On-grid domestic battery storage

Alan_Brown

zeupater wrote: »

Hi

Which completes the circle ... if the voltage presented to the premises is currently that high that it regularly trips the inverter it's a DNO issue ...

It's not quite the same circle.

If you don't have a VO device, then the high voltage shuts down your inverter, preventing energy generation and losing you money through FITS and imported grid energy. You can chase the DNO, but the problem is yours to chase.

If you have a VO device, then your inverter doesn't shut down and so you don't have a problem. The high voltages in the grid is the DNOs problem, not yours.

Personally I'd prefer high voltage to be someone else's problem, I have enough of my own to be going on with.

Martyn1981

Just posting this from another thread, as my thoughts, good or bad, may have relevance on here.

Martyn1981 wrote: »

Originally Posted by warrenb View Post
Saying that I won't be going for a 14kw system as I have never used 14kw in a day so don't see the reason to have such a large battery.

Hiya. That's how I've done most of my battery pondering, suggesting 4kWh useable (around 5kWh Li-ion) would do the job.

But, I'm having second thoughts now, for a number of reasons, though none are entirely compelling:

1. The bigger the batt, the more you can avoid full charging, and discharging, which will extend the life of the battery.

2. Bigger batt, allows for longer viability as it loses capacity, so if 20%+ overcapacity at the start, then if down 20% after 10yrs, it's still going to meet needs.

3. When I'll need it the most, shoulder months, with plenty of export, but still high import, Feb, Mch, Apr & Sept, Oct coincide with when I'll be using the small ASHP. A battery would allow for more ASHP use without import. EG 2kWh per day, could mean 4hrs of heating, outside of generation, and 6-10kWh of heat.

4. The larger batt would allow cross day storage in the 6 best months, allowing for 100% PV supply on days which are extremely poor. Not really a concern normally, as these days are so rare, and going larger just isn't economical on this basis alone, but as part of this list, perhaps.

5. Future EV use. On average in the summer I have 20kWh of generation, reducing import from 7.5kWh to 2.5kWh per day. After allowing for domestic use of the battery I'd still have 10kWh+ of spare charge, or around 30-40miles of motoring per day (which we don't do). So a larger batt may help to future proof for a PV, though the savings here would be smaller as presumably the alternative would be a cheaper night rate for charging.

6. Bigger batt, especially the PWII is cheaper per kWh.

As I say, none of these arguments are convincing, and I'm not sure all of them together are, but worth a ponder I think, if the decision on battery size wasn't clear cut.

[I'll cross post this on the domestic battery thread as it might be useful, or not! M.]

Alan_Brown

Does anyone know if there is an article or paper on the savings from a battery like Power vault that can connect to solar and to Economy 7?

I'd imagine that a 6kw battery and a water cylinder would be a good store for solar in summer and for E7 in winter. In Spring and autumn, both could work in tandem, with the E7 heating the water tank for morning showers and the battery for the day, with solar topping up the battery and water until the early evening?

zeupater

Alan_Brown wrote: »

Does anyone know if there is an article or paper on the savings from a battery like Power vault that can connect to solar and to Economy 7?

I'd imagine that a 6kw battery and a water cylinder would be a good store for solar in summer and for E7 in winter. In Spring and autumn, both could work in tandem, with the E7 heating the water tank for morning showers and the battery for the day, with solar topping up the battery and water until the early evening?

Hi

I've not come across much other than sales data, but this site gives an idea of thermal & PV seasonality linked into energy efficiency ... Solar-PV-Thermal-Seasonal-Variability---So-whats-it-like-in-Winter ? , also touching on addressing domestic battery storage requirements & resultant energy usage ...

Apart from that, if you're looking at efficient use of your generation, have you looked through read the ' Discussion ... ASHP(Air/Air) with Solar pv ....' thread yet ?

Happy Reading ...
HTH
Z

Martyn1981

A bit boring, but a brief analysis of on-grid v's off-grid storage in the US, and the increase in on-grid deployments.

US grid-tied residential storage surpasses off-grid use, finds GTM report

Until 2017, most residential battery storage systems were installed off the grid. However, GTM Research says 2017 is the year that changes, and changes dramatically.

Martyn1981

I have only skimmed this, but want to post as I need to [STRIKE]run[/STRIKE] waddle off and it looks very interesting.

Started with this article (not crucial to the issue)

Electric car owners 'can drive for free by letting energy firms use battery'

And saw this last paragraph:-

Nissan and Ovo have also collaborated to sell a £4,800 home battery system to households with solar power, similar to the Powerwall made by Elon Musk’s Tesla. The battery is pitched as a way for buyers to make more money from their solar panels, and Ovo will pay owners about £350 a year for allowing it to offer services to the power grid.

So that led me to this:-

Solar energy, supercharged

They are going to pay you for use of the battery, and initial glance suggests it's quite a bit of money. Though the additional leccy savings seem optimistic.

Can't find the batt size, but need to go.

theboylard

Martyn1981 wrote: »

I have only skimmed this, but want to post as I need to [STRIKE]run[/STRIKE] waddle waddlw waddle

So that led me to this:-

Solar energy, supercharged

They are going to pay you for use of the battery, and initial glance suggests it's quite a bit of money. Though the additional leccy savings seem optimistic.

