Renewable energy set up please help.

[Mayesemma]

Hello. I am a newbi here so apoligies if someone has already posted something along similar lines.  We are currently setting up an off grid system using wind turbines and solar panels using a battery bank to store the power. I am looking operate a washing machine (Max 2.5kw), small fridge (110w), laptop, Lcd tv (one big and one small) as well as a few lights and the occational blender. Any advice on what batteries to use, etc would be greatly apreciated. I am trying to look into Lithium ion batteries but I dont know that if they are hugely better than deep cycle. Any help please. Many thanks
Emma

[biff]

welcome to the forum mayesemma,
                 it is a good idea to sit down and take account of everything in terms of watts or power requirements. of all the things you mentioned the fridge is the one which people always underestimate,so maybe you should consider a gas fridge. you can purchase a dyson 600watt vacuum cleaner and you will find it exellent,washing machines have large heaters which make huge demands on the inverter,so it might be an idea to go direct drive and buy a lister geni which can run on veg oil.
          my wife and i have been off grid for years and managing quite well on our 2kw turbine and solar arrays, we have a 5kw geni as backup but it only gets used once in a while or when there is not enough power to drive the washingmachine.
    its just something that takes a while to get used to but you will get the hang of it,there is no problem generating power,its how you use it and store it.,,,,good luck.
                             biff

[clockmanFR]

welcome mayesemma,
We are on grid but not selling our energy or claiming Feed In Tariffs.

We have PV and 3 windturbines (max 8KW) Hugh Piggott designs, and a 52.6v 660amp hour battery system, and a APC UPC (computer back up supply) 48v 3.7kw Inverter. Installing more, 3KW, PV - photo Voltaic panels.
 
Running the washing machine with our Inverter and batteries would within half an hour have the batteries down to shut down voltage.

I think biff's right regards having a Genny ready/on standby for that extra loading. Us, we then draw from the mains supply.

Battery choice is difficult and really will have to be your choice for what you actually want.
Quated to me, "Batteries are a Black Art".  

[Mayesemma]

Thanks for your advice we have been offered a cheep lister that needs a little work so think i may go down that route was also concidering maybe ditching the washing machine and returning to hand wash as will have loadsa hot water from our back boiler in winter and solar in summer. We did it before in a lil caravan while traveling, mind you didnt have 2 kiddies then. Looking forward to experimenting. Thanks again
Emma

[Eleanor]

Emma, we've got one of these which works well :

http://twintub.co.uk/epages/eshop188917.sf/en_GB/?ObjectPath=/Shops/eshop188917/Products/%22Polar%20Quiet%20Storm%20Twin%20tub%20Washing%20Machine%22

It only uses a small amount of electricity and can take pre-heated water. The clothes are nearly dry after being spun. You have to be fairly thick skinned to put up with the twin tub jokes though 

[EccentricAnomaly]

At the moment almost everybody off-grid uses some form of lead acid battery: typically either deep cycle, forklift or the in-between golf cart/off-grid (e.g., Trojan) types.

From what I've seen most people who try deep cycle kill off one set learning that they're not really as suitable for deep cycle as some would have you believe, though they're much better than car batteries and the like. I'm hoping to skip that episode.

There are two fundamental problems with lead acid: they don't like being deeply discharged and all the time that they're left standing in a somewhat discharged state they "sulphate" (the lead sulphate on one of the plates forms into bigger crystals which are difficult to remove and reduce the cell's capacity). Forklift types are less vulnerable to the deep discharge than most but I've yet to see any convincing evidence that they don't sulphate. The people I most respect to give a straight opinion on them seem to charge them up fairly quickly after use.

Another problem with lead acid is that they need to be charged quickly at first (fine for a generator) but then need a long absorption phase at low current which is a bit more awkward (or, at least, wasteful) to provide from a generator.

In general, the way you'd like to use a battery for off-grid living: charging it up during the day then using some energy during the evening, leaving it sitting overnight a bit discharged, then maybe partially recharging it the next day and so on until there's a windy/sunny day to fill it right up again is almost designed to destroy lead-acid batteries. The solution generally adopted is to oversize the bank so that it doesn't spend much time too discharged.

For these reasons the use of lithium ion batteries is, indeed, intriguing. They are in many ways a much better fit for off-grid. For example, it's actually better for them to be left in a partially discharged state.

The big problem, of course, is cost. Some figures I came up with a while ago were 48 p/W·h (pence per watt·hour) for LiFePO4 (lithium iron phosphate) vs 8 p/W·h for forklifts. When comparing LiFePO4 against sealed deep-cycle batteries the contrast is not so great as you really need to only count a fairly small proportion of the "sticker" capacity of those batteries (maybe 20%) to get the practical capacity you can use without reducing their life significantly.

