On-grid domestic battery storage

joefizz

mmmmikey wrote: »

So the answer to getting your batteries to work overnight seems to be eating out and drinking lots of tea

In a way thats what Ive found ;-)
To recap Ive the sofar solar and pylontech and find once it kicks in at night it sort of stays kicked in but there are variations on when the kick in occurs.

When I first got the system you could hear it kicking in and out muliple times before settling into a steady state at night but either it has stabilised or Im more used to doing things differently (could be the addition of the 3rd freezer, but again thats a transient thing and not a constant load). My 'normal' background load is quite small relatively speaking and as I mentioned in previous posts Ive learned to increase my background load to get the most use out of the way I use my batteries.
Counter intuitive to increase consumption to use less import but Ive only imported 14 units since 1st April.
Will be interesting to see how it works this month with only background load at all times, I might end up importing more electricity for the month Im away from home than the previous 3 months using it all!

Martyn1981

JKenH wrote: »

The DC input voltage for one roof with 6 panels per string however is typically 30v lower at around 190v than the one which tripped out which has 7 panels per string and operates at about 220v so what exactly is the “DC input voltage” and is the issue completely unrelated to the AC grid voltage?

As Solarchaser points out the issues are unrelated (DC v's AC voltage) as it's your inverters job to take the DC side and pump out on the AC side.

If you Google your inverter make and model it will state the DC side limitations that it operates at, such as max DC watts, minimum and max DC volts etc.. Obviously they all vary, but 270V DC side sounds pretty normal, some inverters will go up to 400, 600, 800V etc depending on what they are designed to do, and how many strings they can cope with - two strings will halve the voltage and double the amperage for example, so the inverter should be chosen (and set up) to match the number of panels, panel specifics, etc..

BTW, whilst PV panels vary, they generally operate at about 30V (or 50V for higher cell panels), so your strings varying by 30V with a one panel difference, sounds fine. Again, a quick Google of the specific panel will give its voltage figures if you want to do a quick check, look at the 'operating voltage' figure.

mmmmikey

joefizz wrote: »

Counter intuitive to increase consumption to use less import but Ive only imported 14 units since 1st April.
Will be interesting to see how it works this month with only background load at all times, I might end up importing more electricity for the month Im away from home than the previous 3 months using it all!

Thanks - be interesting to hear how you get on. Having looked at the various charts a bit more carefully I'm now fairly confident that my background load is between the "kick in" and "kick out" thresholds. There are very few days where the panels don't cover the background load, so the only time this is noticeable is late afternoon / early evening as the generated power diminishes on a day when I'm not at home in the evening to cook dinner. On those days, the battery never starts and I use grid power all night (albeit very little!)



My theory is that by putting something on a timeswitch that draws a few hundred watts at about 19:00 for a few minutes I should fool the battery into starting and keep running, I'll let you know how I get on. It's not going to make me rich though, maybe save 2p or 3p a night, but as everyone here knows these things are a matter of principle!

1961Nick

I've had a look at my grid voltage & it's between 232v & 241v. The lowest readings are at peak times as you would expect.

Martyn1981

First the good news. National Grid will pay homeowners with a Tesla Powerwall II upto $1,000 per year for the right to use the battery during peak periods for grid support.

The bad news ........ well, the $ isn't a mistake!

Power Companies Want to Tap the Tesla Batteries in Your Home

mickyduck

Forgive me if covered already but I’m on my phone so not easy to read etc...
Just seen the edf power vault 8.2 kWh for 5k
Is this now seen as a reasonable buy are we at the point when battery storage is sensible?
Link to thread / posts opinions please

legoman62

mickyduck wrote: »

Forgive me if covered already but I’m on my phone so not easy to read etc...
Just seen the edf power vault 8.2 kWh for 5k
Is this now seen as a reasonable buy are we at the point when battery storage is sensible?
Link to thread / posts opinions please

Is this it?
https://batterystorage.edfenergy.com/powervault/powervault-with-grid-services/

zeupater

mickyduck wrote: »

Forgive me if covered already but I’m on my phone so not easy to read etc...
Just seen the edf power vault 8.2 kWh for 5k
Is this now seen as a reasonable buy are we at the point when battery storage is sensible?
Link to thread / posts opinions please

Hi

Good question ....

The majority of the manufacturing cost of a domestic storage system will be the cells themselves, with other components being relatively minor ...

At £5k you're looking at £600/kWh in total, so somewhere around £450-£500/kWh for the battery content .... that's against a background of bulk supply cell prices of around £135/kWh (~$175) in 2018 which is widely forecast to fall to below £80/kWh (~$100) sometime next year and around £40/kWh (~$50) for 2025 ....

For ourselves (and most others!) it doesn't make any sense to get too interested until a fully installed system comes in at below £200/kWh with serious research and thoughts of sourcing starting at around £150/kWh .... of course, much will depend on government attitude to kick-starting the storage sector, but with recent announcements (VAT etc) it's not really worth holding your breath ...

If you're looking at some kind of shared cost/shared service offering, be wary at the moment as most probably make more financial sense to the company offering a package than the customer who is paying what is effectively the full cost of the installation as well as shouldering the majority of the risk ....

HTH
Z

mickyduck

Yes that’s it

mmmmikey

Quick update on the PowerVault performance. Following an update to the battery management system firmware a week or so ago, the overnight perfromance has got even better and I'm now covering all but a couple of hundred Wh per day with the battery. Not a big impact on the econmoics but every little bit helps.


In relation to the "does it make sense" question my answer would be it depends on (a) what you're trying to achieve (b) what assumptions you make about future electricty pricing structures and (c) you're pattern of usage.


If (a) you're doing this primarily for environmental reasons (as opposed to simple cost savings) (b) you assume time of use tarriff mean that you can save 20p per unit by using the energy stored in the battery at peak times and (c) you use enough energy and are able to manage your usage to optimise nattery usage, then it might make sense on the basis that you've a fighting chance of seing your money back. This is the case for me and what drove me to buy the PowerVault but I suspect that I'm in the minority.


When you look at the PowerVault cost, don't forget thst this includes installation, a full manfacturer backed warranty and some state of the art hardware that allows you to make an income through the frequency response market. In my view, the PowerVault T's and C's fairly spread the risk between the consumer and supplier and I was happy to place a bet on this, but this really does depend on how you view the risks and your appetite for risk.