Archive for November, 2013

Too Much of Nothing

November 14, 2013
A Christmas Gift Suggestion from New Scientist

A Christmas Gift Suggestion from New Scientist

As I surmised, the envelope containing nothing was indeed a publicity mailing for the book ‘Nothing’, available at tax-paying bookshops for just £5.59 including UK delivery.

As a contributing author I received a copy a few weeks ago and quickly read through to rate ‘my Chapter’ – about Absolute Zero – against the others. I was relieved to find that it didn’t obviously stand out as worse than the others.

And can I recommend it for a Christmas gift as New Scientist suggest? Well of course I can! It is an entertaining and stimulating read for almost anyone – particularly if they have a yen for science.

Is this too much of nothing? Can the topic sustain an entire book. I think it can, or as Bob Dylan so inscrutably put it:

Now, it’s all been done before
It’s all been written in the book
But when there’s too much of nothing

Nobody should look
(Lyrics from Bob Dylan.com)

You might think that I am biased because of the amount of money that I will earn when people buy the book. Let me reassure you on this issue.

I was paid £1800 as a contributors fee which I thought was pretty generous. However I felt the money came my way because of my role at NPL, and so even though I wrote this in my own time, I passed the money on directly to NPL.

And as for royalties, well, the title of the book says it all :-).

Weighing a candle

November 14, 2013

This is a short movie of a candle being weighed on a precision balance. It is a boring movie, and badly made too. But as Winston Churchill once said:

If a thing is worth doing, it is worth doing badly.

There is one other such movie on You Tube, but well-made though it is – the director clearly used a tripod – I prefer mine.

In fact it is obvious that a candle must be losing weight, and you can make measurements on a much less sensitive scale for a longer time and get a good estimate of the rate at which the cancel is losing weight. But somehow, it is still shocking to see it happen ‘live’.

That’s all.

“News-ertaintment”? No Thanks.

November 11, 2013
Why isn't BBC news distinctly different from other News Web sites?

Why isn’t BBC news distinctly different from other News web sites?

I love the BBC. I read the News web site and listen to Radio 4 every day. Occasionally I watch the Television news. I am really proud that our collectively-owned broadcaster is as good as it is. But I think that – freed from the need to make money – the BBC News service should be even better. For example:

  • Speculation is not news. If a report is going to be released on a certain date, it is not ‘news’ until after it has been published. Having people discuss what reports might contain when they are eventually published is not news. It is ‘News-ertainment’.
  • News is numbers. When reporting about Fukushima, I want to know the numbers. I want to know what the radiation levels are in rational units – in this case dose rate in micro-seiverts per hour, or the number of becquerels of activity in the soil. These numbers are the news. Some people won’t understand the numbers, but others will. Terms like ‘high’ and ‘low’ are meaningless, and pictures of people in special suits are not news.
  • Cross-Promotion: The BBC is in the habit of believing that its own programmes are news. So that what is apparently a ‘news’ story on a web site or TV report, will in reality be nothing more than promotion of other BBC output. This is fine for commercial web sites – I am not paying for them – but the BBC should not do this.
  • Corrections. When good news sites make a correction to a story – they note that a correction has been made. This is common practice at The Guardian or the LA Times. But it is not practiced at the BBC who change stories – but leave no record that they ever got anything wrong in the first place.

The BBC Trust is holding a consultation on BBC News so if you have anything you want to say, now would be the time to speak up.

Candle Mass and Candle Power

November 5, 2013
Weighing a candle. By determining the rate at which the candle lost mass, I could work out the rate at which it was using up the chemical energy of the wax.

Weighing a candle. By determining the rate at which the candle lost mass, I could work out the rate at which it was using up the chemical energy of the wax.

The other day I was looking at a slender candle flame when the thought occurred to me: “How much energy does a candle use to produce that light?“. After a moment of reflection, I thought of two ways to estimate it:

The first method was to weigh a candle as it burned and estimate the mass loss per second. Then I would need to look up the chemical energy of wax per gram (its so-called calorific content) and multiply the two numbers together to get the rate at which energy was released per second.

The second method was to measure the heating power of the candle. To do this I would need to put the candle under a container with a known heat capacity. Then by measuring the rate at which the temperature rose, I could work out the rate at which the candle had delivered energy to the container.

The experimental details are below, but here – for the impatient amongst you – are the results.

  • The candle lost mass at a rate of 1.78 mg per second. Multiplying this by what Wikipedia tells me is the calorific value of wax (43,100 joules per gram), I calculate that the candle is consuming chemical energy at a remarkable 77 watts. Wow!
  • That’s a lot of power and it is pretty clear that the candle is not producing anywhere near 77 watts of light – I guess the efficiency for producing light must be below 0.1%. Most of the energy must be producing heat.
  • I repeated the weighing experiment on a second (nominally identical) candle and I calculated that it consumed chemical energy at a rate of approximately 73 W. Within the uncertainty of measurement, I think this is consistent with the first measurement.
  • I used the second candle to heat 250 g of water in a lightweight (105 g) camping saucepan. The rate of temperature rise indicated that the candle was delivering energy at a rate of approximately 44 W.
  • So approximately 59% of the chemical energy was being delivered as useful heat. This seems reasonable given my previous experience heating water with flames, and considering that some of the wax may go un-burned (to make the soot in the flame)

So these two quite different experiments seem reasonably consistent, which is pleasing. But the results beg the question: “Could we use that 40 watts of thermal power to produce light more efficiently than a candle can?”.

