Archive for June, 2011


June 27, 2011
Asteroid Trajectory

Asteroid Trajectory projected for the object known as 2011 MD. It will miss the Earth by 7600 miles. Click for Larger version.

The LA Times reports that a ball of rock between 5 metres and 20 metres in diameter will flash past the Earth today, missing us by just 7600 miles. This is just under one Earth diameter away, and in cosmic terms it counts as ‘close’.

Wikipedia tells me that similar objects hit the Earth roughly once a year and make a really big bang, like a ‘small’ atomic explosion. Larger objects can create explosions equivalent to large nuclear devices and the Tunguska Event in June 1908 provides direct evidence for this. Wikipedia tells me that  a Tunguska-sized event is likely roughly once every 300 years.

I just find it amazing that we all get by in this cosmos of terrible chance. It makes me want to be nicer to people tomorrow. I hope you feel the same.

UPDATE: The Daily Mail reports that the UK is near the top of league of dangerous places for an asteroid to crash. Just thought you would like to know.


June 26, 2011
Solar Reserve

Solar Reserve scheme for generating solar electricity 24 hours a day. Click for larger version.

I suppose that despite my better judgement I am a technological utopian. I still hope that somehow we can get it together to invent and engineer our way out of the energy mess we have created by our addiction to the intense energy ‘high’ that only fossil fuels can provide. And the other day I read something that gave me a little bit of hope. Let me share it with you…

I read that among the billions of dollars given to banks and bankers, the Obama administration had granted a $737 million loan guarantee to Solar Reserve to build a solar thermal generation plant near Las Vegas, generating solar energy 24 hours a day if necessary. The key trick is the use of molten salts to store thermal energy at high temperature and then release the  energy to generate steam and electricity when required. Apparently the key problems envisaged involve coping with the corrosion caused by the molten salt.

There are many small and medium size solar thermal schemes around. But the fact that this looks like it will actually be built and generate 100 MW 24/7 gives me cause for hope. Of course its not a solution for the UK, but there are plenty of countries where sunshine is plentiful, and if this works it is easy to imagine how rapidly it could be replicated around the world.

Hope is a delicate flower, and not often seen. Best enjoy it when it shows its head.


Hydroelectricity from Teddington Lock 2

June 26, 2011
Teddington Lock HydroElectric Scheme

Teddington Lock Hydroelectric Scheme. The top shows an artists impression of the system in place and the lower part shows a plan view of the weir. Click for larger image.

After my piece last week on HamHydro I got a very nice comment from James Heather about how in fact all the data was available on the web at And lots of it is – see my composite above. I have reproduced James’ comments below because they are very long and I am sure no one will read them as a comment to the previous article. James comments made me wonder if I had been over critical in my previous article and I spent the week feeling bad but I didn’t have a chance to update the blog until now – and its now gone midnight on Sunday!

Basically I was frustrated because I couldn’t find out even basic figures for the scheme. I have now got to the root of this. Searching for ‘Ham Hydro’ or ‘HamHydro’ currently does not return the above web link on the front page of Google. In my world, that means the page doesn’t functionally exist on the web. If you are running a project and you are not on the first page of  Google then IMHO, you need to do something about it. By adding a link to their page and not to the other junk news stories I am doing my bit here. Maybe if everyone clicks on the link then Google will somehow sort itself out.

James Heather’s comment

Hi Michael,

My name is James Heather and I am a director of Ham Hydro CIC and also the project manager. First I would like to thank you for joining our energy share group as a supporter and for wishing us well in your blog.

I would like to take this opportunity to briefly address some of the points you have raised although if you (or any of your readers) would like further information please get in touch with us via or our website

First we are not looking for the public to invest £2.4M. We are planning to borrow money from the bank and the share issue you are referring to will be for a much smaller amount. Since the banks will be providing a large amount of capital we have entered into detailed negotiations with them and provided equally detailed information about the project to them. When the time comes that we are ready to approach the public about the idea of a share issue we will issue a comprehensive prospectus which will enable any potential investors to make an informed decision about whether our project is a suitable investment for them.

