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.
The window over the kitchen sink faces due east and the top of the 199 m-high chimney at Ratcliffe-on-Soar power station is just visible over a hill, nearly 7 miles away. It makes for an interesting contrast to the wind turbines visible from windows facing north.
Ratcliffe-on-Soar Power Station Chimney from Kitchen Window
I quite like being able to see the power station and it only takes a glance to check whether it’s running or not. Over the summer it was rare to see it operating at all. Now autumn is here I’ve noticed it seems to be running most of the time – though not at full capacity, judging from the modest amount of steam from the cooling towers. Today’s news reports help to explain why: Polluting UK coal plants export power to France as cold weather bites. Personally I’d prefer a less sensationalist headline since the French Interconnector has a maximum capacity of 2 GW compared to a total UK consumption figure typically in the 30 – 50 GW range. The underlying data shows this interconnector has indeed been exporting at full capacity to France recently whereas normally it’s importing nuclear-generated French electricity to the UK.
Ratcliffe-on-Soar has quite a lot of pollution mitigation measures installed and hence isn’t too bad for SOx and NOx emissions, but coal is still fundamentally a high-carbon fuel – significantly worse than gas. Why is this important? Because Marsh Flatts Farm is all-electric for cooking and heating – and the addition of an electric car will further increase the reliance on electricity. It’s all very well having zero carbon emissions at the point of use but if those translate to high carbon emissions at the power station that’s clearly no good overall.
When specifying the heating system I initially had some misgivings about “wasting” electricity by using it for heating. Initially it seemed better to preserve electricity for things which absolutely demand it and to provide heat by burning wood or gas. In particular, why burn gas at a power station and suffer the unavoidable losses from turning that into electricity and transmitting it over a long distance when you can just burn gas directly? Well: a) there’s no mains gas available at Marsh Flatts Farm, and b) with a good heat pump it’s easy to get much lower carbon emissions than with a gas boiler – especially now that the carbon intensity of the UK electricity grid has reduced so much.
A good (91% efficient) gas boiler produces 240 g of CO2 per kWh (ref. this CIBSE Journal article) but that’s not far off the typical overnight figure for UK Grid Carbon Intensity (ref. the Carbon Intensity API website). A good Ground Source Heat Pump will deliver more than 4 times as much heat as it consumes in electricity, which equates to roughly 60 g of CO2 per kWh. (I used the overnight figure for the grid since a GSHP will typically do most of its heating overnight – when it’s colder outside – than in the daytime.)
As evidence of “..more than 4 times as much heat as it consumes in electricity”, in the past 24 hours my NIBE F1145 Ground Source Heat Pump consumed 8.53 kWh of electricity and generated 36 kWh of heating water at a nominal 30 degrees C. That’s a coefficient of performance of 4.22.