Can't find the batt size, but need to go.

From the second link, to Ovo's page, Nissan xStorage, Power: 4.6kW Capacity: 4.2kWh Up to 5 year warranty, subject to Nissan’s terms and conditions

Example costs are £50 battery installation survey
Battery itself £4800
Approx install cost £500

Some of their specific terms, there are more but I just wanted to highlight these bits, I currently pay 10.29p/kWh, so thats a big jump per unit, plus the standing charge is a mahoosive 28.77p/day, which is more than double my current 12.6p/day ...

e) The specific assumptions used to calculate the estimated annual average energy bill savings of £240, for OVO Energy’s modelling are as follows:

(i) You are on the OVO Energy ‘Better Energy" tariff with a unit rate of 14.7p per kWh as of 16.09.2017;

(ii) Your usage being Ofgem typical domestic consumption values of a medium user (3,100kWh
electricity consumption per year), with and without a battery installed;

(iii) You have a 4kW solar array system installed in your home (which generates on average 3,500kWhs per year);

(iv) Prior to taking the OVO SolarStore (Beta) offering, you used only an average of 33% of the energy generated by the solar array system (as modelled and estimated by OVO Energy);

(v) You have a Nissan X-Storage home battery unit (4.6kW/4.2kWh) installed and activated as part of the OVO SolarStore (Beta) offering for 12 months from your battery activation date;

(vi) You waived your entitlement to receive the yearly FIT export payment of £88 (based on a 50% deemed FIT export credit for a 4kW solar installation); and

(vii) As part of the OVO SolarStore (Beta) offering OVO charges and discharges the battery as required in order to provide grid services, energy trading, and increased solar self-consumption.

silverwhistle

Your usage being Ofgem typical domestic consumption values of a medium user (3,100kWh
electricity consumption per year)

Do they actually mean usage or do they mean import?

Martyn1981

silverwhistle wrote: »

Do they actually mean usage or do they mean import?

Hiya, 3,100kWh would suggest consumption (as that's roughly the medium household figure). Ours is probably about that, perhaps high 2,000's, made up of roughly 1,500 import + 1,500 PV.

Martyn1981

theboylard wrote: »

From the second link, to Ovo's page, Nissan xStorage, Power: 4.6kW Capacity: 4.2kWh Up to 5 year warranty, subject to Nissan’s terms and conditions

Example costs are £50 battery installation survey
Battery itself £4800
Approx install cost £500

Some of their specific terms, there are more but I just wanted to highlight these bits, I currently pay 10.29p/kWh, so thats a big jump per unit, plus the standing charge is a mahoosive 28.77p/day, which is more than double my current 12.6p/day ...

e) The specific assumptions used to calculate the estimated annual average energy bill savings of £240, for OVO Energy’s modelling are as follows:

(i) You are on the OVO Energy ‘Better Energy" tariff with a unit rate of 14.7p per kWh as of 16.09.2017;

(ii) Your usage being Ofgem typical domestic consumption values of a medium user (3,100kWh
electricity consumption per year), with and without a battery installed;

(iii) You have a 4kW solar array system installed in your home (which generates on average 3,500kWhs per year);

(iv) Prior to taking the OVO SolarStore (Beta) offering, you used only an average of 33% of the energy generated by the solar array system (as modelled and estimated by OVO Energy);

(v) You have a Nissan X-Storage home battery unit (4.6kW/4.2kWh) installed and activated as part of the OVO SolarStore (Beta) offering for 12 months from your battery activation date;

(vi) You waived your entitlement to receive the yearly FIT export payment of £88 (based on a 50% deemed FIT export credit for a 4kW solar installation); and

(vii) As part of the OVO SolarStore (Beta) offering OVO charges and discharges the battery as required in order to provide grid services, energy trading, and increased solar self-consumption.

Many thanks.

My quick thoughts (these are based on personal consumption etc):-

£4,800 is very expensive for a 4.8kWh battery.

Standing charge is a little high.

e (i) 14.7p isn't too bad, but I pay about 12p, so not particularly good either. *

(ii) 3,100kWh seems reasonable.

(iii) 3,500kWh gen from 4kWp seems reasonable.

(iv) 33% prior to batt seems reasonable. We use 30-33% with 4 to 4.5 thousand kWh's.

(vi) Don't get that one about waiving export payments. Why not meter them, impossible for us to consume all generation, and not convinced OVO could use it all either, unless they mean they will pay for all export (not just battery discharge to grid)?

(vii) Fair enough.

* 14.7p might be less relevant as I'd expect to import far less by having a battery. However, as the batt is relatively small, and OVO might be using some of 'my' PV gen, leaving me a little short, I'm not clear if import would drop as much as if I had say my own 14kWh Powerwall - so overall I think that relatively high tariff rate remains an issue?

All very interesting.


Big leap of faith here, but will lots of companies start to offer similar deals, even if you've bought your own batt? If I had a PWII at around £6k installed, and could get paid £350pa for its use (on top of leccy savings) then that would make it viable, especially if I had say 5kWh to myself, which I could charge off E7 in the winter and discharge through the day - then I'd pretty much import no day units at all, all year, and perhaps just 500kWh of E7 units.

This is getting fun!