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Author Topic: FiT and battery storage etc  (Read 21426 times)
TedStriker
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« on: March 19, 2016, 08:22:39 PM »

Hi,

Well it's been a few months now since my installation and I'm starting to want more! Basically I don't use much electricity during the day and end up exporting probably 70-80% of my generation - more on a decent day. I use 7-10kWh a day usually. I have a iBoost so that helps using some but I'm living alone at the moment so a shower a day only takes half an hour or so of decent sun to have the HW tank whistling again!

So... being slightly nerdy and sort of into electronics I want to investigate the possibilities of battery storage. I'm not really doing this to save money, more that I really like the idea of not exporting electricity but actually using it and minimising electricity bills. Basically if I didn't save a penny overall but paid the supplier less I'd be happy as a pig in **** Smiley

Obviously there's things like the Tesla Powerwall but I've been thinking (probably too much) and can see a financial problem with such things. At present I get paid on the pre January FiT rate for every unit generated. However, if I have the traditional DC battery storage system I'll be taking out power before it hits the inverter and hence anything that goes to battery storage won't be recorded by the TGM, right?

So, other than the standard 'Powerwall' type pre inverter storage or a hybrid inverter, wis there a way of using the electricity post inverter to charge batteries? I have been toying with the idea of using the iBoost to do this as it would automatically divert any unused generated electricity to a charger. Of course, the charger would have to be an unsophisticated transformer/rectifier/voltage regulator type so it doesn't mind the (PWM?) AC from the iBoost but I can't see how that would be a problem.

Also... Since having the system fitted (11x 285W panels on house roof facing SE), I've realised I have a SW facing garage roof, pretty much unshaded which now the days are getting longer, is basking in sunshine for hours after the main panels have pretty much given up. I could fit 4 or 5 panels to this. My inverter is a dual MPPT so would it be a good idea to move some of the roof panels to the garage to spread the generation out at the expense of peak power? Would this destroy my FiT eligibility? How about adding a few panels in the process instead of just moving some from the main roof? My inverter is 3kW max and that's what the system has been declared at so it won't go over that.

Thanks!

Graham

(getting slightly obsessed, but enjoying every minute...)

Feel free to tell me I'm bonkers - it wouldn't be the first time!
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11 SunEdison SE-R285CMC-38 Panels in strings of 5 and 6
SAJ Sununo - TL3KA Inverter
Sofar ME3000SP charge controller
4x Pylontech US2000 Plus 2.4kWh battery packs
Intelligent Immersion I2W diverter
TheFairway
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« Reply #1 on: March 19, 2016, 09:27:24 PM »

With DC side storage such as PowerWall, the energy recorded by TGM is not lost, just delayed as it passes through the same inverter as Solar. You only lose out on inefficiencies of the DC/battery/DC process which for Powerwall, is claimed to be 9x% efficient. On monetary terms, for me thats about 30-50/year loss of FIT income but I would gain by about 260/year in reduced energy costs.
« Last Edit: March 19, 2016, 09:35:37 PM by TheFairway » Logged
RIT
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« Reply #2 on: March 19, 2016, 11:47:28 PM »

You are going to hit 3 problems

- The first is the use of an iBoost PWM type device, these take an AC based wave form and turn it into a DC pulse where the width of the pulse can be varied to reduce the overall power draw. This means that you can not drive AC based devices (such as a unsophisticated transformer).

- In the UK the cost of electricity makes it currently very hard to recover the cost of the equipment you deploy to store your generated electricity.

- The improvements in storage solutions are moving so fast (capacity and cost) any system purchased today will not be able to recover the reduction in cost you are likely to see over the next 12 months.

As a general example that the UK based Powervault, this as a 4kWh unit and an estimated cost of 2,800 before any installation costs. If you are able to shift/smooth 5kWh for 260 days of the year you will save 1,300kWh of imported electricity, which at 12p a kWh is only 156 and so you end up with a simple payback of 18 years. At the same time the makers of the Powervault claim that in 3 years they hope to reduce the purchase cost by 50% or 1,400. So over 2 years you have spent 1,400 (half the cost of the device) to save 312 of electricity.
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billi
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« Reply #3 on: March 20, 2016, 05:35:43 AM »

 ... i guess   , just get  some PV panels  and a battery and a GTI to feed your home grid  during the night

a controller for that , one can get here   http://www.solarelectrix.de/4_panel_uk.html    for 390 that  provides baseload 

an AEconversion INV250-45 EU   GTI  for 200

1000 watt PV  for another 500
A 12 kWh  battery  for 700  (with over 3000 cycles at 50%DoD)


So system costs of   about 1800 for a  1 kW  battery based PV with 250 watt  base load supply

And an AC-DC charger for the existing FiT  install ?
 
