Hitting the roof
Richard Courtney argues that solar power cannot replace conventional power because of its effect on the climate (Letters, 24 June). Clearly, solar collectors could only have an effect in their immediate vicinity. If we were to envisage solar collectors which were of the order of square kilornetres in size, his argument might have some validity, but this approach would in any case be uneconomic because of the cost of acquiring the land.
However, there is a huge acreage currently standing idle, which could be put to productive use 鈥� namely rooftops. Assume for the sake of argument that there are 10 million houses in the country with an average area of 50 square metres, that they are covered in solar panels of 20 per cent efficiency, and that mean solar radiation is 347 watts per square metre. Then the mean power produced would be 107 脳 50 脳 347 脳 0.2 watts, or about 35 gigawatts. This happens to be almost the same as Britain’s electricity production, averaged over the year.
Readers who have access to the World Wide Web may like to look at . This describes the Maine Solar House, which is designed to be heated and powered by the Sun as far as possible.
The real problems with this approach on a large scale would be the cost of investing in a new power generation infrastructure, and regular and irregular variations in output. But investment could be gradual, and largely funded by prudent private individuals and tax relief from a forward-looking government, and by building companies. Variations in production could be offset by the use of other renewable energy sources such as wind, wave, tidal, biomass, etc., and by storage using pumped hydroelectric, flywheels, electrolysed hydrogen, etc.
To return to the climate question. The mean solar radiation incident on Britain is (using Courtney’s figures) equal to 347 脳 106 脳 242 429 watts, or about 84 000 gigawatts. Britain’s mean rate of electricity production of about 36 gigawatts is a drop in the ocean by comparison. Any electricity generated from solar radiation would end up as heat anyway, so the only effect on climate would be that of shutting down our coal, gas and oil power stations and thereby eliminating major sources of CO2 and other undesirable emissions.
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Fortunately for Courtney, the first law of thermodynamics ensures that all the energy absorbed by his solar collectors pops up somewhere else.
The convection which prevents our houses and factories heating up unbearably will also prevent his collectors cooling down too much (why only to the temperature of the North Pole?). And who on Earth wants to live under a field of solar collectors?
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Courtney’s letter is full of egregious mistakes.
Ratcliffe has to be repaired and maintained. Over a year, it would be lucky to put out 75 per cent of its rated output. That brings output down to about 1450 megawatts. Another 8 per cent of this electricity is then lost on the way to consumers. Again that brings the amount down, this time to 1330 megawatts 鈥� 1.3 million kilowatts.
Regarding solar power, a photovoItaic system bought today could be expected to be at least 12 per cent efficient. An array of 20 square metres integrated into a south-facing roof, will thus produce about 240 watts or 0.24 kilowatts in our cloudy climate. However, if the lighting and appliances in this house are energy efficient they can all be powered by far less electricity than this.
In fact, solar cells could provide a significant amount of Britain’s electricity. They almost certainly will do in the long term, complemented by other renewable sources. Solar thermal collectors could also provide a significant amount of our heat, but that’s another story.
Courtney claims that the ground below solar energy collectors is rendered dark and uninhabitable. This is nonsense. They would never cover 100 per cent of the ground area and would never be concentrated into a single array occupying 5.59 square kilometres of land. If these collectors are sited on rooftops, which generally makes more sense in a densely populated and overcrowded country, the argument does not even arise.
If one carries his point to absurdity, and wishes to replace the output of Ratcliffe entirely by solar cells, then in the long term, siting 20-square-metre systems on the roofs of five million houses will more than do it, even assuming that their efficiency has not risen above 12 per cent. If they are mostly roof-mounted, they will occupy less land than Ratcliffe power station, let alone the area of the opencast coal mines which are needed to fuel it.
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Your issue of 24 June provided food for thought: Fred Pearce (“Breaking up is hard to do”) discussed the problem of disposing of oil platforms and the idea of leaving them in place as research facilities and no-fishing areas. Courtney (Letters) explained why land-based solar power cannot be sufficient to supply Britain’s needs.
Why not extend the lateral thinking and suspend solar collectors between oil platforms? And why not put windmills on the platforms? And what about wave energy?
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Taking the biscuit
“Fair shares for all” (17 June) used cakes to explore the mathematics of envy. There is another cake-related problem which opens up a completely new investigation, this time into the mathematics of guilt.
The problem is this: the vicar’s wife has invited five friends round for afternoon tea. She brings in a plate with biscuits on it, including four which are chocolate. All the guests love chocolate biscuits. The plate is offered to the first guest, who takes a chocolate biscuit. The same with the second and third. The fourth guest of course sees only a single chocolate biscuit on the plate and knows that if she takes it she is depriving the fifth guest of a chocolate biscuit. She feels guilty and so doesn’t take it.
The question is: should the other guests also have felt guilty and if so, how do you allocate the amount of guilt each guest should feel? Is the third guest more guilty than the first?
I would be fascinated to know if anyone has resolved this problem, since as a guilt-ridden biscuit-eater I encounter it regularly.
