Storage - The Way Forward ?

[Worcester]

OK; so with slowly degressing PV FiT payments, though still the loophole (until everyone has smart meters ) of deemed export - and probably even then, the future is definitely looking towards options that will include storage so that you can use the generated power when you actually need it.

Additionally more and more products seem to be coming on to the market.

As yet we have no experience on installing 'on-grid' storage systems, has anyone else yet carried out an analysis of the capital and maintenance costs / returns / quality - or even got a list of all the offerings currently on the market place?

Perhaps here would be a good place to start - what experiences have you had, what equipment have you installed or had installed for you?

 

[amlu]

give it a couple of years...battery technology is picking up very fast.
heard of tesla motors, very popular with electric cars in US developing some off-grid storage.
in the meantime time to repurpose some immersion tank heaters and hook them up to the solar.

 

[Worcester]

Ok: So here's a starter for 10

Needap Power Router
Sunny Boy Smart Energy
Midnight Sun
Mage StorageTec
Antaris Solar eKiss BOX
Solax X-Hybrid
Moixa Technology Maslow
SMA Sunny Island?

What are your experience of these, typical price, components, usable storage power (kWh), duty cycles, cost of replacement parts, support etc..

What other units are on the market?

 

[whinmoor]

Growatt have brought one out - the SP2000 - available from Segen and Midsummer amongst others. I caught a glimpse of it at Ecobuild.

 

[SRE]

Going to the SMA training with Segen in a couple of weeks, will know more then but CCL are suggesting a minimum 10 year payback at which point the inverter & batteries need replaced. Segen quoting round £3750 for SMA. That's as much as I know at the minute.

Tesla are a bit behind - Nissan already has a unit that allows storage of pv in their Leaf that can be used in the house later but it's only available in Japan as yet and they haven't worked out how it's going to affect the battery guarantee that Nisan provides for the Leaf. When we were at Milbrook last year they were trying to see if there was a solution to this. I think it will be a while before they resolve the guaruntee issue and Tesla appear to already be having battery issues so I'm not sure they'll be any quicker.

 

[SolarCity]

Ok: So here's a starter for 10

Needap Power Router
Sunny Boy Smart Energy
Midnight Sun
Mage StorageTec
Antaris Solar eKiss BOX
Solax X-Hybrid
Moixa Technology Maslow
SMA Sunny Island?

What are your experience of these, typical price, components, usable storage power (kWh), duty cycles, cost of replacement parts, support etc..

What other units are on the market?

We're going to take a look at the Solax X-Hybrid at the end of the month. Figures still don't seem to add up but we're getting asked for this more and more.

 

[The Solar King]

Looked at the SMA unit. Even SMA now admit they got it wrong with this one. Battery pack is too small and cost is eye watering. They reckon it will boost self consumption to 50%.... Better fit a good quality proportional controller at this point in time and achieve the same or better.

Looked at the Growatt unit. Appears attractive at first sight, but still needed to be half the current price to be viable. Were some technical issues with it. As far as I could see, can only be attached with a single MPPT inverter.

Samsung/Panasonic offering looks interesting but again, not a viable proposition at this stage. The person selling it at both Solar Power UK and Ecobuild did not seem to fully appreciate the economics (or otherwise) of the thing.

There is a real and present danger of massive mis-seling of storage. Products are coming to market because of incentivisation in Germany. It should also be remembered that their unit cost of electricity is far higher than that in the UK. These two factors taken together can make storage worthwhile in that market.


It is possible that in the not too distant future we may even see limitation of export from PV even at a domestic level as the operators of the Grid find it increasingly difficult to balance the system due to injection it was not designed for. Unless they are forced to invest heavily in Smart Grids, this is almost inevitable. It is already being discussed. We could could even see additional charges levied against PV owners as happens in other markets.

These kind of factors could drive the market for storage.

Watch out over the issue of technical standards. These are being discussed and worked on. Those involved are endeavoring to produce a framework that does not restrict technical development but ensures compliance with current regulation. This could be a can of worms.

