Energy Smart in action

Here we have the system in action earlier today.  With 1542 Watts coming from the solar panels, the house (including the PowerVault storage battery) is running at a maximum of 1097 Watts, with the balance of the available power controlled by the ImmerSUN- 410 Watts to water heating and at the point of this snapshot 35 Watts into the grid.  At this moment that’s 97% of generation used as such self-consumption and 100% of energy being consumed coming from the solar panels.

if the ImmerSUN had priority then it would have taken all the available power leaving nothing for the PowerVault storage battery.

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Zappi?

It’s now over a year since I built my solar-powered car charger which is enabled automatically by surplus electricity output from my solar panels, but can also be run on a timer when required to use cheap night-time power too.

However since then a new product has come to market from myenergi (a new company led by some of the team responsible for developing the ImmerSUN) which provides the same sorts of capabilities although in a professionally-produced solution. I don’t own one, I’ve never used one, but I think that this is a solution which I’d be seriously considering if I hadn’t already made something similar.

The only downside that I can see is that it’s available in either Type 1 or Type 2 forms with tethered leads only, so if you have a mixture of EVs then a single Zappi may not be compatible with all your vehicles; whereas a charger with a Type 2 socket outlet would be.

You can learn more about Zappi here

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An attack of the clamps

In a prior post I described the use of current clamps to prioritise smart loads that are enabled by surplus solar power to maximise self-use of this ‘free’ electricity.  That’s free in the sense that a deemed export tariff doesn’t pay any more for an extra kWh exported, or pay any less for an extra kWh used, and so the marginal cost of using that (and every other) kWh is zero.  In that post three current clamps were visible in the picture – though I described only the function of the right-most.

In fact my home currently has 6 current clamps which is probably more current measurement than the substation that supplies my area.  The six clamps are as follows:

 ImmerSUN PowerVaultData Logger
Solar panel outputReport (1)-Report (4)
Immersion heaterControlMeasure sum (3)-
Import / ExportMeasure (2)Report (5)
Battery In / Out-ControlReport (6)

I’ve tried to distinguish between their functions as follows:

  1. Control – is an output current actively controlled by a device so there’s generally no need to measure it with a clamp.
  2. Measure – a clamp whose output is analysed automatically to create a control action such as divert more or less power to some device.
  3. Report – it’s just reporting something for the purposes of understanding, but it’s not used to directly control anything.

So the 6 clamps are:

  1. The optional ImmerSUN monitoring package adds a clamp to measure the output of the solar panels which then enables the charts and self-use calculations that I’ve used before to illustrate system behaviour.
  2. The ImmerSUN fundamentally operates by measuring export via this clamp and then responding to minimise that export.
  3. The operation of the PowerVault uses this clamp.  In most installations that’s simply around the live of the incoming supply, but for me it’s also around the live feed to the immersion heater to set priorities.
  4. I also have 3 data loggers at my home to provide a year’s data for UKPN around self-usage so that they can assess the impact on the grid from large scale battery adoption.  Each logger measures one of the fundamentals for battery behaviour: output from the solar panels, ..
  5. .. import to / export from my home, ..
  6. .. and current to / from the PowerVault.  From those three you can infer what is being used by my home in its entirety, but not how power is divided between (for example) car charging and water heating.

 

 

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Prioritising smart loads for self-consumption

This week I was discussing how to maximise the benefit of self-consumption with an installer.  The issue here is, where one has multiple independent systems (such as a battery and a water heater) each looking to use any surplus self-generated electricity, how does one set the priorities of the devices or is it just a lottery which gets the surplus power first?  In my own case, for example, I recognise that the surplus invested in my battery storage  is better value than investing that surplus in hot water as electricity is considerably more expensive than gas.

I have previously written on this subject Prioritising the battery, but the installer was unaware of my solution and recommended an alternative which I consider flawed. The solution recommended by the installer is to enter the maximum charging power of the battery as the export threshold in the ImmerSUN controller. This does indeed create headroom for the battery to charge, but I believe does not use the ImmerSUN to best advantage. Let me use a table to contrast what might happen at 3kW generation with both the installer’s and my own solutions:

 Installer's solutionMy solution
Total load / total generation3.0 kW3.0 kW
Baseload of house0.2 kW0.2 kW
ImmerSUN Export threshold0.8 kW-
Battery charging0.8 kW0.8 kW
Balance for water heating1.2 kW2.0 kW

The installer’s solution will potentially always waste an amount of power equal to the maximum battery charge power / ImmerSUN export threshold. My solution doesn’t do this, although there is an aspect of immersion heater operation that may or may not concern you.

In my scheme I modify use of the current clamp for the priority device – the battery for me. Such current clamps have the property of summing the current in all the cables which they surround and, as you’ll see from the pictures, my control clamp for the battery surrounds both the incoming power cable from the grid and the outgoing cable to the immersion heater.

The effect of this arrangement leaves the ImmerSUN acting normally – it sees any export and diverts it to hot water.

The current clamp for battery however sees the sum of the export current and the current diverted to the immersion heater, so it doesn’t matter how much the ImmerSUN diverts (and thus reduces the export) – the battery ‘sees’ what would have been exported without the ImmerSUN and responds according.

The ImmerSUN clamp then ‘sees’  the export current drop as the battery charge current increases and  thus reduces its own current proportionately.

To gain access to both the incoming live mains supply cable and the outgoing live feed to the immersion heater, my current clamp is located within the consumer unit.  It’s the blue clamp on the right around the larger incoming cable and the smaller brown cable for the immersion heater.  You need to be a competent person to work inside a consumer unit.  (There are two further blue clamps to the left but their function isn’t relevant to this post.)

The aspect of this that may concern you (but doesn’t bother me) occurs if you want to run the immersion heater from stored electricity rather than just using surplus from the solar panels immediately.  If you turn on the immersion heater using the Immersun (known as ‘boosting’ in ImmerSUN vocabulary) then the current from the consumer unit to the immersion heater is equal and opposite to the current from the grid to the consumer unit, which is summed by the battery’s current clamp to zero and thus the battery neither ‘sees’ that current nor discharges to meet that load.  To me this isn’t an issue as I consider transferring energy stored in one device (a battery) to another storage device (a hot water cylinder) is poor practice; and in any case the battery doesn’t have enough power capability (maximum 1.2 kW) to run the immersion heater at full load (3 kW) so you’d always be importing at least 1.8 kW to run the immersion heater.

As a final note – it is critical to orientate the two cables in the battery’s current clamp correctly for the system to work as intended.  Current from the consumer unit to the grid, and from the consumer unit to the immersion heater, must flow in the same direction through the battery’s clamp.

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Smart appliances

I was at a meeting earlier today which prompted some discussion on smart domestic appliances.  Having recently replaced our washing machine I though I’d reflect on progress in smartness.

Around 25 years ago I purchased my first washing machine.  Smart capability was optional – it came in the form of an electro-mechanical timer which allowed the operation of the washing machine to be shifted into the Economy 7 hours with absolute confidence.

Recently I replaced said washing machine.  The new washing machine (my second) isn’t compatible with external timers, instead it offers a pushbutton which delays the start time by one hour every time that it is pressed.  However that doesn’t give absolute confidence of the cheapest energy costs because these days it’s a lottery between will the day be sunny (and thus free solar electricity) or will Economy 7 be cheaper?

Where are the smart controls?  Where are the washing machines that link to smart meters to automatically operate on the cheapest energy?   It will potentially be another 25 years before my washing machine is smart – if I live long enough to buy my third.

(And in case you’re thinking that you can use some sort of smart socket to control the washing machine, turning on the power externally will just get you to the point that you can configure the washing machine program and options, not start a washing cycle.)

 

 

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Fundamental rules for smart boiler control

Each rule in the smart home can consist of triggers, conditions and scenes. Triggers consist of one of more alternative events any of which cause the rule to be evaluated. The optional Conditions consist of one or more statements all of which must be true for the rule to be satisfied. Scenes consists of one or more scenes that are set when the rule is satisfied.

