There is an error in a post above about the number of poles in generators.

The required number of poles refers to the number of poles of magnetism in the rotating part of the alternator. To generate 50 Hz (cycles per second) we need 50 x 60 magnetic passes per minute which corresponds to 3000 RPM and 2 magnetic poles, one N and one S. If we want to rotate at 1500 RPM we need twice as many magnet passes so 4 poles. 6 poles gives 50 Hz at 1000 RPM etc.The confusion is that a 3 phase machine has the same number of poles but 3 sets of output windings, one every 60 degrees rather than 1 set every 180 degreess.. These are not poles they are windings!

@luciano, the ImechE link actually says

" One thing that is not going away is natural gas. We have plentiful supplies, driven by fracking expansion in the US in particular, and it is used across our energy system. That is going to make decarbonisation difficult, but does incentivise the development of hydrogen as a low-carbon alternative. "

I.e. that it's likely that a hydrogen economy is going to be important in the mid term. The decarbonisation of the atmosphere is a long long term project (natural removal rates are low, so the integrated effects of human activity are bad because of the mismatched timescales)

Those of you who are somewhat concerned about CO2 levels may care to watch this lecture on the thermodynamics of warming by gases. Very thought provoking. If you see any problems perhaps you would care to comment here? The maths used is not very complex, but the concepts in thermodynamics may be new to you.

https://principia-scientific.org/webcast-no-radiative-greenhouse-effect/

I haven't got 1 hour 10 mins to watch death-by-powerpoint!  Can't somebody do a potted summary?


The greenhouse gas effect of CO2 was first demonstrated in 1859 by John Tyndall.  And it's not exactly a difficult experiment to do.  It just needs two table lamps, two glass jars, two thermometers and a bottle of CO2.

If you can read faster than he can talk, you may prefer his  written publication, which is easier to follow  here 


He talks a lot of waffle, and correctly points out that the text book model of global warming is often illustrated using a flat earth, and therefore it must be wrong, as the earth at the top  of the atmosphere is larger than at the earth surface, and this must  throw the whole analysis off.  He neglects to  consider that the atmosphere is very thin compared to earth radius, and flat is not a bad approximation for that. He then adopts the flat model himself, and calculates the average illumination needed to get the earth to its current temperature, based on the earth being flat, non rotating, and facing the sun, and having a perfectly insulated backside so no cooling. Unsurprisingly he gets a silly answer, circa 25%  the sun brightness we really have.


The problem is that his method of analysis also suggests  that at night we should freeze to death, despite the obvious fact that this not happening ,and not happening mainly due to the atmosphere containing the heat in the very way he is trying to disprove happens.

Because the earth rotates, and therefore presents a sinusoidal varying capture area to the insolation flux, the effective average insolation is about 1/4  of that  seen by a body at 1AU from the sun that is perfectly normal to  it all the time. He then labours expressing surprise at this. All those of us who know about RMS know that cos^2 averages to 0.5, and illumination from one side only give you another factor of 2, and are not so shocked. He then tries to prove that the earth should be twice as far from the sun as it should be to get the (wrong) value of solar flux he predicts.

A moments thought shows that angle of presentation is important - that is why the poles are cooler than the equator, but not absolute zero  as his model would predict.


Yes flat earth diagrams can be a misleading over simplification. (None of the big climate models use them, though the power points for politicians do ... ) His analysis is also a different misleading over simplification.


The man is no doubt clever,  (Joseph Postema's PhD is astrophysics, mine is in solid state and opto-electronics, ) but here I believe he has the wrong end of the stick. However as he has quite a following on the alternative science fringe, I suspect many others who are not up to critically checking his sums are mistakenly reassured by his conclusions, without really thinking too deeply about them.

I presume he has never done the bottle of CO2 experiment at school, if he had he might have made a different argument.

There are indeed holes and sweeping assumptions in the current climate models, but this is not one of them.


Unfortunately it makes me question the quality of his work on the UV imagine telescope (UVIT) sensors, which look quite good.


Potted enough Simon ?

I think you have missed the thermodynamic points Mike, this is not about the illuminated area or intensity, the important bit is not the numbers but the analysis. Whilst I do not consider myself an expert thermodynamicist , he has some very good points about the heat transfer process. This stuff about 2 jars, one of nitrogen and one of CO2 does not actually work, it cannot because it is not measuring anything about the gasses. The suggested process of greenhouse gases is fundamentally flawed, that is the point in question.

An interesting report from Cambridge University on how to reach zero greenhouse gas emissions by 2050. No flying, no shipping.




The key points missing are actual resource requirements and costs. Otherwise it's a bit like an updated 'Without the Hot Air'

https://www.repository.cam.ac.uk/bitstream/handle/1810/299414/Absolute-Zero-digital-280120-v2.pdf?sequence=6&isAllowed=y


Is it feasible? Do we need to do it?


Best regards


Roger

Not feasible. There is too much food (and other goods) transported by shipping to phase all shipping out in 30 years. There have been emission free ships in the past (Cutty Sark for one) but to replace a large container ship today you would probably need somewhere in the region of 150 sailing clippers. If you look at how much of our food is imported then you will realise the problems that will arise. What do we do about the Channel Islands and the Isle of Man which do not have rail links? There are a lot of islands off Scotland which would be similarly affected.

Next, replacing cars/trains with electric alternatives is all very well but we don't have the carbon-free generation. The one line that is missing from the table seems to be power generation which needs to be addressed first, particularly when you consider how long it takes to build and commission a new Nuclear Power station. I know that there will be renewables, but what do you do on a windless night at slack tide.

There are other objections but I would suggest the intention is good, but not the timetable.