Longtime lurker going offgrid

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Longtime lurker going offgrid

Postby offgridCBR » Tue Feb 02, 2016 11:37 am

Hi everyone,

I have been a forum reader for a while and have finally arrived at the point of building a new home on a semi rural block. I am looking at going off-grid mostly due to grid connection costs of roughly $25k.

I have read through a few handy topics here including the sub 25k system thread. Thanks for all the great tips!

I have been quoted 25k for the following system:
20x Trina 260W panels
SMA sunny boy 5000TL inverter
SMA 8.0I Sunny Island Inverter Charger
Sunny Home Manager monitor
Hopergy mounting
16x 3.2v Winston 400Ah LiFePO4 batteries

Need a compatible BMS still and possibly some small battery charging generator or small wind turbine.

What are everyone's thoughts?

* Should also mention current use is approx 5kwh a day for just two of us, but looking to start a family soon.
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Re: Longtime lurker going offgrid

Postby Gordon-Loomberah » Tue Feb 02, 2016 12:53 pm

Welcome to the Energy Matters Forums OffgridCBR :)

5kWh is very economical with the energy use, do you have gas or electric for cooking and hot water?
I'd recommend not wasting money on a wind generator unless it is unpleasantly windy for much of the time where you are, the money is much more productively invested in more PV panels. Depending on how far away the neighbours are, local government restrictions may prevent using a wind turbine too.

With ~4kW of PV (on trackers) I went nearly 2.5 years without needing to use a generator after installing 21kWh of LiFePO4 in 2012, using about 12kWh on average per day, so if you buy a generator it wont get much use if you only use 5kWh per day and grab yourself a few more panels, even if you get 4 or 5 days of cloud straight, and are able to economise on the energy use if necessary.
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Re: Longtime lurker going offgrid

Postby offgridCBR » Tue Feb 02, 2016 2:35 pm

Hi Gordon,

Thanks for the welcome. I haven't done any testing but the site is 800m above sea level in a clear area on a hilltop and I imagine the site is close to 3m/s average over the year. Restrictions might make it useless anyway. The neighbours are approximately 800m-1km away.

Is that 21kWh at 100% DoD?

Extra panels is definitely on the cards. I expect our usage will go up due to being in the process of building a new modular home and having aircon etc. The house will be 3br ~150sqm.

I was also going to ask about HWS as it gets pretty cold in winter (down to -8) and some people have had issues with solar HWS's pipes bursting from the water freezing.

I have no idea (/am open to any) what to do for heating and HWS between gas, solar, heatpump and r/c.

* also if anyone has suggestions for the best offgrid septic systems? Require an aerated system.
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Re: Longtime lurker going offgrid

Postby Gordon-Loomberah » Tue Feb 02, 2016 2:59 pm

Most small WTGs reach their rated output at 8-12m/s, so you'd need a fair bit of wind of at least 6m/s, but solar will still generally be more productive.

offgridCBR wrote:Is that 21kWh at 100% DoD?


yes, CALB 16 X 400AH. The long term average voltage of my pack is 53.0V so 21kWh to 100% DOD

Evacuated tube SHW, so long as you insulate the pipes to and from it properly, shouldn't have an issue with -8C,they use them to -20C in Europe.

Gas is going to cost you (and the environment), but a HP can be run from solar, essentially for free.
A HP can be used for hydronic house heating too.

I use a Clivus Multrum for the loo, I steered well away from aerating systems that have to run pumps a lot of the time- a waste of energy IMO. Of course, it does mean having to shovel sh1t occasionally, and a bit of stirring it too! :)
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Re: Longtime lurker going offgrid

Postby tailend » Tue Feb 02, 2016 4:47 pm

Hi OffgridCBR,

I am in the late design phase of building a new home just outside of Canberra that will be off grid. I have come up with a preliminary design (or three) for the off grid system I would like to install, although I have not identified an installer as yet. I am planning 13 kW to 20 kW of panels (13 to start with then upgrade later after observing my usage) and 600Ah of lithium. I do not want any gas appliances, or a wood heater, so the demands on the off grid system will be significant, however I am designing a highly energy efficient house so heating and cooling requirements will be minimal.

