Feedback: your letters

We start this year discussing a brainy pair; wind power is still creating a stink; we're in the dark about saving energy and students fighting bacterium, whatever next? Plus more.

All in the mind

The 'brains issue' of E&T (Vol 3 #5) estimates that there are 1015 synapses in the brain, but neglects to estimate the proportions of inhibitory synapses, memory synapses that increase weight with use and fixed-weight synapses.

In 1964, I proposed a differential memory synapse hypothesis with an equal number of excitatory and inhibitory synapses operating in pairs (Proceedings of The Royal Society Part B, Vol 159, p466-478). As an experimental model, I designed and constructed the 4,000 memory synapse simulator units in the Department of Anatomy at UCL (pictured above).

These were connected as differential pairs, one excitatory and one inhibitory. Each unit had a dial that showed the value of its weight that increased in proportion to the number of impulses received by the unit from a photo multiplier in a 10x10 matrix 'retina'.

The memory stored in each pair was proportional to the difference in their weights, initially zero and increasing with the strength of the memory. A simulated neural learning network was constructed with ten response units, each simulating a pyramidal cortical neuron and driven by 100 differential synapses from the 10x10 matrix of photo multipliers. Connectivity is thus simply each stimulus unit making two differential synapses to each response unit and this remains fixed throughout learning by weight changes.

Each response unit could be trained to respond maximally to a specific image projected onto the retina by inhibiting either the excitatory or inhibitory input of each differential synapse as it is 'gated' through intermediate simulated stellate-type neurons, depending on whether the response unit elicits a punishment or reward.

On 27 May 1969 the BBC televised a demonstration in which a 2,000 differential synapse simulator network learned to recognise ten faces for the programme 'Frontiers of Science - Mechanisms of Recognition'. The training required over 100 presentations of the faces over several hours, after which they were all correctly classified even if half of each face was covered.

The same network was trained to recognise a range of visual stimuli including print and handwriting. The only requirement seemed to be that there were sufficient differences between stimuli.

The existence of neurons that only respond to specific images, as proposed in my hypothesis, was confirmed in 2005 by Professor Quian Quiroga of Leicester University, in a paper published in Nature.

Ken Taylor MIET, Uckfield, East Sussex

Wind power's place in the UK

Bill Hyde's response (Letters, Vol 3 #20 ) to my letter about wind turbines standing idle confirms a suspicion I have held for some time that wind power generation is not all it is cracked up to be. While it may make some contribution by supplying a small percentage of the country's energy demand, the claim that it can replace a large chunk of thermal generation is just a big con.

All so-called renewable energy systems are either too erratic or too unreliable and the energy density of these systems is too low. To secure our future electrical energy demands, there is still no alternative to nuclear power generation.

Dr R Barnes CEng FIET, King's Lynn, Norfolk

What power generation would you use when the wind doesn't blow, Bill Hyde wants to know. As an old power system man, he must know the answer. You use the other plant that is available on the power system. It is the same as it is for any other power plant - we help each other out when the need arises.

For example, when Mr Hyde's letter was published, half of the 11GW of UK nuclear plant was shut down. What do you do when you lose 5.5GW of your nuclear base load? The answer is the same. You use the other plant on your power system.

It is a pleasing thought that there are already 3.2GW of wind turbines installed on the UK power system, which have been doing more than their fair share by making up as much as one-third of the shortfall.

EurIng Donald Swift-Hook CEng FIET, Woking, Surrey

In the short-lived interest in wind generation in about 1952, a number of experimental installations, including a few in the UK, came to grief, mainly by throwing off blades in underestimated peak winds. I lived in the country, without mains electricity, and tried to boost the output of a few hundred Watts from a 12V petrol generator and tank battery by improvising a pretty useless 12V wind generator. Yes, it threw a blade too.

Twenty years or so later, I was involved with a 250kW experimental turbine for the Orkneys and was surprised at the low figure the developers quoted for the maximum windspeed. I recalled the past history of the subject and mentioned the one machine of that era that had survived and they laughed it off, condemning its inefficiency. This was the English Electric De Havilland Enfield prototype, which had hollow blades with trailing edge slots that acted as a centrifugal suction fan drawing air up the central hollow support mast. An air turbine and generator sat on the floor at ground level.

It was never able to demonstrate its capability in the UK, since the only place local authorities would accept it was in a sheltered part of London. There was belief that it had been written off years ago. Not so - it was still generating happily in an oilfield in Algeria where it had done for many years. There is a moral there somewhere.

John Weaver CEng FIET, Stafford

Bill Hyde's load factor comparison takes a 'best case' example for nuclear and a 'worst case' example for wind. Sizewell B has a much higher load factor than many other nuclear plants and the worldwide average is less than 70 per cent with some power plants operating at below 25 per cent in a year (Torness in 1996, for example). The typical load factor for wind is over 30 per cent, but the important point is that it is much higher in winter when electricity demand is higher.

