On-grid domestic battery storage

Martyn1981 · 26 December 2016 at 10:53AM

Another fascinating video. Not exactly domestic storage, but it's an iKube (fold up PV panels with inverter), mounted on a trailer that has batts, plus tool storage for multiple 'gardening' tools for example. The trailer has socket connections for cabled tools, like disc cutters, plus multiple chargers for cordless tools.

Theoretically I assume it could be used for domestic purposes, pop an iKube in your back garden, and it's 9m2 so just meets UK planning rules. Or go the whole hog, with the trailer, batts etc.

As the video explains this is a package that they rent out to contractors for work sites, or perhaps for off-grid work, instead of hiring a generator. They also mention that the military use the iKube, which reminded me that the US says it costs several hundred dollars per gallon to get diesel to forward bases (eg Afghanistan) due to the amount of trucking, soldiers, military support etc that is needed.

Power Trailer by Green Energy

michaels · 26 December 2016 at 5:36PM

Martyn1981 wrote: »

Just back from a Xmas visit to some friends, and have to share an idea that was suggested. My mate is a builder, but one of those folk who can see round a problem, or view it from all angles.

He asked me jokingly when I was going to get a battery, and later on asked why the Severn Barrage isn't happening. He then put the two ideas together and said, 'perhaps in the future we'll all have batteries in Cardiff and then charge them off the tidal lagoon?'.

Well .... my head nearly exploded. Is that a perfect solution or not, my mind can't cope.

Here's the reasoning.
You know when it's going to generate (almost irrelevant) and that it will be twice per day. So intermittent, but predictable.
As it's twice a day, you can half the battery size.
The battery cost could be heavily subsidised (shared) by Western Power Distribution (the DNO) as this would eliminate all peak loads and save them money.
So the household chips in £x and gets a batt that charges up say 5kWh (x2) per day at a low leccy price, then you pay the normal rate for any extra. A bit like E7, perhaps E4by2 (well he is a builder!)

If the cheap leccy was say 5p less, then that could save you £180pa at 10kWh per day.

Sorry for the waffle, but the idea interested me. I'm trying to think of another form of RE that would really benefit from such a partnership? :think:

Putting my economist hat on, if the generation is not distributed, what is the benefit of distributing the storage? Perhaps there is an effective 'balance' on the peak grid transmission required but I would suspect that was more than offset by the diseconomies of scale resulting from multiple small batteries installations/maintenance.

However the idea of tidal plus some form of buffer storeage (is battery the most efficient?) definitely sounds like a goer if the capital costs are sensible and the enviromental impact acceptable.

Unless we are expecting an imminenent breakthrough in generation the current low interest rate environment would seem to make it an ideal time to invest in high fixed cost low operating cost long lifespan energy infrastructure (except perhaps for Hinkly C!)

Martyn1981 · 26 December 2016 at 5:59PM

michaels wrote: »

Putting my economist hat on, if the generation is not distributed, what is the benefit of distributing the storage? Perhaps there is an effective 'balance' on the peak grid transmission required but I would suspect that was more than offset by the diseconomies of scale resulting from multiple small batteries installations/maintenance.

However the idea of tidal plus some form of buffer storeage (is battery the most efficient?) definitely sounds like a goer if the capital costs are sensible and the enviromental impact acceptable.

Unless we are expecting an imminenent breakthrough in generation the current low interest rate environment would seem to make it an ideal time to invest in high fixed cost low operating cost long lifespan energy infrastructure (except perhaps for Hinkly C!)

Hiya, yep, I know exactly what you are saying, and the problem is that I can't quite explain what I'm thinking.

Tidal is predictable, and if it coincides with peak demand then that's great, but ideally the tidal lagoons want to let the water in, when the tide is near to peak (greatest head), and let the water out when the tide is near to low (greatest head again). The use of storage means that the guaranteed double daily dose of tidal can be used to aid the peaks, if they miss by hours.

How? Well, if they had their own storage, they could deploy it in the evening, but if it's used to charge domestic batts, then they can be expected to be used in the evening, as that's what causes the peak - domestic demand.

I (like you) would also expect a large storage system (not necessarily batteries, could be CAES or LAES, or many others) to be cheaper than domestic batts, but here's the trick .....

if the national or local grid build it, then they pay the whole cost, and the whole cost falls on leccy customers. But if you can get the demand side to chip in, perhaps PV households first, then the cost can be shared across multiple partners.

I think what I'm thinking (see how confused I am), is that the nation needs storage, and if householders invest in batts, then the nation doesn't pay for those out of leccy bills and leccy investment funds. The same applies to say low energy lightbulbs, if you or I buy some, then leccy demand goes down, without funding (post subsidy) from the supply side, and without expenditure on the supply side to generate more leccy.

