Tesla News & Discussion

1961Nick

Martyn1981 wrote: »

Hard to be certain, but averages should play out. You might have a hot spot of power showers in the morning, but I haven't heard concerns about those, and they could be expected to be used most days, whereas an average BEV'er would use a 7kW charger infrequently, perhaps once a week.

So back to that +340/680W draw.

Not dismissing that issues could arise, just not convinced that it's a big problem, and some simple smart charging interaction that 'takes turns' or 'reduces output' based on locality would resolve the issue.

Not many of us take a 4 hour power shower!:rotfl:

The difference with EV charging is the certainty of overlap ... unless smart charging is effectively rolled out.

As well as EVs, there's also the plan to ban gas boilers. That'll be an increasing number of heat pumps with 5-7 kWh compressors in the mix coupled with resistance heaters for DHW top up.

1961Nick

GreatApe wrote: »

The grid can cope for sure but the economy tarriffs as they stand can't cope

It's the local grid that's the potential problem. I have it on good authority that a significant amount of the network doesn't have enough headroom to cope with the planned EV roll out if home charging becomes the norm.

Martyn1981

1961Nick wrote: »

Not many of us take a 4 hour power shower!:rotfl:

Are you confusing power and energy?

If you are concerned about peak loading (power) on the local infrastructure, then perhaps power showers would be just as 'bad'.

If you are talking about energy, then we are back to average loadings, as not all cars will be charged every day.

1961Nick wrote: »

It's the local grid that's the potential problem. I have it on good authority that a significant amount of the network doesn't have enough headroom to cope with the planned EV roll out if home charging becomes the norm.

But as I explained earlier, we are probably talking about an average draw per property of 340W (680W more realistic assuming nighttime charging). So if the grid can cope with the evening peak, why wouldn't it be able to cope with a lower draw through the night?

Also worth noting that we have around 25yrs to upgrade the distribution networks, if necessary, assuming a very rapid increase in BEV sales of 10%pa, taking us to 100% of sales in 10yrs time, plus 15yrs for the ICE fleet to be displaced.

GreatApe

1961Nick wrote: »

It's the local grid that's the potential problem. I have it on good authority that a significant amount of the network doesn't have enough headroom to cope with the planned EV roll out if home charging becomes the norm.

Whoever advised you is wrong and it's easy to prove

The residential grid was designed for a time when peak useage was a good deal higher primarily because of light bulbs. 3 X 100 watt light bulbs doesn't sound a lot but multiply by 25 million homes and it's 7.5GW of demand replaced by less than 1GW of LEDs plus many offices shops etc have also replaced their light bulbs

Interestingly peak demand is down about 15GW in the UK
We used to hit almost 65GW during the winter now we seldom pass 50GW the reason is primarily light bulbs but also more efficient appliances

Can the grid cope, yes definitely because it has already proven itself capable of much higher power loads just 10-15 years ago. The Grid has at least 15 GW headroom to accommodate BEVs. And that's during peak hours. During other times it has much much more headroom

This is enough spare capacity for 2 million BEVs charging at 7.2KW at any one time
And they won't all be plugged in at the same time
Also bear in mind that the average car will only need a 45 mins charge per day to cover the average 20 miles driven per day

And you are probably assuming short windows for EV charging like the 4h go tarriff for 5p
That will dissappear instead we will have 3 or more windows with different prices or more likely a 21h window with variable prices like the agile tarriff

This way BEVs can be charged over a 21h period
This is good because it's less strain on the grid
It's also good because it means we don't have to deploy 30 million 7.2KW chargers at £800 a go = £24 billion. Instead we can deploy mostly slow 3 pin plug chargers which might cost just £50 each

The vast majority of people would be fine on 3pin plugs since the average car sits around for 22h a day it's got plenty of time to charge up


Personally I think the government should scrap all EV support the £3,500 per car grant is ridiculous. Instead the government should deploy millions of slow chargers and provide the electricity for free. With perhaps as many as 5 million slow chargers they would be everywhere and for free people would use them all the time.