In the mean time we have provided information to the public which is designed to generate interest in the scheme and develop an awareness about what we are undertaking. We have always made ourselves available to anyone who was interested in gaining greater knowledge regarding the project via email, phone or at our office. As you will know from the extensive local press coverage and over 12 pages of google articles about Ham Hydro there is a lot of information available for anyone who is interested.

In addition to using press releases, the internet and our website we have given to presentations to many local groups and societies and are already scheduled to give many more. We have had a stand at most of the large summer fairs including the Richmond and Ham Fair. We have also held a well publicised (via local papers, community groups, emails, schools and a poster campaign) public meeting at which we both presented a wealth of information and answered all questions the public had. We also took the opportunity to talk about the range of studies we have undertaken including Environmental Impact Assesments, Flood Risk Analysis and Fish Studies.

We completely agree with you that this project represents an opportunity to raise consciousness of energy generation issues in schools and the community. In a fact we believe it provides a good platform to teach about sustainability in general along with the obvious focus on renewable energy. As such I have visited local schools and talked to them about potential projects. This has been met with much interest and several ideas are being developed. One school is looking at building a model of the scheme and studying how varying flow affects electricity production and other schools are looking at how the project could form the basis for coursework projects. We have also talked with the local universities and colleges and were happy to provide data to them for undergraduate projects. We have used the scheme as a reason to talk to schools about their energy usage and possible ways to reduce wastage. We have also tied up with the Ham and Petersham Low Carbon Zone as we feel both schemes are complimentary to aid their efforts to encourage lifestyle changes and implementation of energy saving measures in people’s homes.

Thanks again for your support. Please do email us if you have any further questions.

Kind regards,

Cancer Risk and Mobile Phones

June 26, 2011

Scroll down to the bottom of the graphic to find my story!

Cancer risk from Chemicals

Graphic designed by Professor John Adams. The orange square in top left represents the 30 chemicals we know that cause cancer. The beige area around it represents the 3000 chemicals we have fully tested. The grey area represents all the chemicals we know exists. Are you worried? Click for full size version.

The above graphic was part of a surprisingly lucid article on the BBC about our attitude towards activities where the risk of harm is simply unknown. This blog post is simply to show the above graphic and remind myself that BBC can still write good stuff when they put their minds to it.

Static Electricity Re-visited

June 26, 2011
Mother and child enjoying electrification

Mother and child enjoying electrification

An interesting article over at Ars Technica claims that a recent paper in Science means that everything you thought you knew about static electricity is wrong. I would put it differently, and rather less dramatically. The paper reports an experimental investigation into the process of ‘contact electrification’ in dielectrics (insulators in everyday parlance). This is the process which takes place when you rub a balloon on a jumper. Their experiments show that when two uniform flat  insulating surfaces touch, the physical and chemical behaviour is more complicated than had been envisaged and the concept of a simple ‘transfer of charge’ is really overly simplistic. However, for anyone who has studied electrostatic phenomena it hardly comes as a surprise to learn that ‘its a bit more complicated’ than the simplistic story of the triboelectric series.

What the paper says:

  • When two uniform flat dielectric surfaces touch, the physical and chemical behaviour is more complicated than had been envisaged. Please note that the word ‘touch‘ which we all understand colloquially is actually not properly scientifically defined if we look at the nanoscale. Broadly speaking it means the surfaces get ‘close enough that the electric forces between atoms in the surface become very strong’.
  • If two different dielectrics ‘touch’ there can be a net transfer of electric charge from one surface to the other. This is as envisaged in the simple model. The paper shows that even in this case electrical charge goes both ways leading to a mosaic pattern on both surfaces of regions of positive and negative charge.
  • There can also be transfer of ions as well as electrons. If the paper were written by physicists, that would be the end of it. But because the effects involve a transfer of electrons AND ions the authors now say the reactions are chemical. I think this is a case where some chemists are trying to barge in on physics territory!
  • The surface charge pattern decays with a time constant of around 1000 seconds (15 minutes) but not due to surface charge transport, rather due to interactions with ions in the air. Again, anyone who has stuck a balloon to the wall could testify to the lifetime of the electrification effect.
  • Even two nominally identical surfaces when brought into ‘contact’ and then separated will charge in a ‘mosaic’ pattern, with charge going both ways. This is because on the nano-scale, the surfaces are not identical. On average there is approximately zero charge transfer, but this made up of lots of small transfers in both directions.