An argument against lithium ion batteries is that they need a battery management system to keep the charge on the cells even. In an ideal world, though, you'd have a BMS on lead-acid batteries, too. People get away with not having them by a) using a closely matched set of cells and b) slightly overcharging ("equalizing") once in a while to make sure all the cells are the same level of charge (there are other reasons for this overcharging as well - it's also something you can't really do with sealed batteries).

The conservative answer is to use forklift batteries or similar but smaller "wet" (not sealed) cells. If you're willing to take a bit more care then sealed batteries can work fine.

Lithium ion are a possibility but the technology is less well understood as yet and therefore all a bit more risky.

[wookey]

Lithium ion, or Lithium Iron Phosphate(LFP or LiFePO4) (and Lead-acid) are as EA has described. The people who know all about them are electric vehicle (bike/scooter/car) people. Read all about it on Endless sphere, V is for voltage and similar forums. You do need a BMS, and a particularly good one is the 'zephyr' that has been designed on Endless Sphere over the last few years. You can buy a pre-built one for about $200 or build your own.

Lithium is _loads_ better than lead-acid if you need to move them as they are less than 1/3rd of the wight for a given capacity. For off-grid use that's not much of an issue so it comes down to cost, ease of use and lifetime. LFP cells last a lot longer than Lead-acids do in vehicular use (heavy discharge to maybe 1/3rd capacity at high rates once or twice a day) - typically 3-5 times as long, although data is still quite thin on the ground. (I bought a high-rate ~1.5kWh pack a couple of years back for £700 direct from china and it's been very good so far - it looks like prices have nearly halved since then). LFP is actually cheaper than LA for EV use because although it costs about 3 times as much to buy but  it lasts more than 3 times as long.

You need to work out what discharge rate and capcity you need. LFP cells vary enormously in max discharge rate from 2C to 20C - the cheaper ones have the lower discharge rates.

Let's say you use 2kWh/day average and want 5 days backup (is that the sort of time people use?) - that'll need ~10kWh of battery (unlike LA you don't need to oversize, or at least not much). Assuming 12V for system compatibility, that's ~800Ah, so 8 off 400Ah cells would do the trick. They are 400 euro each, so that's about 3 grand for the battery pack (using winston/thundersky cells - which are now available from Germany - cheaper cells are available). Your biggest load would be the 2.5kW washing machine, which is ~230A at 12V. That's less than 1C with 400Ah cells so just about any cell will do. I haven't really looked at the really big cells before, but Winston's go up to 7000Ah! http://www.ev-power.eu/index.php?p=p_55&sName=lifeypo4-big-cells-%283.2v%29

Charging requirements are simple - much the same as lead-acid in fact: bulk charge at high rate (up to 2C), then careful voltage control to fill up. Lower topping voltage (3.5V) will increase cell life. So existing kit designed for lead-acid banks can probably be pressed into service.

You would definately be an 'early adopter' if choosing LFP rather than LA. Here's an outfit selling portable PV + LFP systems: http://www.powerenz.com/store/index.php?_a=viewProd&productId=234 so it is already a commercial reality.

[EccentricAnomaly]

Let's say you use 2kWh/day average and want 5 days backup (is that the sort of time people use?) - that'll need ~10kWh of battery (unlike LA you don't need to oversize, or at least not much).

I think that's both a bit optimistic and pessimistic at the same time which probably cancels out.

2 kWh/day doesn't seem like a lot. A fridge will probably use roughly 1 kWh/day for starters. Anybody who's at home all day will use a considerable amount more - Emma mentions she has two kiddies, for example.

On the other hand, it's not like you'll have five consecutive days of pitch darkness (though you can easily have five days with wind less than the cut-in speed of a turbine). This is assuming you have enough access to the panels to clear snow off them. Your PV will generate some electricity whatever. It seems like you can reasonably hope for at least the equivalent of half an hour's production on all but the very worst days.

Another consideration is that you can adjust your usage to match the conditions and the state of the battery. E.g., let the washing pile up a bit to be done on sunny days (which are good for drying, anyway) so the electricity for the washing machine never needs to go into or out of your batteries at all. Similarly, use of a slow cooker during the day avoids use of the batteries. Batch cooking on sunny days to be frozen then microwaved (high power but quick so low energy) on dull days would also help.

Also, you're probably going to want a generator (as mentioned) as backup, particularly if you have small children. If you invest in that then never use it it's a) not ideal for the life of the generator and b) an indication that you've wasted money and resources by over sizing the battery bank.

I'd suggest reversing Wookie's figures: 5 kWh/day but 2 day's backup (meaning you'll actually "survive" four days in typical bad PV conditions before you need to run the generator, a bit more if you wind your neck in on energy use sensibly) so the same answer (10 kWh of battery) in the end.

