Archive for August, 2010

Progress in lighting

August 31, 2010
Picture of some LEDs

Picture of some LEDs

Occasionally, something in the world moves on: progress is made: and today is such a day. And on this day I just want to pause to celebrate the progress that humanity has made through its collective appreciation of metrology.

I will leave the details to the NPL web site, but today we moved to new paradigm for specifying lighting. In the UK, light bulbs must now be labelled according to how much light they produce – how many lumens they emit – whereas previously they were labelled according to how much electrical power they consumed. This change reflects the reality there are now many different technologies which produce different numbers of lumens per watt. This change is critical to driving people towards more efficient lighting technologies. As I mentioned last week, this won’t save the world, but it will at a least save a little energy.

Would you eat a radioactive banana?

August 31, 2010
A picture of a radioactive banana

A picture of a radioactive banana. All bananas are (slightly) radioactive.

Would you eat a radioactive banana? Well obviously not. We wouldn’t eat anything that we knew to be radioactive! But as my colleague Peter Woolliams pointed out to me, ALL bananas are naturally radioactive because they are a good source of potassium and all potassium contains a naturally radioactive isotope potassium-40. Peter alerted me to a new (informal) metrological standard – the Banana Equivalent Dose – the amount of radioactive dose that one receives from a standard 150 gram banana – this amounts to ingesting around 520 picoCuries of radioactivity. And eating one banana a day for a year would result in a dose of around 36 micro-sieverts – which is a significant fraction (1.5 per cent or one seventieth part) of our expected dose of 2400 micro-sieverts per year.

Although this may seem like trivia, it is actually an important metrological development. The purpose of measurement is to allow us to quantitatively compare one thing with another. Not just to say that one thing is bigger or smaller than another thing, but to say how much bigger or smaller. For this purpose it is useful to have units of measurement which familiar to us: for example it is easier to measure the size of a television screen in centimetres than in kilometres – though strictly either comparison would be a valid measurement.

This might not seem significant until one considers the fear and anxiety that accompanies any statement about radioactivity. To state that milk contains 20 picocuries/litre of radioactivity might well cause alarm – it might cause one to pause before pouring such milk on one’s cornflakes. To find out that a glass of such milk would contain one seventy-fifth of the amount of amount of radiation in a banana might cause one to feel differently about breakfast. And that is before one even thinks about the tasty electrons surrounding a nourishing proton and neutron core. Mmmm…  I never eat anything else 🙂

Consumable light

August 26, 2010

Imagine that after all the talk and hype, scientists and engineers finally came up with affordable LED lighting solutions which cost less to use even than compact fluorescent  light bulbs. This could actually happen within 5 years. But imagine it were true now! Wow! What would happen?

  • Would we simply use the same amount of light and pocket substantial savings in cash, energy and carbon?
  • Would we revel in the technology and – since it was now so cheap – find new ways to consume more light (and electricity and carbon)?
  • Would the third world – in which people spend many evening hours in near darkness – consume more light?

These questions were addressed in a recent scientific paper (which seems to be free to download for the moment!) and the analysis really moved me. Of course no one knows what technology will actually become available. Or when. Or at what cost. And no one knows how these technology developments will interact with human society worldwide. But the paper considers a wide variety of possible scenarios. Reading the paper I was struck again and again by the straightforwardness and thoroughness of their analysis, and the contrast between the sophistication of their analysis, and the naivite of my own prior thoughts on the matter. It’s a long paper and quite technical, but there are two things I would like to comment on: the concept of light consumption, and my own technological utopianism.

Light consumption

I had never thought of light itself as a product, but of course in can be thought of that way. A lumen is the unit used to measure the amount of useful emitted by a light bulb. It is a product of the amount of amount of light of all frequencies (colours) emitted, and the sensitivity of the human eye to those colours. Although we are not usually aware of it, when we are buying light bulbs we are actually seeking devices to produce (consume) a certain number of lumens of light in our homes. By quantifying this consumption, and charting historical ‘consumption’ over several centuries, the authors can make plausible estimate for how consumption might change  as new technologies become available.