Two surface maps showing a nano-scale voltage measurement across the surface on a insulator called polydimethylsiloxane (PDMS). The top map shows an area 4.5 micrometres square before touching another piece of PDMS. The bottom map shows the same are after contact electrification. Notice the surface has become negatively charged in some areas and positively charged in others.

To me main point is that the details of the charge transfer processes between two different surfaces are more complex than had previously been envisaged. In particular, the charge transfer depends on the local situation on each surface, where local is referring to areas [a few hundred atoms] x [a few hundred atoms]. The researchers are not saying the previous view was wrong, merely that it was oversimplified. But as I mentioned above, for anyone who has studied or thought about these phenomena it can hardly come as a surprise to learn that ‘its a bit more complicated’ than the simplistic story.

What is nice about the work is that it is mainly phenomenological – it just says ‘we did these experiments and saw this’. And it is great to revisit ‘the familiar’ with new techniques and see the complex and the mysterious in the process taking place around us every day. It helps to keep us all on our toes and make sure the stories we tell our children are truly based on best science, and are not simply fictions that sound scientific.

New Bike

June 26, 2011
Globe Daily Bike

My new bike: A 'Globe Daily' costing more than I ever imagined I would pay for a bike. It's OK because the government - i.e. you -will pay for half!

The underlying Moral IssueI have just ordered a new bike even though my old bike is not broken. I feel terrible about this, but since I have had the old bike for roughly 10 years and it has been stolen, beaten up, and then recovered and repaired, it is probably not an offensive self-indulgence. However the reason I bought a bike now is because the government is subsidising the cost of bikes bought for travel to work and NPL offer a scheme in which I (as a higher rate taxpayer) pay only around half the cost of the bike. And even that is taken in 12 interest free installments from my salary. So given that I would probably need a new bike in the next 5 years, it made sense to get it now for half price. So if you are a taxpayer, I would just like to say: Thanks 🙂

But how can that be fair?: The aim is to encourage people to cycle more and in particular to cycle to work, and I think there are probably are marginal cases where it does achieve its aim. But personally, I would have cycled to work anyway. So the government is paying me to do something I would have done anyway. IMHO the money would be better spent on cycle paths which would encourage me to use the bike for more journeys than I currently do. Similar issues occur whenever any activity is subsidised.

  • Why – with the noble aim of encouraging production of renewable electricity – should people with £10,000 to spare be subsidised to buy solar PV panels which will reduce their electricity bills and give them a guaranteed return on their investment. We all know that the most effective way to reduce national energy wastage would be to invest in  insulating homes.
  • Why – with the noble aim of encouraging production of renewable electricity – should wind energy providers be subsidised not just for the useful electricity they produce, but for electricity they produce which no-one can use. Here the government spending might have been better targeted to increasing the capacity of the national grid to capture and store wind energy surges from remote parts of the country. Unfair stories here and here.
  • Why – with the noble aim of encouraging agricultural production – do we pay billions of pounds to farmers, but let high tech businesses go bust for want of investment?
In each case, subsidies direct investment, and in each subsidies are very blunt instruments. The only rational reaction to this essentially random unfairness is to take advantage of the subsidies when they are available., and otherwise just do the best one can
What we should really be subsidising: After having just ordered my bike, I saw this:

A bike with a flywheel to capture energy lost on braking.

 a bike with a built-in flywheel. A switch allows the rider one of three choices:
  • to store energy in the flywheel (e.g. when freewheeling down hill or instead of braking);
  • to leave the flywheel to store energy (the normal state)
  • to extract energy from the flywheel (e.g. when starting or going uphill)
Now I haven’t worked out the energy economics of this in terms of extra weight and the amount of energy that can be stored. Neither have I worked out whether the gyroscopic effect would affect the steering. And the high speed rotating disc next to the riders knees looks lethal. But assuming that these issues can be resolved, then my guess is that for a number of urban cyclists, this would be a great idea. I wonder if they will be subsidised?

Hydroelectricity from Teddington Lock!