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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
TheFairway
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« Reply #4 on: March 20, 2016, 10:14:18 AM »

Ive just done some more accurate power savings calculations based upon actual 5minute interval figures from last year.

Using my daily data exported from pvoutput.org, capped at 4kWh and 6kwh of export offsetting my import and electric unit price of 0.13, the potential for eel trinity savings came in at approx. 98 and 105/year respectively.

More would be saved if excess power was prioritised for battery rather than offsetting gas usage for hot water.

Should also be noted that the pvoutput import figure was approx. 15% low compared with actual meter reading which may also mean my export figures are equally adrift - a function on the inaccuracies of clamp on type meters and taking spot readings at 5 minute intervals. So these figures could be similarly inaccurate.

I think my earlier estimate of 260 saving was optimistic and 100-130 probably more realistic. The difference being down to a significant number of days where less than 100% of surplus  could be stored and used for self consumption.

I had set a target price for battery storage at -3k/3.5k if I was going to jump. This gave payback period approx. 13years everything else remaining even which of course they will not be. Looks like I will need to reassess my target but its not all about the money.
« Last Edit: March 20, 2016, 10:24:20 AM by TheFairway » Logged
Stig
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« Reply #5 on: March 20, 2016, 11:08:04 AM »

..
Also... Since having the system fitted (11x 285W panels on house roof facing SE), I've realised I have a SW facing garage roof, pretty much unshaded which now the days are getting longer, is basking in sunshine for hours after the main panels have pretty much given up. I could fit 4 or 5 panels to this. My inverter is a dual MPPT so would it be a good idea to move some of the roof panels to the garage to spread the generation out at the expense of peak power? Would this destroy my FiT eligibility? How about adding a few panels in the process instead of just moving some from the main roof? My inverter is 3kW max and that's what the system has been declared at so it won't go over that.
..

I think as far as the FIT is concerned you'd be OK to move your existing panels around if you wanted, have a think about how it would affect generation in winter though.

Adding more panels would affect the FIT though.  If, say, you added another 1kWp to a 3kWp system you'd have to tell your FIT provider and they'd reduce your payments to 3/4 as you can't get any payment for an extension to an existing system any more.  If you put the new panels through a separate inverter which didn't go through your generation meter that would be fine, although you'd have to ask your DNO if they're happy with the extra generation (generally up to 3.6kWp it's no problem).
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TedStriker
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« Reply #6 on: March 20, 2016, 08:48:08 PM »

..
Also... Since having the system fitted (11x 285W panels on house roof facing SE), I've realised I have a SW facing garage roof, pretty much unshaded which now the days are getting longer, is basking in sunshine for hours after the main panels have pretty much given up. I could fit 4 or 5 panels to this. My inverter is a dual MPPT so would it be a good idea to move some of the roof panels to the garage to spread the generation out at the expense of peak power? Would this destroy my FiT eligibility? How about adding a few panels in the process instead of just moving some from the main roof? My inverter is 3kW max and that's what the system has been declared at so it won't go over that.
..

I think as far as the FIT is concerned you'd be OK to move your existing panels around if you wanted, have a think about how it would affect generation in winter though.

Adding more panels would affect the FIT though.  If, say, you added another 1kWp to a 3kWp system you'd have to tell your FIT provider and they'd reduce your payments to 3/4 as you can't get any payment for an extension to an existing system any more.  If you put the new panels through a separate inverter which didn't go through your generation meter that would be fine, although you'd have to ask your DNO if they're happy with the extra generation (generally up to 3.6kWp it's no problem).


Thanks for the reply. As my inverter is only 3kWp and my panels total 3.185kWp already, would adding more panels actually increase my peak output? I'd have thought not so why would the FiT be affected? Or is that not the way they look at it?
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11 SunEdison SE-R285CMC-38 Panels in strings of 5 and 6
SAJ Sununo - TL3KA Inverter
Sofar ME3000SP charge controller
4x Pylontech US2000 Plus 2.4kWh battery packs
Intelligent Immersion I2W diverter
Justme
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« Reply #7 on: March 20, 2016, 09:19:31 PM »

The two big factors in this are:-

1, Cost of installing a system large enough to meet your demand without over discharging (and hence killing) your bats.

