Fast E.V. Charging.

Tesla tried battery swapping stations, but nobody was really interested.  They would rather quick charge at a service station while they take a break, rather than driving to a battery swap station.


There's no compatibility between batteries - they are all different shapes and sizes to fit the vehicle.  Battery technology is advancing so fast that a battery from a 2 year-old car may not be compatible with the latest version of the same model.  The charge capacity just keeps going up with every model refresh.

The 1000 volt restriction is because in the uk and some other places, this is considered as the upper limit of "low voltage" Higher voltages are not specifically prohibited but would require a whole raft of additional safety precautions that would almost certainly render anything over 1000 volts not viable.

Use of a three phase supply for charging might not alleviate concerns regarding a broken CNE in a PME system. The so called earth, which is actually the neutral in disguise, will still be connected to a metallic vehicle and thereby exposed to touch.

For a large vehicle charging facility that has a dedicated transformer, it might be best to go back to TN-S.

For one or two EV chargers of modest capacity connected to an existing system it becomes more complex.

And that is sort of my point - there is nothing that changes sharply between 999V and 1500V in terms of lethality, but years ago the line was drawn in the sand  between LV and HV, at a nice round number to set a working limit that seemed high enough not to be a problem to normal loads.

I suggest that perhaps for higher powers, for charging lorries and so on,  that may well now become a decision worth revisiting.

I am well aware that for years various bits of equipment  have generated far higher voltages inside - the microwave oven for example at 4 or 5kV with a lot of ripple on the cathode of the magnatron, or the EHT on the old CRT tellies (at about 20kV, but current limited)

But for working on AC wiring, 1000V is the magic phase to phase voltage in IEC land. UL limits are a bit different, but similarly limiting.

All this worry about charging is not really the problem in my view. The whole idea of electric vehicles sounds good to those who think any combustion is bad, but is simply impractical and ridiculously expensive unless the whole basis of our economy becomes stone age. Examine the HGV problem above, in terms of supply. 250,000 Trucks at an average consumption of 100kW each. Supply required 25GW. So we need to increase the entire electrical infrastructure by 50% or so, and then there are cars and vans, perhaps another 25GW (25million units x 1kW average each), taking us to doubling everything. What have we achieved? We have moved the burning from the vehicle to the power station at immense cost! You say nuclear, wind or solar sources but how do we do that, these are already a serious problem in many ways at perhaps 15% average supply? It may be that gas is fairly "clean", but so was a coal station with flue treatment! It may be that gas is a bit more efficient but not spectacularly so. New build of 25 new nuclear plants of 2GW each is pretty much impossible in any reasonable timescale, doubling the grid the same, and the local distribution enormously expensive. It cannot be afforded without a tax on electric vehicles of perhaps 200%, and at that point the economics become clear to the proponents of this impossible scheme.


So the conclusion must be that the aspiration to electrify transport is impossible without a huge reduction in transport overall. It seems that electricity is thought to be "free" because it cannot be seen and is nearly non-polluting at point of use, but the whole system is not and cannot be. Society as we know it without virtually unlimited transport is basically pre-industrial revolution, and cannot support anything like our current population.


The problem is not the connector or cable at the charging point, it is the overall system design, which is fatally flawed although it seems that no one else has realised this! The fundamental misunderstanding behind the whole concept of electric transport is that CO2 is harmful to life. It is not, cannot be and in fact is the opposite! Do all these batteries, wind generators, solar panels, power stations etc. have no CO2 footprint? Of course not, it is just as big as the present system!

