Hello, Adam,

thank you for your comments. Like you I thought the NE facing roof would contribute almost nothing, however according to the simulation they use it contributes over 900 kWh, 20% of the total so well worth while. 
the most efficient layout involves 12 x 375w high efficiency panels producing 4.46MWh net (after losses) per year according to the simulation. A larger or smaller panel layout is less productive due to the restrictive roof space.

The property is a dormer style house with velux windows on the productive roofs, limiting the available space.

From the simulation (using a powerwall) we can run the house for 7 months of the year and the EV for 3 months so it’s looking promising.

Barry

Everyone’s comments are very much appreciated

I’ve a further update to my original post.

Since last posting on this site I’ve been talking to several installers while doing my own research and have finally concluded I have a proposal that fits my aspirations at what I believe to be a fair price.

However, I would appreciate opinions from the forum members.

The proposal is from a midlands based MCS approved installer with business awards and good customer reviews so I feel comfortable.

The system:

12 x Hyundai 400W VG series shingled panels, spread over 3 roofs, 5 x SW, 3 x SE & 4 x NE, totalling 4.8kWp. Estimated output 3.8kWp.

12 x SolarEdge panel optimisers.

SolarEdge 5kW inverter/EV charger

SolarEdge 10kWh battery, 5kW charge/discharge.

Fully installed, commissioned & optimised, DNO submission etc, subject to site survey.

I understand the DNO will likely require additional equipment to limit export.

Currently waiting for a response from Octopus re a Feed in Tariff before pressing the button.

@yachtsman - I'm unsurprised that installers are recommending that you have a SolarEdge system. This costs more per raw kW of panel capacity than a string-inverter would. However it is much more tolerant of shading and panels that are divided across roof sections facing in differing directions.

Basically the SolarEdge has a DC-DC Converter (the 'Optimiser') for each individual panel. This contains the MPPT (Max Power-Point Tracking) technology which balances the voltage/current in order to provide the maximum possible power output (in Watts). The capital outlay is about 10% more than a PV array wired to feed a generic string-inverter. However, on multi-faceted roofs, you are likely to recoup this within a couple of years.

The downside of SolarEdge is that your entire system must be supplied by them. You can't mix and match component parts with other manufacturers.

As for export to the grid - yes you'll require G99 approval from your DNO because the theoretical power available from the inverter and the battery is greater than 3.6kW. However it is likely that the Electrical Networks Association (ENA) will have already approved the SolarEdge system software to constrain grid export to the usual 16A/phase. The power provision for the house itself is in addition to this.

Finally, although you're now veering away from thoughts of having a Tesla Powerwall2; yes it's expensive. But it also has the lowest £-per-kW rating of domestic storage batteries which have grid-connection approval for the UK. That's a better indicator than the basic purchase price.

@transparent  Thanks for your valued comments.

Ive decided to go ahead with the SolarEdge system in spite of the premium price. The ROI has always been off the scale so a few more % won’t make a huge difference & ROI was never that important to me.
The Tesla PW2 is in short supply & is at a premium so I don’t think worth it. The SolarEdge is available in 5kWh banks so easy to increase capacity at reasonable cost if needed. If I dont increase my consumption the 10kWh should be sufficient.

My intention is to export zero energy so I will be applying for G100 approval from the DNO.

I’m currently waiting for a site survey & then DNO approval.

SolarEdge certainly sounds the best option for your roof @yachtsman.

I'm unfamiliar with their Storage Battery. However I've spent a year on a Storage Trial with OVO/PowerVault, through which I've learned a lot about what is and isn't viable. My system losses vary between 20%-40% depending on day-length. No one would seriously contemplate such wastage at this time of rising energy bills!  😥 

Therefore I have two further questions for you to consider:

1: Does the SolarEdge inverter/storage combination have a setting which allows you to prevent export to the grid?

2: Are the solar-panels connected directly to the storage battery (DC), or do they go through an inverter first?

The difference is crucial.

If the inverter is ENO-approved then it will almost certainly be one with export limited to 3.6kW (16A). Any solar-generation beyond that gets discarded.

That in turn limits the amount which can be stored because the house will take first dibs on what it requires.

As you can see, I think in diagrams rather than words.

If possible, try to translate what your potential installer(s) have specified into your own diagram. Then write in the max/min kW figures where I've got the red labels.

If you can't do that, then the system being proposed isn't yet adequately described.

HTH

@yachtsman, SolarEdge are a terrific company and I'm really keen to hear how your storage fares. Please keep us updated.

@mars I certainly will however I’m possibly 4 months away from installation

@transparent Q1 yes it does and I will be applying for G100 approval since I don’t intend to export any energy, since there will be no excess.

any excess that the EV can’t take will go to supply a immersion heater.

Q2. I have requested a schematic diagram of the proposed system, when it arrives I will post it here.

Posted by: @transparent

Does the SolarEdge inverter/storage combination have a setting which allows you to prevent export to the grid?

Posted by: @yachtsman

yes it does and I will be applying for G100 approval since I don’t intend to export any energy, since there will be no excess.

OK, I understand that's the correct response from a technical viewpoint, but it's not how the G100 Application gets assessed.

Your DNO will add together the total possible export from all the grid-connected devices and then subtract the Load Diversion to the immersion heater.

So it you have an AC connected battery, you have two devices with export capability: the inverter and the battery itself.

Even if the battery is configured by you to constrain grid-export to zero, its potential output of 3.6kW is still added to that of the inverter before the export control logic is assessed.

This is why it is crucial at this stage to know whether the installer is proposing an AC- or DC-connected battery.

I have precisely this problem with my own installation of an inverter and a PowerVault battery. Each has a current-clamp on the 'live tail' between meter and consumer unit. And the battery is configured by design not to export if the inverter is also exporting.

However my G99 certification was issued subject to the inverter being rated at 3.6kW. The better technical option was to install a 6kW inverter with grid export limited to 3.6kW by using the current clamp and the inbuilt software. That would've enabled the battery to charge at the same time as the house consumed some of the available solar. But that fails the DNO checks.

When first installed my PowerVault battery was DC-connected, allowing all 5.1kW from the solar panels to be used during peak-sunlight hours. As there was only one grid-connected device (no AC-inverter), that was approved immediately under the simpler G98.

Rewiring the installation to use the inverter resulted in a major loss of available energy.

Just because the design of inverter or battery includes a system for export limitation does not mean that such a design feature will be permitted under the G99/G100 assessment.

@transparent The SolarEdge battery banks are all dc. I understand the inverter is a hybrid. If the DNO want to play safe and restrict any export to 3.68 I won’t object since the inverter will still charge & discharge at 5kWh.

@transparent 

So how would V2G be assessed?

@derek-m My EV is not capable of V2G, but I wish it was.