question

Hi

Do the load calculations for each cabin, then do voltage drop calculations for the cable size to suit

so to give an idea what requirement are needed for the main inverter which could be mounted center between the the 2 cabins either side so there will be less of voltage drop.

If you give me the details of the loads and intended cable size and supply voltage, i can work it out for you to see what is possible, with one main inverter feeding all four cabins etc.

Note: you are allowed 5% to 6% voltage drop over a length of cable.

Regards

Rob D

NZ

This is a very interesting project. In order to plan it well, you need to provide (or at least make yourself aware of) some quantitative data:

* Cable quality/thickness of the 100m cable between the cabins. Does it exist already or will it be installed?

* What is the power requirement of a single cabin (usual/peak)?

* What is the said "potential for its own solar + battery + inverter installation." I.e. how much of Wp is installable, how much space is there for batteries etc.

There are many ways how to achieve a solution for this, where "having a Solar 'power station' at one location with big inverter(s), and a thick copper cable" is the most boring one. ;-)

I have a fancy spreadsheet to forecast the power loads / generation, but it is a bit of guesswork as the occupancy will vary a lot.

The main house is the main consumer (central) and outliers are mainly Hue LED lighting

- Day consumption (from Solar) 2500-5000 Wh, depending on empty/occupied

- Night consumption (from LFP Battery) 1800-3300 Wh, empty-occupied

Rob's thinking about a central inverter and 5-6% voltage drop was my starting point. Perhaps it is a simple case of weighing up cable cost versus inverter cost.

There is no cable or anything at this stage, a fresh start! But I know that Victron VRM + Venus OS on Pi and BMV/MPPT (+Hue +Smart Life +Meross) will be essential parts of the solution.

I was also wondering about micro-inverter / power grid / ESS. I understand (ish) the concepts but no idea of current state of technology. Hence my question.

Aside:

- On my 44 foot boat, I have two batteries located next to their major loads (120A+) with a 60A power sharing cable between. This was a good design at the time, as most often the energy is stored closest to it's consumer, and then steadily restored by solar. This was the concept that I was thinking of replicating.

Further Observations:

- Solar power is now so cheap now, that I am leaning towards excess panels and taking care to not overcharge the lithium battery. (170W below $43 direct from China, $0.25 per watt.)

- Lithium power is still an investment, but definitely value from money ($4/Ah@12V direct from Winston China.) So battery storage is considerably more expensive that solar generation.

- I have essentially unlimited area for solar panels. Based in 12deg N, Philippines, so fairly safely can expect 4-6 hours a day.

- Of course, I have a little silent-type generator as well, but this is gasoline, unreliable and manual start, so this could help to supplement generation when occupied, and LFP batteries can allow the noise during the day and the silent consumption at night (nice!)

In Summary:

- So are we looking at a trade off between cable cost versus multiple inverter cost?

- Is there any funky technology from Victron to address this kind of distributed generation / unpredictable consumption system?

We are working on a project at the moment that requires power (maybe centralised) for distribution to 4 simple guest cabins (gas hot water, gas cooking) and possibly more cabins in future. Would be keen to read thoughts.. There is ample space for a ground solar array and internal space for batteries and inverters etc. We are thinking to also include include Fronius inverters for hybrid power. The distance for 240 volt to go from equipment shed to cabins is 50-100m. I am mindful of the above observation "If you centralise and it goes down, you lose power for everything. If you distribute (all elements, not just generation), a single failure is nominally contained to at most 25% of the system." Please let me know if I should start a new post/topic. Looking forward to any comments. Nick

I came across some secondhand solar panels and decided to install a central power station. Actually I think it will be easier maintenance because everything is in one place and easier to secure from curious fingers. I have. 2 quattro 8kVA also, so some redundancy. I came across programmable ac power meters and breakers which connect to WiFi. So the whole system could be remote controllable. Installation will be finished by Christmas hopefully. So can't offer much further ideas or experience myself.