2, Battery replacement costs per kWh used. The last time I checked just the battery replacement costs were 8p per kWh used.

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Navitron solar thermal system
30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
2 x Victron Multiplus II 48/5000/70
Cerbo GX & GX 50 touch
BMV 700
6kva genny
48v 1000ah
Grid Possibly coming soon
Stig
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« Reply #8 on: March 20, 2016, 09:23:59 PM »

Thanks for the reply. As my inverter is only 3kWp and my panels total 3.185kWp already, would adding more panels actually increase my peak output? I'd have thought not so why would the FiT be affected? Or is that not the way they look at it?

You guessed it, that's not the way they look at it.   Wink
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TedStriker
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Don't call me Shirley


« Reply #9 on: March 20, 2016, 09:32:59 PM »

The two big factors in this are:-

1, Cost of installing a system large enough to meet your demand without over discharging (and hence killing) your bats.

2, Battery replacement costs per kWh used. The last time I checked just the battery replacement costs were 8p per kWh used.



The vast majority of my usage is background - I run quite a few servers 24/7 and my background load is around 300-400W. If I could just cover this I'd be happy. High draw devices don't use that much in the grand scheme of things as they're not on for long and also you'd need a much bigger system to cope with occasional heavy load. I can get my hands on almost unlimited numbers of UPSs in the 500-5000VA range but not sure how much use they'd be. I know you can extend the batteries on them to pretty much what you want in parallel - could they be of any use? Something that could supply the 400W or so of base load but import from the grid when there's high current draw would be ideal.

I think I'm seeing that this is not the right time to be seriously doing stuff like this with the impending fall in battery costs (Gigafactory etc), it's more a proof of concept thing to iron out any problem until such a time that batteries do become economically viable.

How about second had Fork Lift batteries? They seem to offer a pretty good Wh/ ratio and don't mind deep discharge.

I guess there must be forums around that are dedicated to such things - any suggestions?

Thanks
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11 SunEdison SE-R285CMC-38 Panels in strings of 5 and 6
SAJ Sununo - TL3KA Inverter
Sofar ME3000SP charge controller
4x Pylontech US2000 Plus 2.4kWh battery packs
Intelligent Immersion I2W diverter
RIT
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« Reply #10 on: March 20, 2016, 10:20:01 PM »

The two big factors in this are:-

1, Cost of installing a system large enough to meet your demand without over discharging (and hence killing) your bats.

2, Battery replacement costs per kWh used. The last time I checked just the battery replacement costs were 8p per kWh used.



The vast majority of my usage is background - I run quite a few servers 24/7 and my background load is around 300-400W. If I could just cover this I'd be happy. High draw devices don't use that much in the grand scheme of things as they're not on for long and also you'd need a much bigger system to cope with occasional heavy load. I can get my hands on almost unlimited numbers of UPSs in the 500-5000VA range but not sure how much use they'd be. I know you can extend the batteries on them to pretty much what you want in parallel - could they be of any use? Something that could supply the 400W or so of base load but import from the grid when there's high current draw would be ideal.

I think I'm seeing that this is not the right time to be seriously doing stuff like this with the impending fall in battery costs (Gigafactory etc), it's more a proof of concept thing to iron out any problem until such a time that batteries do become economically viable.

How about second had Fork Lift batteries? They seem to offer a pretty good Wh/ ratio and don't mind deep discharge.

I guess there must be forums around that are dedicated to such things - any suggestions?

Thanks

At the moment most UPS batteries are not well suited for constant reuse as the UPSs are expected to only be used very infrequently. The odd lithium powered UPS is beginning to show up but not for the type of usage you are looking for. Also most UPS have their own very high current draw as their design is not focused on power saving.

You may have more luck looking at your server design depending on what you do. I run a 4 core 3.4Ghz Xeon system with 32GB RAM and 1TB of SSD storage + 1 TB of rust storage and it has an average pull of 25w (under load about 60w). This was my solution when looking at the same problem as you seem to be looking at. The server I had before was a lot older and designed for a data center with a draw of about 300-400w.

