Solar divert by matching power to load and/or EVSE charging (also UK grid tie requirements?)

Hi, everybody I am new here :slight_smile:

I’ve skimmed some surface of this subforum and am still continuing to do so and still will and I’d be grateful even for google keywords for further reading :slight_smile:

… but here is an idea that kinda appeared / dawned on me:

I have recently acquired the OpenEVSE wallbox (and had it professionally installed, with new extra switch and paraphernalia) - although as in the part of the country where I’m at, the EVSE of the most visible charging point operator is (free when available) but I got the wallbox anyway as this will not be the case forever. Anyway that’s not the point of this post so pls read on.

I am eyeing on adding a Solar PV installation to my home kinda… gradually, possibly in £1000-£2000 portions at a time.

My roof(s) I plan on adding that on, are East-West (I am on a northern half of a semi-detached building so no access to a south facing anything…)

I have a 0.9/1 storey-ish high ‘garage’ (or more like, metal shed) to which I could add the PV panels myself, without asking for assistance of any roofers (the main house is 2 storey, with concrete roofing ‘shingles’) with really awkward access from the ground, requiring awkwardly positioned ladders or a cherrypicker to do anything there. So I’d rather delay adding any substantial work to the main house until the ‘pilot plant’ on the garage ‘proves’ itself…

( just to provide the sunshine context, in december last year I only had 34 hours of sunshine in this COUNTRY… but that can rise to 74h around March and 250+ in April/May - generally stays above 70h per month Apr-Aug - per, but yeah I am at ~54-55 deg lat north; also it starts to get enough sunshine to see things ~4AM in May-June, and stays lit until ~10pm, vs 8AM to 4PM in December… ).

Apart from the EVSE unit i also have only pretty small (standard, I believe, 200-250l maybe?) UK Standard hot water tank available (original heating installation in the house is OFCH, and for now, I need to keep it…) with just one electric heater ‘booster’ up top. Not much chance changing that for something else too soon either.

Having these in mind here is what I am thinking about:

  • initial installation : 2 to 4 200-400W panels, (1-2 per side of roof) with grid-tied microinverters, on the garage/shed

  • there are e.g. Y&H solar microinverters (available e.g. on Amzn or Eb*y) that don’t seem to be interfacing with any sort of monitoring system, wired or wireless - but this is actually a good thing for this idea, please read on -(apart from, the price being substantially less than £100 per unit) so I’d match these to some cheap/available PV panels;

  • use emontx to monitor grid supply and pv (for a type 2 install) at the main ‘consumer unit’ fuse box (the below emonpi or base hub station being actually in the garage)

  • use the MQTT relay per panel WiFi MQTT Relay / Thermostat - Shop | OpenEnergyMonitor (it’s kinda expensive, so on second thought, maybe rather slap-add a 4-8 relay board to emonpi?) to control the inverters on or off - using emonPi Energy Monitor - Solar PV Bundle - Shop | OpenEnergyMonitor (sorry could not link the second link with being a beginner…) as the starting point

  • with emonpi/emoncms programming on the pv-bundle, interact to the OpenEVSE and the hot water heater such that, if the car isn’t connected, or its battery is full, and the tank heater isn’t taking power when it’s thermostat trips at e.g. 65-70 deg (i tend to like to keep my hot water hot), I do not export anything out to the grid. I won’t be going off-grid with this system

  • and if i can’t sink the pv energy in the house altogether, use the relays of whatever kind i end up using, to when not needed…

Hopefully the above makes sense :slight_smile:

Kind Regards from first-time-poster


Welcome, LS, to the OEM forum.

You should be able to now - I’ve pushed your privileges up a notch.

So you’re somewhere between Lancaster and Edinburgh, in terms of latitude - I can understand your daylight hours being “restricted” in the winter.

I take it you’ve got a reasonable Wi-Fi signal in there? If the metal shields it, you’ll most likely need to run an Ethernet cable from your router, or use powerline adapters, in order to be able to communicate with the emonPi and see what’s going on.

What’s puzzling me is, why do you want to switch the inverters on and off? If you’re not able to use all the energy generated, they’ll export to the grid - though you’ll only get paid peanuts of course.

If you go for Robin Emley’s Mk2 PV Router, that will look after itself and mop up any remaining PV (while the tank can take it, of course), and then any excess will be exported.

Thank you very much :slight_smile:

Surprisingly so, the shed is only 5-6m away from the the place in the house where the internet router sits, at the end of the driveway. Full WiFi bars all the time.

I was hoping to kinda dip my toes first and be prepared for the bigger roof system later, without my provider even knowing (as they might want to install a different meter - which might actually be worth it later when I change to off peak when I start using the EVSE ), and with such microscopic system at start it probably would be worth even less…

(Of course… I am aware of importance of safety code and such so I will be at least consulting a qualified electrician for the parts tying it to the grid in the house :slight_smile: )

And grid tied it will need to be anyway, because the EVSE and the water heater is.

So that is my rationale for the panel switch system. Not to omit, the PV bundle will anyway be acting as the ‘gateway’ then, recording the generation and performance of the panels.

Thanks for your reply
Hopefully it makes sense what I am thinking about :slight_smile: