I'm afraid I did not delve into 3 phase balancing requirements, since the majority of the population struggle to understand single phase systems. You are certainly correct that much more thought needs to be given before encouraging everyone to have a heat pump and EV, and of course solar PV and banks of batteries. Having 3 phase heat pumps and EV chargers would go some way to solving the problem, but most, if not all, DNO's want to charge an arm and a leg when someone requests a 3 phase supply. Tends to defeat their objective.
By balancing the grid (maybe a bad choice of words), I was referring to reducing demand at peak periods by moving it to periods of lower demand.
Heat-pumps are worse however. They 'cycle' at intervals between 30-mins down to 5-mins, depending on how well your installation has been optimised.
Here's snapshot I've just grabbed from an 11kV local substation in an urban area of SW England during today (Mon 23rd Jan)
This graph shows the three phases (L1 L2 & L3) on one of six 440v feeds which serve the surrounding area. Sampling of the average current occurred over 10-minute intervals.
Phase L1 is higher during most of the daytime because houses on that phase have fewer solar-panels.
Phase L2 supplies much more current towards the end of the afternoon as the sun sets and the early-evening peak arrives.
I've shown in dotted lines the 'trend' for both L1 & L2 so you can see them both climbing during the day, but L1 at a steeper rate.
I happen to know that there are several houses with heat-pumps in that area, although it isn't local to me. I suspect that the majority of the fluctuations throughout the day are due to heat-pump cycling. These have been well optimised and are typically operating with longer cycles than most do in the UK.
When phases are unbalanced, as in the above illustration, the 'spare' magnetic flux in the transformer gets wasted as heat.
I've often wondered what the effect of lots of ASHPs would have on the grid. However, I'm not sure it's as bad as you say. Modern ASHPs are inverter heat pumps, which use a variable speed compressor to modulate output to match heat demand. This avoids much of the cycling you describe. A properly sized ASHP in a well designed system won't be cycling when it's 5-7 degrees outside. My ASHP is using a steady 1.5 kW in these conditions. When it does cycle in warmer weather it generates spikes but still only 3kW or so. If your neighbours are using their ASHPs like gas boilers and making them switch on and off constantly then this will cause bigger spikes but even then they wouldn't match some some of the spikes on the graph.
Electric showers, washing machines and dryers and EV chargers might be more likely culprits.
If your neighbours are using their ASHPs like gas boilers and making them switch on and off constantly then this will cause bigger spikes
Let me clarify... these are not 'my neighbours'. The substation readings are made available to me remotely, courtesy of WPD. This arrangement enables me to provide real data for discussions such as this, and hence raise the level of public understanding. Big thumbs up to Western Power 👍
It is unfortunately the case that many (most?) installers are commissioning heat-pumps, but not optimising them, nor continuing to monitor the data over the next week/month in order to ensure that all is functioning properly. It's not that the customer is "using their ASHP like a gas boiler", but rather that systems are being regularly installed in such a way that they are repeatedly cycling.
The customer is simply not being provided with adequate documentation or instruction on their new system to enable them to operate and maintain it. Yes, this in in contravention of Building Regs Part F. I'll be flagging this up in a new topic shortly.
Those like @hydros who are on the BEIS-funded SE England trial have been communicating to each other and sharing what they learn about cycling and optimisation.
Following that, other group members used the new-found knowledge to check the cycles/hour on their own heat-pumps. They then adjusted controls to lower the cycling and increase the COP.
Not all Trial Participants could undertake the optimisation because a proportion of the trial-sites have been fitted with new ASHPs which do not provide the relevant data! 😠
Very few people are in possession of the more detailed understanding of heat-pumps which is discussed here on this forum by the likes of yourself @kev-m . They are being left fending for themselves and battling ever-increasing electricity bills.
As I was one of the trial group participants without a heat pump(!), I took note of what the others had been sharing and did some further background checks with WPD engineers and others.
In particular I trawled through recent substation data for a location in which I knew that heat pumps had been installed and properly optimised several years earlier. Here's a portion of that data which was selected due to weather conditions in that area for a couple of days. This clearly demonstrates the effect of heat-pump cycling on the substation current
The pink area I’ve highlighted is showing 2.17 cycles/hr. That compares favourably with participants on the SE England Trial who were recording 10+ cycles/hr.
Modern ASHPs are inverter heat pumps, which use a variable speed compressor
... which is a source of the losses due to harmonics which I referred to in my previous post.
Unlike phase-imbalance losses which adversely affect the local 11kV substation, harmonics are passed back up the grid to all other transformers. The accumulated losses are huge.
The graph shows the percentage of voltage imbalance at a 33kV feed from a Bulk Supply Point Transformer. The x-axis has 1000 readings taken at 10min intervals.
Perhaps it's now clearer why I'm interested in running heat-pumps from an off-grid electricity storage system.
This would be beneficial financially for any customers on a ToU tariff, and also for DNOs as they start tackling the system losses under the RIIO-ED2 Agreement.