Take that to the next step, and say I buy a batt, and shift some of my daytime export, to evening time demand reduction, then the supply side benefits, but the investment came from my pocket (the demand side).

It's a hard one to explain, as I'm being honest and can't quite get my own head around it - I can see that there's something there, but I don't know if it's viable and sensible.

Anyways, it's probably just a thought exercise, and means nothing more than that, but hopefully all of these little gains will keep adding up.

The good news - well, I don't see any reason why storage needs to be thought of ahead of the tidal lagoons, (though storage might make them more valuable) so we can wait whilst storage costs fall, and possibly new types are tested and improved, and there's a mid way solution too, which would be the DNO installing its own batts in areas that have peak issues, perhaps 100kWh rather than domestic 5kWh or major 1,000kWh systems. I bet there are tons of possible solutions, assuming batt/storage costs continue to fall.

I just hope the Swansea Tidal Lagoon gets the go-ahead. It's pretty expensive, perhaps 50% more than Hinkley C, but should lead to the Cardiff scheme at 10x the size and a much lower cost if the build out of Swansea works. Fingers crossed.

Martyn1981 · 26 December 2016 at 6:05PM

michaels wrote: »

However the idea of tidal plus some form of buffer storeage (is battery the most efficient?) definitely sounds like a goer if the capital costs are sensible and the enviromental impact acceptable.

Just had a thought, I may be re-inventing the wheel. We already have Dinorwig which we charge up from cheap nightime leccy, or even excess French nuclear (when things are going a bit better in France, given their recent nuclear problems).

So we could just charge up Dinorwig. If you know that the tide isn't going to coincide with a peak, then you use a bit more from Dinorwig to help bring the spot price down, then charge it back up from tidal, as you know in advance (hundreds of years in advance) when the tidal peak and generation will be.

Pumped hydro (PH) is about 70% efficient, and whilst not local grid, but national grid, it's already there and waiting.

michaels · 26 December 2016 at 8:50PM

On the household vs network storage as I say it only appears to make sense if you have household generation or peak transmission is very costly (which I guess it could become as gch ramps down and ev ramps up).

Savings resulting from differential pricing between the wholesaler and consumer don't seem to be real savings. Schemes that let those with capital make savings over the longterm we know are problematical on fairness grounds....

zeupater · 27 December 2016 at 2:01PM

Martyn1981 wrote: »

Just had a thought, I may be re-inventing the wheel. We already have Dinorwig which we charge up from cheap nightime leccy, or even excess French nuclear (when things are going a bit better in France, given their recent nuclear problems).

So we could just charge up Dinorwig. If you know that the tide isn't going to coincide with a peak, then you use a bit more from Dinorwig to help bring the spot price down, then charge it back up from tidal, as you know in advance (hundreds of years in advance) when the tidal peak and generation will be.

Pumped hydro (PH) is about 70% efficient, and whilst not local grid, but national grid, it's already there and waiting.

Hi

We seem to keep coming back to this solution, the problem however remains with the highly vocal NIMBY lobbyists ....

zeupater wrote: »

lstar337 wrote: »

I was thinking pumped storage, but its the space it takes up!
I know what you mean. I live in the south west and would love to see the Severn Barrage project go ahead, but I don't think it ever will.

Hi

There was a sub-discussion a few years back involving large scale pumped storage ... here's an idea of what space/volume would be involved (this post and a few around it) ...

zeupater wrote: »

Hi

Not talking about Dinorwig, but something similar is possible on a larger scale, both in generating capacity and stored water volume, which could be used for generation over a period of days ..... a system comprising somewhere around 100,000 megalitres of high/low capacity with around 150m between the two levels would do for a start with a massive increase in volume of flow compensating for the loss of elevation differential available at Dinorwig, but to place that volume in context, we'd be talking about a pumped system which would be equal in scale to the Elan valley reservoirs .... we're talking massive numbers for the Severn barrage, massive numbers for windpower, massive numbers for nuclear, massive numbers for gas-fired plant, so if we need to create a hydroelectric 'battery' (or series of batteries) to smooth generation to demand, then we'll need to spend massive numbers on that too, it might just mean that less generating capacity duplication will be necessary elsewhere ....

HTH
Z

It's not easy, but a little political will and accepting that the 'usual suspects' will be upset for a while is all that's required ... the problem is that most of our current politicians have absolutely no backbone and even less comprehension of what is and isn't really important, let alone how to prioritise ... they'd rather debate the 19th century slave trade or the current trends in women's fashion than something important ... give them a set of simple logical puzzles (such as the good old 11+ exam) and you'd find that most would struggle to scrape a pass, so no wonder nothing ever gets done ! ..

