Electric Nation Electric Car Charger Installed

As reported previously, my application to join the Electric Nation research trial was accepted a few weeks ago. The eVolt EVSE unit was installed today.

A few of the reports from the Electric Nation project are being published on the Western Power Distribution website, for example this one about Algorithm Development and Testing.

eVolt EVSE unit installed outside

The outdoor eVolt unit has a high capacity 230V mains connection and a wired Ethernet network connection. The two cables run alongside each other which can cause electrical interference but the installer assured me the outdoor-grade Ethernet cable would cope with this – I presume it includes a foil shield.

In addition to the EVSE unit itself (outside) three smaller units were installed inside:

  • A small distribution board containing a 63A 30mA RCD, a 40A MCB for the eVolt unit and a 6A MCB for the power supply to the comms units (top-centre in the photo below, labelled DB/1B)
    • While the EVSE is rated for up to 32A, I’ve heard elsewhere that no MCB likes running at its full rated capacity for long periods so it’s correct for the MCB to be rated a bit higher
  • A CrowdCharge device which provides some of the remote control functionality for the trial (bottom-right in the photo below)
    • I haven’t studied this in detail but the box contains two boards, one of which seems to be a multi-port Router (it has a MikroTik MAC address) and the other is presumably some sort of single-board-computer
    • Each board takes a 5V USB power supply, hence the two USB leads
  • A hard-wired twin-socket USB power supply (with its own fused spur) for the CrowdCharge device (bottom-left in the photo below)

Electrical supply and communications units inside

I already had a spare Ethernet network socket near the distribution boards to provide a hard-wired connection for the CrowdCharge device; if that was not available they would have installed a WiFi Bridge unit as well.

I’m well aware that the electrical installation at Marsh Flatts Farm is somewhat more complex than you’d find in a standard house so I was very careful to explain exactly what it consists of in the self-survey response. Despite my best efforts the engineers at the installation company had missed the fact there are 4 distribution boards (consumer units) in total and the installer was concerned about not having 32A of headroom from the 80A supply so the EVSE has initially been capped at 16A.

The installation company is going to send me an OWL monitor so they can check how much of the 80A I’m normally using. My own monitoring shows there’s never less than 40A spare so that should be a formality. Once they’re happy, the EVSE will be remotely re-configured to supply up to 32A as originally intended.

Real-World Heat Pump Efficiency Data

Since I’m the kind of person who likes to measure things “because I can”, it seemed sensible to include Heat Meters on the outputs from the NIBE F1145 Ground Source Heat Pump and also to include an Electrical Sub-Meter on the input. Doing this makes it possible to compare the output power with the input power and calculate the real-world Coefficient of Performance (CoP) of the Heat Pump – a bit like recording all the fuel you put in your car so you can calculate its actual MPG.

The Heat Meters are Kamstrup Multical 302 units with wired M-Bus interfaces which are automatically read every 2 minutes as described in this Technical Article page. Data is published via MQTT and loaded into an InfluxDB database where it can easily be plotted using Grafana.

Two separate Heat Meters are required because there are two separate output pipes from the GSHP – one for the Central Heating and one for the Hot Water. (Within the GSHP unit there’s only a single heat source but there’s a diverter valve that sends water to the appropriate output pipe; the return pipe connection is shared.) While the downside is the cost of the extra heat meter, it does make it easy to see when the heat pump is in ‘heating’ mode versus ‘hot water’ mode – which is important.

The results are quite interesting and reinforce the basic physics of the heat pump operating principles. In summary, the data for my NIBE F1145 shows:

  • In ‘heating’ mode, the unit is delivering an instantaneous CoP of as much as 5
  • In ‘hot water’ mode, the unit is delivering an instantaneous CoP of as little as 3

Read on for further detail on how these numbers were derived.

Note that at this time of year the ground is still relatively warm and the ‘brine’ coming in from the ground loop is around 10 degrees, returning at around 5 degrees.

Heating

In ‘heating’ mode, the heat pump is configured to deliver water just hot enough to compensate for the heat loss from the house at a given outside temperature. For example, at 4 degrees outside it calculates it wants water at 31 degrees but since the F1145 does not have such a low setting it actually generates water at about 37 degrees. (However it measures how much it is over-delivering by keeping track of the ‘degree minutes’ of the water it produces and won’t turn on again until the average delivery matches its calculated target.) Producing water at 37 degrees, the heat meter records a power output of almost exactly 10 kW while consuming almost exactly 2 kW, giving a CoP of almost exactly 5.

Note that this is an ‘instantaneous’ figure and doesn’t take account of the ongoing low consumption of the GSHP when the compressor isn’t running (consistently showing as 60 W even with the circulation pump running at 30%). Note too that as the weather gets colder outside the water temperature required will increase and the CoP will tend to reduce.

Hot Water

In ‘hot water’ mode, the heat pump is configured to bring the stored hot water up to 50 degrees (except when running the special anti-legionella sterilization cycle where it goes to 60 degrees instead). To do this, it produces water at up to 55 degrees and when doing so the heat meter records a power output of 8.8 kW while consuming up to 2.85 kW – i.e. with a CoP of 3.09.

The ‘up to’ is because the heat pump ramps up its output temperature as the hot water tank heats up, so when the tank is only at 40 degrees the heat pump only bothers delivering water at 45 degrees where it has a much better CoP of around 4.5.

Summary

Overall, the conclusion is that the NIBE F1145 is performing in accordance with its (excellent) published performance figures and has been installed and commissioned well (kudos to Carbon Legacy for that). It’s significantly beating mains gas on both cost and CO2 emissions grounds.