General > General Technical Chat

“Battery EV” vs “Hydrogen Fuel cell EV”

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tom66:

--- Quote from: MadScientist on November 18, 2021, 08:35:51 pm ---Home charging has little future , in the uk the typical house limit is 60kw , and hence a 32 amp circuit is the max feasible limit. ( in fact for 32A you’ll need priority switching in some cases ) in fact many installers will only fit 16a EVSE in many cases.
--- End quote ---

I assume you mean 60A, to which I say, "bollocks!"  I have never lived in a home with less than 100A service.  60A homes do exist, but most of them are supplied with 80A cabling and DNOs will install 80A fuses FOR FREE, if the customer requests so.  That gives you an 18kW supply.  DNOs will let you have two EV chargers on 80A if you pass diversity, usually one 32A and one 16A, but sometimes you can have two limited to 20-24A if they support it.

Most of continental Europe has at least 3x16A service (~11kW) and 3x32A (~22kW) is also quite common.  The 3ph 16A people might need to limit themselves to 3.6kW single phase charging.  That's still plenty fast for most.


--- Quote from: MadScientist on November 18, 2021, 08:35:51 pm ---Modern EVs currently have 60 kWh and trending towards 100 kWh batteries. , recharging 60kwh , on a 32A circuit takes 8 hours ( including taper charging ) , recharging 100kWh will be practically impossible in the typical night time available ( usually 12 -6am )

Hence home charging will be a fill-in activity

Remember the average mileage per week in the uk is very low. Most users drive short distances each day. With 60-100kWh batteries these users might only charge once a  fortnight.  These are most likely to take place at very high energy delivery sites.
--- End quote ---

These statements are contradictory. Most EVs won't need to charge up much or at all on a given night because their batteries are big and their mileages are low.  And yet you think that we'll need to use rapid chargers for all EVs?  The reality is, EV charging will mostly happen at home, or parked on the street using slow AC chargers.  3.6kW is enough for 80% of the population every night, 7.2kW would be enough for 95% (my estimation).  Some EVs support more, Audi e-tron supports 40A single phase, and early Model S in Europe could charge at 63A single phase too, but I believe they have dropped that because the demand is so low.


--- Quote from: MadScientist on November 18, 2021, 08:35:51 pm ---Furthermore various grid studies show the primary concern of grid managers vis a vie EV charging is high density home charging at coordinated times like night time. The typically suburban estate ( with driveways ) has an electrical infrastructure simply incapable of supporting high density coordinated charging. The cost and sheer inconvenience makes it virtually impossible to upgrade this houses.
--- End quote ---

The typical suburban estate actually has sufficient capacity to supply 23kW to every home, it's the downstream DNO capacity where there are shortages.

The uptake of EVs will be over 10-15 years so DNOs will have sufficient time to upgrade. No doubt it will be a lot of work but heat pumps are another driver of this type of demand.


--- Quote from: MadScientist on November 18, 2021, 08:35:51 pm ---On top of that smart metering will in time penalise home charging of EVs , both by increasing the cost of  the time of charge where  co-ordinated charging is happening , ie night time. Smart meters are largely grid/ generator promoted as they want to monetised inelastic electricity usage times.

--- End quote ---

Well even on normal rates my (PH)EV is still much cheaper than petrol to run, about 5-6p/mile compared to 15p/mile.

Regarding cheap rates at night.  Some say they will go, others not so sure.  Personally I think as renewable energy becomes more common they will stay but the pricing will vary. Some nights no benefit others the price will plunge.

Right now there's roughly a 50% difference between daytime usage and nighttime usage.  If everyone switched over to EVs and average mileages didn't change, then overall electrical energy usage would go up by about 20%.  There would still be a night time gap.

