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Author Topic: Off Grid Back Up System  (Read 5060 times)
Rupert
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« Reply #15 on: February 25, 2011, 03:33:27 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.

Very similar to you with gusts same and higher. I would feel a lot safer if they were ground mounted at least i could build something that could be tempory protective to them when needed.
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Outtasight
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« Reply #16 on: February 25, 2011, 05:35:05 PM »

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.

Tumble drier...  hysteria  He said tumble drier....  hysteria hysteria

Water heating - use gas and get a modded washing machine that has the heater disabled.

Kettle - no problem.  Use a lot of power but not a lot of energy.  I can run a 900W one on battery power in the spring, summer and autumn no probs.

Oven - gas or wood or get one of the mini halogen lamp ones to cook chickens or a 400W mini toaster oven.  I get away with that on battery.  A microwave is good too.  For hobs, use a gas one or if it must be electric get an induction one (try one for 30 from a Chinese supermarket or occasionally in stock at Lidl).  I can make a fried egg in under 3 minutes using 700W of battery power.  Need special pots and pans though.

You do have to weigh the cost of a generator against the cost of batteries.  A set of 12 1050Ah fork lift cells will cost about 2300 and last maybe 10 years if you treat them right.  Without grid charging or a generator to keep them topped up to full at least once a week, you'll get a lot less than 10 years use out of them, as partial charge from wind and solar plus daily discharges from loads is a sure-fire way to shorten a lead acid battery's life.

Unless you go mad on oversizing the renewable charge sources and the inverter, you'll need a generator to service large loads like an oven plus a kettle at the same time (6kW easy...).  People tend to use the generator to do the hard stuff and top up the batteries at the same time and then run the small stuff off the batteries to keep the generator hours down.  Generators also don't like running at low loads, causes cylinder glazing and the like.

For every 1kWp of PV you can expect no more than an average of 295Wh of solar DC power per day in December into the battery (and that's my experience in the "sunny" South...).  If you're becalmed as well for a few days with no wind power, you'll be snookered without a generator (or a fall-back to grid).

Try and size the inverter to run a 6kW load and you'll murder the battery in the winter (as a large inverter has a large idle power when just turned on and doing nothing much).  My 3kW inverter draws 45W when running a 10W CFL bulb load.  Just having the inverter on for 24 hours would cost me 840Wh a day in idle power alone, with an average of 545Wh coming in from solar...  Dead battery time.  Spin up a pair of modular 3kW inverters and you're burning 70W of power before you've even turned the load on.

Next year, I'll probably swap out my 3kW inverter in November and use a 1kW one for November, December and January.  You just don't get much use out of a 3kW off grid inverter in the Winter with PV only charging.  At least the 1kW one uses only 10W in idle power.  There's probably a case for designing a modular parallel inverter that has a titchy 100W module, a 1kW module and a 2kW module that can automatically come on stream independently or together as the load changes.

Nowhere is renewables lack of baseload capability more painfully obvious as a dark and dank December week while staring at a dead battery and a dark house, knowing it's going to take a week to recharge without assistance from the grid or a fossil generator.  Billi gets away with it because he's got hydro that is much more reliable in winter (It rains a lot in winter, which is good.  If it's -20C outside though it might still go a bit Pete Tong).
« Last Edit: February 25, 2011, 05:38:07 PM by Outtasight » Logged

http://solarbodge.blogspot.com/
3.58kWp & 800Ah LiFeYPO4 off-grid(ish). See 'Cobbled together PV in W.Sussex' (in "Show Us Yours")
skyewright
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« Reply #17 on: February 25, 2011, 06:05:00 PM »

         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.
<SNIP>
 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.
Very interesting, and particularly wise words at the end.

I have a 750VA APC smart-ups that I decided not to replace the battery on maybe that would be adaptable? For my main uses, i.e. defending mains powered computers from our erratic mains, I find the cheaper back-ups models do the job fine.

I'm currently running some "simulated" small wind turbines (a navitron and a futurenergy, I'll probably repalce the navitron with a miniwind soon) on my weather computer to see if there is any scope for a system that was mainly intended to dump heat. Such a system would need at some batteries too and that could come in handy in a powercut. The 750VA smart-ups would not run as much as yours, but then I don't often want to use a grinder during a powercut.  Wink

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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)
Rupert
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« Reply #18 on: February 25, 2011, 06:09:35 PM »

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.

