Tesla to unveil home storage batteries

zeupater

Hi All

A lot revolves around the normal usage pattern .... a daily commute of (say) 25 miles each way would seriously deplete the ability to power anything in the home anyway - and forget about solar to recharge the EV, that becomes a weekend top-up luxury. For most the normal pattern would be:- morning routine, unplug car, drive to work, park, return home, eat, maybe followed by short trip or two in the evening (kids etc), plug the car in on timer, go to bed, repeat ...

As for EV charge points on public car parks, well we've found them to be an absolute joke almost everywhere we've been .... they're either taken already, out of order or decommissioned, it's a good job we decided to have a PHEV for the extra flexibility as there are a number of times where, for lack of usable charge points, it would have been 'iffy' whether we would have made it home . If MrsZ didn't have access to charge at work then ours would simply be used as a regenerative hybrid all of the time ... three years of EV ownership under the belt and I can't see how the case for reducing the evening 'peak' demand by powering the house with the aid of the car's batteries could actually work, unless the owner is at home most of the time & the EV is hardly ever used ....

HTH
Z

almillar

I can't see how the case for reducing the evening 'peak' demand by powering the house with the aid of the car's batteries could actually work

Yes, you can, you said it yourself...

a daily commute of (say) 25 miles each way

That's 50 miles. No problem in a Renault Zoe (or Nissan Leaf) starting from full in the morning from cheap overnight charge, go out, come home, plug in, run off the car (I'd have at least 5kWh left after 50 miles), then off the grid if necessary, then car charges overnight (4 hrs on the charger provided with the Zoe). Wake up to a car with a full charge.
So yes, it is possible for LOADS of people, who have a commute of under 50 miles per day. And that's only going to get better. We just need the home electric technology to catch up.

zeupater

almillar wrote: »

Yes, you can, you said it yourself...

That's 50 miles. No problem in a Renault Zoe (or Nissan Leaf) starting from full in the morning from cheap overnight charge, go out, come home, plug in, run off the car (I'd have at least 5kWh left after 50 miles), then off the grid if necessary, then car charges overnight (4 hrs on the charger provided with the Zoe). Wake up to a car with a full charge.
So yes, it is possible for LOADS of people, who have a commute of under 50 miles per day. And that's only going to get better. We just need the home electric technology to catch up.

Hi

So why not leave the quote in context " ..... unless the owner is at home most of the time & the EV is hardly ever used ...."

Don't get me wrong, EVs are great, we've got one ... but without some form of backup (think Ampera / BMW i3 / PHEV ) things can already become a little 'hairy' on return journeys more often than many would think.

The 25 mile daily commute mentioned was specifically used to describe what the upper ceiling of expectation would likely be on existing vehicles. Of course, the average commute in within major urban areas would likely be well below 25miles (I seem to remember reading ~11miles(?) from the 2011 census, with those in higher earning brackets to afford an EV commuting considerably further than average) leaving a larger margin for domestic usage, but the question remains as to exactly how low would the average owner expect to run the battery before switching the house fully over to mains? (previously raised) - and don't forget the unforeseen journey (emergency, pick kids up, no milk, work phone call ... etc). As for range, after some time living with an EV you'll find that there's a massive difference between seasons with lights, heater, wipers, battery warmer, added drag (water etc) having a pretty major impact on the overall range, possibly as low as 50% of summer range expectations when average temperatures are around freezing, that's at the very time of year that the domestic energy demand is highest ....

..... "Did you forget to plug the car in again last night dear? - it's out of juice again" ... "Noooo, I didn't forget, it's just that it was cold, dark, blowing a gale & pouring with rain and you told me that the charge would last at least a couple of days when we bought it, furthermore, can I help it if you keep running that silly fan-heater under your desk for hours on end just to make use of cheap E7 prices during the day instead of putting the GCH and not telling me - spend all that money on a car just to prove that you're too tight to buy a proper domestic solution like the Jones' have on the garage wall next door ...!" ... or ... <insert alternative probable scenarios resulting in domestic argument here>

I'm afraid that when the phone rings at 2am because an elderly relative has fallen over again, the last thing on my mind would be to remember what was eaten a few hours ago, whether it was grilled, boiled or baked followed by totting up all of the other loads which had been used the previous evening and how long the batteries had been charging on E7 and how accurate the electricity meter's dual tariff clock was the last time it was checked ... before eventually deciding whether to chance that there was enough range or call a taxi. At that time in the morning, when being woken up from a deep sleep most would have a pretty 'fuzzy' thought process, so unless there's a spare vehicle on the drive all fuelled up with liquid carbon and ready to go, I for one would stay well clear of a pure EV, especially so of it was to be expected to cover some of the evening domestic load too.