Storage can be on either the AC or DC side of the inverter. Both have advantages and disadvantages.

Storage is an exciting prospect but should be approached with caution and buckets of due diligence.

 

[Somecamel]

Glad I read this, looking forward to future updates

 

[Gavin A]

We've had a couple of nedap systems in since last summer using 6-800Ah 24V battery packs.

There've been a few teething problems, some of the settings were just plain wrong for the batteries, which took me a while to figure out.

Should be fitting an sma battery system shortly on a 24kW system, the issue with the SMA kit (the sunny islands) is that it's 48V, so it has to be really big system before it makes financial sense.

 

[SibertSolar]

Gordon - I won't repeat what others, and particularly Peter, have already said but if you have the time, take a look here as it might contain some useful info to base your judgements/decisions on. Personally, I'm looking closely at the Bosch offering at the moment....

For me, the key to you guys offering suitable/correct battery storage solutions to your customer-base, is understanding their existing load-profile first. I encourage customers to fit monitoring equipment for a few weeks, even before PV is installed, to ascertain the baseline load profile. Then can you put some numbers against what would be a suitable solution and the likely benefit to the end user, especially when considering battery storage integration.

Array orientation is also a consideration - moving away from a focus on ROI with due-south facing arrays, towards orientation favouring peak consumption matching is possibly something that might be a consideration for some clients, particularly in the domestic arena where the demand profile is often not in line with the yield profile.

 

[danesol]

Seen my post on the new units from Tesla ???

 

[Worcester]

OK, so Tesla are getting close

Powerwall | Tesla Home Battery

7 kWh $3,000 guaranteed 10 years = 7*365*10=25550 kWh vs buying leccy, 25550 * 15p = £3832.5;
so if dollars OK if translates $1 = £1 , not worth it ----YET , getting there, needs to be £2k to go mass market



Oops all sold out
Sold OUT! Tesla's Powerwall home battery - Manufacturing Talk Radio

"Homeowners will be able to get a Powerwall battery in 7 and 10 kilowatt-hour modules for $3,000 and $3,500 respectively. Tesla will also offer 100-kilowatt-hour modules for industrial applications at $25,000 each"

Really good article here: http://www.forbes.com/sites/christo...ery-hype-should-make-tesla-investors-nervous/

 

[TedM]

The batteries have a peak output of 2kW continuous so perhaps not ideal, and more than just the battery will be required to make a fully working system (unless you already have a Tesla EV sitting in the garage perhaps), pushing the price up even higher.

Nonetheless a good opener for Musk to get major media attention.

 

[sharpener]

Figures still don't seem to add up but we're getting asked for this more and more.

As a prospective purchaser I am struggling with the economics of storage systems, much as I would like to have one for reasons of self-sufficiency.

Suppose there are 300 days in the year when there is enough sun to fully charge the battery. At 16p per kWh of grid power my maximum possible saving will then be £48 per year per kWh of usable battery capacity. So a 2kWh Growatt will save £96/yr and a WattStor 3/3 will save £144/yr, hardly a great return for a capital investment of ~£3k in either case. In fact 16p/kWh will not even cover the cost of battery depreciation for most if not all battery technologies on the market.

Am I missing something here? How can the manufacturers justify claims of < 10 years payback?

Some other factors which make the economics even worse:

- Battery storage will cannibalise the savings already made with an immersion heater controller, as there will be days when there is only enough sun for one or the other but not both.
- Battery inverter needs (paradoxically) to be turned off at night since it is not worth sacrificing battery life to save off-peak electricity at only 7p/unit, I have not seen any system offering this.
- This also makes sizing the storage very difficult, if it is not to be too big in the summer it is likely to be too small to be much use in winter.

 

[bxman]

Would you not use the 7p off peak rate to charge the battery on the 150 or more days when generation was insufficient to bring them back to a safe level of charge .

I know prediction of production is not easy with English weather . But being grid connected means that there should be no need to draw in the battery when SOC is low and no point in using at all when off-peak is available .

