Newbie Advice Sought

[kla456]

Nowty wrote:

]Whether the DNO is allowing you an extra 4kW or 5.4kW inverter is debatable and so is whether you have another 1.4kW of additional export allowance or not. Their response to you does not match your current system but it may match what you told them if you said you have a 7.4kW system. They may have assumed you already have 7.4kW of inverter power which you don't.

I resubmitted G99 and received approval for an additional 5kW inverter (I specified LX5K hybrid) subject to 7.4kW export limit.

Taking your advice so far (very much appreciated all contributions) this is my preference: maximize generation, not disturb FIT, plan for and cable for battery but wait one year to see the export justifies a battery, do the work this year, take delivery of 2nd EV (77kW battery) late 2021 or early 2022, defer usage cut-backs until I see where all that leaves me (net zero), the fall-back position is usage cut-backs or more PV direct to battery.

Btw, what is an LX5K compared to LX5KHB?
I can fit 26 more standard size panels on a South-facing roof - should I part-fill with high-rated panels (leave room for more) or fill space with lower-rated panels (better visually)?

[Stinsy]

Nowty wrote:

]Whether the DNO is allowing you an extra 4kW or 5.4kW inverter is debatable and so is whether you have another 1.4kW of additional export allowance or not. Their response to you does not match your current system but it may match what you told them if you said you have a 7.4kW system. They may have assumed you already have 7.4kW of inverter power which you don't.

I resubmitted G99 and received approval for an additional 5kW inverter (I specified LX5K hybrid) subject to 7.4kW export limit.

Taking your advice so far (very much appreciated all contributions) this is my preference: maximize generation, not disturb FIT, plan for and cable for battery but wait one year to see the export justifies a battery, do the work this year, take delivery of 2nd EV (77kW battery) late 2021 or early 2022, defer usage cut-backs until I see where all that leaves me (net zero), the fall-back position is usage cut-backs or more PV direct to battery.

Btw, what is an LX5K compared to LX5KHB?
I can fit 26 more standard size panels on a South-facing roof - should I part-fill with high-rated panels (leave room for more) or fill space with lower-rated panels (better visually)?

I understand the "HB" model is for "High Voltage" batteries (I have a problem with the misuse of the term "High Voltage" but along with correct apostrophe usage it is probably something I need to chill out about.)

[kla456]

Duly admonished Stinsy (for the second time), but your speedy and reliable advice is always appreciated.

[Stinsy]

Duly admonished Stinsy (for the second time), but your speedy and reliable advice is always appreciated.

No admonishment of you intended. I just answered your question.

LuxPower on the other hand referring to a 90-450V battery system as "High Voltage" is factually incorrect. The term is formally defined, anything above 1500V is "High Voltage" in a DC system.

Don't get me started on Earl's Court...

[nowty]

Btw, what is an LX5K compared to LX5KHB?
I can fit 26 more standard size panels on a South-facing roof - should I part-fill with high-rated panels (leave room for more) or fill space with lower-rated panels (better visually)?

Unless you have a particular battery in mind which is compatible with the HB version I'd stick with the 48v battery version as you will have more choice of compatible batteries.

As your other question, its swings and roundabouts, toss a coin. I think the main issue is whether you end up going 3 phase, then you can fit even more PV, but then you would be doing a total re-design anyway.

[Stinsy]

I too would recommend the 48V model (technically "Extra Low Voltage") where you add extra battery packs in parallel to each other.

HighER voltage battery arrays have their advantages, mainly in keeping current levels much more sensible. While PylonTech and other battery manufacturers do make battery packs suitable for connecting in series, you cannot do this with the standard 48V battery packs. These "series capable" battery packs are much harder to come by at the moment.

In my opinion if you're planning to charge/discharge at anything in excess of 6kW you should consider a pack voltage higher than 48V.

[kla456]

Stinsy said:

1) Leave your existing system alone so as not to disturb your FiT arrangement.

2) Fit an additional solar array, inverter/charger, battery system to take up the rest of your DNO allowance./quote]

If I go this way with a LXP5K inverter and a 8kW PV extension, what battery size is advised, bearing in mind that I've no export and I'm importing 8MWh/annum.

[Stinsy]

If I go this way with a LXP5K inverter and a 8kW PV extension, what battery size is advised, bearing in mind that I've no export and I'm importing 8MWh/annum.

Up to you!

There is no right/wrong. However a few points that will help your decision:

- The PylonTech 2.4kWh batteries are limited to 25A per battery. So 1200W for one, 2400W for two, and your inverter will run at it's max for three or more. So I'd suggest a minimum of three.
- You can start with a few and increase the number of batteries later if you want.
- A small battery pack would even out solar generation vs electricity demand. So if your washing machine heating element kicks in at the exact moment a black cloud rolls over the sun then the batteries will ensure solar-generated rather than grid power is used.
- A larger battery pack will get you through the night on solar-generated electricity in summer, and will ensure a greater proportion of your imported electricity is low-carbon/cheap "Octopus Go" electricity in winter. How much power do you use overnight?
- Other batteries are available, but frankly none (that I know of) offer the same reliability, service-life, or price!
- I have 3x my solar kWp in kWh of battery storage, or half my typical daily electricity usage.

[nowty]

I'd say Stinsy's 3 x kWp in kWh of battery sounds a good rule of thumb, but it does depend on your needs. I've got 6 times but I could easily manage most of the time on a battery half the size.

Interestingly SMA think up to 4 times.
https://www.sma-sunny.com/en/sizing-a-s ... -capacity/

[kla456]

Ok, is this the product?
PylonTech US2000 B Plus V2 95% D.O.D 2.4kWh Li-Ion Solar Battery, or the C series?
[img]/img]
I'll go for three, for now, to get started and provide a structure for bidirectional charging.

We will have bidirectional wall chargers within 12 months
[img]/img]

A family with two EVs (one big, one small) could have 100 kW potential battery capacity

(not sure if I have successfully pasted two images into this post)