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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.
 
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 .
 
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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
 
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.

 

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!
 
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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.
 
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.
 
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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
 
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