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Technology / Is renewable energy good for the environment?

« on: 06/07/2019 14:25:05 »

Wind turbines convert at best about 70% of incident wind power to mechanical power, though this is only over a narrow range of wind speeds. 50% over all conditoins is a sensible figure. About 90%  of this is converted to electrical energy, with 5 - 10% further losses in distribution transmission and maintenance ( not just ohmic and transformer losses, but including routine helicopter inspection of power lines and the replacement of pylons, switchgear etc.) to the consumer. 0.5 x 0.9 x 0.95 =  42.75% overall efficiency. Where does the rest go? As heat.

Solar panels probably convert 20% of incident radiation to electricity. In doing so they occupy land that would otherwise be used for crops (which absorb carbon dioxide) and distort drainage by forming an impermeable sheet over the soil. About half of the remaining 80% is reflected as longwave infrared, contrtibuting to atmospheric warming by radiation, and the remainder is removed by convection, heating the lower atmosphere (I regularly fly over a solar farm on the approach to my local airfield - what a ride!). Allowing 5% transmission losses once again, we have a system that generates four times as much heat as electricity!

Now put that electricity into an electric car. You can recover about 90% of the input energy from a new battery,  and maybe transfer 90% of that to the wheels, but by the time the battery needs replacement (and never mind the energy cost of making a new battery) it is down to 50% recoverable capacity. Say over the life of the car, a total of 60% of input energy is useful, 40% wasted as....heat!

Whatever the merits of renewable energy, it adds a heck of a lot to global warming!

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That CAN'T be true! / Healthy Eating or Dodgy Science?

« on: 10/02/2019 17:27:47 »

Just copied this from an apparently authoritative on-line source

Gouda cheese has 819 mg of sodium per gram, and American cheese has 1,671 mg of sodium per gram. That’s a lot! Next time, make sure to cut down on the amount. It’s not bad if you cut it out completely, but this would be a sad day indeed.

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General Science / Why is the atmosphere transparent to CO2 lasers?

« on: 30/09/2018 16:22:11 »

The object of laser weapons is to deliver a huge amount of energy in a short pulse, to cause failure by adiabatic heating of the target. Most work has been done with carbon dioxide lasers because they are easy to make up to very large sizes, and considerably more efficient than most other solid or gas lasers. Nobody seems to have told the military that atmospheric carbon dioxide has a strong enough infrared absorption to destroy the earth's climate, and they just go on merrily shooting down drone targets, oblivious to the facts of global warming enthusiasts, which clearly prove that they can't work.

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That CAN'T be true! / Do 40% of driving accidents really happen at night?

« on: 01/03/2018 11:12:16 »

An advert for yellow spectacles just appeared amongst the good stuff on this forum, with the shock horror headline "40% of driving accidents happen at night!" So obviously I won't buy the specs or drive during daytime.

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Plant Sciences, Zoology & Evolution / Do dogs think like us?

« on: 24/11/2017 23:49:23 »

Dogs come in a huge range of sizes, shapes and colours, but we assign them all to one species. Selective breeding has produced breeds that hardly resemble wild dogs or wolves - indeed  many that would probably not survive without human assistance.

Cats, foxes, badgers, and many other medium-sized quadrupeds, are based on the same general form as dogs.

If you take your young mutt to a dog park where he can run free with others, it's pretty clear that he recognises everything from a chihuahua to great dane, whippet to St Bernard, as a dog, and at such long range that it can only be by sight. But unless he has read the Kennel Club breed standards book, he won't have seen many quadrupeds apart from his parents and siblings, and there's not a lot of morphological difference between, say, a miniature pomeranian and a fluffy cat. But somehow Rover classifies them all as canis familiaris, just as we do.

How? Why?

6

Physiology & Medicine / How to survive in the desert?

« on: 24/08/2017 18:02:43 »

Due to a minor navigational error, ace pilot Alan has run out of fuel in the Sahara instead of landing in Dublin (180°, 280° - anyone can make a mistake). Fortunately he has some water and has finally worked out how to locate himself with the GPS.

What is his best strategy for survival if he is (a) 20 (b) 100 (c) 300 miles from the nearest town and has (i) 5 liters (ii) 20 liters or (iii) 100 liters of water?

You may assume that he is, of course, athletically fit and has a reasonable number of Mars bars or non-melting equivalent, or that he is prepared to eat his dead passenger. 

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The Environment / Is global warming essential for the continuation of terrestrial life?

