Excess Solar - Divert to appliance

Im DIY installing 1.5kw solar at my home and at the moment battery storage is out of the question for me due to cost and availability. During the summer months i will be producing excess solar that i will not be paid for if exported so i am trying to see how i can use that. I have an immersion heater so devices like solar iBoost could be useful and id already looked at the emonPi project.

It got me thinking as to what other options i have to dump unused energy into some use. My thoughts were to have energy monitoring from a CT clamp device to detect excess solar then support IFTT or something to trigger smart home/alexa plugs to turn on. Applications for this could be an electric heater, fan, AC unit, Spa, crypto miner etc.

So could emonPi control a relay to turn on the immersion heater as well as turning on other appliances ?

Welcome, Jon, to the OEM forum.

Yes it could, but not directly. If you want a relay or contactor to switch loads on and off then the emonPi can send commands to the Wi-Fi Thermostat/Relay.
However, that can’t respond rapidly to changing load demands of the house, so I’d still recommend Robin Emley’s Mk2 PV Router to dump excess to your hot water cylinder, because it’s capable of maintaining a much better balance than commercial devices (which are often designed to deliberately ‘leak’ a few tens or hundred watts of export).

I’m not an expert in this the emonPi and MQTT, so I can’t say just how many relays it could control.

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Hi @Jon0881,

I suspect your problem is going to be that a 1.5kWp array is pretty small and will only produce 1.5kW output during decent sunshine. Most of the time it will either be producing very little output (a few 10’s of W in winter) or crashing up/down as clouds pass overhead. The few 10’s W will be eaten by your house load and the crashing up/down isn’t great for fixed loads like a fan heater as it may be switching on/off hundreds of times a day. I’m not saying you can’t achieve what you’re after, but buying loads of wifi plugs (be careful running large loads on them), or running relays/contactors will be expensive and I suspect won’t pay back for a long time.

As @Robert.Wall mentioned, Robin’s PV Router is pretty cheap if you buy a kit and it will adapt rapidly to changing conditions and use ALL of the excess PV to heat hot water with no thought or planning.

But the cheapest thing to do are just to watch the sunshine casting shadows or the EmonCMS dashboard and run the washing machine/dishwasher, do the ironing, vacuuming, lawn mowing, etc when the solar panels are producing. This can make a sizeable difference to electricity bill by swapping paid for electricity for free solar electricity.

Unfortunately, UK Trading Standards prevent Robin from selling anything other than a kit.

The stupidity is, you can (I carefully don’t say will) ignore his instructions, assemble the kit badly and make a complete mess of it, then power it and use it in a potentially dangerous state, and that’s completely legal.

As you can see from his photos, Robin’s assembly is immaculate and safe; but it’s illegal if he sells an assembled ready to use apparatus.

Uhm, can you not get around that, my wife use to work in Germany at an electronics manufacturer. Almost everything was assembled in China. All she did was solder in a couple basic components and connect a few wires and that was enough for it to be labelled made in Germany

Not really as the German manufacturer is liable for any and all issues arising from problems with the product. Be it fully constructed in China or not. The manufacturer is also liable for CE marking, Low Voltage directive and EMC testing.

Which is what Robin is trying to avoid.

I have not CE marked and completed EMC testing on a product for over 20 years but it was £800 a day for an EMC test house when I did do it.

Indeed. Robin isn’t trying to get around “Made in …”, even though most if not all the components are probably sourced from China, his problem is the one you allude to: the cost of formal certification (now UKCA marking), which has to go on the price he charges, in some form or another.

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that what i was referring to avoid formal certification. simply assemble to a certain degree 10 - 80% what legally allowed or break it up into modular sections , ie the portion that people you say mess up on… and as a kit allow them to assemble the rest of the way basic stuff and a few rudimentary components that are hard to mess up on. ie like say with arduino products you buy this piece that piece put it together and you got a fully functional device.

Oh, been a while since I looked at his site.