Don’t bother with the heaters for your batteries at all. The batteries warm themselves up as they charge overnight (but them on long and slow using charge rate). And a bit of surrounding insulation (bubble wrap/ polystyrene packing cases/plastic covered loft insulation etc) under your snow shelter lid will keep them nice and warm.

Our givenergy one has a temperature monitor you can keep an eye on over winter. Despite -2deg air temperature the battery internal has not gone below +4C yet

@misterB consider tariffs such as Cosy Octopus that offer two 3hr low rates a day. If you can get an EV tariff then so much the better 😉

Posted by: @misterb

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i think economy seven or similar, will be around for quite a while as the power companies want us to use more power when there is little demand and less power when there is greater demand

As I have access to real data for local substation transformers, I've been able to keep an eye on this.

Here's a table with a few randomly selected local substations sited at towns in the Home Counties within reach of the M1

We already have many transformers where the night-time demand is higher than that during the day.
This is typically happening in towns/suburbs towards SE England.
And yet the number of connected EV Chargers (Low Carbon Technology) hasn't yet risen to 10% of connected properties.

That is a more populous region of the UK, and will have a greater uptake of EVs due to the expansion of ULEZ during 2023.

There are two other factors which make matters worse from the perspective of DNOs:

• those transformers are operating close to or above their specified maximum
• 10% of single-phase connections with high demand is statistically the most likely to cause losses due to phase-imbalance, assuming a random allocation of phase to each property

There are a number of solutions, but Ofgem's stance thus far is that they will not consider nodal-pricing (based on geographical location) until the end of 2025.

In those circumstances, the DNOs and National Grid Electricity Transmissions (NGET) will be forced to act, due to their obligations under the terms of their licences.
The cost of those grid enhancements (new transformers and cabling) will come from increased charges for electricity. A substantial quantity of that rise will be derived from the Daily Standing Charges, which disproportionately impact on households with pre-payment meters and/or in energy poverty.

Conclusion: retaining a Economy-7 tariff is technically and ethically a poor decision, for whatever reason we use it.

I would expect the new Independent System Operator and Planner (ISOP) to consider this earlier than Ofgem has indicated.

Posted by: @misterb

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@curlykatie

 

Thanks to lots of help from people on this forum, ive eventually landed on a Sunsynk 5kw Hybrid inverter and a 14.3kw Seplos 280L battery, my next purchase will be either another Seplos 280L @14.3kw or sell my Seplos at a loss and buy two 15kw batteries that have built in heaters as my storage batteries are in an unheated area.

the point i am trying to make is that there are alternative options if you can find a competent electrician - my sunsynk and seplos cost around £4k to buy and around £1k to install - another battery would cost around £2.5k - so for around £7.5k i will have close to 30kw of storage capacity. we are all electric and easily use 20+Kw per day in the winter, so i am trying to get all our power bought (and stored) at the offpeak period.  

the big question is though, is it really cost effective? im not totally convinced, but its a long term project, we have no intentions of moving, but for me (and not necessarily others) its tied in to not just the cost of electricity, but when it can be bought cheaply. if i can buy in the early hours and then later in the afternoon (Cosy Octopus), then i prob dont need as much storage, but if i can only buy in the morning, then i need bigger storage capacity. 

i think economy seven or similar, will be around for quite a while as the power companies want us to use more power when there is little demand and less power when there is greater demand, hence my reasoning for additional storage. i am also lucky in that we have an existing solar panel system paying good rates under the discontinued Feed in Tariff scheme, which has more than paid for itself and is now offsetting the cost of the storage battery installation by around £1k per year (with another guaranteed 15 years).

So if you do have the services of a competent electrician then there is a lot of money to be saved with home battery storage systems by 'doing it yourself', though actually, the only diy aspect is that youre sourcing the materials and the labour!! 

 

Thanks for posting this, it's really useful, especially on the total cost of your system + installation costs. That's what always gets me - I know I'm going to get a better deal with a "source it yourself" option but then the big unknown is the cost of labour. £5k for 14kWh of storage + inverter is very nice.

My current GivEnergy battery is also in an unheated area (garage) but it hasn't given me any problems. I've calculated the total round trip loss is about 10% and doesn't vary much in winter.

I worked out that Cosy Octopus didn't save very much money compared to Octopus Go - a few pounds a month - so I stuck with Go. I am now, luckily, on Intelligent Octopus as they've added my EV charger to their compatible list, so Cosy now makes even less sense.

Posted by: @transparent

↑

Posted by: @misterb

↑

i think economy seven or similar, will be around for quite a while as the power companies want us to use more power when there is little demand and less power when there is greater demand

As I have access to real data for local substation transformers, I've been able to keep an eye on this.

Here's a table with a few randomly selected local substations sited at towns in the Home Counties within reach of the M1

-- Attachment is not available --

We already have many transformers where the night-time demand is higher than that during the day.
This is typically happening in towns/suburbs towards SE England.
And yet the number of connected EV Chargers (Low Carbon Technology) hasn't yet risen to 10% of connected properties.

That is a more populous region of the UK, and will have a greater uptake of EVs due to the expansion of ULEZ during 2023.