The major advantage of a smart grid with EVs is it's dispatchable.  If there's excess demand you tell all the EVs to soak up now and drop the rates to incentivise this usage.  When there's a demand shortfall you reduce or stop charging altogether.  Customers can override, but they'll pay a bit more.  Some places in the US have a scheme where you can have your air-con scaled back in times of peak demand, this is exactly the same. And in the end, as long as your car has enough range for your next journey for the day, do you really care when it charges?

james_s:
Several of the EV drivers I know charge almost exclusively from a 15A 120V receptacle because it's what they have available, the charger draws 13A and charges at about 5 miles of range per hour. The capacity of the batter is irrelevant, the primary charger need only supply enough energy to cover the average amount consumed between nightly charges and commutes over about 20 miles a day round trip are relatively uncommon. It's certainly nice to have faster options but they are only needed occasionally. Fast charging will degrade the battery faster than say <10kW.

Marco:

--- Quote from: MadScientist on November 18, 2021, 08:53:51 pm ---Large scale Slow charging is not an option in general , firstly urban planners are determined to limit long term street parking in urban areas

--- End quote ---

Which they can only get away with when there is an extreme limit in available homes AND voters don't wake up to the fact they do have power. Sure, if those kinds of idiots are sufficiently politically entrenched normal people might have to vote for someone Trumpian but if you push them far enough that is what they do.

Like 1% of people wants that for their housing, until they get a family and then they don't want it any more either.

As I said, any time you lay fiber you could in theory also lay down the cabling and pits for chargers at essentially no cost. Then you can just finish it when the distribution network is ready. For a competent government, high density roadside charging would not have been a problem.

ejeffrey:

--- Quote from: MadScientist on November 18, 2021, 08:35:51 pm ---Home charging has little future

--- End quote ---

Wtf?

Home charging is going to be the dominant way people with EVs and homes charge always.


--- Quote --- , in the uk the typical house limit is 60kw , and hence a 32 amp circuit is the max feasible limit. ( in fact for 32A you’ll need priority switching in some cases ) in fact many installers will only fit 16a EVSE in many cases.

--- End quote ---

That is fine.  16 a seems a little low but acceptable.


--- Quote ---Modern EVs currently have 60 kWh and trending towards 100 kWh batteries. , recharging 60kwh , on a 32A circuit takes 8 hours ( including taper charging ) , recharging 100kWh will be practically impossible in the typical night time available ( usually 12 -6am )

--- End quote ---

Who cares?


--- Quote ---Remember the average mileage per week in the uk is very low. Most users drive short distances each day. With 60-100kWh batteries these users might only charge once a  fortnight.

--- End quote ---

Or they could do what basically everyone with a driveway and an EV does which is to charge every night.  As long as they don't do back to back 300+ km journeys without a few days/nights to get back near full you don't have to worry and it doesn't matter if you can get a full charge overnight.  As long as you can comfortably charge more than an average days use in a single night it's fine.  32 amps is plenty for that and even 16A is often sufficient. 
 

--- Quote ---The future therefore is high energy specialised charging sites , rather exactly as petrol is done today. Home charging will be incidental.
--- End quote ---

Nobody who has the option to home charge is ever going to do more than a incidental fraction of their charging at high power dedicated chargers. Even if they could charge in the 5 minutes it takes to pump gas.  It is a waste of time, money and effort.  Fast charging is an important option to have for long trips or back to back range limiting trips but not something people want to do regularly.

If you can't do the majority of your charging at home (or at work if you have that option) then an EV probably just isn't for you yet.  Which is fine.  We are far from saturating the potential EV drivers who can and infrastructure is rapidly expanding and will eventually be better at accommodating those who can't.

PlainName:

--- Quote ---The supermarket idea isn’t working and the trend is dedicated high energy sites rather like petrol filling stations.
--- End quote ---

There's a Tesla super-charging thingy down the road from here. About 20 berths, I think. I have only ever seen one car in there and every other time I've been past it is empty. My local supermarket, OTOH, has 4 berths and there is always at least one car on charge there.

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