[w0067814]

welcome mayesemma,
We are on grid but not selling our energy or claiming Feed In Tariffs.

We have PV and 3 windturbines (max 8KW) Hugh Piggott designs, and a 52.6v 660amp hour battery system, and a APC UPC (computer back up supply) 48v 3.7kw Inverter. Installing more, 3KW, PV - photo Voltaic panels.
 
Running the washing machine with our Inverter and batteries would within half an hour have the batteries down to shut down voltage.

I think biff's right regards having a Genny ready/on standby for that extra loading. Us, we then draw from the mains supply.

Battery choice is difficult and really will have to be your choice for what you actually want.
Quated to me, "Batteries are a Black Art".  

(This could be read as teaching you to suck eggs, but I've written this for those who don't know, so please don't take offence.)

Hi,

I think you have a serious problem with your system. You should not experience any issues running your washing machine from a system with the specifications yours is.

Your battery bank (48v, 660AH) stores 31.68kWh of energy. Let's assume that your washing machine draws the full 13 amps allowable from UK mains sockets and your inverter voltage is high at 240v, then your washing machine draws 240v * 13a = 3.12kW.

Lets assume your inverter is not very efficient - say 80%. The 3.12kW draw from the washing machine is presented as 3.12kW / 0.8 = 3.9kW to the batteries.

So multiply the power by the time to find the energy usage: 3.9kW * 0.5 Hours = 1.95kWh.

1.95Kwh / 31.68kWh = 6.2% of capacity used.

If you prefer to work direct in Amp-Hours...
3.9kW / 48v = 81.25 amps drawn from the battery.
Multiply current by time = 81.25 * 0.5 hours = 40.625Ah.
40.625Ah / 60Ah = 6.2%.

Of course this is a worse case scenario as the machine will not be running the heaters all the time, and your inverter is likely much more efficient and set to 230v...

I can see the following scenarios why you inverter is cutting out:

1. Your batteries are shot and the voltage really is collapsing to the cut off voltage of the inverter.
2. Your inverter is struggling to power the load and is thermally limited, thus shutting off for a safety reason to prevent damage / fire.
3. Your inverter (Computer UPS manufactured by American Power Conversion) is not of the "XL" product line and is shutting down prematurely due to its internal assumptions about the battery state.
4. Your inverter (Computer UPS manufactured by American Power Conversion) is of the "XL" product line, but is mis-configured and is shutting down prematurely due to its internal assumptions about the battery state.

Item #1 is easy to diagnose and will require new batteries if this is the issue.

Item #2 could be resolved by increasing the air flow and lowering the ambient temperature - I hope it is not operating in a small cupboard or shed in which the air temperature can rise. UPS are designed to be run in air conditioned data centres at a constant 21'C.

Item 3# cannot be resolved so easily. A UPS must provide power to the load for as long as it can, however it must ensure that in the event of the mains power not being restored that all connected computers etc receive a shut down signal in a timely manner, so that there must be sufficient battery time left for the machines to perform the shut-down process. In heavily loaded server environments this can be quite a few minutes. In order to do this the UPS knows the capacity (in watt hours) of the battery that the UPS was fitted with at the factory, and it can measure the connected load. The UPS can then estimate the battery state and time the shut-down sequence accordingly. The UPS will prevent excessive discharge of the battery in order to maintain the quality of the system - no point having a UPS that is unreliable! If you have added external batteries to a standard UPS, it will be under estimating the size of the battery, and timing everything too early.

Item 4#: The XL versions allow additional external battery packs to be attached. The UPS in this case needs to be informed how many external battery packs are installed so it can perform the functions outlined above, otherwise you shall experience the same issues of premature shut-down. To configure the number of external battery packs you need to use the APC UPS management software. Unfortunately APC do not specify their battery packs in terms of voltage and Amp-Hour, but you can work them out with a little Googling. You shall need to select the number of APC batteries that is the closest match for your bank.

Hope this helps

-Tim

[Eleanor]

Emma, maybe worth a look at the Victron site for information on offgrid inverters which can work with Lithium ion batteries. We have the MultiPlus inverter charger for lead acid batteries and have had no problems.

I suspect that it will come down to how deep your pockets are  

http://www.victronenergy.nl/upload/documents/News%20-%20Lithium-Ion%20Charging%20(3).pdf

http://www.victronenergy.com/upload/documents/Brochure%20Lithium%20Ion%20-%20SAL064130020%20-%2000%20-%201103%20-%20EN_web.pdf

[clockmanFR]

woo67814
Hi tim,
I have posted in "Wind Turbines, REAL FACTS 48V BATTERY SYSTEMS".

I shut down manually, hit the off button or remove the load at 49.2v to really care for my batteries. The Inverter UPS is great, cold starts, and is very hardy but its own internal LVD low voltage disconnect is set at 42v, at that i lost 2 of my batteries within 3 months.  