It will need some careful monitoring and management . No non essential loads when conditions are unfavorable and no wasteful water heating that will not be used simply because the immersion heating controller finds there is surplus generation that would go back to the grid if not used .

 

[sharpener]

Would you not use the 7p off peak rate to charge the battery on the 150 or more days when generation was insufficient to bring them back to a safe level of charge .

No, it does not make sense to do that on a regular basis. Assuming you need something like 4 kWh to recharge a nominal 3kWh battery we would achieve that on 271 days/year on average here in S. Devon and 9 days/month even in January (the worst month), so the need to do a maintenance charge from off-peak mains would be pretty infrequent.

It will need some careful monitoring and management . No non essential loads when conditions are unfavorable and no wasteful water heating that will not be used simply because the immersion heating controller finds there is surplus generation that would go back to the grid if not used .

Nothing wasteful about it, the immersion heater will only consume sufficient power to replace the hot water actually used in the previous 24 hrs. A full tank is about 9kWh so it would take >13kWh to have enough to replenish both, we get that on 141 days in the year on average. It is probably sensible to give battery charging the priority as this will maximise the utilisation of the expensive charger/inverter, my controller would do this automatically as the immersion is the load of last resort. As noted above, the battery itself is at best revenue-neutral as its depreciation per cycle is about the same as the value of the peak rate electricity saved (based on Wattstor's published figures, however they assume the Chinese-made batteries are good for 1500 cycles whereas Sonnenschein who have been making them for decades only claim half as much).

 

[Worcester]

Battery technology needs to change completely to really change the game.

Things are happening, with materials such as graphene ( a superconductor at room temp ) and a range of other single molecule / atom thick materials being developed / discovered. Already people are working on 3D printed batteries using graphene, these and other materials / chemicals are getting over the memory and charge speed limitations of current technologies.

We're not there yet, when these new technologies go into production, then prices will fall and it will become a de-facto part of an installation, and a massive retrofit opportunity.

 

[marconi]

By Marconi. To fuel the discussion may I contribute something about storing energy, in large amounts, densely? I invite you to take a new PP3 nine Volt alkaline battery, short out the terminals using a piece of wire, and then hold the battery in the palm of your hand as it discharges. Then consider storing 2kWh (say) compactly in a battery somewhere in the typical home and consider the risks to dealt with to make it a safe proposition.

 

[sharpener]

By Marconi. To fuel the discussion may I contribute something about storing energy, in large amounts, densely? I invite you to take a new PP3 nine Volt alkaline battery, short out the terminals using a piece of wire, and then hold the battery in the palm of your hand as it discharges. Then consider storing 2kWh (say) compactly in a battery somewhere in the typical home and consider the risks to dealt with to make it a safe proposition.

I think this is a bit alarmist. I agree there are potential problems with lithium batteries but the industry is eventually getting to grips with them. OTOH lead-acid and nickel-cadmium batteries have been around for decades and the only protection you need against sudden release of all the stored energy is a fuse in each lead. When did you last hear of a fork-lift truck exploding?

We think nothing of having a 22mm gas pipe coming into the house and when there is no-one there using a timeswitch to light a 30kW boiler in a garage with a car and 60 litres of petrol in its tank. Or storing 1200 litres of oil in a tank right outside the back door, ditto.

When I worked on this stuff at the DTI there were very very few accidents due to technical malfunction. A more typical case was the man who wired the earth wire of a toaster to the live pin of the plug and vice-versa. Even though it didn't work he then left the toaster plugged in and allowed his baby to play on the kitchen worktop, with predictable fatal consequences. Some people would see this as Darwinian evolution at work in a present-day situation.

 

[marconi]

Battery Fires Reveal Risks of Storing Large Amounts of Energy - Scientific American

This is an interesting article I turned up which chimes with what sharpener has commented and setting out a feel for the current maturity of the technology. It will be interesting to follow over the next decade how battery technology evolves and, as both the article and sharpener say, the risks will hopefully/eventually become 'grandfathered'.

