On-grid domestic battery storage

Martyn1981

Solarchaser wrote: »

If you look for a user called Nowty on the Navitron forum, he has done this sort of thing, but with lithium cells from growatt batteries which come up on ebay quite often, and is very pleased with the result, but certainly his expertise is far above mine.

Nowty's a star, and talking of Navitron, and Leaf batteries, you might be interested in the link from this posting made before you joined us:

Martyn1981 wrote: »

Hello again.

I've watched a few things on Youtube, but a lot goes over my head. This article has the story of a battery build using a written off Leaf batt, very yum yum!

See from reply #20 August 17 2014

michaels

Thanks all, have pv, have the leaf already (april 2015, 45k, 90% by leafspy).

Would be nice if I could just leave the batts in the leaf and use it as storage as well as a car

I have also donwloaded the octopus stats and worked out the average half hourly payments. However our panels are only 5 degrees S of W so our peak generation is 11-6 which actually already works well with Octopus...but means there is less scope for using a battery to timeshift supply, also we don't export much as we charge the leaf in the day and then mop up the rest with an iboost (although I know this is only worth about 3-4p/unit as we have gas and a system boiler)

So with Octopus go (5p min for 4 hours at night) plus octopus export we could:
upsize the hot water tank (current is 210l) so that all our hw was from night rate
fit night store heaters that we could use in conjunction with GCH
charge the car at night so that we maxed value of solar export
get batts to timeshift from cheap supply ay 5p/min to export at 14p/min+ and/or avoid daytime usage rate of 14p/min

Only problem might be how many kwh we could draw during the 4 hours with a 100a main fuse.....

I am also thinking about ashp/gshp with the grants. Our garden is not big enough for horizontal coil gshp but vertical might be an option but depends on installation cost vs subsidy assuming fuel cost of gch and heat pump at scop of 4 are broadly comparable.

JKenH

michaels wrote: »

Thanks all, have pv, have the leaf already (april 2015, 45k, 90% by leafspy).

Would be nice if I could just leave the batts in the leaf and use it as storage as well as a car

I have also donwloaded the octopus stats and worked out the average half hourly payments. However our panels are only 5 degrees S of W so our peak generation is 11-6 which actually already works well with Octopus...but means there is less scope for using a battery to timeshift supply, also we don't export much as we charge the leaf in the day and then mop up the rest with an iboost (although I know this is only worth about 3-4p/unit as we have gas and a system boiler)

So with Octopus go (5p min for 4 hours at night) plus octopus export we could:
upsize the hot water tank (current is 210l) so that all our hw was from night rate
fit night store heaters that we could use in conjunction with GCH
charge the car at night so that we maxed value of solar export
get batts to timeshift from cheap supply ay 5p/min to export at 14p/min+ and/or avoid daytime usage rate of 14p/min

Only problem might be how many kwh we could draw during the 4 hours with a 100a main fuse.....

I am also thinking about ashp/gshp with the grants. Our garden is not big enough for horizontal coil gshp but vertical might be an option but depends on installation cost vs subsidy assuming fuel cost of gch and heat pump at scop of 4 are broadly comparable.

Like you (and others) I am anxiously awaiting the technology that would let me use an EV battery for timeshifting and trading. I think Nissan are nearer than most to making it happen - or will Tesla get there first? For me a battery is more on my wish list than being a practical proposition at the moment.

As you have an IBoost you will need to think carefully about how best to operate that alongside a battery. I think someone on here has it sorted but when I had a battery my battery supplier put their hands up and said their battery wouldn’t operate satisfactorily with the IBoost and took it away.

In response to your situation have you considered wall mounted ASHPs (aircon units)? No grants available but for anyone at home during the day I think they are great (particularly as I don’t have gas). I bought one and soon bought another. I think there is a thread on here somewhere about them.

We have two separate hot water tanks with the bottom elements in each supplied by the IBoost and the top elements on separate timers. In winter I can leave the top elements on the timer with the thermostat set lower so that they will only operate if the bottom elements haven’t done enough. The most I have diverted by the IBoost in one day to the two tanks is 16 kwh.

Because of the ASHPs and the IBoost it is only in the summer months that I would have any spare for a battery. As I could use more generation in winter I will really need more panels before a battery will be a great deal of use to me - but I want one!

michaels

JKenH wrote: »

Like you (and others) I am anxiously awaiting the technology that would let me use an EV battery for timeshifting and trading. I think Nissan are nearer than most to making it happen - or will Tesla get there first? For me a battery is more on my wish list than being a practical proposition at the moment.

As you have an IBoost you will need to think carefully about how best to operate that alongside a battery. I think someone on here has it sorted but when I had a battery my battery supplier put their hands up and said their battery wouldn’t operate satisfactorily with the IBoost and took it away.

In response to your situation have you considered wall mounted ASHPs (aircon units)? No grants available but for anyone at home during the day I think they are great (particularly as I don’t have gas). I bought one and soon bought another. I think there is a thread on here somewhere about them.

