Looking to buy an Off Grid property.

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Looking to buy an Off Grid property.

Postby blakamin » Mon Oct 02, 2017 3:44 pm

Hi, My partner and I are looking at a property that is off-grid and I'd like to learn some quick basics so I can ask the right questions (and get the right answers) before we get serious.

All I have at the moment are some vague specs:

• Solar (10 panels x 80w each)
• 890 amp hour battery storage
• 2kW inverter

What questions should I be asking?

Thanks, Mick.
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Re: Looking to buy an Off Grid property.

Postby davef » Mon Oct 02, 2017 5:08 pm

Type and age of batteries. 80 Watt panels, how old?

Log of battery usage and PV generated.

Any plans for back-up? LED lighting? Any equipment that needs to be on 24/7?

Documentation of commercial equipment. Any custom or home-made equipment?

Gas cooking and wood heating?
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Re: Looking to buy an Off Grid property.

Postby blakamin » Mon Oct 02, 2017 5:17 pm

Thanks... It has gas cooking and wood heating.
All our current lighting is Philips Hue.
Only 24/7 equipment would be router, a couple of external hard drives, and home automation hubs (philips, logitech)
I would have a back-up gen.

It's just that it doesn't seem much of a setup really. No voltage mentioned for the 890Ah battery farm for a start.

Has a massive shed (nearly bigger than the house) but it's 300m away.

The whole property is 37acres.
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Re: Looking to buy an Off Grid property.

Postby Gordon-Loomberah » Mon Oct 02, 2017 7:58 pm

80W panels suggest they are quite old, so the batteries may well be well past their best. The lack of any specified voltage would suggest it is only 12V, maybe with a slight chance of 24V. Either way, such a system will only supply a small amount of energy in sunny weather, and the generator will be guzzling lots of expensive fuel in cloudy weather.

In the absence of much detail, I suspect you may want to think about setting up a new system with a lot more PV panels and a Lithium battery.

Do you have any idea of how much energy you will be using per day?
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Re: Looking to buy an Off Grid property.

Postby blakamin » Mon Oct 02, 2017 8:03 pm

Thanks, I thought that might be the case.
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Re: Looking to buy an Off Grid property.

Postby lantern » Tue Oct 03, 2017 6:39 am

You will find a lot of answers here.

http://www.rpc.com.au/information/faq.html

It's a great way to start.
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Re: Looking to buy an Off Grid property.

Postby Sunder » Tue Oct 03, 2017 2:47 pm

890Ah of storage would be fairly large. At 12v, it'd be 10,680wh, or about 3 sunny days for the panels to fill from empty to full. Perhaps if they took the advice that you need 3 days buffer to go off grid. It's also possible they used 2v cells, or 6v cells, and just added all the Ah up.

One thing you need to consider that is that if you have even one 24 x 7 mains device (no fridge?), you need your inverter on 24 x 7. Cheap inverters can have a really big idle draw. My powerjack for example, (Which is one of the worst examples), draws about 2A with no load @ 29v. So we're talking 60w to power say, a 5w router. Want to do the maths on that efficiency? :P

Many so called "mains" devices such as routers and hard drives are drawing either 5v or 12v. One trick I've learned is that USB car chargers can make fantastic cheap and efficient power supplies. A 5v router can be run using a USB to 5.5mm cable, available for less than $2 (Well if you buy from eBay, this one is $7):

Image

http://www.cablechick.com.au/cables/usb ... dc-5v.html

12v devices, if they are tolerant of voltage changes can be run straight from a battery, or if they are voltage sensitive, you can use Qualcomm quick charge chargers with a trigger to get any voltage from 5v to 20v in 200mv increments, up to 1.5A. That's usually enough to drive a hard drive - you can always parallel them if it's not enough current.

Anyway, I reckon unless they can show you that it was installed in the last 2-3 years, you should assume the set up is generating well less than spec, and batteries are end of life, and allow budget to do an upgrade soon after moving in.
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Re: Looking to buy an Off Grid property.

Postby blakamin » Tue Oct 03, 2017 4:11 pm

Thanks everyone. The agent just got back to the Mrs.
"The batteries are 24 months old and configured to supply 24 volt DC to the inverter. Actual average voltage is 28 volts approx."
He also included some images.

Image

Image


Any thoughts?

Apparently mains power finishes with the house over the road... Not much help when that's 385m away as the crow flies, or 550m up the driveway :D
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Re: Looking to buy an Off Grid property.

Postby Sunder » Tue Oct 03, 2017 4:26 pm

They definitely look big enough to be 890Ah each.

The inverter looks professionally installed as well. Looks to be a single RCD for the output, then an individual fuses for each circuit, so it should be safe.

Pretty small solar panels for such a large battery: at 24v, that would be over 20kwh.

Are the old owners living there full time, or is it a holiday house?
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Re: Looking to buy an Off Grid property.

Postby blakamin » Tue Oct 03, 2017 4:33 pm

It *looks* to be an older couple living permanently, judging from their furniture.

There's a bank of 6 panels and a bank of 4. All mounted on frames at ground level.
I suppose updating the panels, or even expanding them wouldn't be too hard or expensive if the rest of the system was up to it for the first couple of years.
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