 92 quintrillion joules respectively.  A quadtillion is a million million million or 1 with 18 zeros.

The second law demands that any real process involves an increase in entropy, which is a measure of energy dispersion, essentially lost or wasted energy, and this is also present in the flow charts.  In the centre of the UK chart is electricity generation or conversion with an input totally 82.4 Mtoe [millions tons oil equivalent], an output of 29.5 Mtoe and losses of 48.2 Mtoe, which are demanded by the second law of thermodynamics.  So the overall efficiency of electricity generation in the UK is 35.8% [=desired output/required input].

Footnote: the raw data for the UK and USA energy inflows were 299.2 Mtoe [millions tons oil equivalent] and 97 quadrillion Btu [British Thermal units] respectively which I converted into the SI unit for energy, the joule.  The links for the energy flow charts are:

UK Energy flow chart: http://www.gov.uk/government/uploads/system/uploads/attachment_data/file/65897/5939-energy-flow-chart-2011.pdf

USA Energy flow chart: http://www.eia.gov/totalenergy/data/annual/pdf/aer.pdf