HTH
Z

.... I like the idea of tidal lagoons (if they're well thought-out, designed & engineered !), however, although 'charging' the system is effectively 'free' the low water head severely restricts the generation capacity. Concentrated tidal flow systems and a 'proper' Severn barrage system are what's needed, it just needs the political will to dismiss the 'usual' vested interest parties & their lobbyists ...

Until next time .....

HTH
Z

gefnew · 27 December 2016 at 9:20PM

Hi Mart
A bit of news about When will our electricity come from the sea?
http://www.bbc.co.uk/news/science-environment-38426389
regards gefnew

Martyn1981 · 4 January 2017 at 9:30AM

I'm posting this on the battery thread as that seems the best place for it, but here's a time of day tariff with cheap nightime leccy 5p/kWh (charge an EV?), normal daytime 12p/kWh (avoid with PV?), and expensive peak price 24p/kWh from 4pm to 7pm (PV + battery?)

I still think we are a few years away from being able to jump in with batts, but a package like this would tick all the boxes. In fact the night v's peak difference of 19p/kWh would even allow for arbitrage, as the current cost of storage, using the Tesla PWII is about 13p/kWh over the 10yr warranty period (approx £6.3k / 50,000kWh).

Looks like another piece of the jigsaw is falling into place.

Green Energy UK offers first electricity tariff based on time of day

[Edit: I should add that the gas price is quite expensive, almost twice what I pay, but it's more the idea than this specific package that I think is interesting. M.]

Martyn1981 · 5 January 2017 at 9:34AM

Further to my last post regarding variable time of day tariffs, another battery related thought has occurred to me, a package like this could halve my battery needs!

I've always calculated that I need 4kWh of useable storage, more than that would be a waste as I have too little import in the summer, and too little export in the winter. But at 5p/kWh at night, there's simply no point in having the capacity to 'avoid' nightime import. In fact, I doubt a plug-n-play domestic battery system will get down to 5p/kWh in running costs.

So, now all I need is enough storage to get me to 7pm (to avoid 25p/kWh), or ideally 11pm (to avoid 12p/kWh).

I suppose I also need some clever management rules for the battery, so that it doesn't discharge between 11pm and 6am, possibly charges up in the winter from 5p leccy, and also in the winter keeps about 1-2kWh for use between 4pm-7pm.

My forum friend has confirmed that his batts can be programmed to charge up overnight, so none of this sounds too tricky.

The results, well I estimated that a 4kWh useable (5kWh Li-ion / 8kWh lead acid) battery would reduce my import from 1,500kWh to 600kWh. 450kWh 5p + 150kWh 12p = £40.

I'd estimate that a 2kWh useable battery would reduce my import to 900kWh. 600kWh 5p + 300kWh 12p = £66.

So that's an extra £26pa in leccy costs, but a possible halving in battery costs.

More options, more possibilities.

Martyn1981 · 8 January 2017 at 6:16PM

I'll just post the whole thing, then explain how it's got me thinking:

So I've manually gone through the logs since the battery was installed.

In total the battery discharged 29.39kWh in December since installation on 9th Dec - so I guess that's approx £4.40's worth of imported electricity avoided?!

The ImmerSUN diverted a measily 9kWh to the hot water tank in December.

I generated 57kWh over the whole month - 38.5kWh over the days since the battery was installed - so since the battery went in, it looks like I self-consumed every electron the panels created for me at least, between the battery and the ImmerSUN!

[Edit: Just for clarification for any eagle eyed readers out there - It appears that the total generation post batt install matches the battery diversion + Immersun, leaving nothing for baseload consumption. I've asked about this, and the 9kWh for the Immersun was for the whole of December, including the period before the batts were installed. M.]

Looks to me like the batts captured all the excess, with low daytime consumption, and the Immersun grabbed anything the batts missed, or discharged in excess well dialing down discharge (60 second soft shutdown from 1,200W).

I've always guessed that of my 90kWh or so of December generation, I probably use about 60kWh, and export 30kWh. My battery savings guess, is based on 1.5kWh/day across the bottom 90 days, ranging from 1kWh in Dec through to 2kWh in early Nov or late Jan.

But now I'm having second thoughts as the generation is more concentrated, perhaps 1 to 1.5kW across 4hrs, with 1 good day (double average) and 1 bad day (nearly zero gen). So perhaps my export is higher, and potential savings are greater?

But, before I get excited, even doubling the December potential from say 30kWhs to 60kWhs, is still relatively small potatoes over a year, especially whilst batt costs are still so high, but every little helps.

Hopefully the info I'm getting will help me build up a better idea of how the batts will operate, and whether (or not) they are viable. Hopefully this helps others too, but I'm going to waffle on regardless!

On-grid domestic battery storage

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