I am looking for advice to get me started. I am very frustrated by the functionaility (or lack of) that my SMA system has.
I have an off grid system. SMA Sunny Islands (X2) SMA inverters (x 2) and will soon be adding a home made wind turbine.
I have all the inverters connected to a SMA webbox which receives data over a serial cable and makes it available within the SMA webbox via the web GUI and uploads it to the SUnnyportal (a internet based interface).
What I want to do.
1 See if my batteries have got too low via an alert. I am wondering if all I need is a rasp pi or such like. An FTP job that copies the data to it from teh webbox. And some how monitor the data to see if batterys are below X% and send me an email or SMS. The battery SOC (State of Charge) is available from the data on the webbox.
I also want to be able to:
2. switch on relays (immerssion, or even an electric car charger) when I have excess power. Which is most of the time from March to Sep. The SMA system derates by pushing the frequency up. This tells the inverters to reduce production. The challenge for me is that I currently do this via frequency controlled relays (over 50hz swicthes it on). But when the generator comes on it also takes it over 50Hz and I don’t have excess energy.
So, I need a system that will look at battery charge status, energy being produced, frequency and status of generator.
And makes a decision like: If batterys are above 80% and frequency is higher than 50hz and generator is not on then switch on relays.
3. Purchase relays that work with wifi or some other remote control (getting cable to the the devices I want to control is not easy or feasible). I currently use frequency relays but these are proving problematic.
4. monitor the energy from the home built wind turbine.
5. get the error log off of the SMA devices (the web box currently does not support this) and have it available so I can raise alarms via email or text or web interface.
6. Turn the data in something sensible via a web interface. e.g. take the value that means generator is on and make it a red green light or even an event on a timeline that actually says generator on. Same for derating, boost charging etc. These are all currently very cryptic and I have to look them up every time.
So I guess my question is:
What would you recommend.
Does this Open system fit my needs.
Can this Opensystem use the data from the SMA webbox rather than external sensors.
Or do I need to build a custom thing that uses the data I ‘almost’ have available already via the SMA webbox.
Sorry JD - I can’t necessarily answer your last four questions but I too would be very interested in any good advice on this subject having a very similar (SMA based) off-grid hardware set-up. I have an OE system installed but use it only for monitoring purposes. This has proved very satisfactory thus far (with one or two hiccups) and I may be interested in adding to it and/or extending it’s functionality in future. Some of what you are asking about is achievable via OE system (without needing to use the Sunny Island output) - I think, but I am far from expert in such matters. Indeed the OE system provides information (and probably functionality) beyond that available from the SI’s.
Outside of the OE questions:
I use the frequency shift function to control diversions which are disabled during generator runs and operate only on surplus power and before inverters respond to the frequency shift. This works very well. What type of frequency relays are you using? Are they on your main ring?
Is your turbine going to be “AC coupled” or “traditional” DC? AC is very straightforward for OE monitoring.
Thanks for replying Adrian.
My frequency relays are called amber switch. Www.ambercontrol.com
You configure then via dip switches to come on at 50 or 50.25 or 50.5 and so on.
They then switch off when the frequency drops by 0.25. Which is a right pain. I want to build a latching relay or timer so that when they are triggered they stay on for at least 5 minutes. (One of my load dumps is a hot tub that a friend was throwing away and it primes the pump for 2 minutes before kicking in the heater).
My turbine will be a Hugh piggott design. 800 watt unit. 3M diameter 10 metre pole. I think it will be connected to the DC side. I have asked the installers
How do you get your relays to ignore the generator?
Does anybody have experience of this which I found on the main website
I would live to run this on a rasp pi running OE
Does the OE rasp pi device have the apps required already installed? a mysql DB etc? and would it be possible (or sensible) for this SMA data extractor to populate that database?
James - always interesting to see how off-gridders deal with diversion requirements. DC is well catered for in the market but AC coupling (and I guess you have this only at the moment) or a hybrid AC/DC is less well served.
I know the Amber switches and was given a couple of the original plug in type (originally labelled Econnect I think) a few years ago. They have their limitations and I now use them only for back-up when everything is full and the turbine is likely to need to start dumping at the rectifier. Still going strong though and very conveniently mobile.
I progressed on to using frequency protection relays (still only on/off though) and more recently to phase angle SSRs controlled by a frequency transducer for proportional diversion. You can hang these anywhere off your grid but still need to provide an isolation method for generator runs. Not recommending any of this but it works for me - so far. Not being either an electonics whizz or software developer clunky industrial type installs suit me well. If you have limited access to your grid as you suggest probably too simplistic for you anyway.
Have you not tried using one of the SI relays for your hot tub on either SOC or timer settings? With a couple of SIs in parallel you must have a spare? Again, though, you may be limited by grid access and wiring. I prefer to let the SIs do their thing as charge controllers and simply use their frequency shift as a signal for diversions - this does not seem to be very popular though.
Hugh Piggott turbines are highly recommended. Hugh also does an AC side SSR diversion system controlled by DC side Tristar controllers - detailed on his site. Works very well apparently but, as far as I know, this is only in a SI system which has frequency shift disabled and the SI is relegated to “dumb” charge controller.
I power a simple contactor from the Generator feed which isolates my diversion feeds on start up and in the warm up period before the SI internal relay activates. I am fortunate to have my primary diversions (to DHW and Thermal Store) hanging off the SI CU, so nice and local, and also some spare wiring around the grid.
Although all this works fine and my skills are very limited I am always interested in future possibilities especially having made a start with OEM so will watch to see if you get any useful response beside my irrelevancies!
you could try this software on a Raspberry Pi-based energy monitor (or a linux computer to test) - SMASpot if your sma has bluetooth or speed wire- https://sbfspot.codeplex.com/downloads/get/1575948
here a howto ( just change the wget to the above link)
SMASpot Monitoring in Domoticz - Domoticz
you should be able to get battery status and pv production and ac production i would think but I do not have any sma inverter to verify
then just get the pi to control your electric car charging and diverting
though i am not sure how live the data is but i guess it will be workable, depending how much accuracy you want
Thank you Adrian.
Can you tell.me where you got the solid state frequency relays from please.
I will have to have a think about generator isolation as my house (and thermal store etc) is 100 metre from my solar plant room. I could try and pull another cable through the duct fir the relays but do not think there is room. I wonder of there’s a wireless relay or one that works with signals over the mains like a mains network device.
I will let you know how I get on.
Thanks Stephen. Really appreciate you taking the time.I had not seen this before. I will investigate further.
The SSRs I use respond to low voltage input. This input is provided by a Frequency Transducer.
There are a few makes/options of SSR widely available. Mine are 0-10v Celduc - not the cheapest but the spec suited me.
Transducers are also widely available from major component manufacturers - Hobut, Eltime etc. Mine is configured to provide 0-10v directly proportional to a frequency range of 50.2 - 51.2hz. This works with my Inverter settings.
Google for either of the above.
Frequency measurement is quite well covered on here somewhere if I recall and also elsewhere so you could skip the transducer if you want to DIY.
Quite a lot of stuff about diverters on here may also be of use if you have the skills.
Certainly must be a wireless relay and also probably covered somewhere on this forum.
MartinR’s PLL will definitely measure frequency (there’s a simple frequency-only PLL sketch somewhere on the old forums), and I believe @nchaveiro’s EmonLibPro does too.
Robert. Adrian. Thank you. I will get cracking with a project.