The SMA 8.0I Sunny Island is only a 6kW inverter, which is too small to drive an induction cooktop reliably, so I am looking at either two inverters in parallel mode or a Victron Quattro 9kW inverter. If you are installing an AC coupled system then my understanding is that the SMA Sunny Island can only control a limited amount of power (6 or 8 kW of AC coupled power max) which should be considered in the design and may limit later upgrades.
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Re: Longtime lurker going offgrid

Postby davef » Tue Feb 02, 2016 7:35 pm

Evacuated tube SHW, so long as you insulate the pipes to and from it properly, shouldn't have an issue with -8C,they use them to -20C in Europe.


For my commercially installed system hot water is periodically circulated through the system when the temperature is below 4-5C. Unfortunately, the controller is a mains unit which means I have to have the mains inverter (10-15W/H) on just to supply 1W/H of power to this controller. Should have bought a 24V controller.

If you have a big roof facing in the right direction I would suggest just dumping power from a big PV array into the HWT. At least do the sums.

Good luck!
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Re: Longtime lurker going offgrid

Postby offgridQLD » Tue Feb 02, 2016 9:21 pm

I think your component list looks to be a great start.

As mentioned your kwh / day consumption sounds very conservative but I guess everyone's needs are different.

400ah 48v lithium is ideal size for a typical home. If anything its probably a bit over kill for us but perhaps a good thing as the banks capacity shrinks over time.

5kw of pv sounds fine if your consumption is only 5kwh - AC a day. Though you will never regret going for more PV as your consumption grows. Though perhaps better value having it installed all at once at the same time.

I agree with Gordon on the wind turbine. PV is just so Passive, easy to work with and very good value $/watt. In all but the most windy of locations combined with low sun exposure would a turbine be worth considering over PV.


We run a biolytix wast treatment system (basically a Huge worm farm in a tank under the ground) It has a small sump pump to expel the treated water to a sub irrigation stem that keeps a huge lawn green all year round. Yes the sump pump adds some energy but nothing I'm concerned about over the day. It can be gravity exit if you have the terrain without a pump. Down hill area below it. We actually do have this situation but prefer the water to be used for the lawn than watering down the hill.

It's been in from 2008 and haven't had any issues.It gets a health check and water sample test once a year to keep the local council happy. It's always been very healthy. It never smells even if you stick your head into the tank just has a earthy smell.

Though I will say we are pedantic about treating it well as we want it to last. As in don't tip fat down the sink.We wipe out baking trays with a paper tows befor washing in the sink, say after cooking a chicken.

We don't wash or clean with harsh chemicals. It's a living system so you just have to think will the worm farm be happy with me tipping that down the drain onto them. No massive party's letting spa baths out to them or alcohol down the drain :lol: Though a lot of people in the city treat there toilets and sinks like wast disposal units and tip all kinds of things down them, paint, grease, gallons of chemicals, you name it.

If you building a home from scratch its a great opportunity to tick all the boxes and make the home really sing as a off grid house.

Always better value installing efficient appliance from the get go vs retrofiring a old home. Pay attention where you offrid components are going to go. (battery, inverter room- nook on the south side of the house cool and well insulated)

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Re: Longtime lurker going offgrid

Postby davidg » Wed Feb 03, 2016 6:49 am

offgridCBR wrote:I haven't done any testing but the site is 800m above sea level in a clear area on a hilltop

Some of the following I'm guessing as where you are other than altitude I don't think has been mentioned.
Do you have or is there a PV system installed where you are now? If that is the case in reality you use more than the rather tiny 5kWh's per day mentioned.

---

Hmm, does it snow? It's certainly quite possible at that altitude, if that's the case, do install a proper auto-start generator, while you may not need it often, snow covered PV produces nothing until it's cleared, likewise very heavy fog also produces nothing worth talking about, etc.

I have done one system where this certainly does occur, (730M above sea-level) the generator is the thing that helps the batteries through the very poor weather, snow and ice that occurs. It also keeps the batteries in good condition, without using too much fuel. Wind turbine and ice is a very bad combination.

offgridCBR wrote:Extra panels is definitely on the cards.

This one for the rest of the time in fact a lot more panels is possible.

offgridCBR wrote:I was also going to ask about HWS as it gets pretty cold in winter (down to -8) and some people have had issues with solar HWS's pipes bursting from the water freezing.

Instant gas is a good option for high altitude areas, particularly for winter periods if you looking for a simple option. Works very well for cooking, and ovens particularly for off-grid.

offgridCBR wrote:I have no idea (/am open to any) what to do for heating and HWS between gas, solar, heatpump and r/c


Solar can be useless if it ices over or gets snowed on. Heat pumps / R/C will be VERY inefficient at subzero temperatures. Although a heat pump using ground tubes would work well, but you may well, not have enough power to drive at various time of the year.