Technological Utopianism

The most profound effect of the paper was to puncture my sense that improved light technology would some how ‘solve a problem’. It had seemed so obvious to me that LED lighting would reduce the carbon costing of lighting and thus reduce the carbon emissions associated with lighting. I had been aware of the problem that if I saved (say £100) on my electricity bill, I would use that £100 to consume some other resource – which would have a carbon cost associated with it. But I had not really considered the effects on the third world – which would ‘consume lumens’ voraciously if they were cheap enough – and the effects of the market to develop new ways in which we could ‘consume lumens’ – mood sensitive lights or uniformly illuminated floors and walls – or whatever our collective imagination comes up with. In short, if a perfect lighting technology – and LED lighting is very nearly that – became available it would not definitively solve any societal problems.

The growth in LED lighting still seems inevitable – and I still hope it will happen. Allowing large swathes of the third world to function in the evening will bring enormous benefits. And reducing energy (carbon) consumption in ‘lumen saturated’ societies such as our own is definitely a ‘good thing’. But the problem of carbon emissions that we face collectively is unlikely to be solved by a technological fix. I feel like I have just become a technological realist.

When will renewable electricity become mainstream?

August 21, 2010
A large tidal flow turbine

A large tidal flow turbine ready for testing

Imagine this: a world in which we could all use renewably-generated electricity with some fraction of the gay abandon with which we currently use electricity. Wow! The technology exists to make this possible, so this vision is not an unachievable dream such as a world without, say, unhappiness. The big question concerns how we can ever beat a path from our current situation to the new one? A news story on the BBC involving the installation of a giant-tidal flow turbine near Orkney brought this to mind, and the thought occurred to me: if the journey of a thousand miles begins with a single step, then perhaps I am witnessing here one of those single steps.

If we are ever to reach the promised land of affordable renewable electricity, then several factors must be in place – factors involving consumers and providers acknowledging that electricity derived from fossil fuels is really a very dirty way to make electricity. And thus being prepared to pay some premium for renewably-generated electricity. I think we are on the cusp of that change. But in addition to this willingness to change, there must exist the technical and economic capability to make the change happen. In short, there must be companies to build the turbines and transmission systems, and the companies will need to be large and profitable – possibly as large and profitable as Oil Companies are today. Seeing the colossal scale of this turbine, and imagining the presumably colossal investment required to build it, and the scale of vision for how it will be used, I was moved to think that maybe we are collectively beginning to move towards this promised land. And fleetingly, I felt a small glow of optimism.

One year old

August 21, 2010
Michael de Podesta

A recent picture on holiday in Summer 2010

I notice looking at these blog archives that I have been using this WordPress blog for just over a year. During this time I have written about 80 entries, some of which have been read by other people! And I just wanted to say thank you to that select band of readers. Work has been so busy lately that I have barely been able to sit down at the end of the evening and try and restore some sense of equilibrium by writing. Anyway, maybe things will be a bit easier over the next few months (?) and hopefully I will be able to get through the backlog topics of that have stuck in my mind over the last few months.

Michael.

What are ‘A’ levels for?

August 21, 2010
Percentage of students awarded A grade in A levels since 1965

The UK’s A level results came out this week and amongst all the opinions and emotions expressed I found the above graph profoundly significant. Essentially the whole ‘Exam Debate’ comes down to one simple question: Does this graph indicate a success, or a failure? Those who think it indicates a success attribute the rise to better teaching and those who think it indicates a failure attribute the rise to falling standards. I attribute the rise to what I call ‘wrong headedness’ – a complete inability to understand what A levels – and exams more widely – are for.

Before 1985, getting an A grade at A level meant that a student had  received an mark in the top 9% of results. In most subjects this mark was determined by performance in one or two exams taken at the end of a two year course of study. The purpose of the grading was to discriminate amongst the students. It offered teachers collectively no chance to improve. After 1985, everything changed and has kept changing ever since. The major shift was to a system where an A grade indicated a particular level of achievement. This offered the possibility that if teaching improved then more children would receive A grades. However changes in the style of exam, the modular exam system (which means that no one is ever tested on the whole syllabus) and the frankly appalling system in which the exam boards became wholly owned by publishers, means that a simple interpretation of the above as representing an improvement is not very convincing.

One role of our school system is to pass on the accumulated knowledge and understanding of our culture: this sounds rather pompous but it is true. It is hard to think of a more important task for any culture to undertake. The role of exams within this system is (very broadly) to check that this is being done. More specifically it needs to BOTH check that students know certain things by demonstrating a basic understanding AND to discriminate amongst the students and identify those with special talents or affinities. The above graph – and its seemingly unstoppable linear trend – indicates a collective failure to recognise the second purpose of exams.

My computer has broken. When is yours going to break?

