Evidencing self consumption post FIT

[ToughButterCup]

The end in mind  here is simple.

I want to make sure that I consume as much of my 'own' solar PV production as I can.  How can I do that when the meters fitted don't tell me?

 

The context

3.86 kW peak fitted to a Solis inverter. No FIT. Solis ( Ginlong) supply an app which purports to describe your production. It does so, but in a way that a first year undergraduate coding student could do better.  It is impossible to work out whether I am consuming the PV we produce.

 

These two threads ( Smart Meters ) and ( Self consumption, Making sense of meter readings ) lay the framework for this one.  @ProDave has sorted a similar problem out by fitting his own meter ( but he's an electrical genius)  and @SteamyTea said that  I'll have to get one of those power management sytems.

 

He also hooked my interest by saying that it should be Possible  to do the job with a little ingenuity: 

Quote

I think a normal digital meter has the LED light up permanently if exporting.

Link that in with the generation meter flashing, via a Raspberry Pi or two, job done.

https://forum.buildhub.org.uk/topic/17923-smart-meters/

 

There is a wider context: the issue has been researched for a little while now, so for those who are interested, I attach a pdf  - it's useful because it reviews the current (2015) situation in relation to this issue.

Luthander et al (2015) Photovoltaic self-consumption in buildings: A review in Applied Energy 142

 

So @SteamyTea, hit me with a reading list, or better put, start me off on yet another steep learning curve, please! Thanks.

 

1-s2.0-S0306261914012859-main.pdf

Edited December 7, 2020 by ToughButterCup

[Ferdinand]

Is there a PV-associated wire where a clamp meter can be fitted to measure this, say from the Inverter to the fusebox?

 

I am not familiar with the exact wiring of these, and I expect not - at least without something more sophisticated.

[jamieled]

I couldn't quite figure out from your post if this is more about having the systems in place to ensure you self-use generation, or just a way of monitoring that you are?

 

I have a similar setup for my PV, slightly different brand names but that's not important.

 

Our heating and DHW is all-electric. I have a pv diverter (eddi) with a CT clamp on the supply cable and a CT clamp on the generation cable. It then tells me at a glance what I'm generating, using and exporting and I can scroll through recent days, weeks/year to look at historical figures. Apparently I can also hook it up to a hub/app to get the info on a phone or a computer but it's not a priority at the moment.

 

 

[ToughButterCup]

The inverter is connected to the meter as shown here 

(apologies for the images - I can't undo the distortion)

 

 

Edited December 7, 2020 by ToughButterCup

[ProDave]

I assume you have some form of solar PV diverter to automatically send surplus PV generation to your immersion heater?  That is pretty much a "must have" to ensure maximum self usage.  Roughly 1/3 of what we generate ends up in the immersion heater and would be "wasted" otherwise.

 

Next thing is run the big appliances in the daytime close to mid day, one appliance at a time, here I am talking Washing machine, tumble dryer and dishwasher.

 

I have the timings on my ASHP to only start DHW heating late morning on the basis that is more likely to self use solar PV generation rather than start the DHW heating very early.

 

As to how to measure it.  In theory a smart meter can do that, but they don't seem to present that information to the user.

 

What I did was install my own export meter.  This us just another electricity meter just like the generation meter you have, but you wire it after the suppliers electricity meter and wire it "backwards"  Here is mine:

 

 

This will show what has been exported.  In an ideal world it would stay at 0 meaning you have self used everything.  Mine is currently up to about 240kWh over 2 years.  Most of that is on a really sunny day when nothing is on to self use and the PV generates more than the immersion heater can consume (3.68kW generation, 2.8kW immersion)

 

If I was eligible for the new export payment, at about 5p per kWh I would have earned about £12 in 2 years.  You can see why I think it would have been a waste to pay for an MCS install just so I could qualify for that tiny payment.

 

I take weekly meter readings of total import, total export, PV generation, and I also have metering that measures ASHP consumption for heating and DHW separately.  They all get plugged into a spreadsheet so I can see heating, DHW and "other stuff" usage for the week.

 

If you want a similar export meter setup, just buy another generation meter, usually available cheap on ebay, and any competent electrician should be able to fit it.  Probably worth labelling it as I have done to avoid any confusion.

[Bramco]

1 hour ago, ToughButterCup said:

The end in mind  here is simple.

I want to make sure that I consume as much of my 'own' solar PV production as I can.  How can I do that when the meters fitted don't tell me?