Your comments about optimising ASHP operation are preaching to the converted on this particular forum.
My understanding is that electrical equipment, sold within Europe, is required to cause minimal Total Harmonic Distortion back into the supply.
Please clarify what is meant by 'off-grid electricity storage system', since heat pumps can use quite a considerable amount of electrical energy throughout the day, and the primary source of that energy is from the grid, either directly, or via a battery storage system, which also employs inverter technology.
Please clarify what is meant by 'off-grid electricity storage system'
It was Option-2 in my earlier set of diagrams.
But here's a somewhat more expanded form of that strategy:
The output to the heat-pump is completely independent of the mains supply to the house. As such this arrangement is likely to fall outside the requirement to obtain LCT Approval from your DNO.
There are obvious safety factors still to be considered. As there is no correlation between the grid and the output from the off-grid inverter, there could be 440v between adjacent equipment. I will be checking such details prior to starting the hardware build in about 2 month's time.
Please clarify what is meant by 'off-grid electricity storage system'
It was Option-2 in my earlier set of diagrams.
But here's a somewhat more expanded form of that strategy:
The output to the heat-pump is completely independent of the mains supply to the house. As such this arrangement is likely to fall outside the requirement to obtain LCT Approval from your DNO.
There are obvious safety factors still to be considered. As there is no correlation between the grid and the output from the off-grid inverter, there could be 440v between adjacent equipment. I will be checking such details prior to starting the hardware build in about 2 month's time.
Whilst your proposal will no doubt benefit the DNO's, I cannot envisage that many people will spend thousands of pounds installing a system that has to be serviced and maintain, will require battery storage in the order of 30kWh to 40kWh for the average home, and will take up a large amount of space.
Are the DNO's going to supply such systems free of charge?
A much better alternative to help reduce heat pump cycling, would be to have two smaller compressors within the unit, rather than one larger one. That way the heat pump would be able to modulate its output over a much larger output range without the need for cycling. I remember recently seeing some manufacturers information where I think this idea was incorporated, unfortunately I cannot remember where it was located.
@derek-m The off-grid heat-pump supply I've suggested is to enable operation on a Time-of-Use Tariff, avoiding the expensive high-demand periods.
The financial savings to the consumer would be significant... and the more so now that high gas-prices have expanded the price-per-unit range.
The larger the battery capacity the less power will need to be imported during medium-cost time-slots. That's a trade-off which the customer must decide.
A typical 11kW ASHP like the Ecodan R32 Monobloc draws 3.8kW. That's well within the supply parameters for a 13.5kW storage battery (the same size as a Tesla Powerwall).
Inverter electronics might account for £1200 or so. 13.5kWh of storage battery costs about £3000 (from China) including BMS.
The space which it would require is less than a quarter of that occupied by a water cylinder capable of delivering space-heating for 5 hours during evening peak-demand.
@derek-m The off-grid heat-pump supply I've suggested is to enable operation on a Time-of-Use Tariff, avoiding the expensive high-demand periods.
The financial savings to the consumer would be significant... and the more so now that high gas-prices have expanded the price-per-unit range.
The larger the battery capacity the less power will need to be imported during medium-cost time-slots. That's a trade-off which the customer must decide.
A typical 11kW ASHP like the Ecodan R32 Monobloc draws 3.8kW. That's well within the supply parameters for a 13.5kW storage battery (the same size as a Tesla Powerwall).
Inverter electronics might account for £1200 or so. 13.5kWh of storage battery costs about £3000 (from China) including BMS.
The space which it would require is less than a quarter of that occupied by a water cylinder capable of delivering space-heating for 5 hours during evening peak-demand.
I'm afraid that you now have me confused. I thought that your proposal was to totally disconnect the heat pump from the grid, to prevent disruption due to cycling effects, but now I see it is to move demand away from the peak period, to benefit the DNO's.
As far as the financial savings are concerned, the Octopus Agile TOU tariff is at the moment, and has been for quite some time, much higher than other tariffs throughout the whole day, so I fail to see how this could be beneficial to the consumers.
I've been evaluating a solution to reduce running costs of heat-pumps for about 10-months now, so I'm probably posting too fast about the underlying concepts.
I'm taking a longer-term view than what's available now. It's been very useful to have received input from Grid-Planners who have helped me understand:
what is technically/financially possible
what they are required to do within their licence conditions
what strategies will (and will not) achieve the targets and aspirations of Parliament/public-at-large regarding Zero-Carbon heating
I didn't want to waste time developing a solution which was either unlikely to happen, nor one which would be opposed by the DNOs.
An off-grid hybrid battery-storage solution ticks a large number of boxes... and that includes reducing grid-losses.
I appreciate the need for Octopus to withdraw Agile from being accessible to new customers at the moment.