As you can see We are putting together a Multi LVD that is a PICAXE so i can maximize the batteries use without causing them any damage, (we hope) and the circuit can also store data so we know what each battery is doing and when, and if it needs any tender care.

In my experience half an hour is my tasit knowledge for loading with my present batteries.

[camillitech]

welcome mayesemma,
We are on grid but not selling our energy or claiming Feed In Tariffs.

We have PV and 3 windturbines (max 8KW) Hugh Piggott designs, and a 52.6v 660amp hour battery system, and a APC UPC (computer back up supply) 48v 3.7kw Inverter. Installing more, 3KW, PV - photo Voltaic panels.
 
Running the washing machine with our Inverter and batteries would within half an hour have the batteries down to shut down voltage.

I think biff's right regards having a Genny ready/on standby for that extra loading. Us, we then draw from the mains supply.

Battery choice is difficult and really will have to be your choice for what you actually want.
Quated to me, "Batteries are a Black Art".  

I think you need new batteries Clockman, my 1000ah bank powered the house for almost a week before the generator came on (pre wind and hydro) that would include at least three washes on an automatic cold fill Bosch Clasixx and all the usual trappings of 'civilization'.

It's now down to a couple of days between generator firings if there's been a drought and no wind, but bear in mind the batteries are now seven years old and also supplying an extra property.

Cheers, Paul

[Mayesemma]

Emma, we've got one of these which works well :

http://twintub.co.uk/epages/eshop188917.sf/en_GB/?ObjectPath=/Shops/eshop188917/Products/%22Polar%20Quiet%20Storm%20Twin%20tub%20Washing%20Machine%22

It only uses a small amount of electricity and can take pre-heated water. The clothes are nearly dry after being spun. You have to be fairly thick skinned to put up with the twin tub jokes though 

Thanks for this been looking at them on ebay and get slightly smaller ones for a very reasonable price.

Untill we are living the dream (being self sufficiant on our meadow) we have very little cash input we may go down the lead acid route untill my brain can get round the hole elecy bit. I am slowly getting there! Cannot thank you enough for all of your help keep the handy websites coming especially if they have any cheep or DIY ideas. You guys have saved me lots of headaches and hours of researching. THANK YOU xxxxxx

[Eleanor]

That lot haven't scared you off yet then!  

If you haven't already done so when you were living in the caravan I'd have a little go and buy a 110Ah 12V lead acid deep cycle battery (I think Navitron sell them) and something like this http://uk.farnell.com/belkin/f5c412uk140w/inverter-dc-ac-anywhere-belkin/dp/1226181. Unfortunately they don't make this one anymore but again I think Navi may have something suitable. You'll need a 12V car battery charger (I think they have those as well!) and you can have a go without spending too much money. You'll soon get a feel for how much charging and discharging of the battery you can get away with and when you kill the battery you won't have invested too much. I'd also get a hydrometer (just a cheap one from Halfords would do for this) so you can keep an eye on the acid strength ie state of charge, oh and a low cost volt meter from somewhere like Maplin.

[camillitech]

Hi Emma,

unless you have a hydro resource no matter how large your battery bank is or how big your wind turbine is or how many solar panels you have you will at some point need a generator and that is where I'd start. A good Lister SR2, ST2 or TS2, preferably 'Start O matic' but most definitely a genuine 'Lister power plant' and not just a Lister engine that has had some cheap alternator bolted on the back of it and sat on a building site sucking in sand and cement dust. Avoid anything that says 'Lister Petter' as it will probably be more Petter than Lister.

 Get a good inverter/charger like a Victron, Studer, SMA or Outback that all have good back up. These will start your generator at the correct time, charge your batteries correctly and have a load sharing facility.

I like the sound of lithium ion batteries but would for now stick with FLA forklift truck ones because it's what I know and my bank is now almost seven years old.

Once you have got a reliable diesel/battery system up and running then you can spend all your spare cash trying to make it redundant  Seriously,the heart of any good renewable energy combination is a good combination of generator, batteries and inverter sized to your needs. When the wind does not blow, the sun does not shine and there's a drought you WILL need it.

My generator does little work these days but it's always there for when the burn is frozen, the Proven has sat idle and the solar panel is covered in snow.

Life 'off grid' is great fun but you should not have to live like a hermit, we have all the stuff that most people do, tumble drier, electric ovens, toaster and power hungry Idiot Box 360. I draw the line at a kettle, iron and dishwasher 

Oh and avoid gas fridge freezers like the plague we had one for ten years or so and were very happy with it until it broke down and I replaced it with an energy efficient electric one, our gas consumption went down from 47Kg every 12 weeks to three 19Kg bottles a year and we have a range cooker now with six rings 

Good luck, Paul