On-grid domestic battery storage

Cardew · 19 September 2017 at 1:50PM

snecker wrote: »

I don't think so. Charging infrastructure is rapidly expanding and see Tesla's recent mobile battery swap patent application. I'm too new to post links but google for more info if interested. In most EVs, the battery sits at the lowest point and is usually pretty trivial to swap.

Welcome to the forum.

This is the link on a battery swap patent:

https://techcrunch.com/2017/09/15/tesla-files-patent-for-mobile-battery-swapping-rig/

Given the weight of the Tesla battery at 1,200lbs it is certainly not a DIY job for the layman.

Martyn1981 · 19 September 2017 at 2:02PM

Cardew wrote: »

When electric cars become mandatory, it is going to be a logistic nightmare for those in flats/houses without parking to have charging facilities. Especially as, I suspect, the majority of owners will wish to charge overnight, and 2 car households are common these days.

Highly doubtful. Tesla are already installing 'low' power chargers in carparks, which at 75KW will charge most cars in less than an hour whilst you do the weekly shopping.

It'll also warn you 10 mins before full, and if more than 50% of charging spots are full, will give you a 5min warning to move your car before it begins min by min parking charges.

Regarding their supercharging stations (140kW+) they are already massively expanding these, about 3 or 4 fold.

Average UK mileage is 7,900 miles pa, or about 6kWh per day.

zeupater · 19 September 2017 at 3:42PM

Cardew wrote: »

When electric cars become mandatory, it is going to be a logistic nightmare for those in flats/houses without parking to have charging facilities. Especially as, I suspect, the majority of owners will wish to charge overnight, and 2 car households are common these days.

... :wall:

... and you think that's an issue for the future! ... you only need to look at infrastructure as it was just a couple of years ago and compare to where it is now ... the rate of improvement is rapid now that there are enough EVs to warrant investment in charge points ...

... anyway, 'mandatory' is years away, by the time we get to that point, clean energy will probably be 'too cheap to meter' (:D;):rotfl:) and batteries will be recharged through induction plates/coils in garages, parking spaces and maybe even in the roads themselves!

Interesting times on the horizon if we put the blinkers aside and take the opportunity to look .. :cool:

HTH
Z

Alan_Brown · 19 September 2017 at 8:32PM

David_RC wrote: »

I have a 3.8 kWh nominal PV ground based array 100m from my house which is at the end of a long country lane. Many of my neighbours now have PV systems. On sunny days I often get a message on my SunnyBoy inverter saying that it has shut down owing to grid instability. I note that the output voltage is often at 260V or above and assume my inverter is programmed to shut down at above about 260/265V.
The problem is most likely that the local grid line cannot take the generation load from the group of houses if local usage is low. I'm interested in possible cures for this problem since I'm one of the very fortunate PV generators currently receiving 50.67p/kWh (that includes the assumed 50% export tariff element) on all my output whether or not I use that output in my home. I started generating in 2012. Initial annual output was about 3.9MWh but after three years has fallen to about 3.5MWh as more local generation has come on stream. My panels remain efficient - the inverter was reading 4.1kWh yesterday for a brief period. My annual usage after the PV array installation was initially 2.9MWh but has risen to about 3.2MWh recently, I suspect because of the lag in inverter start up following a grid instability outage when my house load increases.
I am considering buying a battery pack to take the output from my array when the AC output voltage rises above the grid-acceptable level. The economics don't work yet, but the possibility of time dependent pricing of mains supply electricity is a factor to bear in mind.
My technical question is can a battery take the DC output from my array and store it before it goes through the inverter, and then discharge through the inverter at a later time so as to give a total generated output back at the level I enjoyed before the grid instability problem? Can the battery be made to start and stop storing at specified times or automatically if my inverter AC output voltage rises above a set trigger voltage so as to stop the inverter shutting down?
Thanks for your help.

Have a look at a voltage optimizer. Growatt do one that is designed to prevent exactly your issue - high input voltage shutting down your inverter. With your FIT rate, it might be worth it. Fitting a battery won't stop your system shutting down due to voltage spikes.

Martyn1981 · 20 September 2017 at 7:02AM

Something that might have future relevance, or not.

Recently read a thread on Navitron, where an off-gridder was talking about PV and battery storage large enough to top up an EV if it's a bit low, though usually charged elsewhere.

One interesting suggestion was to flip the problem, and get a larger capacity EV, that could act as back up for the house if necessary!

Back to on-grid, I was wondering if in the future with vehicle to grid (V2G) this would be an idea for PV households and time of day tariffs, such as the 5p night, 12p day and 25p evening one seen some time back.

As well as, or even instead of a home battery, you use the car to cover the high evening period, use the cheap night rate for house and charging the car, and PV to displace most of the daytime rate, and some of the evening rate (4pm-8pm I think).

Just a thought.

NigeWick · 20 September 2017 at 9:20AM

EricMears wrote: »

For people without their own garage /parking space there is always the possibility of 'destination charging'.

A number of places in London have already started putting charge points in lamp posts. I am sure it won't be long before petrol stations start installing chargers for when fossil burners are too expensive for people to want.

Martyn1981 · 20 September 2017 at 12:24PM

NigeWick wrote: »

I am sure it won't be long before petrol stations start installing chargers for when fossil burners are too expensive for people to want.

And you aren't wrong.

BP to install electric car charging stations

David_RC · 20 September 2017 at 4:57PM

Thanks Alan Brown - I'll look at the Growatt voltage stabiliser. I contacted my DNO and they advised me to ring the local 105 tel. number for emergency electricity problems and an engineer would visit the same day to look at the problem. I haven't done that yet since I'm waiting for a suitable day.

zeupater · 20 September 2017 at 4:58PM

Alan_Brown wrote: »

Have a look at a voltage optimizer. Growatt do one that is designed to prevent exactly your issue - high input voltage shutting down your inverter. With your FIT rate, it might be worth it. Fitting a battery won't stop your system shutting down due to voltage spikes.

Hi

Can't see how that would help and keep the installation within grid tolerances (/legal) ... the output voltage at the meter (/from the house) needs to be higher than the grid voltage to allow export .... no matter what you do within the house or between the inverter & the grid, you're simply not allowed to inject power into the grid above the upper voltage tolerance ...

HTH
Z

Alan_Brown · 21 September 2017 at 2:45PM

zeupater wrote: »

Hi

Can't see how that would help and keep the installation within grid tolerances (/legal) ... the output voltage at the meter (/from the house) needs to be higher than the grid voltage to allow export .... no matter what you do within the house or between the inverter & the grid, you're simply not allowed to inject power into the grid above the upper voltage tolerance ...

HTH
Z

In order to satisfy the regulations concerning power supply (G83), your inverter matches its power output (voltage) to the supply coming into the building from the grid. If that supply has been optimized (i.e. reduced from a power spike to 230v), then the power exported to the grid will be at 230v.

With your mains power optimized to 230v, your inverter won't trip. Your inverter will always match your optimized mains power and so your export will not be above the upper voltage tolerance.

Interestingly, the voltage spikes that shut down the inverter reduce its life expectancy, so fitting a voltage optimizer would also help to prolong the life of your inverter (and other electrical items in your household).

Also, while the reduction in voltage won't help with items like kettles that use a resistive load, it will reduce the power usage of electrical items like refrigerators and freezers, making a small energy saving though I doubt enough to justify fitting an optimizer. However, if you have solar panels, a high FIT rate and a problematic supply then perhaps it might be worth installing?

On-grid domestic battery storage

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