The cost would be no more than £150/car/yr which is significantly less than the £3,500 EV grant
And phycologicaly people would probably value this higher even though it's worth less. The actual cost would be even less as many people would still opt to charge at home rather than save 50p using a free charger so the cost would be lower still

Such unmetered (at the socket) electricity infrastructure would be so easy so cheap to deploy
Just have a EV plug so people don't go around plugging in their other items bit that that would cost much anyway. They can be on 21h a day and avoid the peak 3h to keep costs down for UK plc

With mass deployment of millions of chargers it makes EVs so much more compelling
If you can charge at both ends that means you can have half the battery cost/weight

Overall BEVs are great they pose no problems
Apart from the fact they are too expensive
Average price of the top 10 selling cars in the UK £16,000
Model 3 £40,000
Sure cheaper EVs exist but we don't really know their costs as the companies selling the other EVs are probably cross subbing to meet emmissions etc. Even Tesla costs are higher as they get cross subbed by hundreds of millions of $$$ to blend their fleet to meet EU regs

zeupater

1961Nick wrote: »

... As well as EVs, there's also the plan to ban gas boilers. That'll be an increasing number of heat pumps with 5-7 kWh compressors in the mix coupled with resistance heaters for DHW top up.

Hi

Isn't there a bit of an issue of understanding of heat-pumps & how they're employed there? ...

We still have a 30kW gas boiler to cope with the really cold periods but even when it's running it's in modulated mode most of the time, probably running at ~25% capacity or even thermostatic cycling.

Most well insulated homes would likely have need for no higher than an 18kW boiler to cope with the initial heat demand and would naturally operate below this level for the majority of the time ...

In moving from an 18kW boiler to a heat-pump it would generally need to be accepted that the maximum system heat output would be lower and that running the system for a longer period would compensate through replacing heat loss over a slightly longer period, using a different supply curve .... it's likely that an 18kW gas heating source could be directly replaced by the provision of an ~8kW ASHP/GSHP capable of achieving at least a SCOP of 3-4.

It is important to note that the rating of a heat-pump is the thermal capacity, therefore an 8kW unit operating at a COP of 4 at nominal full power would be drawing a load of 2kW after a few minutes of initial start-up, before settling down to ticking over at far below this ...

As an example, we're currently heating the house using a heat-pump as well as running all other loads (TV etc) and pulling a mere ~480W, which is similar to what it would have been with just a plasma TV a few years ago! ... above this, it's pretty foggy/cloudy outside but we're still generating ~290W with a PV system, therefore the total load on the grid for powering all devices & heating (currently likely >COP 5.5) a home is little different to the grid to having a couple of average incandescent lightbulbs of last century on! ... It's worthy to note that later this afternoon the demand will likely fall to close to 250W as the replacement heat requirement falls to a background level ....

HTH
Z

silverwhistle

Or to use another analogy, I've just been baking. My energy monitor shows a peak as the oven gets to temperature and then settles down on tick over.


When I get an EV I'll be charging when it's cheapest (or the most solar) and that won't be everyday.

1961Nick

Martyn1981 wrote: »

Are you confusing power and energy?

No ... I'm saying it takes 5 minutes to have a shower but many hours to charge an EV. The probability of everyone in a locality having a shower at the same time is remote, but the chance of everyone charging their EV at the same time is high.

But as I explained earlier, we are probably talking about an average draw per property of 340W (680W more realistic assuming nighttime charging). So if the grid can cope with the evening peak, why wouldn't it be able to cope with a lower draw through the night?

Early adoption of EVs will probably be by high mileage business users because the savings are huge compared to an ICE vehicle. These vehicles will need an overnight charge at significantly more than 680W

Also worth noting that we have around 25yrs to upgrade the distribution networks, if necessary, assuming a very rapid increase in BEV sales of 10%pa, taking us to 100% of sales in 10yrs time, plus 15yrs for the ICE fleet to be displaced.

It might be a case of 80% of the miles are being done by 20% of the vehicles. That 20% are the ones likely to change to an EV in the very short term. There may not be as much time as you think.

1961Nick

zeupater wrote: »

Hi

Isn't there a bit of an issue of understanding of heat-pumps & how they're employed there? ...

We still have a 30kW gas boiler to cope with the really cold periods but even when it's running it's in modulated mode most of the time, probably running at ~25% capacity or even thermostatic cycling.

Most well insulated homes would likely have need for no higher than an 18kW boiler to cope with the initial heat demand and would naturally operate below this level for the majority of the time ...

In moving from an 18kW boiler to a heat-pump it would generally need to be accepted that the maximum system heat output would be lower and that running the system for a longer period would compensate through replacing heat loss over a slightly longer period, using a different supply curve .... it's likely that an 18kW gas heating source could be directly replaced by the provision of an ~8kW ASHP/GSHP capable of achieving at least a SCOP of 3-4.