I asked my colleagues at work – and the answer is most definitely ‘Yes’. You can see a device which does this in action in the movie below, and download instructions on how to make it here.

Experiment#1: Candle Mass

Graph showing the mass loss of candle (in grams) versus time (in seconds). The vertical grid-lines are every 3600 seconds - or one hour. Teh best-fit to the rate of mass loss is 1.78 milligrams of wax per second.

Graph showing the mass loss of candle (in grams) versus time (in seconds). The vertical grid-lines are every 3600 seconds – or one hour. The best-fit to the rate of mass loss is 1.78 milligrams of wax per second.

The rate of mass loss is rather slow. My weighing scale had only 1 g resolution so I needed  to measure for several hours to get a reasonable estimate of the rate of mass loss.

Experiment#2: Heating effect

Graph showing the temperature versus time of 250g of water in a 107 g aluminium container  of candle (in grams) versus time (in seconds). The vertical grid-lines are every 60 seconds - or one minute. The best-fit to the rate of temperature rise is 0.038 °C  per second.

Graph showing the temperature versus time of 250 g of water in a 105 g aluminium container of candle (in grams) versus time (in seconds). The vertical grid-lines are every 60 seconds – or one minute. The best-fit to the rate of temperature rise is 0.038 °C per second.

This is the raw data of temperature versus time taken using a thermocouple thermometer. I took care to stir the water before taking a measurement.

Time (s) T (°C)
0 15.2
60 16.9
120 20.2
180 22.6
240 25.3
300 27.6
360 29.5
420 31.1
480 32.9
slope 0.038056 °C/second

I then worked out the heat capacity of the water and the aluminium

Water
Mass 250 g
Specific Heat capacity 4.2 J/g/°C
Heat Capacity 1050 J/°C
Aluminium
Mass 105 g
Specific Heat capacity 0.904 J/g/°C
Heat Capacity 94.92 J/°C
Combined Total Heat Capacity 1144.92  J/°C

Then I multiplied the  heating rate (0.038 °C/s) by the heat capacity (1145 J/°C) to get the rate of energy input (43.6 J/s – or watts).

Our Energy Trilemma

November 3, 2013
Our energy trilemma is that Energy policy needs to balance three goals that defy simple solutions.

Energy policy needs to balance three goals that defy simple solutions.

“The development of stable, affordable, and environmentally-sensitive energy systems defies simple solutions. These three goals constitute a ‘trilemma’, entailing complex interwoven links between public and private actors, governments and regulators, economic and social factors, national resources, environmental concerns, and individual behaviours”

I couldn’t have put it better myself, so I simply quote from a report by the World Energy Council. And “No”, I have no idea who they are either. But I am grateful to them for enunciating clearly the three strands of the problem. If only our own political parties could speak to us so intelligently.

At the moment the UK’s labour party and the governing coalition are battling over issues of social equity. The labour party advocate an energy price freeze and the coalition advocate some kind of ‘improved’ market.

I don’t think anyone on either side seriously thinks either of these policies addresses longer term issues of social equity. And the arguments ignore the impact on the other two strands. Lower prices are bad for the environment. And in a society that has adopted a market-based way to provide energy, reducing the profitability of energy supply companies is bad for future energy security.

Similarly even the looming environmental threats from climate change cannot justify ignoring the other ‘horns’ of this trilemma. Increasing the price of energy or restricting its availability will have impacts on social equity and energy security.

And focussing on energy security – which means prioritising coal because of its widespread availability – has obvious devastating effects on any attempt to build a sustainable energy infrastructure.

So What?

It is only when we recognise the ‘three-pronged’ structure of our problem that we realise that a rational energy policy – whatever components it contains – will have one key feature:

  • A rational energy policy will disappoint all vocal advocates of one horn of the trilemma.

That means that almost everyone will fight to block it  and that almost no-one will speak up for it. You don’t believe me? Well consider some of the following – any or all of which could be part of a rational energy solution:

  • Fracking – which if implemented well could potentially help both energy security and reduce the use of coal (38% of UK supply today)  – is met with vehement ‘green’ opposition.
  • Wind turbines – which sustainably generated 6.4% of UK electricity supply today – are objected to almost religiously, and its energy generating capacity erroneously dismissed.
  • Nuclear Power – which for all its faults actually works and generated 21% of UK supply today – is objected to because despite being ‘low carbon’ it is not genuinely sustainable
  • The Severn Barrage – which could sustainably generate 5 GW (~7% of UK demand) of electricity for the same cost as Hinkley C – is objected to because of its effects on wading birds.
  • Coal-fired power stations – which generated 38% of UK electricity supply today at the lowest cost – are objected to because they are emit more carbon dioxide than gas-fired Power Stations.
  • Gas-fired power stations – which generated 25% of UK electricity supply today while emitting half the carbon dioxide – are actually being moth-balled rather than opening because they are ‘uneconomic’.
  • Increased energy costs – which are essential to pay for energy investment of whatever kind, and inevitable in any case because of increased worldwide demand – are objected to by almost everyone.

So although I don’t have ‘the solution’, I think that we do collectively have access to all the elements of a rational energy policy. But if we are to choose a rational policy, then we need to understand the nature of our trilemma. If we don’t understand this then democratically more people will object to every aspect of the solution than support it. And proponents of one aspect or another of energy policy will seek ‘victory’ or fight ‘defeat’. And using that language to describe our situation will make us all losers.

P.S. ‘Today’: This post was written on Saturday 2nd November 2013


%d bloggers like this: