Professional Engineering

Heath Reidy’s article on Nasa's research into supersonic travel (29th Oct) quite rightly referenced Concorde, as the major standing success in this field. I was dismayed to see the fantastic achievement that is/ was Concorde downplayed through the authors comments "Concorde didn't have the most successful operation during its almost 30 year lifespan.....". There is something of the tabloid about the need to downplay one achievement in order to help another stand out.

Concorde is widely regarding as having an impeccable record until the Paris incident, and while it was indeed noisy and thirsty, this was the nature of the specification and not some unfortunate flaw. The high power Olympus engines were required to propel a vehicle of that size at that speed, without them Concorde would have still been stylish, but not the remarkable achievement it was.

Naturally technology has moved on and so has the general requirement for environmental compatibility, so let Nasa's project (if and when it bears fruit) be judged against Concorde in the context of the design criteria and technologies of the time (a 60s Mini Cooper S may look rather outmatched against an Mitsubishi Evo but the Cooper won the Monte Carlo in its time!), after all its a long way from a research programme to a 30 year proven history.

Neil Hastilow
Bristol

The hydrogen economy & realism of energy

“Going public” (PE 29.10.08) delves into the cost and complications of storing and distributing hydrogen as fuel, which has either to be done in liquid form and extremely low temperature or at extremely high pressure. Yet the inset on the University of Glamorgan research centre once again confirms that the production of hydrogen requires more energy than the hydrogen produced can provide.

It would therefore make more sense to feed the electricity produced by solar energy and wind power in the Glamorgan research centre into the national grid, rather than using it for hydrogen production, thus reducing the amount of fossil fuels used in stations.

What is really the rational of hydrogen powered cars? Until such times, if ever, abundant electricity can be produced by solar, wind, tidal or geothermal power the only real benefit of using hydrogen as a road vehicle fuel can be the reduction of atmospheric pollution in cities such as Athens and Los Angeles.

I suspect that the real reasons for car manufacturers’ interest in hydrogen powered cars is to reduce their average CO2 emissions to meet the ever lower targets dreamed up by EU bureaucrats, which in turn are based on unrealistic laboratory test cycles, and the aversion of Americans have to fuel efficient Diesel engine cars.

As for the suggestion that open ended pressure vessels could be sunk into deep water and closed off there to provide air under pressure when raised to drive a turbine (Letters, PE 29.10.08) the writer seems to be oblivious to the fact that the pressure energy acquired by the air has been produced by the loss of potential energy of the pressure vessel, which then has to be restored when this vessel is raised again. Thus, to the hydrodynamic losses mentioned by the writer and the dissipation of kinetic energy, there would be an overall energy input in such a system.

Herbert Stern

Wembley, Middlesex

I read with interest your recent report (PE 12 November) on the Carbon Trust Offshore Wind Accelerator (OWA) initiative since my company, Xanthus Energy Ltd, already has products that can reduce the cost of offshore wind farms by more than their target of 10%.

I agree in general with Mike Hay’s comments about the need for improvements in offshore wind turbine foundations. We have also investigated where the major costs are incurred and where engineering solutions could be improved. However, in our view, the foundation systems that have been brought over from oil and gas industry to date appear to miss the mark since they are based on high value one-off products, are not suited to mass production and have a cost basis from the oil industry, not offshore wind farms. Also they do not appear to be optimised for use in the highly fatigue loaded environment in which offshore wind turbines operate.

In sharp contrast, we have developed low cost optimum solutions for marginal oil fields, and from this expertise we have developed and patented offshore wind turbine foundation systems for shallow and deeper waters. A key requirement we identified was to reduce both the costs and risks of offshore operations. Our foundation products are designed for mass production, and are fully assembled with the wind turbine and commissioned onshore. This removes the huge cost for heavy lift vessels which currently runs at around £75,000 / day. With further savings in the design, installation and operational costs, we expect the use of our products will reduce costs by between 15 and 30%.

A final comment: our British technology is ready and proven and would create UK jobs. I am rather concerned The Carbon Trust OWA initiative comes too late to meet the needs of current and future offshore wind farms.

Dr Lewis Lack
Newark, Nottinghamshire


We did not need a think tank to forecast “Production peak will send oil prices soaring...” (News, PE 12 November). In 1979, Sir Alan Cottrell FRS, former chief government scientist, retired as master of Jesus College, Cambridge, wrote in the Financial Times that as oil depleted it would cease to be a high-price commodity and become a high-value commodity, with consequent economical results.

Then, as now with power, we failed to respond adequately until panic ensues and the government runs around like headless chickens, feathers flying, cackling loudly about global warming.

Bob Barnes
Winchester, Hampsire

In Sound Bites (PE 12 November) Andy O’Rourke blamed overpopulation for global warming and a whole host of other problems, this seems to be a recurring theme, but addressing overpopulation is probably much harder than addressing the problems it allegedly causes directly.  The present world population is 6.7 billion and it is likely to rise to 9 billion by 2050.  Short of a massive natural catastrophe or genocide on an unimaginable scale, I can’t see any way of reducing the population.

In fact, it’s probably incorrect to blame overpopulation for global warming and most other environmental problems.  The scientific consensus is that global warming is caused by burning fossil fuels, the developed world accounted for more than 40% of the world fossil fuel consumption in 2007, with only 15% of the population.  China and India, the countries with the largest populations accounted for about 20% of consumption with 37% of the population.  Most of the other environmental problems are caused by over consumption of food (e.g. over fishing and rain forest destruction for cattle ranching) and mineral resources by the developed world.

In the same issue of PE, Herbert Evans questioned the science behind the global warming debate.  I believe Herbert has misinterpreted the basis of the science.  My understanding is that global warming has nothing to do with the heat capacity of atmospheric gases, but is the result of certain gases absorbing infra red energy reflected back into space from the surface, the original energy from the sun in the form of visible light is not absorbed, so the net effect is a small temperature increase of the atmosphere due to the transfer of trapped energy from the greenhouse gases to the other atmospheric gases.  This has resulted in the Earth’s average temperature being 287 K, rather than its black body temperature of 255 K.

The effect isn’t a modern, abstract concept, it was originally discovered in 1824 by Joseph Fourier and is the mechanism that has caused the temperatures of several solar system planets (notably Venus) to rise to very high levels.  If Herbert would like to understand the science, I suggest he visits http://en.wikipedia.org/wiki/Greenhouse_effect where he will find a more detailed, and probably clearer, explanation.

Robin Trow

Maidstone, Kent

Dear "Name and address supplied"

In answer to your question "am I missing something obvious?", I'm afraid you are. To bring up energy from the deep you will require change in the Volume times Pressure product. The compressibility of water is too small to be worth it. Even if it were, since the pressurized water is more dense than the surrounding water everywhere except at the bottom, it would take as much energy to transport it to the surface as you would be able to extract from it when it got there.

Not knowing anything else about you I will refrain from saying anything more, except to encourage you to keep up the lateral thinking.

Peter Shepherd

Perth, Australia

How can one put this nicely? I'm sorry, but I think that William Brunger is talking nonsense to suggest that it is wrong that chartered engineers are not permitted to fix gas boilers or re-wire a house without appropriate registration (Letters, 12 November). We will not get the respect of others if we do not respect the practical know-how of the well-trained fitter or electrician.

Not long ago my daughter's gas fire went wrong so I called in at the local showroom and asked for a gas-fitter to pop round to fix it. "Ah, you want an engineer," said the assistant. I knew what she meant but said, "No way. I'm a fellow of two chartered engineering institutions and thus know that this needs a competent, properly registered gas-fitter who knows the wrinkles".

It has been my privilege in the past to manage tradespeople ranging from toolmakers, electricians, plumbers, carpenters and pattern makers through to builders. I had, I trust, respect for their skills and sought to earn their respect for mine.

For the record, I started out as an apprentice toolmaker at 15 a shade over 50 years ago. I knew that I might not be a good toolmaker but might make a good engineer and so went to college after my apprenticeship. This led to management so I secured an MBA and have had a well rewarded career prior to retiring. 

Finally, it is manifestly not true that engineers do not earn six figure salaries. 
Engineers in leading positions in our major companies are doing very nicely. If the IMechE gets the right person as chief executive their salary will be worth every penny.

