Tag Archives: fossil fuel

Tidal energy

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Photo credit: Tom

Photo credit: Tom

The world is slowing down! According to Max Tegmark, in his book ‘Our Mathematical Universe’, the rotational velocity of the Earth is being reduced as some of its kinetic energy is dissipated as tidal energy. It is possible to estimate the age of planet from the rate of slow down by assuming that at its birth it was spinning as fast as possible without the centrifugal forces pulling it apart. The answer turns out to be about 4 to 5 billion years which roughly agrees with radioactive dating of the oldest rocks in Western Australia and bits of meteorites that imply the solar system came into being about 4.5 billion years ago.

So does this imply that tidal energy is not really a renewable energy source? I think it is just an issue of timescale. Fossil fuels are seen as non-renewable because the formation of coal and oil substrates happens on geological timescales. Biomass is a bit quicker because we skip the fossilisation process and renewal is measured in months. Fossil fuels and biomass are both ways of storing solar energy in chemical bonds. Nature is much better at converting and storing solar energy than mankind. But, solar energy would appear to be the ultimate renewable energy source. Every morning its there, though often hidden by cloud where I live. The sun will eventually die but again this won’t happen anytime soon but on a long geological timescale.

Sounds of the city

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cornerRegular readers of this blog will know that I spent a relaxing day painting railings a few weeks ago [see post entitled ‘Engineering archaeology‘ on July 23rd, 2014].  A day or so later, I went out with my pail of whitewash to paint the walls of the light-well that the railings protect.  ‘The summer world was bright and fresh, and brimming with life’ but unlike Tom Sawyer I was not looking for Jim to do my white-washing for me.  I was looking forward to another therapeutic session painting the walls at the front of our house.  It was an interesting standing in the light-well facing the wall, un-noticed by most passers-by.  We live on a city street close to tourist attractions and there is a constant stream of coaches and taxis stopping to drop-off and pick-up tourists. I have written about the noise insulation in our house before [see Noise Transfer on April 13th, 2013] which means that we don’t notice the constant growl of diesel engines outside but I did while I was painting.  However, there were other sounds in the city.  The voices of pedestrians  deep in conversation as they passed by on the pavement just above my head.  I recognised Chinese, French, Italian and English but there were many different languages that I didn’t recognise.  There were young children asking parents questions as they walked down the street.  For a while I could hear cathedral bells.  When there was a pause in the traffic then it was possible to hear the cooing of pigeons, a neighbour’s radio or television and an ever-present idling diesel engine which I discovered was an ice-cream van dispensing a constant trickle of black soot and an occasional ice-cream.  It is curious that as a society we tolerant high levels of noise pollution at tourist attractions, especially ones that are meant to be places of calm and contemplation. Most tourists are, almost by definition, on holiday seeking relaxation and a lowering of stress levels – how much more pleasant would it be to glide to your destination in a silent electric coach or taxi?

We have the technology to provide such a service [see Are electric cars back? on May 28th, 2014]. Yes, it requires some investment by tour operators and taxi firms in hybrid or electric vehicles and by the city council in re-charging facilities. Induction charging stations at tourist attractions would allow vehicles to recharge while dropping off and picking up passengers. The technology is available and has been used by buses in Genoa and Turin for more than a decade.  So a little bit a regulatory pressure and investment from city councils acting together could create a calmer, quieter and cleaner environment for everyone.

Can we look forward to solar-powered ice-cream vans?

Sources: Thank you to Richard for reminding me about Tom Sawyer.

Energy efficiency

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We were sent a summary of our annual gas and electricity consumption recently by our local utility company. The utility quantified our consumption of both gas and electricity in units of kilowatt-hours (kWh). It is usual to be sold electricity in kilowatt-hours but most people are confused by this unit. Perhaps because they learnt at school that the units of energy are Joules in the SI system and the power rating of appliances is usually given in Watts. They might know that a Watt is a Joule of energy per second, so what is a kilowatt-hour? Well it is about 3.6 x 106 Joules or 3.6 MJ, because it is 1000 Joules per second (= Watt) for one hour. So, I think the utility company should be telling me how many MegaJoules (MJ) we have consumed. After all we are used to seeing the energy content of our food quoted in kiloJoules (kJ), as well as calories.