Dave,

I agree with some of what you say but there are definate benefits in moving the combustion away from certain areas such as inner cities and mountain passes. Some of the reductions can be made with rail and tramways but there will always be a need for transport away from the tracks. I do think that your doubling of the infrastructure is excessive. I did some calculations for Germany, looking at the amount of oil and petrol consumed and calculating the electrical equivalent. This ended up with around a 30% increase in electricity consumption. The calculations are here:
First step how much petrol and diesel is currently used?
From the IEA
www.iea.org/.../GermanyOSS.pdf
Germany petrol and diesel consumption 2010-2011.
Petrol 450 000 barrels per day
Diesel 1050 000 barrels per day
As a cross check on the total consumption:
world.bymap.org/OilConsumption.html
Total consumption petroleum consumption for Germany 2015
2 372 000 barrels per day
Next step what is the electrical energy equivalent of 1 barrel of Petrol/Diesel? From a couple of sources:
peakoil.com/.../how-much-energy-is-there-in-a-barrel-of-oil
1 barrel (crude) is 1,700 kilowatt hours 
letthesunwork.com/.../barrelofenergy.htm
A barrel of oil contains about six gigajoules of energy. That’s six billion joules or 1667 kilowatt-hours
If we take 1.7 MWh per barrel for petrol annual automotive energy input is:
Petrol 765 000 MWh per day= 765 GWh per day = 279 000 GWh = 279 TWh
Assuming an efficiency of 20% for a petrol vehicle the energy required for petrol automotive use in Germany is 55.8 TWh per year.
Taking an overall efficiency for an electric vehicle to be 80% (electricity transmission losses, battery charging efficiency) replacing the petrol vehicles with electric vehicles would require 70 TWh per year.
What proportion of the diesel is for automotive use against road or rail transport is not obvious. Suggesting a total of 100TWh for the annual automotive consumption seems reasonable.
If all the diesel consumers were replaced by electric vehicles the annual electricity consumption would increase by around 220 TWh per year
 Currently Germany produces around 600 TWh of electricity annually.
www.cleanenergywire.org/.../germanys-energy-consumption-and-power-mix-charts
 Increasing this to 700 TWH to allow for the charging of electric cars is not trivial, nor is the reinforcement of the distribution infrastructure. Increasing to 820 TWh to replace all fossil fuelled transport will require significant time.

Germany currently has it's own unique problems with the phasing out of nuclear power and the misguided dash for renewables but that's another issue.

Best regards

Roger

Certainly an interesting analysis Roger, and in principle I agree with your figures. However you have included a huge diversity assumption, because you have integrated the consumption evenly across your numbers. I would suggest that cars and trucks are more like 30% overall efficient, huge improvements have been made in this area, although some of them are lost due to severe emission rules.  As electricity supply must be available (unless one envisages huge demand controls) at all times, a considerable over supply capability must be available, with a range of start up times. There is a complete incompatibility between nuclear generation and widely varying load, and storage in significant quantity is an impossible dream, both on economic and technical grounds. Realistically a few more nuclear stations would be all that can be managed, and gas usage is unlikely to fall.


The question still remains, exactly what are we attempting to achieve? At this time the overall goal is not at all clear, and as the UK is such a tiny part of global energy consumption, but a large part of the world economy the question has to be "is it economically justified?". A larger use of energy is space heating, and this is very difficult to reduce without replacing most of our built environment, but again many people are suggesting that we use electricity in place of gas or oil, but this is crazy, as well as impossibly expensive. The present "cause celebre" is pollution levels in cities, although the statistics often quoted have very little scientific support. "So many people die of air pollution"  is entirely false, there has never been a death certificate with the cause as being "air pollution". The toxicology of NOx products does not support the present limits from the EU, and it is likely we are "tilting at windmills" in more ways than one! The London ULEZ is a great way to add to taxes, but will seriously increase costs in London, and I would expect the NOx levels to only change slightly. A much bigger effect would come from a minimum speed limit of 30MPH and traffic design changed to suit, it is slow and stationary transport that causes the problem, not traffic per se.


The point is that there is no simple or cheap solution, and I am not sure that electric transport is the right one. A much smaller population is one solution which is obviously not acceptable, so perhaps we should just let natural selection take its course?

Dave,

Air pollution is an interesting question. I have looked at it in two ways:


1) Air quality. Without considering health issues combustion engine exhaust is not pleasant. City streets with high buildings or mountain passes with an inversion layer quickly fill up with fumes. The smelly parts may or may not be a health hazard but reducing or elimating them makes for a better quality of life. Does that have a price?

2) Health issues. The various reports suggest that air pollution results in shorter life spans and other health problems. I cosider this to be correct for high levels of pollutants, London smogs of the past or cooking over an open fire in an unventilated building. What is not clear is if pollution effects are LNT (Linear No Threshold) or if there is a safe limit for various pollutants. If the LNT model is used then 'collective dose' models are also used. If one person receives a lethal dose they die. If 1000 people receive 1/1000 of the lethal dose one of them will die. Is this valid?  There was a report in ET last year on Londons low emission zone and the lack of the expected health benefits:
https://eandt.theiet.org/content/articles/2018/11/london-s-low-emission-zone-failing-to-improve-residents-health/

Maybe the models are wrong, maybe we have reached the threshold were minimal further improvements are possible or maybe vehicle emissions are not the problem?


I would rather be walking alongside a line of electric vehicles than a line of combustion engined vehicles but can I justify the investement in money and secondary pollution caused by the manufacture of EVs?


Best regards


Roger

Roger

I am a bit busy at the moment, but will reply later.

LNT models are not the correct way to define toxicity, there is a huge knowledge that says that there are thresholds with virtually every poison. The statistical treatment is also fatally flawed, but more later!