June 19, 2011
Osbaston Screw Turbine

Ham Hydro plan to install 4 larger versions of these 'Archimedes Screw' turbines at Teddington lock. (Picture copied from

I have just registered as a supporter of Ham Hydro’s attempts to build a power station in the weir at Teddington Lock. Having registered as a supporter, I thought I would find out about the scheme! OK. I know that’s the wrong way around, but sometimes things happen that way. But I have been really disappointed. Despite the fact that they are asking local people to buy shares in the scheme to the tune of £2.4M, they have published almost no information about the scheme!

Questions. As I have mentioned previously, our choices about energy require clear thinking and clear accounting both in terms of energy and money. So here, for example are some of the questions about this scheme to which I think Ham Hydro should already have published answers without having to be asked.

  1. How much electricity will this scheme generate each year?
  2. How will the amount generated vary between winter and summer?
  3. What happens if there is a drought?
  4. What happens if there is a flood?
  5. Why is this unusual form of electricity generation a sensible choice?
  6. Why would £10,000 spent on shares in this scheme be better for the environment than putting solar panels on your roof?
These are just the first few questions that occured to me, but Ham Hydro have chosen not to publish answers to any of these figures.
Answers Here are my guesses at some of the answers and why they are important from both an environmental and an economic viewpoint.
  1. After asking questions on the web site I have now been told that the scheme will conservatively generate 1.92 GWh of electricity per year – which corresponds to roughly around 220 kW or around 300 horsepower to give a motoring equivalent. If each unit (kWh) generated was worth £0.15 the scheme would have an income of £288,000 per year. This is just 12% of the total scheme cost.
  2. Teddington lock maintains an almost constant head between winter and summer, but the flow does change significantly. This pleasing web page tells me that the mean flow on the Thames at Kingston is 5.7 million cubic metres per day or 65 cubic metres per second. Applying the formula (mass of water per second x gravitational constant x height of drop) allows me to guess this corresponds to around 1200 kW possible generating power for a 2 metre head. But the scheme only draws 220 kW.  So if flow fell below 1/6th of mean flow then the  scheme might have to reduce generating capacity – the locks need water too! But it should be able to keep generating through a ‘normal’ summer.
  3. In times of drought I think the scheme would have to reduce generating output.
  4. In times of flood I don’t think the scheme could increase capacity to take advantage of the extra water, but the scheme would probably not be threatened physically.
  5. This web site claims that Archimedean Screws are fish friendly and suitable for low heads of water.
  6. My mate Nigel has just spent roughly £10k on solar panels for his roof and they seem to be generating around 3400 kWh per year. So if we all spent this money on solar panels then £2.4M would generate around 0.8 GWh per year. So this scheme appears to be about twice as efficient in its use of capital resources. But of course Solar PV is a much lower risk so that if only £1M was raised, the scheme would still be able to begin. [Figures updated on 20th June] Of course if we could somehow use the money to insulate people’s homes better and then get hold of some of the money these people saved then this would make the most sense of all!
Summary. I wish this enterprise all the best – but I can’t imagine the planet on which they live where they think people will cough up £2.4 million pounds without having any idea of what they are buying. This project offers big opportunities to raise consciousness of energy generation issues in schools and in the community. Ham Hydro’s current efforts are … well frankly pathetic, and they should get their act together or they will fail from a surfeit of goodwill and a lack of good planning and communication.

What’s happening to the Sun?

June 16, 2011
An Image of the Sun

An Image of the Sun taken by Peter Woolliams. Sunspots are just visible in the northern hemisphere. Click for larger image.

Fascinating news this week about a prediction that the Sun is about emit less light over the next 50 years than it has for previous 400 years. This is an amazing prediction because actually we know very little about the internal dynamics of the Sun. What we do know about – and have known about for hundreds of years – are sunspots. These are regions of the surface of the Sun which are slightly cooler than the rest of the surface and so appear slightly dark – you can see one or two such spots in the image at the head of the article. People who counted the sunspots noticed that the number of them visible on the Sun varied on an 11-year cycle – falling to zero or nearly zero in between highly variable maxima.