Now if you can link a 60w server to a 5000VA ups you maybe able to get away with not doing much damage to the battery as the depth of discharge will be very low. As for charging you will need a computer readable current monitor to see what your export is and a control board for the UPS, just turn on the UPS when it makes sense depending on battery level and spare PV power.
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2.4kW PV system, output can be seen at  - https://pvoutput.org/list.jsp?userid=49083

Join the fight against human malware at https://stats.foldingathome.org/team/259956

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Justme
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« Reply #11 on: March 21, 2016, 02:22:01 PM »



The vast majority of my usage is background - I run quite a few servers 24/7 and my background load is around 300-400W. If I could just cover this I'd be happy. High draw devices don't use that much in the grand scheme of things as they're not on for long and also you'd need a much bigger system to cope with occasional heavy load. I can get my hands on almost unlimited numbers of UPSs in the 500-5000VA range but not sure how much use they'd be. I know you can extend the batteries on them to pretty much what you want in parallel - could they be of any use? Something that could supply the 400W or so of base load but import from the grid when there's high current draw would be ideal.

I think I'm seeing that this is not the right time to be seriously doing stuff like this with the impending fall in battery costs (Gigafactory etc), it's more a proof of concept thing to iron out any problem until such a time that batteries do become economically viable.

How about second had Fork Lift batteries? They seem to offer a pretty good Wh/ ratio and don't mind deep discharge.

I guess there must be forums around that are dedicated to such things - any suggestions?

Thanks

A problem with using UPS's is that the current they use to charge / keep battery on float all day could be more than the energy they give out over night.

3-400 watts back ground load for 10 hours what we use all day.
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Navitron solar thermal system
30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
2 x Victron Multiplus II 48/5000/70
Cerbo GX & GX 50 touch
BMV 700
6kva genny
48v 1000ah
Grid Possibly coming soon
TedStriker
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« Reply #12 on: July 06, 2016, 08:18:51 PM »

So.... this has reared its ugly head again, mainly because I have an offer of a load of 2V used but working traction batteries, either 12 or 24 of them, and around 900Ah capacity - for next to nothing. Even 12 batteries at 50% DoD that's still around 10KWh so I am definitely interested.

Been looking at hybrid inverters and there are quite a few around but I guess very few would be G83/2 approved especially ones such as this from ebay:

http://www.ebay.co.uk/itm/SOLAR-HYBRID-INVERTER-2-4KW-3000KVA-24V-PURE-SINE-WAVE-WITH-CHARGE-REGULATOR-50A-/291800361438?hash=item43f0a829de:g:~boAAOSw~FNUag4Z

Do I really need to replace my inverter or are there devices that would allow battery storage to be retro fitted to an existing system?

Also, would a replacement inverter need notifying to anyone such as DNO or FiT?

Thanks!

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11 SunEdison SE-R285CMC-38 Panels in strings of 5 and 6
SAJ Sununo - TL3KA Inverter
Sofar ME3000SP charge controller
4x Pylontech US2000 Plus 2.4kWh battery packs
Intelligent Immersion I2W diverter
Sprinter
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« Reply #13 on: July 07, 2016, 12:49:57 PM »

There are other "less desirable" methods and devices that sit in between the panels and inverter, they then make an informed decision on the following:

Are my panels generating> No > Feed house from battery (if batteries are above lower threshold, if not > feed house from grid)

Yes > are batteries full > Yes > Send to grid
No, charge batteries


When i say less desirable what i mean is "too some of the more technically adept and self sufficient people on this forum" (that's not having a dig, they just have a much better understanding of the available engineering and how to set it up), personally even i can work out what to do with a "Growatt p2000" or P3000, which can run off lithium or lead type batteries, but i suspect it might cost more than the inverter that you mentioned, but these things are pretty much plug and play as far as i can see.
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TedStriker
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Don't call me Shirley


« Reply #14 on: July 07, 2016, 02:22:01 PM »

I have no problem getting stuck in and have a good understanding of electrics so not averse to 'creative' solutions Smiley

The Growatt looks interesting but I'd want it without batteries as I have my own. Any devices like that?

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11 SunEdison SE-R285CMC-38 Panels in strings of 5 and 6
SAJ Sununo - TL3KA Inverter
Sofar ME3000SP charge controller
4x Pylontech US2000 Plus 2.4kWh battery packs
Intelligent Immersion I2W diverter
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