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Author Topic: Off Grid Back Up System  (Read 5154 times)
Rupert
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« on: February 24, 2011, 08:06:36 PM »

For those times when we may not have power i was exploring the way i could build a system to provide essential back up power to the house which could be built on by adding to over the years to be almost self sufficient.

I was just thinking of a generator but after reading many threads diesel would be the only way and i would have zero chance of finding and refurbishing a lister type genny, so my thoughts are with a home built generating system using renewables. I first thought the use of water but my flow and hieght isnt suitable so it comes down to solar PV and wind turbine.

I would invest in a battery bank to provide essential power but what would you lot reccomend to charge these batteries of what??  size & quantity for a house maximum 14 units of leccy per day but this could be reduced with savings.

Location windy spot and south facing.  PV part wind system. PV would have to be ground based to avoid damage and wind turbine would have to be lowered to avoid damage from storms.

What could i do with just a few thousand to start with?
« Last Edit: February 24, 2011, 08:08:09 PM by Rupert » Logged
EccentricAnomaly
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« Reply #1 on: February 24, 2011, 10:20:25 PM »

I think Paul's reply to my questions about petrol generators might be apposite:

https://www.navitron.org.uk/forum/index.php/topic,13005.msg145371.html#msg145371
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Outtasight
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« Reply #2 on: February 24, 2011, 10:38:50 PM »

When you say PV would have to be ground based to avoid damage.  I'd have thought a roof mounted one would be less susceptible to wind damage than a ground based one, unless the house is liable to blow away  Shocked

The main thing is how much backup do you want to provide?  What are your critical loads that you can't do without?  Next question is how long do you want backup for (an hour, a day, a week?).  These two things will determine how big the batteries need to be and what kind of charging is needed.

How often do you need the backup?  If it's just in emergencies, then a generator is the cheapest way.  If it's every day, well then it's not really backup power!  Renewables will be cheaper in the long run (10 years) as you'll save diesel / petrol.

Battery systems should be your last resort, as they are big, expensive, dangerous, and are easily killed.  
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billi
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« Reply #3 on: February 24, 2011, 10:53:49 PM »

.... night time electricity is cheap in Ireland , so perhaps  one could start to save  using mainly night time units  in combination with a system  i described here  
http://www.navitron.org.uk/forum/index.php/topic,13043.msg145767.html#msg145767   but perhaps double or dribble the size  and a smallish cheaper back up generator

But normally i prefer charge controllers to gridtie solar inverters in a battery setup (or a combi of both )

Billi

« Last Edit: February 24, 2011, 10:55:28 PM by billi » Logged

1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
Rupert
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« Reply #4 on: February 24, 2011, 11:47:40 PM »

Regarding this increase billi are you just talking extra PV panels and a battery or two extra? So no more need for extra controls?

Outasight:- Your Sussex weather is totally different to ours.

I dont know how often i would need back-up but i am thinking of spending any cash in the way of renewables than other ways at present just to see if it is viable to get a working system.

Oil fuels are just going to go up and up now.
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Alan
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« Reply #5 on: February 25, 2011, 04:38:26 AM »

Hello Rupert

First step would be wall / loft insulation and stop draughts / air movements.
Second step would be an electrical change over switch at the grid connection point.

This would allow you to switch the house over to a petrol / diesel generator.
Options then would be.
Solar thermal panels for heating.
Ground mounted electric solar panels and grid inverter for export.

Then think battery and off grid inverter.

Regards

Alan
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qeipl
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« Reply #6 on: February 25, 2011, 08:57:45 AM »

Hi Rupert,

When thinking about this you have to start at the consumption end of the picture.

What loads do you use to consume the 'maximum 14 units a day'?
Which of these are critical - the ones that you can't do without when the grid goes down?
What is the rating (kW) each of these critical loads?
How many hours do you need them to run before reconnecting too the grid?
How many times in 12 months does the grid go down?

When you have definite answers to all of the above you can then start to compare the cost/benefit of a genny against PV/battery, etc.

Then the whole picture will begin to become clearer.

Malcolm
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billi
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« Reply #7 on: February 25, 2011, 09:48:36 AM »

Alan ,

Quote
This would allow you to switch the house over to a petrol / diesel generator.
Options then would be.
Solar thermal panels for heating.
Ground mounted electric solar panels and grid inverter for export.
 

where to export to and why , in Ireland ? Have my doubts , that it is worth the hassle and the extra money  to deal with the ESB here
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
Rupert
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« Reply #8 on: February 25, 2011, 09:57:46 AM »

Suppose my biggest load would be kettle, oven and wasing machine and tumble dryer.