 

You need to install a system that will tell you. Take a look at the open energy monitor site  -> https://openenergymonitor.org/

 

They sell a simple system based on a Rasberry pi which will monitor your overall usage and your PV generation - there are tools included to allow you to create your own dashboard. There's also instructions on how to build a PV diverter to divert any excess into an immersion heater. These will only divert when there is excess PV over and above your consumption, so automatically will stop diverting if say you turn on the dishwasher and you aren't generating enough to run it (there are commercial units that do this as well).

 

There are also some apps for android and apple so that you can see what's happening and on the community there's lots of additional info and ideas - for example with a fairly simple bit of code you could light an LED when you are generating enough to run a big appliance - of course you could just look out of the window  ?.  

 

Also follow the advice about running big appliances round midday and only one at a time - you'll get the best self consumption that way.

 

Simon

[SteamyTea]

I shall get back to this, got some sunshine so outside at the moment.

[ToughButterCup]

1 hour ago, ProDave said:

I assume you have some form of solar PV diverter to automatically send surplus PV generation to your immersion heater?  This will show what has been exported. 

...

If you want a similar export meter setup, just buy another generation meter, usually available cheap on ebay, and any competent electrician should be able to fit it.  Probably worth labelling it as I have done to avoid any confusion.

 

Assuming anything on our build is dangerous.... No, I think is the answer, but I will check with the electrician who fitted the system.

I'll get my spark to price the export meter for me : a guess at the price Dave?

 

Thank you @Bramco (Simon). Just what I was looking for - some quiet fireside reading ( Oh hold on,  hmmmm, no fire anymore)

 

PS, the sparky has just texted me to say that there isn't one fitted - yet.

Edited December 7, 2020 by ToughButterCup

[ToughButterCup]

5 minutes ago, SteamyTea said:

I shall get back to this, got some sunshine so outside at the moment.

 

Thank very much . Get your Vitamin D while you can.

[ProDave]

7 minutes ago, ToughButterCup said:

Thank you @Bramco (Simon). Just what I was looking for - some quiet fireside reading ( Oh hold on,  hmmmm, no fire anymore)

 

PS, the sparky has just texted me to say that there isn't one fitted - yet.

Cheapest I can see on ebay at the moment is £20 https://www.ebay.co.uk/itm/Brand-New-Approved-230V-Single-Phase-Electric-Solar-PV-Generation-Meter-100A/324383422000?hash=item4b86c23630:g:J6QAAOSwFn1fuQjX

[ToughButterCup]

Ordered. 

Thanks Dave

[SteamyTea]

Right, I have spent 30 seconds doing what anyone can do.

Got this:

https://medium.com/@simon.aubury/home-power-monitoring-65d0fded7769

 

I am sure with a bit of extra coding, it can sense when the main meter LED is permanently on i.e. exporting.

Then it can either start logging the generation meter pulses, or again, with some extra coding split the data up into times when it is purely imports, purely exports and a mixture of the two.

All nicely timestamped and in an easy to read format.

It would also be easy enough to put an indicator on it as well, or a switch or 10.

[ProDave]

1 hour ago, SteamyTea said:

Right, I have spent 30 seconds doing what anyone can do.

Got this:

https://medium.com/@simon.aubury/home-power-monitoring-65d0fded7769

 

I am sure with a bit of extra coding, it can sense when the main meter LED is permanently on i.e. exporting.

Then it can either start logging the generation meter pulses, or again, with some extra coding split the data up into times when it is purely imports, purely exports and a mixture of the two.

All nicely timestamped and in an easy to read format.

It would also be easy enough to put an indicator on it as well, or a switch or 10.

All very interesting BUT it does not tell you exported power as well as imported.

 

You could have one such monitor on your import meter and one on your export meter and make that calculation ONLY if you check the meters operation first.  Not all meters behave the same.  My present import meter goes to solid red when we are exporting.  BUT my export meter, and the import meter in our previous house both the red lights still flash when power is going the wrong way, but the displays do not count up.  They would be useless for determining direction of power flow.

 

Arguably the best way to make your own bidirectional power meter would be using an electricity meter chip and some DIY hardware, such designs have been published for DIY solar PV dump controllers.

[ToughButterCup]

32 minutes ago, ProDave said:

All very interesting BUT ...

 

Arguably the best way to make your own bidirectional power meter would be using an electricity meter chip and some DIY hardware, such designs have been published for DIY solar PV dump controllers.

 

Ahh, the useful BUT......

 

Anyway, while I'm waiting for the meter to arrive, and the sparky to turn up,  I'm deep into @Bramco's suggestion (Thanks @Bramco).