 

[The Solar King]

There will be an MCS product and installation standard in due course. Installers will have to provide information in a common format to end consumers to help avoid the kind of issues highlighted. First draft has been circulated to MCS PV Working Group members for discussion. The eventual standard will add clarity in many ways.

 

[bxman]

Sharpner

I know I live further north and probably have a smaller system than you.

I have looked at my recent records and unlike you November was my least productive month

Here are my Winter figures



_____________________Oct__ Nov__ Dec__ Jan ___Feb ____Mar
Daily Av KWh _________-_-5.6--- 3.1.__ 3.4 __3.8 ---5.2__ 8.8
no days > 7 kWh 10, 3, 0, 3, 11, 18
no days < 3KWh__ 7 ,19, 14 ,12 ,12 ,3 .



SORRY FOLKS HOW DO YOU GET COLUMN's to format correctly



I take it you are contemplating the Wattstor.

I do not think a Wattstor 3/3 would be anywhere near large enough for your needs
I have no idea how they mange their charging regime but IMO the health of the battery should take priority and I would be be willing to use
off peak at 28 p a day to get them back to a 8-90% state of charge.


It seems Wattstor use a Dutch inverter and you say Chinese batteries .
I have been unable to find the Exeter University paper relating to the system maybe you could give us the link

However I am sure as Gordon says none of these systems are a viable proposition at this time .

with regard to the water heating


My gut feeling is that during the summer months there is an awful lot of energy going into water that never gets used, simply because people have a diversion devices
My Diversion Device simply boils my kettle in summer and runs my storage heaters in the winter

Hope these reading help I am sure they are reflected up and down the country
IMO It is very difficult predict the following days production or to foresee when there are going to be consecutive days with next to nothing .

 

[shanky887614]

I think this is a bit alarmist. I agree there are potential problems with lithium batteries but the industry is eventually getting to grips with them. OTOH lead-acid and nickel-cadmium batteries have been around for decades and the only protection you need against sudden release of all the stored energy is a fuse in each lead. When did you last hear of a fork-lift truck exploding?

We think nothing of having a 22mm gas pipe coming into the house and when there is no-one there using a timeswitch to light a 30kW boiler in a garage with a car and 60 litres of petrol in its tank. Or storing 1200 litres of oil in a tank right outside the back door, ditto.

When I worked on this stuff at the DTI there were very very few accidents due to technical malfunction. A more typical case was the man who wired the earth wire of a toaster to the live pin of the plug and vice-versa. Even though it didn't work he then left the toaster plugged in and allowed his baby to play on the kitchen worktop, with predictable fatal consequences. Some people would see this as Darwinian evolution at work in a present-day situation.

if you have lead acid batteries for this purpose you really need to take precautions to control the acid if they ever rupture

unless you go for deep cycle or the gel filled ones you need to be very careful about containers

 

[marconi]

By Marconi My first ditty was about storing large amounts of electricity in the form of chemical energy densely or compactly to make it convenient for the home environment: this is what troubles me because when a large amount of energy is released in the form of heat from a small volume (or from a densely packed form of storage) there is a rapid rise in temperature which can have a number of effects - a (rapid) rise in temperature, distortion, internal damage, pressure build up, ejection of material, outbreak of fire, conflagration or explosion. A battery needs to have ways of failing safely.

 

[sharpener]

I do not think a Wattstor 3/3 would be anywhere near large enough for your needs
I have no idea how they mange their charging regime but IMO the health of the battery should take priority and I would be be willing to use off peak at 28 p a day to get them back to a 8-90% state of charge.


It seems Wattstor use a Dutch inverter and you say Chinese batteries .
I have been unable to find the Exeter University paper relating to the system maybe you could give us the link

However I am sure as Gordon says none of these systems are a viable proposition at this time .