August 15, 2010
Internal view of my dead computer

Internal view of my dead computer: the faulty capacitor is just visible at the top left corner of the panel marked 'G5'.

A couple of weeks ago, after five and half years of faithful service, my computer died. And today I painfully reconciled myself to its death, and ordered a replacement: cheaper, more powerful, and hopefully longer lasting. But it made me think…

I had used that computer pretty much every day for the last 2090 days. Each day it started with a happy chime, until one day it didn’t. The pictures on the screen became degraded and eventually the computer stopped responding. An internet search revealed the cause: six years ago a bunch of faulty electrolytic capacitors entered the market and were incorporated into a wide variety of computing equipment. The capacitors were manufactured with a trace impurity in their dielectric, and now, all these years later, this fault is causing failures in otherwise reliable equipment. This set me thinking about the longevity of all the computing kit that has become ubiquitous in our lives  – well my life at least. Presumably after some period: 10 years, 20 years or 100 years, it will all break. And as electronics becomes ever more reliable, and we trust it in more diverse environments, these failures will come as a more  of shock. And I was reminded of one of the more shocking of the possible failure mechanisms. It arises from the use of lead-free solder.

‘Conventional’ solder is mainly an alloy of roughly one third lead and and two thirds tin. Lead-free solder is typically made from alloys of silver, copper and tin. If I have understood what I have read correctly, the problem arises with coatings used on components which are soldered onto the printed circuit boards. These used to be coated with lead-tin solder, but are now coated with pure tin. However pure tin is a metal which can grow ‘whiskers‘ – growths of tin which are only a few thousandths of a millimetre wide, but which can grow several millimetres in length. Wow! that’s incredible! The factors affecting the growth of these whiskers are many and varied, so that in service, it is hard to predict when, where, and at what rate they will grow. But grow they will, and eventually they will give rise to failures, typically by breaking off and causing a short circuit. The phenomenon has already resulted in the verified loss of at least one satellite, the recall of pacemakers, and failures within nuclear power stations.

Now I don’t mean to alarm you: engineers are aware of this problem and have been for 60 years – that’s why we used lead-tin solder for all those years – the lead inhibits the growth of these whiskers. Indeed I know colleagues at NPL who are hard at work helping manufacturers to find appropriate solutions. And when there are safety critical systems, exceptions can be made. But in the end – for one reason or another, due to tin whiskers or not – all this electronic stuff will just stop working.

Weather Extremes

August 9, 2010

I have just returned from a holiday in Crete and relaxing there I had a chance to reflect on just how profoundly variations in weather can affect our lives. Looking at data from the Weather Underground, I see that at the start of our 10 day break the maximum daily temperature was 29 °C with a mean relative humidity of 60%: perfect weather for a beach holiday. At the end of our stay, the equivalent statistics were 30 °C – barely warmer – but with a mean relative humidity of 83%. This small change was enough to occasionally bring me to the brink of panic at the thought that I would be unable to get cool. Outside of an air-conditioned room it would be unthinkable to undertake any activity beyond gentle exertion. I mentioned this before when I discussed the role of air conditioning in the US. But weather events around the world also caught my attention

  • In Russia, the warmer than average weather created the potential for wildfires that have killed many and disrupted lives across thousands of square kilometres.
  • Thinking about the flooding in Pakistan in this context may seem insulting. To say that people in Pakistan who have abandoned their homes and farms have been ‘affected’ by flooding is an understatement. Their lives have become dominated by fear and chaos in a way that I can scarcely imagine. But at the root of it, all that happened was that it simply rained a bit more than usual.
  • As in Pakistan, all that happened in China was that it rained more intensely than usual creating soil instabilities giving rise to catastrophic mud-flows.

Weather and Climate

Many news reports state the weather is unprecedented “in living memory”, or they describe it as the worst ‘for a hundred years’. Well every 100 years we need to expect weather events which have not occurred for 100 years! And ‘living memory’ is not a long time. Putting this point aside, the devastation that these events bring to our lives coupled with our complete inability to control them, is simply frightening.

And now I would like to mention Climate.  None of the above events is any indication at all of any kind of a change in global or regional climate. However, these events are so deadly that (a) if the climate were changing, and (b) if these changes might reasonably be expected to increase the frequency of extreme weather events, then we should really pause to consider what we are doing. Even in the face of significant uncertainty about the magnitude and extent of any possible climate change, these extreme weather events are so overwhelming that they hold the potential to create multiple simultaneous crises on a pan-global scale.


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