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Author Topic: considering upgrading a grid tie set up to include storage  (Read 14115 times)
PeterC
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« on: February 06, 2014, 03:10:42 PM »

Hi. Im posting this as im interested in some information gathering rather than actually looking to implement such a project.

I currently have 3.42Kw PV Grid Tie set up with a SMA 3000HF Inverter. If I was considering changing this set up to include some short term battery backup and the ability to run when the grid was “out of action” what additional equipment would I be looking at? Clearly a new inverter but what else do I need to consider?

For the purposes of this post my idea of basic battery back up would be 10 - 20KWh.

I’m looking to obtain a basic understanding of what issues, kit and what broad costs would be required to be considered as I continue with my home renovation project.  I was considering adding some small scale wind to the mix in a grid tie set up but might consider upgrading the solar set up next year to include some battery storage instead.

Thanks for any pointers, suggestions and information
Peter
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Solar PV: 3.42 kWp System - 18 x SHARP 190w panels in 1 string, SMA 3000HF PV Inverter, Orientation Due South, 30 deg roof angle/elevation, Location Staffordshire Moorlands

Solar Thermal: 30 x 58mm Navitron ET, 290 Litre Newark Thermal Store
oliver90owner
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« Reply #1 on: February 06, 2014, 03:32:26 PM »

Would that 10-20kWh basic battery mean you wish to have 1-2kWh of stored available energy or 10-20kWh of battery capacity.  Dependent on battery type, the above figures could effectively be the same or entirely different.

Once implemented there might be a case of actually using the stored energy instead of the grid power - the difference between an UPS and an alternative to the grid.

The first thing is actually how much power you would need in the event of a power failure?   And secondly, for how long you would be expecting the grid being down?

It is accepted that other than for short term interruptions where a UPS would save the day, storing power for later use is an expensive occupation/pastime.

Think generator for grid breakdowns as being likely the most effective, cost-wise.

RAB





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RobertReadman
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« Reply #2 on: February 07, 2014, 01:09:55 AM »

Don't let cost worry you, every time people want information on this, they say its too expensive, but costs and equipment are never mentioned.
Its only expensive depending on finances.
Work on installed capacity required and your ROI and start thinking that you are pre-purchasing power for the next few years in advance.
(As you won't be pulling it from the grid), factor in electricity price increases over each year, and it becomes a great option for energy independence, while still connected to the grid for drawing high loads, or if you only fit a small battery bank at first.

SMA have recently ditched the SMA SunnyBackup range, and is replaced with the new SMA SunnyIsland range, (SunnyBackup always was a re-badged and new firmware Island).

Since you already have an SMA 3000HF, take a look at the SunnyIsland 6.0H, I assume you have single phase you will only need one Master SunnyIsland.
Here are the specs...
Rated power (for Unom / fnom / 25°C / cos ϕ = 1) 4600 W
AC power at 25°C for 30 min / 5 min / 3 sec 6 000 W / 6 800 W / 11 000 W
AC power at 45°C 3700 W
See more at: http://www.sma.de/en/products/off-grid-inverters/sunny-island-60h-80h.html#Technical-Data-79859

If that is not going to suit your load, then take a look at the 8.0h instead.

You will require a 48V battery bank, you can pick the size, but bear in mind, that SMA use C10 capacities and not C100, so it is important to find out or convert battery capacities to C10 (C10 = Capacity over 10 hours) and C100 = over100 hours.
I would recommend a VRLA battery technology (valve-regulated lead–acid battery) such as AGM, they are the most expensive, but also likely to last the longest.

You can have a capacity range from 100Ah to 10,000Ah so you can make it as small (cheaper) or large (more expensive) as you like.

From this you can decide, if you wanting to increase self-consumption and then have the batteries recharge via SolarPV, or if you want to catch a power outage, if you want to catch a full day outage.

Now before I go on, currently (for the next month or so), Sunny Backup will still be available.
It usually comes as a set, so you get a SunnyBackup, Batteries, and the AS-Box-M-20/ AS-Box-L-20 which is the automatic switching unit to switch off the grid in a power-cut and change over within approx 20ms.

Once the SunnyBackup range is discontinued, and using the SunnyIslands, the AS-Box will not be part of the future solution with the SunnyIsland range.
The installer will have to build a similar box to specifications provided, and will have a changeover time of 5-15seconds.