I had an email exchange with Tim Bunhill <Tim Bunhill <[email protected]>> who said the Exeter supplementary paper explaining the cost-benefit analysis is not available for publication but he did send me their spreadsheet and might do so for you. It runs to 14Mb and many, many sheets so is difficult to unpick. But their claim of 6 - 8 years payback is something I cannot reconcile with the cheap and cheerful analysis in my earlier posting which shows that the electricity saved scarcely pays for realistic battery depreciation (which I think is not factored into their model!) never mind the charger/inverter. If you need to condition the battery from the mains the economics become even more woeful.

My gut feeling is that during the summer months there is an awful lot of energy going into water that never gets used, simply because people have a diversion devices

My Diverson Device simply boils my kettle in summer and runs my storage heaters in the winter

Hope these reading help I am sure they are reflected up and down the country
IMO It is very difficult predict the following days production or to foresee when there are going to be consecutive days with next to nothing .

I don't quite understand your argument with regard to power spent heating water being wasted. Our 4kW installation provides enough free hot water for two or three showers every morning, more in summer when we may want to shower in the evening as well. So this saves us about 9kWh every day. If we have people staying then the time switch will if necessary top it up at off-peak rates so we start each day with a full tank. I have thought about storage heaters as well but in winter when they would be useful there is not enough surplus to make it worth while and the controlsand wiring would be more complicated. Total cost of the proportional controller was less than £100 of bits (see my other postings in the very long thread about immersion heater controllers) so the payback period was less than a year. For a commercial one installed for say £400 it would be 2 -3 years so still very worth while given our h.w. usage.

if you have lead acid batteries for this purpose you really need to take precautions to control the acid if they ever rupture

unless you go for deep cycle or the gel filled ones you need to be very careful about containers

Most of the batteries sold for this purpose use either gel or AGM construction, either way they are pretty safe and robust, that's why they are used on aircraft where you wouldn't want an acid spillage. If you are totally paranoid about it you could always put the batteries inside a cheap polypropylene storage box that you can get from Staples for a tenner!

 

[Gavin A]

if you're going for performance then you don't want gel batteries.

 

[snowhead]

These would appear to be the future, once the price comes down;

Energy Storage Battery | Grid Energy Storage | Aquion S10 Battery Stack

 

[sharpener]

These would appear to be the future, once the price comes down;

Energy Storage Battery | Grid Energy Storage | Aquion S10 Battery Stack

Interesting, but the same has been said over the years about flow batteries and sodium sulphur amongst a number of other technologies.

Aquion's chemistry is innovative but not quite as benign as is claimed. Their website talks a lot about "brine" and "salt water" but the original electrolyte was actually sodium sulphate, and according to their Wikipedia article [https://en.wikipedia.org/wiki/Aquion_Energy] they are now using sodium perchlorate which is a nasty strong oxidising agent. But probably no worse than sulphuric acid.

 

[snowhead]

Interesting, but the same has been said over the years about flow batteries and sodium sulphur amongst a number of other technologies.

Aquion's chemistry is innovative but not quite as benign as is claimed. Their website talks a lot about "brine" and "salt water" but the original electrolyte was actually sodium sulphate, and according to their Wikipedia article [https://en.wikipedia.org/wiki/Aquion_Energy] they are now using sodium perchlorate which is a nasty strong oxidising agent. But probably no worse than sulphuric acid.

I'll let you know.
I'm going to be present when one of their Commercial systems is installed soon.

 

[bxman]

if you're going for performance then you don't want gel batteries.

Gavin could you be a little more specific please

Victron are claiming

" VRLA GEL: design life 12 years
VRLA GEL 2 Volt cells: design life 20 years "

Do they lose capacity dramatically over the years.
It is not like we are talking of a high start load

I am at present looking at S/H EnerSys Powersafe

with a " Proven long service life " These as far as I can gather are

"using proven gas recombination technology which removes the need for regular water addition by controlling the evolution of hydrogen and oxygen during charging.Oxygen evolved at the positive plates diffuses through micro porous separators to the negative plates, and, by a series of chemical reactions within the cell, recombines to form water. Each cell incorporates its own safety valve that allows the controlled release of gas when pressure builds up within the cell."
Which is a AGM system I think ?? .


Any advise would be gratefully received
Cheers Patrick