Tumble drier...  hysteria  He said tumble drier....  hysteria hysteria

It rains a lot here in the winter but i am on to it

Water heating - use gas and get a modded washing machine that has the heater disabled.

Wash at 30 degrees and comes out just as dirty

Kettle - no problem.  Use a lot of power but not a lot of energy.  I can run a 900W one on battery power in the spring, summer and autumn no probs.

Oven - gas or wood or get one of the mini halogen lamp ones to cook chickens or a 400W mini toaster oven.  I get away with that on battery.  A microwave is good too.  For hobs, use a gas one or if it must be electric get an induction one (try one for 30 from a Chinese supermarket or occasionally in stock at Lidl).  I can make a fried egg in under 3 minutes using 700W of battery power.  Need special pots and pans though.

Havent got an Aga and an electric oven is more efficient than a gas oven especially when gas is expensive here, but plug ins like george foremans, microwaves and slow cookers are what we will and do use


You do have to weigh the cost of a generator against the cost of batteries.  A set of 12 1050Ah fork lift cells will cost about 2300 and last maybe 10 years if you treat them right.  Without grid charging or a generator to keep them topped up to full at least once a week, you'll get a lot less than 10 years use out of them, as partial charge from wind and solar plus daily discharges from loads is a sure-fire way to shorten a lead acid battery's life.

Your fuel will cost 3 times what you pay now by years end so a genny is a no no now.





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biff
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« Reply #19 on: February 25, 2011, 06:25:58 PM »

hi skye,
        you will find that the 750va will be exellent, our domestic standby is a 800ah yousa battery bank,supplied by 2 x 80watt solar panels,the inverter is a 650va smart ups(the old toggle switch type)400watt continous. this little ups can run our lights,laptops and large led telly,quietly without effort.
                  im not sure but i think that the 750va is the beginning of the 24volt models,that is easy checked.
                                                        biff
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billi
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« Reply #20 on: February 25, 2011, 09:01:21 PM »

Rupert  be carefull  and wise ! And let all  comments settle !


We cook on gas  in winter and in summer we half cook electric ,


And Outasight is right  , that I work on options , but  i have the land , space and its an obsession , so i cannot tell that is the way  for everyone ,

Billi

But sad enough that there are not more  options ,  mainly cause the "whole herd" is sleeping   hysteria
« Last Edit: February 25, 2011, 09:11:09 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 #21 on: February 25, 2011, 10:02:30 PM »

2300 on batteries over 10 years = 5.00 per week. (replacement costs)

My leccy 15.00 per week.

All options open still viable.

billi question......do you get many windless and sunless days together in winter?

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billi
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« Reply #22 on: February 25, 2011, 10:14:26 PM »

Quote
billi question......do you get many windless and sunless days together in winter?

sure some... then i cuttle my son or get kicked ,by my wife or start the 6 kva Diesel  and wait for better weather

But again Rupert we/I spent a lot of money  upfront here .....................................................

nice part is that the money is gone and its fun now even more   Grin



Rupert do you have a car ? I will make you a back up generator out of it  hysteria
« Last Edit: February 25, 2011, 10:21:10 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
Outtasight
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« Reply #23 on: February 25, 2011, 10:25:35 PM »


                  im not sure but i think that the 750va is the beginning of the 24volt models,that is easy checked.
                                                        biff

I've got a smart-ups 750 that I picked up at a car boot. Yes, it's a 24V type.  With the free download remote management software, you can set a parameter to disable the beeping when operating.  You can also extend the wiring from the removable front panel to make the UPS "remote controlled".

The cheaper back UPS models are mod-sine output.  The smart UPS models are all true sine. 
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Rupert
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« Reply #24 on: February 25, 2011, 10:37:24 PM »

Quote
billi question......do you get many windless and sunless days together in winter?

sure some... then i cuttle my son or get kicked ,by my wife or start the 6 kva Diesel  and wait for better weather

But again Rupert we/I spent a lot of money  upfront here .....................................................

nice part is that the money is gone and its fun now even more   Grin



Rupert do you have a car ? I will make you a back up generator out of it  hysteria

Actually on that point is there anyway you can just drop some jump leads over to a battery bank and start charging your off grid that way on the windless sunless days?........may seem a stupid question to some but if you dont ask etc
« Last Edit: February 25, 2011, 10:41:19 PM by Rupert » Logged
skyewright
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« Reply #25 on: February 27, 2011, 02:50:33 PM »

billi question......do you get many windless and sunless days together in winter?
Did you realise that billi has hydro too?
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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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