Quote from section "5.3 Switching Times for Loads" of "SI-Ersatzstrom-PL-en-11W.pdf"
Titled "Planning Guidelines - SMA FLEXIBLE STORAGE SYSTEM WITH BATTERY BACKUP FUNCTION Circuitry Overviews, Schematic Diagrams and Material Lists"

The SMA Flexible Storage System with battery backup function does not fulfill the requirements of an uninterruptible
power supply as defined in IEC 62040. In the event of grid failure, an automatic transfer switch disconnects the battery
backup grid from the utility grid. After disconnection, the loads and the PV system are not supplied for approximately five
seconds, until the battery backup system can provide active power and reactive power again.
If any single load (e.g. a computer) requires an uninterruptible power supply in compliance with the standard or a
switching time shorter than five seconds, this load will need a separate uninterruptible power supply in compliance with
IEC 62040.
Loads integrated in the battery backup grid via phase coupling have a switching time of 15 seconds, as the SMA Flexible
Storage System connects phase coupling with a time delay.

Another document to read is the Installation - Quick reference guide Battery Backup System - Battery Backup Systems with Sunny Island 6.0H /8.0H
Which is available as "Ersatzstrom-IAS-en-20W.pdf"

Anyway, that's enough text for now, just ring SMA for free and ask them, but most may not know about the above changes until after February as its all new stuff.

If you want always on power, then grab the SunnyBackup system now, when SBU is replaced with SunnyIsland, Automatic Switching Box / Automatic Transfer Switch will not be the 20ms, it will be 5-15 seconds.
Meaning even for a brief blackout, setting your alarm and cooker clock. After the grid comes back on, you may need to set the clock again!
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3.6kWp with 15x 240W Sanyo HIT-N240SE10 Panels into an SMA Sunny Boy 4000TL-20.
SMA Sunny Beam, SMA Sunny Sensor, SMA Sunny Portal, SMA Sunny Webbox 2.0
oliver90owner
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« Reply #3 on: February 07, 2014, 08:35:19 AM »

Don't let cost worry you ......  but costs and equipment are never mentioned 

SMA fan,

Any costings for your suggested solutions?  I didn't notice them in your reply.

I would be very interested to read how much it might actually cost for the (possibly rare) grid outages that the OP indicated, or even to purchase sufficient lead acid batteries for a 20kWh (usable energy) system.  Some current pay-back times might not go amiss either.

BTW, how is the Australian weather at the present time?

RAB
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regen
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« Reply #4 on: February 07, 2014, 10:00:28 AM »

"Any costings for your suggested solutions?  I didn't notice them in your reply.

I would be very interested to read how much it might actually cost for the (possibly rare) grid outages that the OP indicated, or even to purchase sufficient lead acid batteries for a 20kWh (usable energy) system.  Some current pay-back times might not go amiss either."

Me too!

Regen

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« Reply #5 on: February 07, 2014, 10:27:36 AM »

Yes i think SMA has a nice solution , as well Nedap ,  Victron and Studer Xtender  are brilliant off grid and on Grid  -backup  solutions ...

Sure RAB  , there are always  two sides  to the coin .... One is very lucky in the UK to get FiT payments  for self-consumption , that is very rare or nowhere else in Europe the case ....

I am surprised , that "only" the Immersun  managed to be a success in the UK , and not more Battery based  Ideas ...., wouldnot it be great , to connect a say 10 kw PV to a 3.6 kw allowed capacity  power-line ?

Ok , different story.....

The "Senec.Home G2" battery storage idea is perhaps the  best price for money ready made home solution for Grid tied FiT people

Including Battery-store  a 10 kw PV  is about £15000 (ex Vat)    bought on ebay germany http://www.ebay.de/itm/141183180650


Of course ..... nothing for silly Billi , too little challenge   Grin and far too pricey   stir


Billi


 
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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
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« Reply #6 on: February 07, 2014, 10:35:56 AM »

Let's be honest, it will never be either economic or be a "geen" exercise just to provide power for a few power cuts - it's an extension of the old "I've got a lambing house on the moors we use for a fortnight every year, how do I provide power using pv and batteries" scenario - to which the honest answer is "buy a gennie, and/or some Tilley lamps" - it's the same reason EVs are not yet viable, batteries are still far too expensive and short-lived to make sense for such a use.........you need to be truly off grid for the sums to make any sense at all
« Last Edit: February 07, 2014, 10:43:55 AM by martin » Logged

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« Reply #7 on: February 07, 2014, 11:21:51 AM »

I would be very interested to read how much it might actually cost for the (possibly rare) grid outages that the OP indicated, or even to purchase sufficient lead acid batteries for a 20kWh (usable energy) system.  Some current pay-back times might not go amiss either.