Early Sunspot Numbers

Sunspot numbers from 1600 to 2010. Notice the period from 1650 to 1700 with almost no sunspots. Click for larger image.

And observations of the Sun from satellites show that the output of light energy from Sun also changes very slightly in synch with the sunspot numbers.


Composite total solar irradiance - how the brightness of the Sun has changed over the last 35 years. Notice the 11 year cycle and that the last minimum was deeper than previous ones. Click to enlarge.

The recent minima in sunspot numbers included a year – 2010 – with almost no sunspots, and corresponded to a slight fall in solar output. Such a long sunspot-free period had not been seen since 1913. Sunspot numbers look to be recovering and heading towards a maximum which would be low, but within the previously experienced variability of sunspot numbers. The current news story is based around a prediction that the next cycle of sunspots will not be normal – that in fact we may now enter a period of many decades with no sunspots whatsoever. This is an amazing prediction and if correct would represent the first significant prediction ever made about the internal behaviour of the Sun.

A period of low sunspot numbers did occur from 1650 to 1700 – just as people began to count to sunspots. The period – known as the Maunder Minimum – lasted for around 50 years and corresponded to a period known in Western Europe as the little ice age.

Is the prediction correct? Well the prediction was made at a conference and not in a peer-reviewed journal so it may be that there is some flaw in the researchers arguments, but ultimately we just have to wait and see. Fortunately we are now in a position to study the Sun in some detail so if something unusual happens we should be able to track it.

Significantly, the prediction of a fall in sunspot numbers implies a fall in solar output, which in turn implies that the surface temperature of the Earth will cool. It looks like the coming decades will be just as interesting for climate research as the previous decades have been.

Rainy Sunday: Jacob’s Ladder

June 12, 2011

One of  the greatest work of English literature begins by recalling two children on a rainy Sunday afternoon

The Sun did not shine,
It was too wet to play,
So we sat in the house
All that cold cold wet day.

I sat there with Sally.
We sat there we two.
And I said, “How I wish
We had something to do!”

Too wet to go out.
Too cold to play ball.
So we sat in the house.
We did nothing at all.

If only they had had a 5000 V transformer to play with. They could have easily made a Jacob’s ladder device and had fun for hours. This is the device seen in the background of a thousand stereotypical depictions of mad scientists in which a spark rises between two electrodes, getting longer and longer until eventually it snaps back to the bottom and begins rising again. Making one of these in my loft today I really felt I was experiencing the present reality of past depictions of the future of mad science.

My very own Jacob's ladder.

My very own Jacob's ladder. This exposure shows several different sparks as the discharge climbed up the two electrodes. Click for larger version.

Awesome Water Rocket

June 12, 2011
Me and my gigantic water rocket in 2008

Me and my gigantic water rocket in 2008. Click for larger image

As we approach the summer solstice, minds at NPL turn inevitably towards the NPL Water Rocket Challenge. Sadly I have been too busy to prepare an entry this year, but I have consoled myself with the thought my gigantic 2008 entry has inspired a few people to ‘Think Big’.

NPL Water Rocket 2011

NPL Water Rocket 2011. The components circled in red are discussed in the text.Click for an even larger version!

And indeed last week I learned that  my colleague Richard Shaw has been working with our design and manufacturing gurus towards the construction of a truly awesome creation. And yes, I use the word awesome with its original connotation of inspiring fear. This device has 14 separate pressurised containers and a total pressurised volume of nearly 300 litres!

My rocket lacked rigidity because it was held together with Duck Tape – but the NPL team working on project Colossus have linked the bottles together with two rigid plates (shown circled in red on the picture above). But they had to make the plates very rigid, AND very light. I thought you might be interested to note that they solved this problem exactly as I described a week or so ago – using corrugated cardboard sandwiched between two sheets of thin carbon fibre.

Early tests indicate that it should make a good flight – but you will have to turn up on the day to see what actually happens. And by the way, I have heard whispers around the laboratory that we may also see one of the world’s smallest water rockets as well. Hope to see you on Wednesday.

  • You can find a guide to building water rockets here
  • And a software simulator for Windows, here,
Special thanks to the NPL team: Rob Roskilly, Mike Harrison, Richard Shaw and Michael Parfitt

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