 

 

The idea of doing a bit of coding is extremely appealing: should be fun.

This diagram stolen fair and square from openenergy.org.uk strikes me as a good first step towards my goal : (identifying what consumes [how electricity] power and when)

 

openenergymonitor even have a discussion board..... addicted to those....

 

[dpmiller]

If you've got a diverter, do you really need to think about this even?

[ToughButterCup]

Maybe,  and maybe not.

It's the fizz that not understanding something gives me. I hanker after doing a bit of coding,  and saving a bit of money as a byproduct. 

 

I hope I have this right; even after fitting a diverter,  it will still be very interesting to quantify significant sources of demand. Ok,  it may not be all that worthwhile financially,  but it's the finding out and the journey to getting an answer that's got me hooked. 

[Bramco]

11 hours ago, ToughButterCup said:

Maybe,  and maybe not.

It's the fizz that not understanding something gives me. I hanker after doing a bit of coding,  and saving a bit of money as a byproduct. 

 

I hope I have this right; even after fitting a diverter,  it will still be very interesting to quantify significant sources of demand. Ok,  it may not be all that worthwhile financially,  but it's the finding out and the journey to getting an answer that's got me hooked. 

 

I've had a lot of pleasure from installing an energy monitor. Another great aspect of these designs is that you can monitor temperatures as well as the electricity flow, so we have our thermal store all wired up. For the new house we're planning to do a DIY thermostat monitoring the temperature of the slab as well as the room temperatures.

 

The guys that developed things are also doing a lot of great work on the open ESVE, so software to manage when to charge your EV using data on the Octopus Agile and Go tariffs.

 

PM me if you are interested in what we have done in the current house.

 

Simon

[ToughButterCup]

30 minutes ago, Bramco said:

...

PM me if you are interested in what we have done in the current house. ...

 

I will. - around lunchtime.

31 minutes ago, Bramco said:

...

For the new house we're planning to do a DIY thermostat monitoring the temperature of the slab as well as the room temperatures.

...

 

I'm using five BlueTooth SensorPush temperature sensors - very easy to use, if a bit expensive. But I now have a data set that I can look at to help us optimise our heating control. 

[SteamyTea]

4 minutes ago, ToughButterCup said:

I'm using five BlueTooth SensorPush temperature sensors

Yes they are.

30 quid each for some DHT11s

[ToughButterCup]

1 hour ago, SteamyTea said:

Yes they are.

...

 

Meaningful, accurate data is priceless. As you know. ?

[SteamyTea]

https://www.ebay.co.uk/i/122891877227

 

https://www.ebay.co.uk/i/383778504246

 

Job done

 

But if you want pressure as well

 

https://www.ebay.co.uk/itm/Blue-Digital-Barometric-Pressure-Sensor-Board-Swap-I2C-SPI-BMP280-BME280-3-3V/222496414823

[Bramco]

4 hours ago, SteamyTea said:

Job done

That's a route I've been down as well. Feeding the data to an emoncms system running on a pi. These though wouldn't be battery powered and you'd need some software. 

 

Another option are the sonof devices (we have some of the switches and a temperature switch in the shed to turn on the heating when it gets too cold).  Sonof devices can also relatively easily be reprogrammed with the Tasmota IOT software which is much more versatile and doesn't use a Chinese cloud server.

 

If you need a battery powered device instead of the esp 01, there's a UK company thingsonedge.com with a new device called iotcricket. Not tried one yet but Pete Scargill has -> https://tech.scargill.net/the-iotcricket-from-thingsonedge-com/

 

 

[SteamyTea]

An ESP has a built in power saving function i believe.

I really need to set up a network at home ans have a play with them again. They have been gathering dust for 2 years.

[Bramco]

1 hour ago, SteamyTea said:

An ESP has a built in power saving function i believe.

 

They do and I think the IOTCricket is based on either the original or the ESP32.   But of course you need the software to handle the sleep, awaken and manage the wifi to send the data.  The IOTCricket seems to have solved this, although it's worth reading Pete Scargill's blog.

 

For us the ESPs were in a place where power wasn't an issue, so they ran continuously without using the sleep functionality - it's a lot easier if you can do this.

 

1 hour ago, SteamyTea said:

They have been gathering dust for 2 years

 

Tsk tsk - and you've had many months of Covid idling when you could have .......    ?

 

Simon

[SteamyTea]

2 hours ago, Bramco said:

Tsk tsk - and you've had many months of Covid idling when you could have

I went to work for most of it, I keep suggesting that I get furloughed, but seems I am needed, no matter how useless I pretend to be.