« on: 08/06/2017 13:05:01 »

We have great ice core records of global temperature and CO2 concentration, going back over a million years. Lots of peole argue over their interpretation, but what about their existence?

The fact that we have a sample of snow that fell a million years ago means that it didn't evaporate. And the fact that it is umpteen meters below the surface means that neither did the subsequent snowfalls.  In other words, Antarctica is - or at least has been for the last million years -  an unlimited sink for water. For as long as the ice caps have been accruing, there has been a net transfer to the polar regions: some layers are thinner than others but AFAIK there are no actual gaps - accretion is continuous and inexorable. So eventually, all the water in the atmosphere will be frozen at the poles, gradually replaced by evaporation from the oceans and then frozen, until the planet consists of two ice caps with no water liquid or gas anywhere else - a bit like Mars?

Fortunately the planet seems to go through occasional warming cycles, and since life depends on the availability of water, global warming appears to be essential to the maintenance of life.

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Technology / All-electric transport for the UK?

« on: 08/06/2017 00:25:09 »

Attracted by the latest Tesla X in a showroom, I wondered what would happen if the idea caught on and everyone  used electric transport? So I did some calculations...

There are about 30,000,000 cars in the UK. Average use is say 2 hours per day, so divide by 12 and multiply by, say, 20 kilowatts per car, and we are using about 50 GW  of power for personal transport.

There are about 5,000,000 trucks, vans and buses. Average use say 10 hours per day at 50 kW means we are using a bit over 100 GW  for shifting goods and passengers.

So in order to keep moving, we need to supply 150 GW of electricity (assuming 100% battery efficiency).

The present generating capacity available to the national grid is 55 GW, of which 70% is already committed in winter.

"Who Killed the Electric Car"  is an excellent DVD which points the finger of conspiracy at the oil industry,  General Motors, and the vehicle component manufacturers and service organisations for suppressing the very successful GM "EV", but I think there may be an even bigger elephant in the room - the sheer impossibility of generating enough electricity (from what?)  and distributing it, if the idea of electric road transport really catches on..

9

Technology / Can you email me a sandwich?

« on: 12/05/2017 21:55:15 »

Cool, please email me a sandwich.

Happy to help. Since I gave up pointless commuting and started working from home, I've occasionally ordered lunch by email from a local sandwich van, pizza shop or curry kitchen. Vastly more efficient for all concerned (especially if I'm holding a 3-way Skype conference with a manufacturer in Germany and a technician in Scotland) and far less polluting.   

10

The Environment / Is sea level rising, or land sinking?

« on: 20/04/2017 23:29:45 »

I heard a radio program last night on how rising sea levels due to global warming had drowned significant areas of he Solomon Islands. Shock, horror, doom, loss of traditional and indigenous etcetera. No figures were given but there was a strong implication that the mean sea level had risen at least 60 cm in 50 years.

Now AFAIK all the oceans are connected, and water flows. So if the South Pacific has risen by two feet in a lifetime, so has the Mediterranean (much easier to measure as it is almost tideless). Has it? I think not.

There was just one tiny hint of a flaw in the strongly implied Global Warming is Killing Everything hypothesis. The reporter  mentioned that the Solomons are volcanic islands. Yep, right on the Pacific ridge. Here today and gone (geologically speaking) tomorrow.   

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Geology, Palaeontology & Archaeology / What was the atmospheric composition in the carboniferous [period?

« on: 30/11/2016 17:10:57 »

There is a useful quantity of carbon buried in the ground in the form of coal, oil, gas and shale, and a whole lot more deposited as limestone and chalk carbonates.

All this carbon must have come out of the atmosphere.

Now the amount contributed by volcanic activity is pretty small: if it were significant, we'd find loads of volcanic dust particles (silicates, aluminates, ferric compounds....) in among the coal and chalk, but we don't. So there is no obvious source of continuous replenishment of carbon dioxide. Therefore all the carbon in fossil fuel, chalk etc must have been in the atmosphere before the plants and animals appeared on the planet.

This makes a carbon-rich atmosphere seem a lot less apocalyptic than the climate change hyperbolists would like you to believe. Plant life and sea life will simply become more abundant.

12

Technology / Smart or superdumb?

« on: 14/11/2016 11:26:02 »

I just received this email from a company I deal with. They supply excellent space heating systems but I wonder if they have lost the plot?

It's time to make your Heating Smarter.