There are two other factors which make matters worse from the perspective of DNOs:

• those transformers are operating close to or above their specified maximum
• 10% of single-phase connections with high demand is statistically the most likely to cause losses due to phase-imbalance, assuming a random allocation of phase to each property

-- Attachment is not available --

There are a number of solutions, but Ofgem's stance thus far is that they will not consider nodal-pricing (based on geographical location) until the end of 2025.

In those circumstances, the DNOs and National Grid Electricity Transmissions (NGET) will be forced to act, due to their obligations under the terms of their licences.
The cost of those grid enhancements (new transformers and cabling) will come from increased charges for electricity. A substantial quantity of that rise will be derived from the Daily Standing Charges, which disproportionately impact on households with pre-payment meters and/or in energy poverty.

Conclusion: retaining a Economy-7 tariff is technically and ethically a poor decision, for whatever reason we use it.

I would expect the new Independent System Operator and Planner (ISOP) to consider this earlier than Ofgem has indicated.

i bow to your better and more informed knowledge !! hopefully i should be ok for a few years yet, but who knows, if i can get onto octopus cosy it will be helpful, however i suppose it could go the same way as you suggest economy 7 might go???

i have been making full use of the 'free power periods' to recharge my battery and it has been really helping !

Posted by: @transparent

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Conclusion: retaining a Economy-7 tariff is technically and ethically a poor decision, for whatever reason we use it.

There appears to be a bit of a leap from the data to this conclusion. Do we know that Economy 7/Economy 10 users are generating this peak? Also characterising the electricity demand curve from an extreme point (max) leaves something to be desired. Other percentiles might give a better idea about what is really going on (on the assumption that the transformer is OK to operate at N% above its rated capacity for X minutes before meltdown).

Posted by: @chickenbig

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characterising the electricity demand curve from an extreme point (max) leaves something to be desired.

I think we need to see this from the viewpoint of DNOs and NGET.

They most definitely are basing their strategies on peak/max demand.
Their licences require them to maintain the security of the electricity supply.

We shouldn't be anywhere near the rated maximum for a grid transformer.
To do so means that it's already getting too hot before they factor in the increasing losses due to phase imbalance.

It matters not to a DNO whether the max nighttime demand is due to loads which they know about (and have approved) such as EV chargers, or caused by storage radiators and batteries which did not require their permission.

It is reasonable to conclude that householders or their Energy Suppliers are switching on such nighttime loads because it is financially better for them to do so. Whether they're applying that load to an Economy-7 tariff or a bespoke EV tariff doesn't matter either. It's not the name of the tariff which is relevant, but rather that the pricing isn't in sync with periods of greater renewable generation. Crude time-periods are no longer the way forward.

Pulling this back on-topic, those of us with domestic storage batteries won't mind the time of day when they get recharged from the grid.
But EV's are much more likely to be parked 'at home' overnight.
So the more useful strategy is to remove the single low-cost period tariffs, such as Economy-7 and Octopus Go.

The night then needs to be prioritised for EV charging but on a much smarter system than is currently being implemented.
The data to achieve this is already available, but Energy Suppliers would need to add code to their Billing Systems to support such an approach.

Posted by: @chickenbig

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Other percentiles might give a better idea about what is really going on

That's not so easy. There are very few 'smart' local substations in the UK.
I do have access to a group, and I'll have a look to see what data I can post from those.

At the moment, almost all the data I've gathered from those monitored transformers has been related to specific fault conditions.

@transparent

I fully agree, just as heat pumps don't play nicely with heatmisers, averages don't work well with both electricity generating capacity and the associated transmission systems.

Think what would happen if they only built sufficient power stations to supply average demand, my guess is that there would be frequent daily power cuts. With the move towards more renewable generation this problem is made even worse, not only does the systems have to cope with going from 60% renewable supply one day, to only 10% the next, but also the source and direction from which the renewable supply is coming may be different, meaning all the transmission systems may need to be upgraded.

Just as a heat pump performs more efficiently when operating in the 'low and slow' mode, people need to be educated that, wherever possible, they should draw electrical energy from the mains supply in the same manner.

Posted by: @transparent

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Whether they're applying that load to an Economy-7 tariff or a bespoke EV tariff doesn't matter either. It's not the name of the tariff which is relevant, but rather that the pricing isn't in sync with periods of greater renewable generation. Crude time-periods are no longer the way forward.

OK, this refinement is more something I am more aligned with. We need greater demand flexibility; the problem is not Economy 7 but this idea of fixed time-slots when we can get cheap electricity. However it does interest me that there is a diurnal demand but when overall demand is lowest the demand from the transformers you selected is the greatest. In the table you posted, which period counts as night, and across what length of time is power bucketed (1 minute, 5 minutes, 1 hour)? Also is this national drop in demand related to commercial industrial customers?

Posted by: @transparent

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domestic storage batteries won't mind the time of day when they get recharged

I'm currently manually operating a Sunsynk inverter to maximise the Octopus Savings Session benefits. I would really appreciate a single demand side response API to determine when it is beneficial to charge/discharge. Something to crystalise development effort for Sunsynk and other inverter manufacturers (for Home Assistant contributors).