Wind energy is only a small part of the renewable portfolio, as the excellent E&T article on wave energy demonstrates. It is also useful to appreciate that many renewable technologies can complement each other; so, for instance, a solar installation installed in the same area as a wind installation will typically produce electricity when the wind installation is dormant and vice versa. When combined with properly designed grid energy storage and local backup supplies for critical users, the customer should experience minimal blackouts.

Andrew Kelly, By email

The variability of demand that is the Achilles heel of distributing power as electricity accounts for a further reduction in the contribution of wind turbines. Wind and other renewables could make a much greater contribution if we made more use of the gas network to provide storage.
We should electrolyse wind and other renewables to add up to 10 per cent hydrogen to our natural gas supply.

Instead of using the large amounts of gas we recover from landfill sites to generate electricity to feed into the national grid, we could feed it much more efficiently into the gas network.

These could and should be the first steps to change from central electricity generation to distributed generation by means of fuel cells at the consumer, leading eventually to a hydrogen economy where carbon is captured centrally, and the waste heat from generation is available free to the consumer.

Bill Powell CEng MIET, Atherstone, North Warwickshire

Energy saving

In trying to be reasonably green I try to switch off unnecessary appliances, but one thing in particular discourages me from powering down my PC during the day. The time taken to boot up and exit Windows is far too long. If this action could be virtually instantaneous there would be a lot more incentive to switch off between sessions.

Dave Coustick MIET, Bridge of Allan, Stirling

The Scottish Executive is funding infomercials to encourage domestic users to switch domestic electronics off, rather than leaving them on standby. The suggestion is that to do so would assist in reducing the receding polar icecaps and save up to 8 per cent of a domestic electricity bill.

Perhaps local government could assist in saving the planet by switching off street lights between midnight (or earlier in residential areas) and 6am.

Philip Hartley MIET CEng, Helensburgh

Forum misuse

I am a regular follower of the IET website forums and, when someone is stuck on a point, am happy to try to help point them in the right direction but (and it is a big but) some students are, it seems, posting their course questions and hoping that we will answer them.

This worries me. The object of any course is not just to get marks but to learn to do a job. These people, if we answer their course questions, will pass their courses but will they be safe engineers? There have always been students who copy from a fellow or who get a fellow to do their work. Now, however, with the Internet and forums such as ours, it is becoming an epidemic. It seems to range from National Certificate level up to degree level. I am happy to say that I have not seen this practice spread to the domestic installer course students.

It is not enough to say: "If you suspect that this is their practice, do not answer". Usually, when I have declined to reply, someone else does. We cannot expect the moderator to monitor the forum for this sort of abuse but maybe it is incumbent on a tutor from each college to read the forum and, if they see one of their students doing this sort of thing, take whatever action they deem appropriate.

Alan Gordon CEng MIEE, Shoreham-by-Sea, West Sussex

Bacterium's not so bad

Your report on the iGEM competition (Vol 3 #20) was very interesting in that it showed what undergraduates can achieve. However, I hope that the winning team from Slovenia have read widely in the medical journals as they press ahead with a vaccine to attack helicobacter pylori.

The overwhelming majority of people carrying this bacterium, which is most of us, have no problems and there is evidence that its absence is linked with cancer of the oesophagus, obesity and asthma in children. See, for example, the work of Blaser et al reported in the May 2008 issue of the Journal of the British Society of Gastroenterology, and an article in The Economist which predicted that "hunting it [heliobacter pylori] to extinction, however, may be a mistake".

Terence Boley FIET, Keston, Kent


What they're talking about on the Internet

A contributor to the transport discussion forum on the IET website asked: "Are double-decker trains impossible with the UK's current height limits? By making changes such as lowering the floor, is a double-decker vaguely practical?"

The Swiss have two versions of double-deck carriages, one with wide stairs and doors for use on suburban lines and a second with more restricted access for use on intercity services. Both were successful in increasing the number of seats available without having to extend platform lengths.

Double-decker trains are possible, but not practical. The doors would have to be at the present height to line up with platforms. Therefore, steps down to the lower deck and up to the upper deck would be required. The stairs would occupy a fair bit of space. Neither deck would have standing headroom. The biggest problem is that the space under the floor is not empty, but is crowded with batteries, air tanks, A/C equipment, water tanks, traction motors, diesel engines or transformers. Where else is this to be put?

Crowding could be reduced by longer trains. This may require platform alterations, but we need to return to full length trains. The rail industry has received a lot of money to replace full length trains with shorter ones. My local service suffered 'total route modernisation'. As a result the eight-car trains were replaced by six-car sliding door trains with consequent overcrowding.

Thinking laterally, staggering working hours would have the greatest impact. There is a huge problem in the south-east where most of the rolling stock is only needed for two hours a day. This makes the justification for investing in more/longer/taller/wider trains much harder.

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