Prime position
C. Kennedy writes about the notice to those who want to stand on the toilet at the Isaac Newton Institute in Cambridge (Letters, 17 June). Perhaps she has forgotten that in the Third World most people use the toilet in a squatting position. Worldwide, this may be regarded as the norm.
As one of the minority who prefer to sit, I for one certainly do appreciate it if the seat is first lifted by those who wish to stand on the toilet.
Loud and clear
I note with interest the compromise plan for the ATOC acoustic ocean temperature measurements (This Week, 17 June). These are vital for the assessment of global warming, given the huge heat capacity of the sea.
It would help to dispel some common misunderstandings if the strength of the signal were better described. Many readers will be familiar with the sound pressure levels used for airborne noise, measured in dB(A). A noise limit of 90 dB(A) Leq (a time-averaged intensity) is used in factories. They may thus conclude that the “195-decibel booms” to which the article refers exceed this limit by 105 dB, a power ratio of over 30 billion. The poor whales!
The reality is very different. The 195 decibels quoted in the story is actually a source level. It describes the power of the source, not the intensity at the receiver.
Such an omnidirectional source in the sea is more simply described as a 263-watt projector. Whilst the sound intensity close to it will be large, it falls quickly as the sound spreads into larger volumes. This source power is minute compared with many other regular sources of noise, both artificial and natural.
It has proved very difficult for acoustic scientists to convey to the public and even other scientists the relative sizes of underwater noise sources. I hope you will provide reference levels for any future data quoted in decibels.
Compared with the ATOC bangs, for example, seismic air guns really boom, with a peak power of 330 kilowatts, repeated every few minutes all day long. Nevertheless, whales have been observed following seismic survey ships voluntarily.
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A loud bang is particularly disturbing to any animal if it is unexpected. The effect on marine life of the proposed 195-decibel booms could be both reduced and monitored by preceding them with lower-intensity warning signals.
If the main bangs are indeed harmful, then the animals may be able to limit their exposure (can whales shut their sonar receivers?), and are likely to give an observable conditioned response to the warning signal.
Reviewing power
Robert Mathews’s article about peer review concerned only those cases where powerful reviewers may unfairly criticise aspiring authors (“Storming the barricades”, 17 June). Let us consider the opposite case, where a paper by a powerful author is reviewed by someone who is knowledgeable but vulnerable.
Some time ago I was asked to review a paper by a senior scientist. I criticised it, not so much for its scientific content, but for excessive verbosity, convoluted grammar, and the inclusion of irrelevant material.
I know the author well enough to be sure he was extremely annoyed by these criticisms. He is politically powerful within the scientific establishment, and could do me great harm. If I were not assured of strict anonymity, I would simply refuse to review any papers written by him, or by others in a similar position. Let the editor find some other mug to stick his neck out.
But consider another aspect. If reviewing is not anonymous, what a wonderful opportunity it presents to the yes-men of this world to butter up the big names. This is equally true if reviewer anonymity is optional.
Please let us have strict anonymity for all reviewers. Anonymity for the authors would surely be preferable to disclosure of the reviewers.
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In the discussion of the relative merits of publication in journals and the wider access to papers distributed through electronic networks, the emphasis seems to be on the role of referees. However, most of the work in making papers acceptable for publication falls on the editors of the journals.
Very few papers are fit to be published in the form in which they are submitted. Even authors whose mother tongue is English have difficulty writing in simple, grammatically correct English. Papers by authors for whom English is not the mother tongue often require extensive modification or correction. Many submitted papers are repetitive, unnecessarily complex or irritatingly verbose. Economists, in particular, are fond of adding large numbers of footnotes or endnotes which break up any flow of meaning in the presentation. Only one author in five seems to be capable of ensuring that the citations within the paper match the list of references at the end.
Who will take on the task of editing the flood of papers submitted to a free-for-all electronic publishing system? Or must we resign ourselves to wading through a mass of poorly presented and unedited information in the hope of finding a nugget of pure gold?
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Most journal paper referees are conscientious and unprejudiced, and will resent the disparaging comments made by Robert Matthews.
However, many people will welcome the increased opportunities that the Internet will provide for the publication of incorrect, plagiarised, fraudulent or simply incompetent work. For example, in my own field of mathematics, relaxation of the need to provide accurate, verifiable proofs of theorems will undoubtedly increase output and productivity.
Seeing red
We would like to contribute a few comments that will add to the discussion of lunar rainbows (Letters, 29 April, 20 May and 24 June).
The brightness of the rainbow depends upon the brightness of the illuminating light source. The luminance of the Sun is approximately 1.0 脳 109 candelas per square metre for an elevation of about 30掳, whereas that of the Moon at the same elevation is about 4000 cd/m2.
Therefore, the lunar rainbow will be approximately 4 脳 10鈭�6 the brightness of the solar rainbow. This is close to the value of 1/450 000 quoted by Reginald Titt (20 May). The brightness of the solar rainbow depends upon the rain density, but if we assume that it is about that of the background cloudy sky, which is about 3000 cd/m2, the brightness of the lunar rainbow will be at best (a full Moon) about 0.01 cd/m2.