I have closely followed the development of OVO's in-house billing/tariff system. That will also deliver ToU capability, and I have had the opportunity to speak directly about this with Stephen Fitzpatrick, Founder and CEO of OVO Group.
The UK is unlikely to meet its 2050 zero-carbon targets without the majority of domestic customers moving to ToU Tariffs. This logic is not based solely on financial concepts, but also on the fluctuations in generation output available from renewables.
There is likely to come a time when Ofgem will require all Energy Suppliers to offer at least one ToU option. This will necessarily take into account an increased %age of renewables in the mix rather than just supply & demand as Agile has done thus far.
Two other points:
a: my practical experience over the past two decades is primarily concerned with off-grid energy technology. My experiences of grid-connected solar and battery-storage over the past year have not been favourable. 😥
b: I live in an area where there is often an abundance of renewable energy to the West (beyond the capabilities of the National Grid to take it), and CMZs (Constraint Management Zones) to the East and North. Those insights have been helpful in evaluating the best way forward.
That's a synopsis of the background which leads me towards developing a strategy to decouple the direct connection between heat-pumps and the distribution grid.
Like you, I too have a goal, that I have tried to carry out in my 50+ years in power generation and many other industries, plus the 10 years or so since my solar PV system was installed, the 5 or so years since I improved my heating control system, along with my involvement on the forum for the past 11 months.
That goal has been to reduce energy consumption, which in itself often leads to cost savings. During the past 10 years I have reduced my electrical energy consumption by 50% and my gas consumption by 25%, in the main by fully utilising the energy provided by my solar PV system.
In an ideal world, where money and space is available in abundance, we would all have a roof filled with solar panels (both PV and thermal), a wind turbine at the bottom of the garden, a large battery bank capable of powering our home for at least 1 day, a GSHP and one or more EV's parked on the drive. I forgot to mention, a home insulated to at least passivhaus standard.
As no doubt you are fully aware, we don't live in an ideal world. It is therefore necessary to have realistic expectations, particularly where the larger part of the population is concerned, many of whom are concerned about global warming, but expect others to do something about it.
For me the primary objective should be to reduce energy consumption by improved insulation and draft proofing. The next objective should be to ensure that the designers and installers of heating system are adequately trained and sufficiently knowledgeable to provide systems that operate in the most efficient manner. Once those two objectives have been achieved can you then start looking at further improvements that may not be as cost effective.
At the end of the day you will only convince the majority through their bank balance.
During the past 10 years I have reduced my electrical energy consumption by 50% and my gas consumption by 25%, in the main by fully utilising the energy provided by my solar PV system.
Thanks for sharing that background. So you are not only from the energy sector, but have also hands-on experience of using solar micro-generation to reduce your energy import. 😎 The deeper I've looked into the roll-out of grid-connected solar panels over the last 20 years, the more uneasy I feel.
1: The Government's FIT incentive may have been viewed as successful from the customers' viewpoint, but it is the major reason that we now face such high technical losses due to phase-imbalance. The FIT scheme made no distinction between generation for in-home use and that for exporting for a profit.
I fear the same issue is going to blight the incentivised roll-out of single-phase LCT devices (heat pumps and EV chargers).
2: I live in SW Region which often has surplus renewable generation. To illustrate this I've just downloaded (and annotated) the Western Power Network Capacity map for the area, as of yesterday, 26jan22.
(Ignore the arrow pointing to Fraddon at the moment. I'll return to that if we need to)
The issue here is that the Distribution network is already full, for both solar and wind. There's effectively no room to add more grid-connected generation although home-owners are still being granted consent.
I find it ethically unacceptable that neighbours living in fuel poverty are unable to utilise the excess generation whilst commercial producers might be receiving compensation if they're required to remove a proportion of the plant from the grid.
There's a strong moral and financial incentive to move speedily towards a smart-grid and ToU tariffs.
It also makes it even more likely that a storage battery feeding a heat-pump would be an attractive option. The RoI would be lower for those in areas which have times of excess generation.
I fully appreciate the problems, though the primary one is that the decision makers don't fully understand the problems and don't pay sufficient attention to detail, and we all know where the 'devil' resides.
I am probably the exception to the rule, in that I not only try to limit my import from the grid, but I also try to limit my export to the grid. I only have a 4kW solar PV array, so I don't need to warn grid control that I am coming on line as the Sun rises in the east.
By installing a power diverter some 5 years or so ago, I can now divert any excess generation from the solar PV system to any one of three individual loads of up the 3kW. In that way the majority of our hot water from Spring through to Autumn is provided by our solar PV system. When the hot water is up to temperature, any further excess generation is used to provide heating to help reduce our gas consumption.
Last year I installed an A2A ASHP, that can further utilise any excess solar PV output for both heating and cooling, which again helps control any possible export to the grid.
Obviously the addition of batteries would help even more, but with our present setup would not be cost effective.
I believe that Iron - Air Batteries are being developed to provide large grid scale energy storage, which would probably be much more cost effective than each individual home having their own system.