It is important to note that the rating of a heat-pump is the thermal capacity, therefore an 8kW unit operating at a COP of 4 at nominal full power would be drawing a load of 2kW after a few minutes of initial start-up, before settling down to ticking over at far below this ...

As an example, we're currently heating the house using a heat-pump as well as running all other loads (TV etc) and pulling a mere ~480W, which is similar to what it would have been with just a plasma TV a few years ago! ... above this, it's pretty foggy/cloudy outside but we're still generating ~290W with a PV system, therefore the total load on the grid for powering all devices & heating (currently likely >COP 5.5) a home is little different to the grid to having a couple of average incandescent lightbulbs of last century on! ... It's worthy to note that later this afternoon the demand will likely fall to close to 250W as the replacement heat requirement falls to a background level ....

HTH
Z

I think your house is about as far from typical as it's possible to get in terms of energy requirements! My boiler will run at around 16kW for at least an hour before it settles down to maintaining rather than increasing the temperature. With a COP of 4 (on a very cold day) that's still 4kW for heating plus another couple for DHW.

GreatApe

1961Nick wrote: »

I think your house is about as far from typical as it's possible to get in terms of energy requirements! My boiler will run at around 16kW for at least an hour before it settles down to maintaining rather than increasing the temperature. With a COP of 4 (on a very cold day) that's still 4kW for heating plus another couple for DHW.

The UK grid was designed to work at a much higher power level than we see today
Mostly because it was designed with incandescent lighting in mind
But LEDs and more efficient appliances have greatly reduced peak loads
Peaks used to get close to 65GW now they seldom pass 50GW

As a guess a peak load of 75GW is doable with current infrastructure
By comparison the peak today is about 45GW
That's upto 30GW spare capacity during the day

That's more than enough for cars
It's also enough for at least 10 million homes on resistance heaters
Or 20 million homes on heat pumps with COP 2x
Or 30 million homes on heat pumps with COP 3x
Or 40 million homes on heat pumps with COP 4x

Regarding everyone charging at once, you are right that would be a problem
But that is resolved easily by giving different households a different cheap rate time
You might have a cheap rate from midnight to 4am
Your next door neighbor night be 00:30 to 4:30
The house in the other side of the road might be 01:00 to 5:00
And so on

So everyone doesn't start at the same time
You'd allocate these slots to inversely match other electrical demand
Such that the grid goes from whatever it is now
To roughly a steady flat demand at night
No problem at all

This isn't required now
But it would be required if there were 1+ million EVs on the road

Plus none of these things will happen overnight
It's going to take 30-60 years to electrify heating and transport
It can be done quicker, perhaps in just 20-30 years but that doesn't look likely

zeupater

1961Nick wrote: »

I think your house is about as far from typical as it's possible to get in terms of energy requirements! My boiler will run at around 16kW for at least an hour before it settles down to maintaining rather than increasing the temperature. With a COP of 4 (on a very cold day) that's still 4kW for heating plus another couple for DHW.

Hi

But that's where the need to understand the heat provision profile changes required to effectively use HPs comes in ...

The need for the initial 16kW is down to the way you use your heating ... 16kW of heat provision before modulating down to normal operation could just as easily be achieved through setting an 8kW heat provision HP to ramp-up around 60minutes earlier ... that's a pretty large saving on up front capital cost & future replacement costs as required!

As for DHW, the issue isn't as bad as you may think .... it's not as if you need to switch resistance immersion elements on to heat all of the water from cold, it should be set up to provide the majority of heat from the HP to a reasonable level, then use the immersion to top-up to the desired store temperature as & when necessary.

Unlike basic gas boiler heating systems for DHW the HP control system is normally pretty advanced & many seem to make use of this through being a little smarter with both their scheduling & thermostatic settings based on the reality that it's not necessary to always raise the water temperature to sterilisation levels and many simply time this to happen (~60C) once a week or so, therefore further increasing the percentage of water heated at >COP1 ....

As anticipated earlier, the house is currently drawing 260W, that's background, TV, lighting & heat provision of ~900W, yes it's in an extremely energy efficient property, but then again it's one which is considerably larger than average for the UK (~3x(?)), so it's not that it's impossible to do ... all it needs is a little grey-matter application and the scale of the problem can easily be reassessed!!

HTH
Z