Solar is good for the better weather, you should ensure you use a heat exchanger type system that uses glycol based liquid heat exchanger transfer rather than moving water around directly. Then have an instant gas boost for it so that when there is not enough sun or if it's iced over, you still get hot water as wanted.

offgridCBR wrote:also if anyone has suggestions for the best offgrid septic systems? Require an aerated system.


Arerated system on offgrid, absolutely dreadful idea eats power requires regular visits you get charged for, just NO. A Traditional Septic if you can get approval is your best option, otherwise a worm system is the next best. They use either no power or almost no power, as long as there in the ground deep enough will keep working just fine. I've posted on the ATA forums about septics and what you should not put into them a number of times. The answer to long lived septic systems is, if it's a "poison", "antibacterial" or "antiseptic" when it comes to cleaners only use "ECO" or "earth" friendly types, the same goes for shampoos, dishwasher detergents, detergents, soap, washing machine powders, NO fabric softeners (basically salt), etc. Ensure that oil, fat and grease don't enter a septic (better off with a grease trap to stop it) as far as is possible, ensure toilet paper used is truly designed for septic system regardless of the type installed, they are designed to broken down by bacteria, definitely no sanitary pads, tampons, disposable nappies and the like all these will clog ALL types of septic systems and cannot be digested by bacteria that are present in all types of septic systems.

A septic system regardless of the type installed is a LIVING ECOSYSTEM. Sending stuff that is either poison or completely indigestible into them will only cause them to fail in remarkably short periods of time. Properly looked after and doing basic maintenance will allow the system to be very long lived with minimal costs to maintain.

No matter what a builder might say INSULATION, INSULATION and more INSULATION is far, far better than trying to add heat in other ways, such as R/C aircon which will use lots of power and will be VERY INEFFICIENT when it's very cold, you don't want to have to generate that power in the first place, use a wood burner if you really need to heat looks good, needs no power or almost no power to function.

At the altitude I'd suggest that's far too cheap for the system. An under-designed system / under spec'ed system at that altitude could easily windup becoming an expensive problem requiring even more than spending it upfront to resolve shortfalls. #just saying.
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Re: Longtime lurker going offgrid

Postby offgridCBR » Wed Feb 03, 2016 10:44 am

Hi everyone and thanks for the responses.

- I will definitely steer away from wind and go with some more panels if I have left over coin. If I was to go with a cheap/ok auto-start genset for battery charging what would you recommend?

- Pretty much everything is going to be new (and made as efficient as possible, so definitely happy for any advice on appliances, including separate fridge and chest freezer) and we are in the process of finalising the design for the DA.

- Looking at using bottled gas (or fixed tank..?) for cooking and for instantaneous boosting of an evacuated tube SHW system at this stage.

- Current usage of 5kWh per day is from bills over the last 12 months renting in an old late 1800's era cottage with no insulation and only gas heating (no aircon). Though this is very likely to go up with the new house and associated amenities.

- Can't go with the traditional septic system sadly. Geotech did a Site & Soil Assessment for On-site Effluent Disposal, result was topsoil to 300mm, clay to 600mm then weathered granite from 6-800mm. Report stated surface or subsurface irrigation and an aerated wastewater treatment system. Would a worm farm system work here? (I will definitely check out the biolytix system - thanks Kurt!). I had the same concern with power usage of an aerated system... :?

- What BMS would work well with the Winston batteries and quoted system?

- I was also hoping to be able to do the occasional welding in the shed... what inverter rating would be required to support that?

- Also definitely upgrading the standard insulation, current standard is:
R 4.0 ceiling insulation batts
R 2.0 wall insulation batts + 7mm plywood bracing and cladding (looking at weathertex)
Heavy Duty roof sarking & wall wrap
R 1.5 under floor insulation

- It rarely snows and is usually quite light if it does where the property is located. Davidg, why would the altitude dictate the price of the system? And why do you envisage that it would be under specified/designed, outside of the number of panels and inverter rating?

- Also any other advice regarding the system is greatly appreciated! Thanks everyone for the feedback!
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Re: Longtime lurker going offgrid

Postby offgridCBR » Wed Feb 03, 2016 10:47 am

Also have been looking at greywater recycling purely for the yard/garden, and have found most systems to be prohibitively expensive until I stumbled upon this:
http://www.greywater.com.au/greywater.php
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