For my heating control I have two scenes that set the boiler on or off, and triggers and conditions reflecting the status of the radiators.

TriggersConditionsScenes
Any valve goes to closed .... and all valves are closed .... then cancel boiler.
Any valve moves off closed ..{none}.. then enable boiler.

As an alternative I considered rules using temperature, but that would make things more complicated if the temperature set point is adjusted as you might need to change the rules; whereas by having rules based only on (fully) closed and (partially) open then the set point can be adjusted without issue.  Additionally you can control around a very low vacation set point for frost protection.  Effectively there are four set points:

  1. Closed – which is forced by a summer setting, but also occurs at other times when no heat is demanded.
  2. Vacation temperature – 5 C for me – a low set point for frost protection, but from which it might take an extended period to warm up.
  3. Economy temperature – 10 C for me – a lower temperature limit during normal scheduled operation.
  4. Comfort temperature – 24 C for me – a minimum temperature avoiding complaints from my wife!

My system retains the original 7 day timer, which these days I use only to control water heating.  If I did enable the 7 day timer as well as the smart controls then the boiler would be enabled when either the 7 day timer or the smart controls demanded it.

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Advantages of smart heating

I thought that I’d describe some of the features of the smart heating controls versus the prior single zone system with TRVs and a 7 day timer. My main interest is of course to save gas by heating the home more selectively, but there are other opportunities that you may consider significant.

I don’t yet have sufficient data to illustrate any operational savings, but continue to record gas consumption to compare with prior years.

 

 Prior system with 7 day timer and TRVsCurrent smart system with some eTRVs
ZonesSingleMultiple
Schedule7 day - working week plus weekendsInfinitely flexible home / working schedule based on iPad calendar
Adjustment of timers and thermostatsManualvia App (with voice control!)
Remote adjustmentNoYes - enabled by Apple TV as hub
Holiday settingNo Yes - sets low level heat for frost protection
Summer settingNo Yes - closes all valves
Integration with non-heating smart devicesNoYes
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Generations of my solar charger

I just came across some of the pictures from last year of different iterations as I was developing my solar powered car charger.


The left picture shows my first attempt using a Mode 2 charger (i.e. one that plugs into a standard socket outlet). The design attempted to turn the car on and off by the equivalent of pushing the latch button on the vehicle connector. That approach stopped charging effectively, but starting charging was subject to long delays so that wasn’t a practical solution.

The middle picture show the second attempt using a commercial Mode 3 charger (i.e. one that’s hardwired into the fixed wiring). In this iteration the commercial charger was gutted so that, although it retained the original external appearance, inside was all different content including a protocol controller and a radio receiver. This was an effective on/off solution.

The right picture shows the third iteration which addd a programmable logic controller to generate a variable charge rate for the electric car i.e. more than just simple on/off. The hardware to achieve this is too bulky for the case of the commercial charger, and so it was repackaged in consumer unit case. A consumer unit case is cost-effective solution for a bigger box to house the DIN rail mounting components, but is of course only suitable for indoor use as it’s not waterproof to the required standard for outdoor use.

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Oops no heat

No heat this morning (not that its absence is a major issues as the weather is fairly mild). Initial analysis via the Apple Home App is that some of the radiator valves can’t be reached, and thus I assume that the rules that enable the gas boiler can’t be satisfied.

As a short term fix I could have turned on the boiler manually via the app or using the central timer which is normally set to off for space heating (but not hot water) when using the smart controls, but I didn’t need to do that as I quickly found the root cause.

I initially thought that there was some corruption in the configuration of individual valves, so I was planning to delete them from the App and then re-pair them, but then I spotted that as I moved around the house I was losing different valves, so I turned my attention to the hub i.e. the Apple TV box.

Turning on the box it appears that it downloaded a software update overnight. As soon as I acknowledged a screen describing the changes then all the valves became reachable, the control rules were satisfied, and the gas boiler was enabled.

It would be more robust if you could specify a default value in a rule to be used if the actual value was unavailable from the device.  The actual value being unavailable would also happen with a flat device battery for example.

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