Given that the OP has stated that this is to cover grid outages, which are quite rare, this can be treated as a UPS type situation. Therefore usable capacity is 100% of battery capacity. Good quality batteries will withstand many hundreds of cycles to 100% DoD. The 10% - 20% rule only comes in to play with cyclic applications such as off grid living when the life of the battery is dictated by the usage pattern rather than just the life time of the battery.

A good quality battery such as a Rolls should last many many years with occasional deep discharge providing it is well maintained and recharged promptly throughout it's life. Say you did it twice a month for 15 years (pretty ropey mains supply!), that is only 360 cycles, which should be within it's capabilities.

Our hosts sell the low end Roll batteries here:
http://www.navitron.org.uk/product_detail.php?proID=798&catID=157

They are £253.32 each, and you require 8 for 48v system (such as suggested SMA Sunny Island), giving 48v * 530ah = 25,440Wh assuming moderate draw - which you would hope the OP did in a power emergency situation. Battery cost of £2,026.56 + VAT.

The OP doesn't state whether the system needs to be whole-house, or whether he requires a uninterruptable supply. In which case it may be the case that a simple stand alone inverter could suffice, or a moderately sized UPS from eBay, in which case the inverter side of things could be just a couple of hundred quid. The SMA Sunny products, whilst nice, are expensive if not required.

Cheaper batteries may be available. 20+kWh of storage is a large amount, and probably better serviced with a generator.
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« Reply #8 on: February 07, 2014, 12:31:25 PM »

"Good quality batteries will withstand many hundreds of cycles to 100% DoD" - herrrumph! I'd like to know which ones! (Even the very best batteries can't withstand that!) whistlie
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biff
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« Reply #9 on: February 07, 2014, 02:07:00 PM »

The one thing you never do to a battery,
                                             Is flatten it 100%,No matter how good the batts are,once you flatten them,you shorten their life drastically,that is if you don,t kill them there and then.If you want piece of mind and want to be serious about living off grid trouble free,then you stay above 12.4volt for every unit of 12volts.That is what you have to learn to do.That means of course that you have to size your bank to achieve this.
                                                                                                    Biff
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An unpaid Navitron volunteer,who has been living off-grid,powered by wind and solar,each year better than the last one.
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« Reply #10 on: February 07, 2014, 02:42:11 PM »

"Good quality batteries will withstand many hundreds of cycles to 100% DoD" - herrrumph! I'd like to know which ones! (Even the very best batteries can't withstand that!) whistlie

Flow batteries.

They cost ~3-4 figures per installed kWh though.
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billi
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« Reply #11 on: February 07, 2014, 06:45:09 PM »

Who , should care too much about battery technology ? All we need is a    good value per stored kWh ...

We have already  ( for home users ) a "quite cheap , easy to set up PV  idea "


Quote
Given that the OP has stated that this is to cover grid outages, which are quite rare, this can be treated as a UPS type situation

Is that so ??

He/Peter  states as well
Quote
I’m looking to obtain a basic understanding of what issues, kit and what broad costs would be required to be considered as I continue with my home renovation project.  I was considering adding some small scale wind to the mix in a grid tie set up but might consider upgrading the solar set up next year to include some battery storage instead.

FiT Schemes  will come and go  onpatrol , like Politicians are , ....


Get yourself  , an independent supply ,  and do not pay those Utility companies any more

Where is the Problem  ?

 Billi

« Last Edit: February 07, 2014, 06:56:16 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
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« Reply #12 on: February 07, 2014, 07:05:58 PM »


Get yourself  , an independent supply ,  and do not pay those Utility companies any more

Where is the Problem  ?


The cost of batteries is the problem - unless you're off grid, a battery bank will cost more per kWh than a grid supplied kWh.

For occasional power cuts? Buy a small generator.

Worried about fuel degrading? Buy an LPG generator and a LPG cylinder.

I'm sure we would all love to be free of the Utility companies, but until it makes economic sense, I'll stay on-grid.  Smiley
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« Reply #13 on: February 07, 2014, 08:11:09 PM »

Quote
The cost of batteries is the problem - unless you're off grid, a battery bank will cost more per kWh than a grid supplied kWh.

That is not right !   Pure battery costs should be easy below 5 pence per kWh

« Last Edit: February 07, 2014, 08:39:11 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
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« Reply #14 on: February 07, 2014, 08:53:45 PM »

Quote
The cost of batteries is the problem - unless you're off grid, a battery bank will cost more per kWh than a grid supplied kWh.

That is not right !   Pure battery costs should be easy below 5 pence per kWh



Billi - please tell me where I can get batteries that come in at less than 5 pence per kWh. The best I have found is 10 pence per kWh for fork lift batteries.
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