Raspberry Pi to measure solar kilowatts and turn on the immersion heater when there's surplus

[George Miles]

I'd like a Raspberry Pi mini computer to measure kilowatts in my house coming from the FIT solar panels, and my consumption of electricity, and how much is coming or going to the grid, and then to turn on the immersion heater when there's surplus, and turn it off when i'm paying for electric.

I've seen a few DIY raspberry Pi's relays but I dont think they look very permanent, and as there is a huge amount of electricity being switched I'd like to see professional boxed relays with heat sinks as I'm scared of fire and electrocution.

I dont want to waste me time reinventing the wheel, there must be people who are already doing this but who and where?

This one is 5 amps:

George

[Martin Brown]

You can buy intelligent solar PV switchovers to do exactly this probably more cheaply than you could make one from component parts. It has almost become the standard MO of more recent solar PV installations. Make the electricity, turn it into hot water and pocket half the output as FIT.

I am with TNP on this one - it is a crazy market distortion. Almost as bad as the Northern Ireland renewable heat incentive aka "cash for ash".

[Adrian Caspersz]

You have FIT. When the sun shines, your electric meter is "driven backwards" with surplus. Doesn't matter if it's going for the heating or the freezer.

If you had panels independent of FIT, then yep - you could probably lash something up.

[Martin Brown]

But that isn't how it works. You get paid FIT for half of what you generate irrespective of what you do with it so most people now use it to heat their hot water with an immersion heater. It is crazy.

It is a flaw in how the FIT is determined. They don't measure export of power for most domestic users just total generated and pay half of that.

[Michael Chare]

I have a Raspberry Pi running emoncms. It records my electricity usage. The data comes form an Openenergy monitor circuit board which measures voltage, current, powerfactor and aslo counts the pulses of my electricity meter.

See

[alan_m]

Why would a mechanical relay require a heatsink?

"Quote" All the safety requirements are designed-in to prevent any faults resulting in a fire "/Quote"

Protected with a fuse and MOV

[harry]

Google "Solar Switch" There are two sorts . One turns the immersion heater off when solar power gets too low.

The other modulates the power to immersion heater to match that available fro solar panels. EG

[harry]

NO It does NOT

[harry]

Total Drivel. You get paid for ALL you generate. Plus extra for half on the assumption you use half.

[Mark]

Afternoon George, i have been doing this for 11 years now and have 5 houses running on system, Which sums the power generated against the power consumption of the house. The excess is proportionally fed into the immersion tank, most days my tank is hot by 11 and stays hot all day, its a large couple of hundred litre tank, You can buy commercial systems but i am an engineer, so made my own one when commercially they weren't available. I monitor all the data and send it to any device in my house that can access the wifi. I have a digital meter so i cant turn it backwards anymore. ead some of the comments, and yes you can buy cheep units, some of which i have seen in a pile of ash, after decent storm and brown outs.

[Theo]

That's quite neat. Are you doing triac dimming of the immersion coil, or something like that? Have you thought about open sourcing the design?

By the way, you may find the Home Owners Hub interface awkward - please see:

background and other ways to access this uk.d-i-y newsgroup.

Theo

[Brian Gaff]

Awkward was not the word that sprung immediately to mind, it was basically complete crap seeing as usenet do not accept binaries and half the time they forget to adjuust their archive for the year so you get replies several years after a posting.

Brian