Navitron Renewable Energy and Sustainability Forum

Energy/Electricity Storage and Use/Grid Connection => Off-Grid, Batteries & Inverters => Topic started by: Rupert on February 24, 2011, 08:06:36 PM



Title: Off Grid Back Up System
Post by: Rupert 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?


Title: Re: Off Grid Back Up System
Post by: EccentricAnomaly 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 (https://www.navitron.org.uk/forum/index.php/topic,13005.msg145371.html#msg145371)


Title: Re: Off Grid Back Up System
Post by: Outtasight 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  :o

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.  


Title: Re: Off Grid Back Up System
Post by: billi 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



Title: Re: Off Grid Back Up System
Post by: Rupert 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.


Title: Re: Off Grid Back Up System
Post by: Alan 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


Title: Re: Off Grid Back Up System
Post by: qeipl 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


Title: Re: Off Grid Back Up System
Post by: billi 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


Title: Re: Off Grid Back Up System
Post by: Rupert 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.


Title: Re: Off Grid Back Up System
Post by: martin 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........ :)


Title: Re: Off Grid Back Up System
Post by: Rupert 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.?


Title: Re: Off Grid Back Up System
Post by: biff 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


Title: Re: Off Grid Back Up System
Post by: skyewright 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)?


Title: Re: Off Grid Back Up System
Post by: skyewright 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.


Title: Re: Off Grid Back Up System
Post by: biff 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


Title: Re: Off Grid Back Up System
Post by: Rupert 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.


Title: Re: Off Grid Back Up System
Post by: Outtasight 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).


Title: Re: Off Grid Back Up System
Post by: skyewright 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.  ;)



Title: Re: Off Grid Back Up System
Post by: Rupert 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.







Title: Re: Off Grid Back Up System
Post by: biff 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


Title: Re: Off Grid Back Up System
Post by: billi 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


Title: Re: Off Grid Back Up System
Post by: Rupert 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?



Title: Re: Off Grid Back Up System
Post by: billi 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   ;D



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


Title: Re: Off Grid Back Up System
Post by: Outtasight 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. 


Title: Re: Off Grid Back Up System
Post by: Rupert 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   ;D



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


Title: Re: Off Grid Back Up System
Post by: skyewright 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?