Posted by: @derek-m

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Just as a heat pump performs more efficiently when operating in the 'low and slow' mode, people need to be educated that, wherever possible, they should draw electrical energy from the mains supply in the same manner.

It feels like "low and slow" is rather at odds with the feast/famine nature of wind. I've yet to resolve this in my mind, just like whether a fast EV charger is better than everyone having granny chargers (or equivalent power and with demand response capability).

@chickenbig

It feels like "low and slow" is rather at odds with the feast/famine nature of wind. I've yet to resolve this in my mind, just like whether a fast EV charger is better than everyone having granny chargers (or equivalent power and with demand response capability).

I believe large scale energy storage will be required in the future to help smooth out the peaks and troughs.

It could be in the form of grid scale battery storage, the production of green Hydrogen when excess generation is available, or some form of thermal energy storage.

Because energy supply is now a large commercial business, we will have to wait and see what the powers that be decide will be most profitable.

Posted by: @derek-m

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I believe large scale energy storage will be required in the future to help smooth out the peaks and troughs.

There are a number of commercial battery storage sites in GB, and others currently passing through the planning process. Many of these are marginally below 50MWh and therefore use the same G98/G99 rules which govern domestic connections. See also my later correction to this point.

They are controversial in a number of respects, as can be seen by looking at the correspondence/submissions made during the period for public consultations. A typical example is Planning Application 1116/23/VAR being decided by West Devon Borough Council. The Applicant has not revealed:

• the size/capacity of the proposed installation
• the chemistry of the storage batteries to be used, and hence the safety requirements to prevent any possible contamination, leakage, fire precautions etc
• the control and monitoring technology, or who oversees it
• any approval or acceptance by National Grid (the site is not listed on the register with Offers to Connect)

Large scale storage like this, particularly in rural areas, present an intrinsic threat to the security of the grid. To be effective, they would be exporting to the distribution grid during periods of heavy demand. They will be the bulwark which allows the remote corners of the grid to maintain the supply voltage within the specified 230v +10 -6% (216v - 253v).

But if such a commercial storage site were to suddenly fail during the early evening peak, the resultant drop in voltage to all the remote farms and villages would cause all their grid-tied inverters to disconnect from the grid. That's a requirement of G98 of course.

That creates a cascade effect which rapidly sweeps across the area as ever more inverters stop exporting when the line voltage drops below 216v.

Again, we need to see this from the viewpoint of a DNO. Hundreds of individual houses with storage batteries is a far more stable solution than having large companies install batteries with megawatt capacity. Grid stability/security shouldn't be compromised by allowing 3rd parties to install batteries on which we rely, especially if they propose control systems which are operated remotely.

It's increasingly important for this Forum to provide as much help as possible to those wanting to install their own domestic-level battery storage.

Posted by: @transparent

↑

Posted by: @derek-m

↑

I believe large scale energy storage will be required in the future to help smooth out the peaks and troughs.

There are a number of commercial battery storage sites in GB, and others currently passing through the planning process. Many of these are marginally below 50MWh and therefore use the same G98/G99 rules which govern domestic connections.

They are controversial in a number of respects, as can be seen by looking at the correspondence/submissions made during the period for public consultations. A typical example is Planning Application 1116/23/VAR being decided by West Devon Borough Council. The Applicant has not revealed:

• the size/capacity of the proposed installation
• the chemistry of the storage batteries to be used, and hence the safety requirements to prevent any possible contamination, leakage, fire precautions etc
• the control and monitoring technology, or who oversees it
• any approval or acceptance by National Grid (the site is not listed on the register with Offers to Connect)

 

Large scale storage like this, particularly in rural areas, present an intrinsic threat to the security of the grid. To be effective, they would be exporting to the distribution grid during periods of heavy demand. They will be the bulwark which allows the remote corners of the grid to maintain the supply voltage within the specified 230v +10 -6% (216v - 253v).

But if such a commercial storage site were to suddenly fail during the early evening peak, the resultant drop in voltage to all the remote farms and villages would cause all their grid-tied inverters to disconnect from the grid. That's a requirement of G98 of course.

That creates a cascade effect which rapidly sweeps across the area as ever more inverters stop exporting when the line voltage drops below 216v.

Again, we need to see this from the viewpoint of a DNO. Hundreds of individual houses with storage batteries is a far more stable solution than having large companies install batteries with megawatt capacity. Grid stability/security shouldn't be compromised by allowing 3rd parties to install batteries on which we rely, especially if they propose control systems which are operated remotely.

 

It's increasingly important for this Forum to provide as much help as possible to those wanting to install their own domestic-level battery storage.

I don't disagree with what you are saying, but when I talk about large scale energy storage, I am thinking more along the lines of GWh size systems, which should be operated and controlled by NG. It should then be possible to store excess renewable generation during 'times of plenty', rather than paying wind farm operators not to generate.

We really need the development of Iron - Air batteries (or something similar) to be sped up, so that affordable large scale energy storage can become a reality.