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Technology / Are heat pumps viable in areas of high density housing?

« on: 22/06/2020 23:34:42 »

It is proposed that in the near future most houses will be built using ground source heating instead of gas heating. I am fully in favour of such schemes, but given that, according to one estimate, an average house requires 300 - 700 square metres of  land to accommodate the heat collecting pipes, in areas of high density housing (surely the largest sector) how can sufficient heat collecting pipes be accommodated. Given that an enormous quantity of heat would be extracted from the soil, what effect would the lowering of temperature have on the flora and forna in and on the soil? If the solution to these problems was to be the use of air source heat pumps,  would the effect on the outside temperature lead to similar problems, ie more severe frost when wind speed is low.

2

Technology / Is this a stunning breakthrough in petrol engine thermal efficiency?

« on: 23/09/2019 22:59:43 »

I refer to a magazine advert for the BMW 3 Series Plug-in Hybrid, in particular the quoted fuel consumption figures:-
Mpg(ltr/100Km) (weighted combined): 176.6 (1.6) to 201.8 (1.4). CO2 emissions (weighted) 36gm/Km.
Electric energy consumption (weighted combined) 15.4 - 14.8 KWh/100Km.
To make it easy I assume that 1ltr of petrol contains 10 KWh of energy

I don't know how these figures are arrived at, but on the face of it, 1.6 ltr/100Km = 16 KWh/100Km. If the "Electrical energy consumption" is 15.4 KWh/100Km, does this mean that the overall thermal efficiency is 15.4/16 = 96%?
What am I missing?

3

Technology / How do heat pumps perform in real life?

« on: 04/01/2019 23:41:35 »

I understand that heat pumps these days claim a co-efficient of performance in excess of 4. Can anyone confirm that these devices can actually achieve such performance in real life (as opposed to laboratory testing)?

4

Plant Sciences, Zoology & Evolution / Why do most humans have traces of Neanderthal DNA?

« on: 26/11/2018 23:55:23 »

It seems that human DNA (except native African) contains a small percentage of Neanderthal DNA, the suggestion being that humans mated with that species in our early history. Could this be attributable instead  to the presence of  Neanderthal DNA being the result of both species having the same ancestors?
 

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Technology / Is there any hope of effective action on climate change?

« on: 16/09/2018 13:48:49 »

 Is there any hope of effective action on climate change?

I quote from  an article in New Internationalist 515 September/October 2018:-

'The UN's International Civil Aviation Organisation has identified a new kind of low-carbon aviation fuel...."kerosene". Apparently the old fashioned jet fuel will now be classified as a climate-friendly "alternative fuel" so long as it's processed in a refinery powered by  renewable energy. This handy new definition of "clean oil" was agreed by the ICAO thanks to pressure from the US and Saudi Arabian delegations, according to the European Federation for Transport and Environment....'

The article goes on to criticise the ICAO's carbon offsetting scheme known as "CORSIA" and then continues;
 
'Airlines can also classify their flights as "lower carbon" by using biofuels - even though the majority of biofuels have been linked to (direct or indirect) deforestation, often making them even worse for the climate than burning fossil fuels. Despite these loopholes, the promise of making aviation growth "carbon neutral" frequently crops up as an excuse for airport expansion.....
The creation of climate - friendly fossil fuel is likely to be the final sputter of CORSIA's engine before it heads towards the ground: aviation isn't going to become low - carbon anytime soon....'

Any comments?

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The Environment / Is there any hope of effective action on climate change?

« on: 14/09/2018 23:41:40 »

Is there any hope of effective action on climate change?

I quote from  an article in New Internationalist 515 September/October 2018:-

'The UN's International Civil Aviation Organisation has identified a new kind of low-carbon aviation fuel...."kerosene". Apparently the old fashioned jet fuel will now be classified as a climate-friendly "alternative fuel" so long as it's processed in a refinery POWERED BY (my capitals) renewable energy. This handy new definition of "clean oil" was agreed by the ICAO thanks to pressure from the US and Saudi Arabian delegations, according to the European Federation for Transport and Environment....'

The article goes on to criticise the ICAO's carbon offsetting scheme known as "CORSIA" and then continues;
 
'Airlines can also classify their flights as "lower carbon" by using biofuels - even though the majority of biofuels have been linked to (direct or indirect) deforestation, often making them even worse for the climate than burning fossil fuels. Despite these loopholes, the promise of making aviation growth "carbon neutral" frequently crops up as an excuse for airport expansion.....
The creation of climate - friendly fossil fuel is likely to be the final sputter of CORSIA's engine before it heads towards the ground: aviation isn't going to become low - carbon anytime soon....'

7

Technology / Will a hybrid aircraft be more efficient?

« on: 08/03/2018 20:34:30 »

I notice that there are various projects in progress by aircraft manufacturers to build hybrid aircraft.
I refer not to heavier/lighter than air hybrids, but to conventional aircraft powered by petrol(or jetfuel)/electric power trains as in hybrid cars.