<Back on topic> .... At least it looks like Tesla have understood the need to provide a degree of separation between domestic and automotive power ... sharing base technology is fine, but sharing source is currently pushing the envelope a little more than many (/most) would consider to be within their comfort zone.

HTH
Z

Martyn1981

Hi Z. Of course all of this is speculative unless some sort of attractive tariff / time metering is used. Unless householders are offered a large credit for supplying power, or save a large tariff by importing less, nobody will bother anyway.

But fun to ponder.

You've mentioned something that lots of other people seem to say, and that's the problem of charging when out. In an ideal world cars will charging during the day (when people are in work) absorbing PV generation, and at night, absorbing extra wind generation. Levelling out future excesses and spot prices.

I reckon most people will be in, in the evening, or have a choice of cars perhaps.

With 25m housholds, just 5m with an EV plugged in and limited to 1kW (2kWh) would be enough for the evening peak.

Hope I'm not slogging this side too much, it's just part of a potential future with increased grid storage, industrial storage (looking to make money in the evening on storage investment), interconnectors, domestic storage and EV's.

I don't think I'm being overly optimistic suggesting that the problem isn't that hard when we start to consider the various options, and the potential number/scale of storage that might rollout ...... say by 2030?

BTW, am I right to think 5GW / 10GWh is roughly enough to remove the worst of the evening peak, it looks good on Gridwatch, but their graphs seem to distort/flatten out a bit on the yearly scale. I'm ignoring existing pumped storage (3GW?) as that will already be reflected in supply and prices.

Mart.

almillar

zeupdater
Sorry if you think I quoted out of context - I quoted to make my point - that so very many people do have small commutes. Your first post gave the impression that hardly anyone does. I've got a Renault Zoe do I do have experience of range anxiety, heating, wipers, hills, drag etc in an electric car.

So many of the problems you state are solved when the EV is the second car in the home. Having a petrol/diesel AND an EV gives you a massive range of usage possibilities.

the question remains as to exactly how low would the average owner expect to run the battery before switching the house fully over to mains? (previously raised) - and don't forget the unforeseen journey (emergency, pick kids up, no milk, work phone call ... etc).

OK, the user sets a minimum level in the battery. Problem solved. If I try to pre-heat my Zoe, and the battery is below 46%, it won't do it, so that it doesn't steal range. I can't change that, but the system's there. Same could apply to the house stealing battery charge you need.

Martyn1981:
The efficiency of using electric overnight isn't just about wind power, it's about evening out the supply throughout the day, and getting rid of peaks. Peaks mean having to switch on and off generators - that's inefficient. It's more efficient to have everything running all the time. You'll need some redundancy, obviously, but far less than is required now.

zeupater

almillar wrote: »

....OK, the user sets a minimum level in the battery. Problem solved. If I try to pre-heat my Zoe, and the battery is below 46%, it won't do it, so that it doesn't steal range. I can't change that, but the system's there. Same could apply to the house stealing battery charge you need ....

Hi

That really assumes that the vehicle manufacturers would readily build the proposed controllability into the vehicle. Of course, in the case of your Zoe you likely have a lease contract for vehicle and battery, the monthly payment value being conditional on the annual contracted mileage, therefore is there a base assumption that the additional battery cycling from powering appliances wouldn't be reflected in an additional lease charge .. as you say 'Problem Solved', the enabling software could simply meter the domestic supply with a view to raising an additional 'domestic supply' invoice as part of the service schedule .... of course, purchasing the battery pack outright would negate this being an issue, but the replacement cost risk would pass to the owner.

One of the major trade-off issues with utilising vehicle batteries for domestic supply is the related necessity to transport 'dead weight' ... it's not free - at a power storage density of around 13kg/kWh(290/22), lugging a mere 5-6kWh of additional storage around would have an effect equivalent to having an extra adult on board at all times, possibly reducing average journey start-stop usage range by somewhere around 5%-10% for any given remaining charge ....

Me, well I'll wait for the domestic storage costs to fall to a price-point which makes some kind of sense, then have a unit bolted to the garage wall where (a) - it's always available to be charged by excess pv and/or overnight cheap-rate E7 (before it's pulled!) .. and .. (b) it's always available to track and supplement pv for daytime high demand (kettle etc) and track/meet demand as much as practicable overnight ... the EV, well that can stay on the drive to be used as a form of transport and we can sleep well at night knowing that the car's useable if needed - after all, isn't that why people buy them?

