Smart solar systems
- Thread starter Bowden89
- Start date
- Location
- Co antrim
I have an eddi for turning on the water heaters
- Location
- North Norfolk
It would not be difficult with a Siemens Logo, an input from the solar system as to how much is generated, and a contactor (if not in place already) for each load.
- Location
- Burton on trent
I write all this kind of stuff myself (to save money), then I can get exactly what I want and can add to/improve it as I go along.
I use ethernet relays to control 3 phase heating fans on my biomass system:
https://www.robot-electronics.co.uk/products/relay-modules/ethernet-relay/eth002b.html
I then write simple code in Node Red which I run on a raspberry pi, or any PC that is always on.
Coding in Node Red only requires a web browser and the program is free (even for commercial use).
I then setup something to read the solar output, in my case the RS485 modbus on my ABB inverter (30kw), node red can read RS485 modbus directly if you use a USB to RS485 adapter.
But I've also done this using the pulse output on a generation meter on solar arrays. Which works well with node red or even ESP32 arduino boards.
The relay board above, just needs to be connected to a contactor to run the heater or compressor or whatever the item is.
I use ethernet relays to control 3 phase heating fans on my biomass system:
https://www.robot-electronics.co.uk/products/relay-modules/ethernet-relay/eth002b.html
I then write simple code in Node Red which I run on a raspberry pi, or any PC that is always on.
Coding in Node Red only requires a web browser and the program is free (even for commercial use).
I then setup something to read the solar output, in my case the RS485 modbus on my ABB inverter (30kw), node red can read RS485 modbus directly if you use a USB to RS485 adapter.
But I've also done this using the pulse output on a generation meter on solar arrays. Which works well with node red or even ESP32 arduino boards.
The relay board above, just needs to be connected to a contactor to run the heater or compressor or whatever the item is.
Daniel
Member
- Location
- Mildenhall, Suffolk
Presumably you need an override that knows when you will want the hot water for, or by when you need the milk cool, and switches the system on if it hasn’t been sunny enough for the solar panels to do it?
- Location
- Burton on trent
That's probably right, so you'd put temperature probe(s) on the tank, then if the temperature is not high enough by a certain time of day, then node red would just turn on the heater anyway to get the water hot. You could even write a few web pages to allow control from your phone, such as change parameters of the temperature and time of day override etc
Exfarmer
Member
- Location
- Bury St Edmunds
you can certainly get systems to match the water heaters but compressors are a different matter as they will only run at certain loads so if your switch turns it on thanks to their being 1Kw of export when the 3 HP compressor cuts in it will instantly cut out again as the load will mean, there is no longer export but a 1.25 Kw import. This switching will kill a motor.
Far better to set the compressor on a time switch to the hours of the day when you are most likely to get export so 10-2 say. Then have a system which will divert any spare power into the heating system as these can vary the power going into the immersions.
You can of course have batteries as well but water heating diverters are the cheaper option.
I have just installed a solar iboost on my house and very pleased so far I know they can be modified for 3 phase , but not sure how it works and I suspect is not really designed for what you need
- Location
- Northumberland
You sound like a guy to assist me!
I've also got a homemade board switching various immersions with spare power from my turbine. Trigger is pulses from the export meter. Works well.
The weak link is the actual load switching. Initial attempt with contactors kept resetting the picaxe board. Using SSRs now but lifespan is limited, even with heatsinks/fan, and they have a habit of failing on!
Any tips?
- Location
- Burton on trent
Not exactly sure what your talking here, but I'm guessing:
If your switching loads such as motors or even relays/contactors with a microcontroller, you will likely get transient spikes coming into the microcontroller during switching. (often when switching off)
This will frequently crash the microcontroller and it'll have to be power cycled.
Depending on whether your switching a DC load or AC, you'll need to add a snubber to the circuit.
See info here , there is a pdf on that page with more info.
Some relays you can buy with snubbers integrated, I highly recommend getting those as they cost only a fraction more.
For a DC load you can just use a suitability sized diode. AC loads are a little more complicated. see pdf.
If this is not what your talking about, my apologises and provide a little more info for us...
Exfarmer
Member
- Location
- Bury St Edmunds
As you are off grid, you must ensure that any motor does not attempt to switch on automatically when there may not be sufficient power in the system. Although the battery is rated as 20Kw in reality 20Kwh capacity, they do not necessarily deliver 20Kw. Many domestic batteries will normally only deliver approximately 3Kw. It will of course be affected by the battery/batteries set up and the inverters they feed. Do not of course forget to allow for sharply increased motor start up loads
- Location
- North Norfolk
This is why I use Logos for this type of job, as they are designed for an industrial environment
yes the inverters only take about 10k after that the generator kicks in. my biggest frustration at the moment is once the generator kicks in it stops the solar from working.
Exfarmer
Member
- Location
- Bury St Edmunds
That is because your solar is set up that way. My own installer tells me that any generators on site must be isolated from the solar or the solar switched off when they are running or they will burn the generator out.
There are others on here far more wise to electronics but as I understand the power the generator makes is quite different to the power supplied from the grid. I do not understand that side at all.
I am certain somebody could sort the issue which would entail another inverter
- Location
- Burton on trent
Can see what you mean, but once you have the gen running, you might as well run the site on it... but you might be able to rig something where the solar continues to charge the batteries after the generator starts up. Do you recover the hot water from the generator for the dairy etc. That would be quite useful 'free' heat whilst it's running.
Our 56 kwe CHP generator makes about 85kw of heat (from the block and exhaust gases), which we recover.
Exfarmer
Member
- Location
- Bury St Edmunds
cheapest heat you will get
that's really interesting. we don't currently. I have a good heat recovery unit for my refrigeration compressors. would it be easy to rig it to that? or would i need another unit?
that's really interesting. we don't currently. I have a good heat recovery unit for my refrigeration compressors. would it be easy to rig it to that? or would i need another unit? yeah the solar is currently only kicking in once all the big ticket items have finished. keeping the batteries full through the day ready to go through the night. which is useful but nowhere near the potential.
Exfarmer
Member
- Location
- Bury St Edmunds
is your generator air or water cooled?
Water