We have two separate hot water tanks with the bottom elements in each supplied by the IBoost and the top elements on separate timers. In winter I can leave the top elements on the timer with the thermostat set lower so that they will only operate if the bottom elements haven’t done enough. The most I have diverted by the IBoost in one day to the two tanks is 16 kwh.

Because of the ASHPs and the IBoost it is only in the summer months that I would have any spare for a battery. As I could use more generation in winter I will really need more panels before a battery will be a great deal of use to me - but I want one!

Thanks.

So we would effectively stop I boosting and export as our iboost units are worth about 3p of gas saved whereas export would be worth 6-15p.

We do similar with the iboost at the moment but set the gas hot water to 50 as min needed and the tank bottom iboost thermostat to 70 allowing us to store about 5kwh and push the gas temp up in the winter when there is less spare PV.

mmmmikey

Yesterday's power outtage was a good reason we should all go out and buy battery systems with frequency response built in and enter into a grid services contract.

When the generators failed yesterday, the grid frequency dropped and the national grid went into "(expletive deleted) it, I give up mode" - i.e. it shut itself down.

Battery systems (such as the PowerVault) with frequency response built in start disharging to the grid when the frequency drops, for which the generators pay you a handsome fee. This reduces the possibility of power outtages like yesterday, although clearly there's a long way to go until there is a sufficient battery capacity to make a difference. Many a mickle makes a muckle, though.

So if you're on the borderline of taking the plunge and buying a battery, just do it but make sure it has frequency response built in. Don't think of it purely as a financial investment - see it as a selfless act of charity and a way of helping those poor, stranded train passengers.....

Solarchaser

Thanks for the link Mart, that's certainly some food for thought, and I like the racking, tidying it all up.

Michael's could you add more PV?
Upping your export and potentially still being able to iboost, or even just for additional export?

My understanding (and there is a good chance I misunderstand) that the immersun can be set to only activate over a certain amount of export.
So if for instance you could set it to only work above a 100w export, then the batteries would never discharge to run the immersion as the batteries would only see exported solar rather than a current draw.

Worst case you waste a kw a day, but that would be a small price to pay to have bats and immersion work together.

Reed_Richards

Are there any electrical appliances designed for solar plus battery? I am thinking of something that would ramp its power demand up and down slowly enough for the battery output to keep up and/or demand less power for a longer time so the battery capacity is not exceeded when the solar panels are "off".

Martyn1981

Reed_Richards wrote: »

Are there any electrical appliances designed for solar plus battery? I am thinking of something that would ramp its power demand up and down slowly enough for the battery output to keep up and/or demand less power for a longer time so the battery capacity is not exceeded when the solar panels are "off".

I would assume there is. I say that as I once asked an off-gridder for a theoretical cost on PV, batts etc for off-grid to help with a discussion on here.

One of the items he listed, with a link to the price etc, was a battery friendly A/C unit, which started up more gently, as the 'normal' ones can have a massive spike. I think mine that runs at about 700W shows an instantaneous draw of about 2-3kW, and my freezer has hit similar figures, but you need a plug in monitor that records the peak as they are so brief.

Sorry, waffling again, but if off-grid, batt friendly kit exists, then presumably something closer to what you are suggesting does too, though i seem to recall they are more expensive.


Also, ask Z, as i went for a cheap and basic ASHP to top up shoulder month heating, but he and others went with better models that can run deliberately lower to avoid import, which is a similar task to what you describe ..... I think.

pile-o-stone

Reed_Richards wrote: »

Are there any electrical appliances designed for solar plus battery? I am thinking of something that would ramp its power demand up and down slowly enough for the battery output to keep up and/or demand less power for a longer time so the battery capacity is not exceeded when the solar panels are "off".

I was wondering about this the other day. Maybe you should start a new thread where we can list lower power alternatives to domestic appliances (like lower wattage hoovers)? I was looking at replacing my kettle (it always smashes me back onto mains energy even on really sunny days) with one of those hot water taps, until I saw the price of them! :eek:

I also saw that one of the heat pump manufacturers had released a GSHP with what they called a "DNO friendly low starting current as standard". I'm hoping that also meant that it was solar/battery friendly too.

EDIT: Just read Mart's post where he also mentions heat pumps - great minds and all that.

1961Nick

Reed_Richards wrote: »

Are there any electrical appliances designed for solar plus battery? I am thinking of something that would ramp its power demand up and down slowly enough for the battery output to keep up and/or demand less power for a longer time so the battery capacity is not exceeded when the solar panels are "off".

An ASHP with an eco setting will do a reasonable job of avoiding 'peaks'.

Our heat pump tumble drier appears to have a lower peak demand than the old one.

I've installed a boiling water tap to avoid the 3kWh kettle load. A 1, 1.5 or 2kWh kettle would do the job but take an age to boil.

Cordless power tools, hoovers, mowers etc, enable you to schedule charging & avoid any load when there is little solar & the batteries are empty.

Avoid the 12kWh induction hob!!!:eek:......but it keeps her happy.:)