The situation with our gas consumption is rather different because the utility does not supply energy but gas. The amount of energy that I get from it depends on what I do with it. If I burn it under conditions of constant volume, e.g. in a closed rigid container with exactly the correct concentration of oxygen then it will generate more energy in terms of heat than when it is burnt in constant pressure conditions, such as at atmospheric pressure in air. This is because in constant pressure conditions some of the energy released by combustion is used to expand the exhaust gases against the constant pressure, i.e. to do work, and only what is left is released as heat. So the utility should sell the gas by weight. If they sold it by volume then I would be paying more for the same amount of gas (i.e. number of hydrocarbon molecules) when the supply pressure was reduced.

Oil companies don’t sell gasoline or diesel in Joules for the same reason but they can sell by volume because it is always supplied to our cars at atmospheric pressure and the volume of a liquid is essentially constant.

We like to compare the efficiency of cars in terms of miles per gallon, or kilometres per litres. Efficiency can be loosely defined as what you want divided what you have to put in [See my post entitled ‘National Efficiency‘ on May 29th, 2013]. So for a car, what you want is kilometres travelled and what you put in is litres of fuel. However, when we are all driving plug-in electric cars then we will probably talk about how many kilometres per megajoule our car achieves [see my post entitled ‘Are electric car back?‘ on May 28th, 2014] . Unfortunately, while we are in transition with plug-in hybrids, car manufacturers like to quote very attractive kilometres per litre and ignore the electricity supplied via the plug – as if it were free!

Image courtesy KKN Liebstadt NPP from http://www.nucleartourist.com/systems/ct.htm

War and peace

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The recent negotiations with Iran have brought nuclear weapons back into the forefront of the public’s consciousness, if they ever left it.  This leads to some misplaced sentiments about nuclear energy due to the closely linked history and science of nuclear technology for war and peace.  There is no doubt that nuclear bombs are terrible weapons of mass destruction but so are certain chemical agents and yet there is not the same level of public and political angst about building chemical plants as there is over nuclear power stations.  The civil chemical and nuclear industries are both strictly regulated but the chemical industry has had some horrific accidents, such as at Bhopal, India in 1984 where 8000 people were killed when a pesticide plant leaked toxic gas, or more recently in the US when a fertilizer plant in West, Texas exploded killing 15 people and levelling hundreds of homes.  These incidents are not well-known outside of the engineering industry whereas by contrast the nuclear industry has had a small number of very well-publicized accidents that have killed very few people, or no one in the case of the recent accident at Fukushima.

People will argue that I am ignoring the long-term effects of exposure to radiation so it is appropriate to examine the evidence.  The atomic bomb dropped on Hiroshima killed an estimated 130,000 people, mainly due to the blast rather than radiation, while a long-term study of survivors within 10 kilometres of the explosions has found increased incidents of cancer arising from radiation exposure.  Following the Chernobyl accident in 1986, 240,000 workers were exposed to radiation levels higher than 100 millisieverts and 28 died from acute radiation sickness (ARS) that year.  The World Health Organisation estimates that about 4000 of these workers will die from cancer as a consequence of their radiation exposure about another 9000 amongst the exposed population in Belarus, the Russian Federation and Ukraine.  These are large numbers but represent only about a 1% of the total number of cancer deaths in these populations from other causes, for instance smoking caused about 294,000 deaths in the roughly the same twenty years in Belarus.

It’s time we decoupled the use of nuclear technology in war and peace.  We don’t handicap other technologies used in war and peace with the same indistinguishable associations.  We use fossil fuels to power tanks, jet-fighters and warships and then burn so much of it for peaceful purposes that 1.2 million people died prematurely last year from the pollution it generated [see my post entitled ‘Year of Air: 2013’ on 20th November, 2013].

Sources:

http://news.bbc.co.uk/onthisday/hi/dates/stories/december/3/newsid_2698000/2698709.stm

http://www.huffingtonpost.com/2013/08/01/obama-chemical-plants_n_3688272.html

http://news.bbc.co.uk/onthisday/hi/dates/stories/august/6/newsid_3602000/3602189.stm

http://www.rerf.jp/glossary_e/lss.htm

Little, M., 2009, Cancer and non-cancer effects in Japanese atomic bomb survivors, Journal of Radiological Protection, 29(2A):A43-59. http://iopscience.iop.org/0952-4746/29/2A/S04;jsessionid=7838AA7D498065F13C23094F1D01DBBA.c3

Cardis. E., et al., 2006, Concer consequences of the Chernobyl accident: 20 years on, Journal of Radiological Protection, 26:127-140. http://iopscience.iop.org/0952-4746/26/2/001/pdf/0952-4746_26_2_001.pdf

http://www.ctsu.ox.ac.uk/research/mega-studies/mortality-from-smoking-in-developed-countries-1950-2010/mortality-from-smoking-in-developed-countries-1950-2010/view