Generator as main back up source?  Out of the question now because of recent events and probably the most expensive option.

So i am looking at something i can start with and hopefully build on.
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martin
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« Reply #9 on: February 25, 2011, 10:24:12 AM »

Three of those things are precisely those that you shouldn't be using electricity for......... there are other easily available substitute fuels, -  a good rule of thumb is to only use electricity where nothing else can do the job (it costs so much to produce/capture/store, especially off-grid), get one of these........ Smiley


* Six-Lath-Ceiling-clothes-Airer.jpg (39.81 KB, 650x432 - viewed 315 times.)
« Last Edit: February 25, 2011, 10:37:43 AM by martin » Logged

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Rupert
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« Reply #10 on: February 25, 2011, 12:19:16 PM »

I agree entirely Martin and as i said i can make savings.

Tumble dryer i reckon i could get out of 95% of it's use.

Oven well i just need to buy a plug in slow cooker but that will be done.

billi uses half the amount i do and i think i could get down to his level or not far off.

One thing that confuses me is when PV is only avaliable part time (daylight hours) How is this preferred over wind turbine which could go for 24 hour per day.?
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biff
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« Reply #11 on: February 25, 2011, 12:57:07 PM »

hi rupert,
        it would be nice to think that your turbine would perform 24 hours a day,sadly that is not the case.we are totally off grid and i know from experience that you can have weeks where the wind just will not do its thing.on the other hand solar panels give something every day,be it small lot or a big lot but they work every day,you just have to be able to store enough for 24hours, for your basic needs.,light, telly, laptop,microwave and small chargers.
  you can get the above quite easy with 2 x 80watt solar panels and a 24v x 600ah forklift truck battery, there is absolutly nothing stopping you from fitting a parallel circuit of 8 double sockets in your house and plumbing them into the back of a smart 1500va ups,=980 watt= exellent lecky.
                                                 biff
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skyewright
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« Reply #12 on: February 25, 2011, 02:47:41 PM »

there is absolutly nothing stopping you from fitting a parallel circuit of 8 double sockets in your house and plumbing them into the back of a smart 1500va ups,=980 watt= exellent lecky.
Is that just an ordinary computer style UPS?

Do you just extend the UPS's battery leads out of the case and attach them to the battery bank (ensuring same voltage)?
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Regards
David
3.91kWp PV  (17 x Moser Baer 230 and Aurora PVI-3.6-OUTD-S-UK), slope 40, WSW, Lat 57 9' (Isle of Skye)
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« Reply #13 on: February 25, 2011, 02:51:53 PM »

Location windy spot and south facing.  PV part wind system. PV would have to be ground based to avoid damage
How windy?

I'm on the Isle of Skye and have a roof mounted array. We face WSW, straight into what is typically the direction of our strongest winds. At the start of February we had winds gusting to over 70mph. I was much relieved to fine the panels safe and secure next morning. The mounting screws and rails are very substantial.
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Regards
David
3.91kWp PV  (17 x Moser Baer 230 and Aurora PVI-3.6-OUTD-S-UK), slope 40, WSW, Lat 57 9' (Isle of Skye)
biff
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« Reply #14 on: February 25, 2011, 03:27:20 PM »

yes david,
         it is the ordinary pc ups, best going for a model not less than 5 years old, the new ones have a built in timer which shuts down after 20 mins and cannot be bypassed,,the smart 1500va is 24volt dc. the internal batteries have to be removed and an anderson connection fitted,(preferably a double in the dc inlet,which means you connect another bank on in seconds without shutting down,
       a ups plug and lead (preferably 16amp)approx 300mm long is fitted with a switching type double socket and plugged into the ac outlet on the back of the ups
   sometimes this particular ups refuses to cold start,so a small 100watt or less inverter will be enough to bring it to life in ac,and when the 1500va is running remove the small inverter. the battery condition on the ups will sometimes give conflicting reading for a few days.very few give the full 5 lights, you get used to the beeper after a while and get to depend on it to tell you everything is ok if you are working with small tools such as grinders and pillar drills.
     there are other methods which can update this ups and double it output but 980watt is not to be scoffed at.
 please remember you are working with a very powerfull force of electricity which can kill.do not do anything silly, even when the batteries are removed the caps still have enough juice to knock you out and stop your heart.
                    biff
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