Off-grid

I’ve “almost” completed my house in Noordhoek, and its completely offgrid power-wise.

Currently I have 6 x 300W panels, 2 x 220Ah GEL Lead Acid batteries, an FM80, and a Victron 3KW Multiplus running, which gives me about 2KW of usable battery +- in 16 hr period, or in easier to understand terms – about 125W / hr of usage outside of daytime.

Panels come in from the roof, in 2 strings of 3 panels each.
The FM80 can support 150V / 64A input max, so I have to put 3 panels max per string for safety reasons.
36V x 3 @ 8A x2 / 108V /8A per string.
For a 108V / 16A into the FM80.

This then comes out of the FM80 to a 24V battery bank.
The FM80 charges the in the early mornings, and keeps it topped up during the day if necessary.
The 24V battery bank is connected to a Victron Multiplus 3000/24, which then provides AC out to the house.

Batteries are 24v / 220Ah (5280W total capacity). 12v / 220Ah in series to double the voltage to 24v.
Usable capacity is 2600W overnight assuming a 50% discharge.
Overnight I actually use less than 1KW or so, so I discharge to about 80% overnight from a full battery.
Thats a 20% daily DoD, which should give me a decent lifetime.

This isn’t much!
Obviously the limiting factor here is storage (batteries), as the panels can generate far more than is needed to recharge the batteries or run the house.

What does my house need anyway in terms of power?

Lighting
Lighting is all filament LED, so is minimal
Kitchen = 5 x 3W
Bedroom = 1 x 8W
Bathroom = 3 x 3W

32W inside with all the interior lighting turned on.

Water
Hot water is provided by a solar geyser.
I’m not planning on supplementing the hot water with electricity to heat in winter unless I need to shunt excess power out from the solar panels at the inverter, so thats zero usage.

Fridge
Despite the complete lack of information on most websites regarding power usage for Fridge / Freezers, I’ve decided on this model – Bosch KGW36XL30

It claims to use 227 KWhr/year, so thats about 620W /day (or 25W / hr), which is quite reasonable.

Its R7,000 though, so not cheap!

Useful site for checking KW ratings here – http://www.shopmania.co.za, as most of the manufacturer sites are useless.

Cooking
Gas oven / hob setup, so zero power usage (SMEG 60cm unit).
Electric Kettles, and toasters are a no-no, as they suck too much juice.

Washing
Washing machine should use about 1-2KW a wash, so can only be run daytime when there is sun.

Entertainment
LED TV should be fine, as they’re about 50-70W on average.

Not much headroom for other electronics, but its sufficient for the basics. When I make more money, I can ship over the Lithium batteries 🙂

  • Trevor Stander

    Thanks for sharing interesting read.

  • Grant

    Bosch KGW36XL30 is on special at Game for R5990

  • Peter SolarBoy

    How has you off-grid experience been thus far? I’m close to going there , have Sunny Boy, Mutiplus and batteries but am keen to see how living with PV through the winter works out.

    • 小杜 (xiao du)

      So far pretty good. Zero issues.

      I wasn’t around for last winter though, but I left the house on, and generating over winter. The equipment was running without issue for 6 months while I was away powering a normal sized fridge, and some small loads (wall wart psu’s for some small electrical stuff).

      I’m living in the house at the moment, and have added a little more equipment (HP Microserver+5 drives running 24/7 + wifi router + laptop 24/7). Also have a little Nespresso coffee machine which sucks up lots of power for about 1 minute for an occasional morning coffee. Batteries usually get fully recharged by early morning so far, with a dip of about a volt – a volt 1/2 overnight. eg 25.7 – 24.5

      I’ve was rather tentative about using electricity overnight to begin with, but it does seem to be a case of I was worrying too much.

      Daytime, its a case of look at how much I’m wasting by not using the electricity generated, as most mornings I’m fully charged by 10-11am (or much earlier. Its 8:37am today, and I’m fully charged, and into float already..). I have an ideal setup though, panels are north facing, and I have no shade. Some days generation has been > 14 hours (5:30am -> 7pm+).
      I’m considering getting an Aircon for daytime, as I’m simply wasting all the excess generation in summer.

      I currently have enough battery for overnight in winter (albeit without me there), so I should be fine for that. Whether I’m here, or away, the usage should be fairly similar. Fridge is the main load, then NAS, wifi. I’ll probably power off the NAS while I’m away. The wifi stays on, as I have a small security system setup for recording/ remote monitoring. (2W/hr per camera, so negligible).

      Winter will be the real test though.
      Hot water will probably be the main issue – I’m happy with lukewarm showers though, and I think I’ll be ok. My experience with my other house is that its more than hot enough. Worst case I can add a few dedicated solar panels -> the solar geyser element if it needs it.

      Making sure the house is insulated well, and the north facing windows have Low-E coatings has definitely worked out well too.

      All in all, I’m very happy with my setup. I haven’t faced any issues yet, and in real life usage, it doesn’t feel like I have to worry about limitations – ie not using things at certain times. I don’t have an electric kettle, toaster or microwave though, but then again, I haven’t felt the need for one. A gas stove works well.

  • Peter SolarBoy

    Are you using Victron in offgrid mode then with victron controlling the inverter or do you have mppt charger

    • 小杜 (xiao du)

      Panel DC -> Outback FM80 -> 24V batteries -> Multiplus -> AC

      Using the Multiplus as a simple dumb inverter.

  • Jon Lijnes

    I also live in Noordhoek and have a similar setup
    I have developed extensive analysis tools to determine the most cost effective sizing of various elements required for an installation Drop me a line if you want to discuss
    All the best (021 7891327)

    • 小杜 (xiao du)

      Next time I’m in .za I spend most of my life in .cn these days