Can you help me finalize my summer home system layout?

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psommariva asked Nov 28, '21

Can you help me finalize my summer home system layout?

Newbie here. Setup for summer home in Sardinia/Italy. The house is in use 4m/y Jun-Sep. No, there is no airconditioning, it's designed to stay fresh under the sun.

After asking a dozen installers and getting the same standard answer I decided to do it myself.

Here's the setup:

Installation is at 39°06'34.2"N 8°18'28.5"E with panels at 22º incline to South 178º; space for 13x 175W PV panels = 2275W; blue sky 99% of the summer, no shadows across the day.
Running 24/7: 3 fridges 350W/h; solar water heater circ pump 20W/h; water pump 25W/h; WiFi, netowork 150 W/h ≈ 600 W/h
During the day: w. machine 800Wh; 1 dish w. 800Wh; vacuum 1500Wh; Iron 2000Wh ≈ 5KWh
At Night: quiet night 8kWh; party night (¼) 25kWh (mostly due to oven, induction, teppaniaki, frier, steamer, which are all electric - gaggenau 200 series)
Consider the entire kitchen at work with other loads will be >7kW and if all appliances cycle together it would be close to 10kW but that's unlikely. The grid counter is a 6KVA (I believe that's an 8kVA peak) and it does jump when everyone is active in the kitchen and the oven is in use.

The grid works ok as long as it does not rain. The objective of this PV system is to make this house completely selfsufficient. Eventually we will add more PV panels or a wind turbine to provide more services like desalination of water for irrigation.

The current goal is to never use the grid, if occasionally during major peaks of usage: IF batteries <20% & PV not producing & load >nn kW THEN use grid

During the winter, when the house is closed, only standby consumption for the network is present and all the production can be sent out to the grid and keeping the batteries charged.

So, after reading several spec sheets and watching some great videos, I came up with this. I would be immensely grateful if you have a moment to validate this as it probably not far from feasible, but surely off by a lot. Thank you!!

ESS schematics

solar-pv-project-schema001.png (1.4 MiB)

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Modifications Space

Node Red Space

Answer 1 · 2021-11-28T18:51:22Z

seb71 answered · Nov 28, 2021 at 06:51 PM

Just some points:

Use 60-cell PV panels. I don't see any point in using small PV panels (unless you already got them).

A 2.3kWp PV array is way undersized for your intended usage.

When you make string of pannels (series), the current is not multiplied by the number of panels in a string (like you wrote in your diagram). So you won't have that huge current and you don't need 50mm2 wires for the string of PV panels (modules).

That 1200Ah (at 48V) for the battery is probably also wrong (~60kWh). If correct, it is very expensive. And would require a much larger PV array to charge it.

Get some LiFePO4 battery, not lead-acid (as in the diagram).

Use busbars for DC.

Use fuses.

Add a shunt.

Etc.

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nickdb ♦♦ commented · Nov 28, 2021 at 07:24 PM

Or pay a professional to help?

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Answer 2 · 2021-11-28T22:01:58Z

kevgermany answered · Nov 28, 2021 at 10:01 PM

You show a US spec multi. Sardinia is 240V.

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Answer 3 · 2021-11-28T23:24:50Z

psommariva answered · Nov 28, 2021 at 11:24 PM

Thanks Seb,

newbie's obvious mistakes - corrected schematic.

On the roof I have exactly the space to put those 175W panels, any other size would not fill the space.

Calculated battery requirement to power through the night 8kWh - 95% efficiency - 80% discharge = 10kWh available as a minimum. If there are no other loads during the day, 2.3kWp should recharge in 5h?

For now I'm trying to get the general system right. I'll add the details after.

solar-pv-project-schema001.png (1.4 MiB)

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seb71 commented · Nov 29, 2021 at 06:36 AM

True that using that house only in summer and in a perfect location for solar/PV would greatly help with charging.

But I can't see how you won't have any loads during the day.

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Lithium SuperPack batteries can't be connected in series (and you would need to, because there is no 48V option).

Also their internal BMS will just disconnect the battery if outside the allowed working parameters.

Disconnecting the battery is not that good. If using a BMS, you want one which can communicate with the inverter to shut it down, if necessary, not abruptly disconnect the battery.

This is also the reason why these batteries can't be connected in series.

So if you get LiFePO4 from Victron, go for Lithium Smart (and get the largest ones) and VE.Bus BMS. But those are very expensive.

Or you could get LiFePO4 from other manufacturers (such as BYD, Pylontech, etc.). Not much cheaper, though.

Another option is DIY (with separate LiFePO4 cells).

Check Victron's documents regarding compatibility of various batteries with their systems.

Depending of the chosen battery, a SmartShunt might be or might be not required.

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Since you have a relatively long run of wire from the PV array to the solar charge controller, use 6mm2 PV wire, not 4mm2. Or regular 10mm2 multi-stranded wire in a conduit (the insulation of regular wire is not UV resistant).

Use a PV panel array disconnect.

And it would be good to have SPD devices.

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Answer 4 · 2021-12-08T10:37:10Z

psommariva answered · Dec 08, 2021 at 10:37 AM

Ok, well, thanks. I guess I will add all stuff etc. etc. by myself.

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