type of pv

[Jeremy Harris]

33 minutes ago, Dreadnaught said:

A UK supplier of Nickel Iron batteries? https://www.bimblesolar.com/batteries/nifebatteries

 

 

Yes, they are importing them from China, but you can buy them direct for a fair bit less.  I did get some prices for dry-shipped cells from a similar Chinese supplier a few years ago and they weren't bad, and certainly cheaper than the US/Canadian made ones that are, I believe, still in production.  Note that the company linked isn't selling Edison manufactured cells, they are selling Chinese copies and being careful not to use the Edison name in the actual cell description!

 

BTW, buying dry-shipped cells makes a lot of sense, as the electrolyte is easy to obtain and  mix up and not being filled reduces the shipping weight a great deal.

[Jeremy Harris]

FWIW, I've found that Bimblesolar are importing their Nife cells from Taihang Batteries, part of the Henan Xintaihang Power Source Co. Ltd, Henan, China.  If anyone is after some, then I would expect that they can probably buy them for maybe 20% or so less direct from the manufacturer.

 

Using the manufacturer's bulk price as a guide, a pack of 40 off 500 Ah cells (48 V nominal, 24 kWh nominal) would cost around £10k inc shipping, plus VAT and duty.  That would give a usable capacity that's close to three times that of a Tesla Powerwall, and a life in excess of 40 years, probably closer to 50 to 60 years.  To that you'd need to add in the cost of a charger and inverter, plus, ideally, an automatic watering system, but overall you could end up with a 20 kWh capable house power system for perhaps £15k or so, with an operational life of well over 40 years.  Realistically the charger and inverter would probably need replacing three times of so during that time, so the total cost is likely to be close to £20k through life.

 

If half the usable capacity could be used every day, from a renewable charge source (so effectively "free") then at a unit price of 15p per kWh the battery could save up to around £1.50 per day, perhaps £400 a year (allowing for cloudy days where the pack can't be fully charged.  At £20k, it still looks like the investment wouldn't be recovered until around 50 years, though, so probably not yet a viable solution.  It does have the advantage that the cells are probably still going to be fine after 50 years, though, based on my long experience of using and abusing them.

 

A smaller capacity system would probably reach pay back a bit more quickly, but it's still marginal.

[SteamyTea]

As NiFe are large and heavy, could they be redesigned and incorporated into the foundations of a house.

Might sound a bit 'whacky', but be already use timber, steel and concrete beams to do that.

[richi]

14 hours ago, JSHarris said:

The main difference is life and efficiency. 

...

BTW, a 110 Ah 12V leisure batter might do 400 to 500 cycles.

 

I figured I'd missed something obvious. Thanks, Jeremy!

[Jeremy Harris]

I've just been looking through the costs for a 3 kWp on/off grid charger inverter system, running from a nominal 48 V battery pack.

 

The Sofar system looks to be about best value, in terms of the charger/inverter unit, and 3 kWp is probably OK for a low energy house.  The ME300SE charger inverter is around £900 (probably a bit less if purchased with batteries).

 

Choosing 4.8 kWh as a realistic minimum battery capacity, then using the cheapest reasonable quality lithium packs I can find (the Pylontech modules) 4.8 kWh would cost around £1,900.

 

4.8 kWh of 100 Ah NiFe cells would cost about the same, around £2,000.

 

Both the inverter charger and lithium batteries have a life of around 10 to 15 years, probably closer to 10 years.  So a £2800 investment in the inverter/charger and lithium battery pack, assuming that you managed to usefully use around 75% of the total stored capacity all through it's life, and assuming that the charging electricity was "free", from excess generation that's already available, would just about pay for itself, at a unit price of 15p/kWh,  after about 15 years, around the time the system would be at the end of its life.

 

The NiFe system batteries would still be as-new after 15 years, so the system would have paid for itself, only needing the investment in a new charger/inverter to give another 15 years life.  Electricity delivered over the second 15 year period would be around 1/3 of the current grid price, using the assumptions above.

 

On the face of it, the NiFe system wins hands down, but you will be waiting many years before you see your investment start to pay off.

[Gone West]

@JSHarris would you need a lot more storage space for the NiFe system compared to the lithium system?

[Jeremy Harris]

1 hour ago, PeterStarck said:

@JSHarris would you need a lot more storage space for the NiFe system compared to the lithium system?

 

 

Yes, the batteries are a lot larger and heavier, and ideally need an automatic watering system, so are best placed in an outhouse. 

 

The lithium packs, like the Pylontech units, can be mounted in a standard 19" electrical rack I think, their dimensions seem to indicate they will.  I've seen several suppliers for the Sofar charger/inverter and Pylontech battery combination, like these:

 

http://www.thesolarpeople.co.uk/shop/sofar-solar-4-8kwh-energy-storage/

 

https://thinkrenewables.co.uk/sofar-solar-48kwh-battery-storage-system

 

The last link seems suspiciously cheap to me, at £2,412 inc VAT and shipping, as that's about £500 cheaper than the same system was a couple of weeks ago.  The first link is still the same price as before, £2,795 inc VAT and shipping,

 

At £2,412, with an expected battery life of 12 years (according to their info) then if you could self-consume 75% of the total capacity every day, then you could possibly get back close to £200 a year, which is getting close to breaking even on the capital outlay, assuming 15p/kWh through life.

 

Add in the convenience of having up to 3 kW of emergency back up supply, from a dedicated emergency outlet that's included with this system, and it's looking pretty close to making sense to buy one.  Easy to install, too, according to the instructions.

 

I will admit to being tempted by the Sofar offering, if only to give us security of supply during power cuts.  Subtracting the cost of a 3 kW emergency generator from the system cost makes the economics look more favourable.

 

 

 

 

[richi]

This pleasantly kooky lady claims 8,000 cycles at 80% DoD gets you to 80% SoH. Price seems to be about US$1 per usable Wh. BMS included in each 12V pack. LiFePO4.

 

So, including tax and shipping, say about £1.50/day for 10 kWh over 20+ years (neglecting time value of money).

 

 

[Dreadnaught]

@richi Could you spell out those abbreviations for the uninitiated?

Edited July 20, 2018 by Dreadnaught

[newhome]

3 minutes ago, Dreadnaught said:

@richi Could you spell out those abbreviations for the uninitiated?

 

@richi would you also be so kind as to add them here too please:

 

 

[richi]

Soz.

 

DoD -- depth of discharge (essentially the opposite of state of charge)

SoH -- state of health (a percentage of how much charge it can hold, compared with the as-new spec) 

Wh -- Watt-hour (a measure of energy; a thousand Wh is a kWh)

BMS -- battery management system

LiFePO4 -- lithium iron phosphate (a rechargeable battery chemistry)

Edited July 20, 2018 by richi