Clive Bone

Bideford, Devon

The replies to the idea proposed for ‘Power from the Deep’ rightly pointed out the major disadvantages to the technique. However, in an attempt to be more positive towards ‘off-the-wall’ ideas, the reply from John Stubbs that mentioned ‘squashy water’ reminded me of an article I saw some time ago.
Some years ago while looking at novel refrigeration cycles I came across a certain ‘Malone’ heat engine cycle.
It was essentially a sort of Stirling cycle but instead of using gas it used liquid near its critical point. The liquid being alternatively heated and cooled to produce power via a piston/cylinder arrangement. A regenerator was used to increase the efficiency of the cycle which was said to be relatively high. The cycle inventor (J.F.J. Malone) had used a variety of liquids to achieve a working cycle including oils and mercury but the best all-round solution had been found to be water - though I have got to concede this is not exactly the ‘squashy water’ in the current debate.
Far from being just a theoretical study Malone had constructed a number of machines which worked successfully and which produced appreciable amounts of power.
Why do we see no Malone machines around at present – the answer is that it appears the work had been done in the 1920s and 30s and the great depression put his company out of business.
The article from ‘The Engineer’ dated July 24^th 1931 and authored by J.F.J. Malone is entitled ‘A New Prime Mover’ and it outlines in sufficient detail how a machine could be constructed together with several advantages of the Malone cycle over those available at the time.
The article concludes ‘A liquid engine locomotive would give the same power for half the coal consumption ….for marine purposes the engine can generate power 33% cheaper than the most efficient superheated steam engine’
Obviously these advantages may not still hold in the light of progress since the 1930s but for someone with sufficient interest and decent workshop facilities the cycle is certainly worth a serious look.
Could the Malone cycle be resurrected for niche applications, for example as an alternative to the Stirling engines currently proposed in small CHP applications?
Frederick Murphy
Frodsham, Cheshire

Whilst not wishing to help promote debate on the question of status yet again, I do think that William Brunger's comments regarding the fitness of qualified engineers to carry out work such as domestic electrical, or gas fitting, deserves support.

In a letter published in ''The Times'', I made the point that preventing someone from carrying out work for which they were amply qualified was a breach of any reasonable interpretation of the concept of ''human rights''.

Correspondence with my MP on the subject, brought an answer from someone in the government who clearly had only the vaguest idea of what being an engineer is. The professional institutions should pressurise the government to accept all their members as 'competent persons' within the meaning of this Act. Is any member of a professional institution really likely to exceed their capabilities in this area?

Ron Bullen
Chepstow, Monmouthshire

On a cruise holiday my cabin door was a poor fit in its frame. It had to be pushed quite hard and there were extensive rubbing marks on the frame edge. The door and frame were of robust metal construction. If the door jammed because of distortion caused by fire, explosion or collision damage, there was no secondary means of escape from the cabin.

I have written to a number of organizations, universities, government departments, maritime sites etc. seeking information as to who, or what body is responsible for the safety of ships; in particular, whether there are any design codes or design guidelines for cabin doors. On the Internet I can find regulations regarding life jackets, fire equipment, and fire drill and practice, but nothing about structural requirements for cabins and cabin doors. 

I would be interested to know whether other engineers with experience in ship design share my concerns.  In particular I would ask:

Has any consideration been given to, or a safety assessment made of, secondary escape means from cabins in the event of collision, fire or explosion causing distortion of the cabin door frame and consequent jamming of the door? 

Are there any records or reports of such occurrences in the maritime records?

A possible simple remedy in the design would be the inclusion of break-through panels between cabins or manhole-size kick-out panels in the cabin doors. Do any ships have such features?

Terry Bryant

Weaverham, Northwich Cheshire

Sir I am moved to write thanking you for the last 2 issues of the PE which were most interesting. Top of the list of reports for me was the Steam Loco magic and I long to be one of the first passengers.  Not far behind was the Archimedean Screw generation in Devon which surely could be applied to all our rivers and estuaries. Wind Power is only available when there is wind as one reader points out and although we generally accept that wind farms destroy beauty and habitat we forget that they will rot out and be difficult to dispose of at the end of their useful life. Also they will have blighted the best wind spots and may be difficult to replace.  So give me water power for we have plenty of water already and likely to get more with climate change.  A car that will travel at 1000MPH is good engineering but has limited payback and use benefitting one driver and small design team only.  That is why I find the loco report so good for with some alteration steam engines could work on wood to the benefit of the nation, particularly as trees are growing much faster with increasing rain water supply.  Perhaps we shall be back with steam cars before long when oil is dry. Bring back the old Trojan steam wagons!!

