Absolutely my last post in this subject, as we do seem to be going around in circles....
The losses with be in warming the air, and assuming the vehicle has a metal chassis, in warming the chassis.
How Wireless EV Charging Works
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Absolutely my last post in this subject, as we do seem to be going around in circles....
The losses with be in warming the air, and assuming the vehicle has a metal chassis, in warming the chassis.
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I think I've been going 'in a straight line' (i.e. not having anything new/different to add), any 'circling' being down to others.
Are you serious?
I agree that's a potential issue, which is why I wrote ...
In practice, if such an approach were attempted, it would clearly be necessary for the vehicles to be constructed in such a manner as to prevent appreciable induced currents in the structure of the vehicle.
Yes, of course!
How would you tackle that issue, perhaps glueing the chassis together, and have a plastic body?
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Are you suggesting that an electromagnetic field can induce significant currents into air, and that large amounts of power can thereby be dissipated in that air?
I don't think I'd bother, since, as I keep saying, I don't see it as an effective (practical, sensible) way of transferring electrical energy to a car, even if it is an 'efficient' method.
However in other contexts there are, of course, recognised ways of reducing/eliminating induced/eddy currents, even if the objects are metallic.
No, of course not, that would be silly - think about waste heat, from the transformation process..
Quite so.
That will be true with any 'transformation process' and will be roughly proportion to the amount of energy successfully delivered to the desired load. If (due to a very 'ineffective' process,) very little energy gets transferred to the load, then the corresponding thermal loss from the 'source' part of the process will also be very small.
To repeat your phrase, "think about it" ... if, rather than being the 'source for attempted inductive transfer, the coil was the primary of a conventional transformer, the secondary of which was hard-wired to the EV, then the situation would be essentially the same - heat loss from that transformer would be roughly proportional to the amount of energy being successfully transferred to the EV. If one somehow inserted some sort of 'current limitation' into that hard-wired connection, dramatically reducing the rate at which energy could be transferred (hence mimicking the 'inductive coupling' situation), then the heat loss from the transformer would again be very low.
That generation and loss of heat from the 'transformer' (or whatever) will, indeed, be a cause of efficiency being less than 100%, but I do not see why it should be markedly different (for the same rate of energy transfer) with inductive or hard-wired 'coupling'.
"There is now evidence from 20mph implementation within the UK which
finds a statistically significant reduction in casualties compared to background levels.
Importantly, such findings triangulate with the evidence on speed reduction and
collision reduction. The fact that for each average 1mph speed reduction in an urban
area there is a 6% reduction in collisions fits well with the findings from the UK
studies reported here.
.
.
For casualty reduction the evidence is consistent that casualties are reduced
as a result of 20mph speed limits. The evidence is moderate to strong."
And insurers, who tend to be statistics-based and pretty risk averse are starting to reduce premiums for drivers who live in or near 20mph areas.
Why the 20mph limit is reducing your car insurance premium
A car insurance company has said that there is clear evidence that the policy is working
www.walesonline.co.uk
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Do you know where that 'evidence' can be found, and exactly what it relates to?
There are an increasing number of 20 mph limits around my area, but nearly all of them in small villages which when the limit was 30 mph, had roughly zero collisions, and even closer to zero the number of collisions which resulted in serious injury or death (which events invariably get reported in local newspapers in these rural areas). There would therefore seem to have been very little scope for "statistically significant reductions".
Of course for a reduction to be 'statistically significant' says nothing about the magnitude or 'meaningfulness' of the reduction (as issue we've often seen with "Pill Scares") and, in any event (again seen in "Pill Scares") a large (percentage) increase or reduction in risk may be of no practical relevance if the risk is tiny - we've had reports of "Pills" which 'double the risk' of something, but when what it is doubles a risk (i.e. a 100% increase) of, say "1 in 5 million women-years", it's probably not something to lose a lot of sleep over
That's a bit confusing. Does it imply that some of the data is not "UK data", or what?
Again, it would be interesting to see that 'evidence'. Per the above, in relation to the many villages around me which have fairly recently implemented 20 mph limits, I recall very very few reports of significant casualties during the pasth 35 or so years- so, as above, not much to 'reduce'.
One certainly has to take the behaviour of insurers very seriously, for the reasons you mention. However, I'm pretty surprised since, even if one lives in/near a 20 mph area, I doubt that driving on 20 mph roads constitutes much of a proportion of the driving they do. It would be interesting to know the nature of the claims upon which one assumes the behaviour of insurers is based.
Kind Regards, John
I've got an idea - let's reduce speed limits to zero, then there will be no road accidents (maybe).
I've already made that observation.
As an alternative, I recently heard it said on TV (without seeing the evidence) that a high proportion of fatalities and serious injuries on the roads involve HGVs in one way or another (including injury/death of the HGV drivers, who are apparently averse to wearing seat belts). So perhaps one could leave speed limits unchanged and simply "ban HGVs"?
That would be about as practical!So perhaps one could leave speed limits unchanged and simply "ban HGVs"?
Exactly. As I've said, although it's not something that politicians etc. like to talk, or even think, about, in the final analysis it comes down to a decision as to what is an "acceptable number of deaths and serious injuries" to balance the obvious desire to have private motor vehicles and HGVs moving people and goods around.That would be about as practical!
It's just 'swings and roundabouts', but people get uncomfortable or 'squeamish' when one of them is human lives or suffering.
Agreed. I believe on speed awareness courses they tell you a lower speed is safer than a higher one, KE proportional to V^2 and all that, but that logic applies all the way down to zero speed, and as you say, in real life there has to be a compromise.
Last time I was done for speeding was about 16 years ago, and there was no way I was going to sit through that, I took the 3 points!
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