Here at XXXX we love to make things simple, and our partnership with YYYY means you can benefit from a host of automated, energy saving and cool ways to control your heating & appliances.

YYYY allows you to trigger your heating based on Weather Conditions, turn your lights on when you arrive home or even send a notification directly to your phone should the temperature in your home drop too low.

Connecting your XXXXStat to YYYY is simple and a great way to enhance the control of your heating.

Now every thermostat they (or anyone else) has ever sold me, includes a "frost protection" setting that just kicks in and overrides the timer if the temperature drops below, say, 5 deg C. No need for a phone call or any action on my part. That's what I call making life simpler. 

As for switching the lights on when I get home, have they not heard of PIR detectors? I've been using them for about 30 years to switch on the lights when anyone approaches the house or walks into an office, toilet or stairway. Amazingly reliable, and again what could be simpler?

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Just Chat! / Weird statistics?

« on: 24/05/2016 20:21:21 »

Our beloved Home Secretary today complained that the Fire Brigade was 95% white and 98% male.

Since 90% of the UK population is white, and those of Asian descent tend to go into more academic professions, the first statistic is hardly surprising.

There being only a limited number of seats on a fire engine, and emergencies tending to happen at family-unfriendly hours, I would have thought anyone recruiting firefighters would look for above-average strength and a willingness to work night shifts, school holidays, etc. So the second statistic doesn't surprise me either.

Is it me, or is Teresa May unfit for purpose?

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Physics, Astronomy & Cosmology / Can we put an end to the nonsense of "duality"?

« on: 10/11/2015 09:28:43 »

Consider a visible photon, emitted from a single event. Its energy is about 2 eV.

Now consider a wave spreading out from a point source. The energy density at any point a distance r from the source must be E/4πr² eV/m² where E is the original energy of the source event.

Now we detect our photon, a light year away from the star that emitted it. Ignoring a bit of red or blue shift, the detection event releases 2 eV. So if "wave function collapse" has any real meaning, all the energy that was dissipated over an area of 4π (light years)² has instantaneously and simultaneously condensed on my detector. This means that some energy has travelled 2 light years in no time at all, and arrived in the right place, with no prior warning or loss.

So let's pretend that relativity is wrong and there is no upper limit to the speed at which information can travel. We still have an anomaly because some of the energy travelled only a very small distance, some travelled 2 light years, and yet it all arrived at the same time. How did it know how fast to travel, let alone where to go?   

The simple fact is that "duality" is completely illogical. The world behaves as it does and we have to choose an appropriate model to predict it, but the model is not the reality, any more than you can grow potatoes on a map of Ireland.

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General Science / Is "organic" food safe to eat?

« on: 12/08/2015 19:43:45 »

I've never eaten truly inorganic food (though NASA's freeze-dried astronaut ice cream comes pretty close), but supermarkets put a premium on stuff they call "organic". I understand that the vegetables so labelled, are grown in soil fertilised with animal (including human) faeces (the human stuff is marketed as "Thamesgro" and suchlike, by sewage companies) rather than clean Haber-Bosch fixed nitrogen.

Now I like to eat raw vegetables, particularly carrots and mushrooms. But I know that a lot of animal faeces contains human parasites and pathogens such as pork tapeworm, salmonella, toxocaria, and probably the viral or prion agent responsible for CJD. I'm fairly certain that most of these can be eradicated by prolonged boiling, but are "organic" vegetables really safe to eat raw or stir-fried?

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Physics, Astronomy & Cosmology / Can a torsion balance be used to measure the speed of gravity?

« on: 26/03/2015 18:08:01 »

Here's a thought experiment.

Imagine two small test masses suspended on a torsion wire, inside an evacuated tube - the classic "G meter". Now instead of two large masses, have a wheel carrying several large "driving" masses around the circumference,  separated by a distance equal to the diameter of a driving mass.

If you spin the wheel around the G meter,the torsion wire will twist under the gravitational drag force.  Spin the wheel faster and it will deflect further...until the time taken for gravity to transfer from the wheel to the test mass equals the transit time of one driving mass, at which point the torsion wire won't twist any further.

Enough theoretical physics. Would any experimental physicists and engineers out there care to put some numbers to the project?
   

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Just Chat! / Neat straplines

« on: 12/06/2014 22:53:45 »

Just came across this delightful sign-off line in an aviation chat room:

"Are old aeroplanes safe? That's how they get old."

Any more bons mots out there worth repeating?