HTH
Z

Martyn1981

zeupater wrote: »

Hi

One of the major trade-off issues with utilising vehicle batteries for domestic supply is the related necessity to transport 'dead weight' ... it's not free - at a power storage density of around 13kg/kWh(290/22), lugging a mere 5-6kWh of additional storage around would have an effect equivalent to having an extra adult on board at all times, possibly reducing average journey start-stop usage range by somewhere around 5%-10% for any given remaining charge ....

Hi Z, interesting discussion, but I'm not following the dead weight issue. There's no need to have larger batteries than needed as a car, and no need to have discharged batteries in the morning, as there's (always?) going to be 8hrs or so of lower demand, lower priced leccy at night.

So, if, and here's a long list of if's:-

if the car is parked in the early evening,
if the car has enough spare capacity left in it,
if the car isn't needed again that evening,
if the car is fully charged up at night,
IF leccy prices reflect time pricing, then

we're simply talking about utilising the car batts for a short time, and a relatively small amount (each) to help levelise demand - reduce peak, boost low night demand.

I appreciate that it's a long list of if's, but none of them seem particularly difficult. Perhaps I'm being overly optimistic, but I'd have thought the majority of EV's could be available, since most households will have one or all vehicles parked up for the evening/night.

Maybe another part of using this as a solution, is ensuring that daytime/workplace charging is available, that way the EV's have more spare capacity on returning home, and more PV can be deployed, using EV's to soak up any excess and levelise costs/demand/supply again.

I find this stuff way too interesting ...... perhaps I should read a book and let my brain have a nap. :think:

Mart.

Exiled_Tyke

Is there not another set of important issues here? Batteries for cars will (I presume) still have a limited life in terms of number of cycles. Also have extra expense in terms of having to be designed for highest performance with minimum size and weight. Aren't those who use their cars to flatten out grid consumption merely cashing in the huge investment they've made in the their cars at a less than optimum return?

Surely then (in theory at least) a battery designed for in home use where weight and size are less critical should be the focus of effort and made cost effective.

almillar

zeupater - yeah - the extra cycling that will result would be like added mileage. It could be even simpler than the metering. There's no doubt that it will cause extra 'wear' on the battery but I repeat my point from earlier - compared to all these little things we do in our houses like light and heat things, moving a car is MASSIVELY energetic. Running a house for a few hours really won't have a big impact. For my 22kWH battery, I can drive about 80 miles, or run my house for 2-3 solid days!

One of the major trade-off issues with utilising vehicle batteries for domestic supply is the related necessity to transport 'dead weight'...

No - battery power isn't being added to cars to power houses, it's being added to make the car go further. That's the big problem being worked on at the moment. No-one is making cars heavier to run homes, it's just a side effect of electric cars that you COULD, in the right conditions, use that massive battery in your driveway in emergencies or just for efficiency. Again, it doesn't suit everyone.
When I'm driving around with 10% in my battery, I'm carrying a lot of dead weight compared to a 10% full fuel tank!

Me, well I'll wait for the domestic storage costs to fall to a price-point which makes some kind of sense

Me too, sounds like an ideal use for old EV batteries. Charge it off solar panels during the day, use it in the evening, right at peak time. Solar panels without storage are going to look so old fashioned...

Martyn1981

Exiled_Tyke wrote: »

Is there not another set of important issues here? Batteries for cars will (I presume) still have a limited life in terms of number of cycles. Also have extra expense in terms of having to be designed for highest performance with minimum size and weight. Aren't those who use their cars to flatten out grid consumption merely cashing in the huge investment they've made in the their cars at a less than optimum return?

That's really important, and was the point I was trying to address / ponder with this comment:

Martyn1981 wrote: »

[Edit: * Just to clarify, I mean free storage in terms of battery costs, not leccy costs, nor system efficiency losses. You can price the cost of storage by dividing the batt price by the number (and size) of cycles. These small domestic kW and kWh draws will probably have no detrimental effect on batt life expectancies or performance as they'd barely be ticking over at such levels, compared to the harsh life they are designed for. M.]

I think I need a battery expert now to chime in, but have read about the C ratings for batteries, such as life expectancies at C100, C20 etc. As I understand it these relate to the number of hours that the battery will be discharged over.

The slower a battery is discharged the more efficient it is, and the more cycles it will probably last.

Looking at the Nissan Leaf it has a 24kWh (or 30kWh) battery but an 80kW motor. So foot to the floor acceleration is placing a massive draw on the battery. Theoretically C1/3(?)

I'm assuming, and I admit 100% that it's an assumption, that a battery that can cope with those rates of draw/discharge will not suffer significant life expectancy reductions from a 1kW or 2kW domestic draw.

But I could be completely wrong, and monies potentially saved on leccy bill will be lost against battery replacement costs.

Hope this makes sense.

Mart.