As far as I know, the advantage of petrol/electric car power trains is that the engine part can be run at it's optional load/speed conditions, ie., constant speed and near constant load, resulting in the high fuel efficiencies seen in series hybrids.
Also as far as I know, the condition in which an aircraft engine operates is not dissimilar in that the propeller pitch is varied to match requirements whilst the engine runs at a near constant speed, so why is the hybrid going to be much better?
Except of course that the battery in the hybrid can be charged whilst the aircraft is on the ground, allowing a lower fuel requirement during take of and climbing to cruising altitude.
• Or maybe these experiments are to evaluate the use of fully electric aircraft?
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General Science / Does pollution from leaded petrol persist in the environment?

« on: 13/11/2017 23:51:09 »

I recently read a couple of articles on Midgley, the inventor of leaded petrol in the early 20th century. Given that leaded petrol was still widely used until the late 20th century, is there any suggestion that increases in the number of brain disorders such as Alzheimer's, Parkinson's diseases, autism, etc., not to mention other disorders including terrorist mentality may be due to the effects of lead from petrol remaining in the environment?

9

Technology / dual circuit hydraulic brakes

« on: 12/12/2012 13:00:36 »

A friend, who does his own car maintenance, posed the following question:-
If dual circuit hydraulic brakes are supposed to allow one brake circuit to remain working ( i.e. the pedal to provide pressure in that circuit) in the event of loss of pressure in the other circuit, why does opening any bleed nipple in the dual system allow the pedal to travel to the floor ( implying that the circuit still closed has also lost pressure).?
I assume he is correct, and this is what happens.

10

Geek Speak / Why does an MP3/4 device not work on one computer only?

« on: 23/05/2011 00:18:51 »

Any ideas why a new MP3/4 player will not install on my computer (Windows XP) but will install on another computer.
On plugging in the computer, it briefly appears on "My Computer" but then is disconnected by the computer.
After uninstalling and re-installing it sometimes remains connected but is not recognised by Windows Media Player.
HELP!!!!

11

Physics, Astronomy & Cosmology / question on the Faraday Disc

« on: 01/07/2009 16:22:48 »

Consider the version of the Faraday Disc based on a disc magnet (disc with North pole on one face and South pole on the other). The conductive disc shares an axis with the magnet, and is in close proximity to one face (pole) of the magnet.
If the conducting disc rotates and the magnet remains stationary, a voltage appears between the rim of the conducting disc and its centre.
I find it strange that if the conducting disc and the magnet both rotate at the same speed, and in the same direction, the same voltage appears between the rim of the conducting disc and its centre.
I believe however that if the conducting disc remains stationary and the magnet rotates (about the original axis) no voltage appears on the conducting disc.
This seems to suggest that the magnetic field is independent of the magnet.
Can anybody explain?

12

Physics, Astronomy & Cosmology / How does the "Laser Interferometer Gravitational wave Observatory" (LIGO) work?

« on: 08/04/2009 13:09:31 »

As a complete idiot, I could do with some help:-

For some years now, the project known as “LIGO” has been in operation in the U.S.A.
This is Laser Interferometer Gravitational wave Observatory. In simple terms this consists of two tubes, a few centimetres in diameter and (I think) 4Kilometres long, arranged in an “L” shape. A laser beam is split into two, each traversing a tube from the corner to a mirror in the remote end many times, before reaching a phase detector at the corner.
The whole arrangement is set up so that each returning beam returns to the origin exactly in phase with it’s source.
The theory is that a passing gravitational wave (resulting from a distant supernova for instance) will alter the length of the tubes, thereby changing the transit path of the laser, with the result that the returning beam will be out of phase, this being detected as proof of the gravitational wave event.

I think there are three of these observatories in operation in different parts of the world.
As one with a poor understanding of relativity, my thoughts are as follows:-
I understand that gravity distorts space. This means to me that the gravitational wave changes the length of a tube by distorting the space which it occupies. If this is true, the distorting of space will result in the laser beam being red - or blue - shifted, with no change in it’s phase on return to the phase detector, i.e. nothing to be detected. I hope my description makes sense.
 
In simple terms, it seems similar to measuring the change in length of a steel bar under thermal expansion with a steel rule that suffers the same expansion. Perhaps someone could tell me where I am going wrong, or is this why no gravitational waves have yet been observed? 

13

Technology / What is the fuel consumption of a typical airliner?

« on: 22/08/2008 17:22:08 »

Can anybody tell me how much fuel an airliner (say 747,380, or others)uses during a flight from London to New York. My interest is from the point of view of climate change.
I believe that any solid body not supported by the ground or other structure, even in level flight, is actually accelerating continously at the rate of at least 9.81 m/sec., requiring a huge amount of fuel.

14

Technology / How does a toroidal magnet behave?

« on: 02/08/2008 17:38:44 »

I have a limited knowledge of magnetism, can someone help:-

Imagine a toroidal transformer having one of its windings energised by direct current to the point where its core became permanently magnetised (assume that the core material allowed this).

The magnetic field in the core would then resemble that around a current carrying conductor.

If placed in a magnetic field, would the core then experience the same force as does the current carrying conductor ie., a force at right angles to the direction of the magnetic field.

It seems to me that the answer cannot be yes, as this would imply a way round the rules that forbid the creation of energy.