John Quallington

Shrewsbury, Shropshire

Name and address supplied (letters 29 October) suggests there is lots of energy stored in the high pressure waters of the deep ocean, but this is not the case. The writer seems to be making an (incorrect) analogy with the water behind a dam; the energy released in a hydro electric scheme comes from the reduction in the potential energy of the water behind the dam as the mean level drops, not the release of energy stored in high pressure water. Even if water from the deep could be brought to the surface in an infinitely rigid container (so it does no work on the surroundings during its ascent), the stored energy in water from (say) 1000m, where the pressure is 100 bar, is only about 22 kJ per m^3, since the bulk modulus of water is so high.

The cruise control correspondents seem to think that you should be able to drive a vehicle up a hill at the same mpg as on the flat. This is not a sensible objective, since the difference in potential energy of the vehicle has to be supplied by the engine, which entails burning additional fuel. If you drive up the hill slowly, you will have a small mpg increase for a long time, if you drive fast, you will have a larger difference for a shorter time. Either way, additional fuel is burnt and the only question is how to get the highest efficiency from the engine. The (few) efficiency vs rpm vs power maps I have seen suggest that internal combustion engines are most efficient at around 85% of full power and 2000 rpm (diesel) or 3000 rpm (petrol), so a gear-speed combination which achieves optimal rpm and 85% of full throttle would seem to be the best way up a hill. If the car accelerates so that rpm goes out of range, a few seconds at zero throttle would remedy. There is nothing wrong with hard acceleration, so long as the engine is near optimal rpm and the acceleration does not get you into a situation where intense braking is required.

Edward Jefferys

Berkhamsted, Hertfordshire

Harvesting pressure

Has your anonymous correspondent hit upon the germ of a workable idea? ('Power from the deep', Letters, PE October). I can see no fundamental flaw in such a system, nor am I aware of it being proposed in the past.

 His/her arrangement of an endless conveyor of pressure vessels that are closed off at depth to trap the ambient pressure, to be subsequently released at the surface to power a turbine, certainly has merit. However, I wonder if it might be better to use air, like in the form of a hydraulic accumulator. Relative to air, water is virtually incompressible, and air might prove to be more logical and manageable.

One could envisage that each pressure vessel in the chain, air-filled at the surface, would be vented to the sea (or lake) during the descent, the air being trapped at the top of the pressure vessels. Rough calculations show that at a depth of, say, 200m, the ambient pressure is approximately 20 bar and the air in the vessel at this pressure would be compressed to about 5% of its initial volume at the surface, ignoring temperature effects. There is no practical limit to the depth of such a system, other than the diminishing volume of air brought to the surface, albeit at a higher pressure.

Critics may point out that the chain of pressure vessels rising up would be heavier than those descending, requiring an excess of power to propel the system. This could be partially be overcome by having a second system, coupled in parallel, but geared to run in the opposite direction.    A further refinement could be to have a receiving pressure reservoir at the surface to balance out the peaks and troughs as the pressure in each vessel was discharged.

The overall economies of such a scheme would require extensive investigations and R & D trials, but certainly at a fraction of the cost of a Northern Rock bail-out.

Robert Wright

Redditch, Worcestershire

Your correspondent wants to extract the "energy" available in deep sea water (29 October). He should know that this energy is the product of the mean pressure during discharge and the change in volume of the water as it "expands". For all practical purposes, water is incompressible. The whole science of hydraulics depends on this.   Thus the change of volume of the water raised from the deep is to all intents and purposes, zero. Thus energy available E = P.dv  which is P x 0 = 0 whatever the pressure and whatever units you use.

This is never going to catch on as a renewable energy source !

John Ball

Weymouth, Dorset

Global warming

“Soundbites” has referred to the Royal Society investigating whether geo-engineering schemes could help reduce the impact of global warming.

The much more important question that should be examined is whether global warming should still be considered a problem and whether CO2 production has any significant effect on it. While many governments – including our own – act as though it is a problem, increasing amounts of evidence suggests that it may not be. These include last winter’s very heavy snowfalls on both North American and European mountains and that this autumn enough snow has already fallen for ski resorts to open 3 weeks earlier than in the past!

Some of the actions that have been or are being taken to “reduce” global warming will have very undesirable effects on this country. The one that I have particularly in mind is that an EU decision that will cause a number of our coal fired power stations to be shut down in about 5 years time – before they will be time expired. Since China has been installing many coal fired power stations for some years, these must be producing far more CO2 than our few so called “dirty” power stations and yet they have appeared to produce no noticeable sign of global warming.

Our Institution needs to look at ALL the facts that relate to global warming and not to ignore any that indicate that it may not be happening. They should also ask the Royal Society to re-examine this question.

Francis Otway

Stroud, Gloucestershire