The ability to distinguish colour decreases with light level. We have investigated colour recognition under full moonlight and shown that for colours with a luminance of about 0.07 cd/m2, only reds and oranges could be recognised with a high degree of reliability. Greens, blues and purples had a very low recognition rate, hardly better than chance. This suggests that no colours would be recognisable at the expected lunar rainbow brightness of 0.01 cd/m2, but if they were, we would be more likely to see reds and oranges, but not blues and greens.
These results were supported by other colour vision investigations which show that at very low light levels, coloured lights are first seen as neutral or achromatic. Colour does not appear until the light level substantially increases, and as it does red is the first colour to appear.
Finally, the spectra of sunlight and moonlight are not the same, as indicated by Andrew Ward (20 May). Moonlight has a greater red/yellow content and thus has much less blue and green in its spectrum compared to the sunlight. This lack of the shorter wavelengths in lunar light would further decrease the ability to detect any greens or blues in the lunar rainbow.
In short, we doubt that the green or blue colours in a lunar rainbow could be seen under any conditions, but perhaps some people may be able to see the red and orange colours with a bright rainbow.
This correspondence is now closed 鈥� Ed
Fishy labels
Your coverage of the wagers involving Paul Ehrlich, Stephen Schneider and myself is mostly very accurate and unusually fair (This Week and Comment, 3 June). There are, however, two errors of fact that I think worth correcting.
You say that I “accept that the [ocean fish] catch will decrease”. Based on the evidence of the past, I think it likely that the ocean fish catch will continue to increase. But I feel no need to make a prediction because this quantity is not the relevant issue.
What is relevant is the total fish available for human consumption, and that includes fish farming.
You refer to me as a “right-wing economist”. This label, and the label “conservative”, are frequently applied to me despite the fact that I have explicitly written many times that I do not consider myself conservative and never have been involved in any way in right-wing political activities or organisations.
Furthermore, I do not understand why a right-left label is applied to me, but no such label is applied to Ehrlich and Schneider, who almost certainly have been involved in such activities.
Quarantine quandary
Of course 84 per cent of the British public backs quarantine (“Britain pussyfoots on pet passports”, 3 June). Brainwashed by posters of rabid animals foaming at the mouth and the possibility, however remote, of their beloved pet being exposed to the dreadful disease of rabies, of course they vote against abolition. Who can blame them?
What is not explained in your excellent article on rabies is that far from keeping rabies out of Britain, the present archaic regulations actually increase the chances of an outbreak.
Present regulations are immensely stressful to owners, especially elderly people whose sole companion is their pet. Wanting to return to Britain in their later years they face six months’ separation from their loved animal, worrying about how the pet will fare in a place of incarceration, where not even the RSPCA is able to inspect. The pet they get back after six months may be totally different in character. Many elderly owners simply do not have the necessary finance to fund quarantine.
So what do these desperate owners do? They look for and find illegal ways of getting their pets into Britain. In a recent BBC television programme in which I took part, an owner from the Costa del Sol told how easy it was for her to take her dog illegally into Britain.
There are many professional smugglers who will transport animals into Britain. One reputable dog magazine estimates that up to 10 000 animals a year enter illegally. Quarantine is a hopelessly outdated method of combating rabies. Introduced in the year that Queen Victoria died, it may have been the best system available then because potentially rabid dogs were imported from the Empire. Technology, especially medicine and veterinary science, has progressed by leaps and bounds since 1901. Should we not use that technology to combat a disease we all fear?
Many people are making good money out of quarantine. Perhaps here lies the real reason for keeping it.
Short-sighted diet
J. R. Scott (Letters, 10 June) protests against Jonathan Beard’s suggestion that close work can contribute to the development of myopia (This Week, 13 May), leans on genetic predisposition as the cause of myopia, aided by a growth spurt at puberty and a deficiency of protein in the diet.
Apparently, Scott is not familiar with Francis A. Young’s 1969 study of “The Transmission of Refractive Errors Within Eskimo Families” (American Journal of Optometry and Archives of the American Academy of Optometry, vol 46, p 676).
Young found “virtually no myopia among grandparents and parents” who had had, in most cases, no more than six years of ungraded schooling (and all whom had been through puberty). He found “approximately 58 per cent of the offspring 鈥� myopic”, the offspring having “had typical American-style schooling” which covers grades 1 to 12, with much close work. The youngsters were eating the typical Eskimo diet of caribou, whale and other mammal foods, ruling out the protein deficiency Scott felt was a factor.
I believe the high and significant correlations Young found between siblings allows for a possible genetic predisposition as Scott suggests, but that the almost zero myopia correlation between parent and child suggests that environmental factors are needed to make that genetic predisposition for myopia manifest itself as measurable myopia.
Other studies by Young, and by others, as well as the clinical experience of many optometrists, support the idea that judiciously selected convex lenses can have a slowing or braking effect on the development of myopia. There are other therapy methods used by many optometrists to improve visual efficiency which seem also to slow the development of myopia.
Intensely sceptical
I am always fairly sceptical of coverage of scientific topics in the popular media but tend to be more credulous when it comes to articles in New 杏吧原创. But do you really expect us to believe that a colour-blind Japanese professor (Feedback, 17 June) cannot distinguish the intensity variation between a bright red spot of light and the surroundings?