Weather compensated control system

stephendv Solar Expert Posts: 1,571 ✭✭
Hi all,

I've been toying with the idea of building a weather compensated monitoring and control system for off-gridders. The basic idea is to have an easily programmable unit that does the following:
- Accepts a wide range of sensors, current, voltage, temperature, humidity, etc. as well as digital inputs
- Has 4 relays on board
- Accesses weather data online
- Have a GPRS modem to download weather data and send SMS messages
- Control the relays by SMS
- Performs data logging for any/all of the attached sensors
- Access data logs over ethernet port
- Allows the user to program rules to control the relays, e.g.: such as:

If the battery state of charge is 60% and there's no sun forecast for the next 8 hours and it's later than 3pm, then close relay 1 (e.g. to start a generator).
If temperature sensor is higher than X then close relay 2 and send me an SMS
If the generator is on and current sensor 1 < 5Amps then turn on relay 3 (turn on optional loads if there's spare generator power)

The point is that the user can connect whatever sensors they want and write whatever rules suit them.

I have two main doubts about such a unit:
Firstly, would off-gridders really be interested in something like this - given that it would like cost somewhere in the $400 - $600 range? Or is it a solution in search of a problem?

Secondly, which of the following features are really essential to the success of the system:
- Sending SMS alerts and remote control of the relays by SMS
- Downloading data through GPRS modem (or is ethernet fine?)
- Is 4W power draw too much?
- Is integration with a battery monitor essential or is a simple voltage sensor good enough?
- Is programming the rules using a high level programming language asking too much from the user? E.g. they'd have to write something like:
if ((sensor1 > 5) && (sensor2 < 3)) then openRelay1();



  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Weather compensated control system

    i can't say one way or the other for the price, but some have their own weather stations and won't have need of some that stuff. maybe you can have various levels available and either see what others say in answer to your thread or do a poll on it.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Weather compensated control system

    POV from one off-gridder: it's a solution looking for a problem.

    Couple of reasons why:
    I monitor my system daily and run the gen as needed to keep them up (could also have the controller auto-start a gen). Weather forecasts here are completely unreliable, no matter what the source. I would not rely on a prediction of "sun to come" and let the batteries go to see what happens. Barometers don't even read right at this elevation, and we've just come off two weeks of sunny sunrises, followed by clouds completely obscuring it at peak solar hours, followed by clearing in time to drop the over-night temp to ridiculously cold for June. None of this was in the forecast.

    But that's just my opinion and others may find such a device would be useful to them. I tend to think there's such a thing as too much automation.
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Weather compensated control system

    another POV... for an off grid installation that does not have an internet connection, and to get one, having just checked 2 days ago, would have to layout about $1200 Cdn due to isolated locale,:cry:..Min $200 for install when they get around to it:grr..... I am definitely not in a hurry right now.

    Have previously thought it would be nice to have Int. Conn. it's a bit too pricey.

    we manually start the genset to bulk if too much power used.

    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    Re: Weather compensated control system

    Off Grid 3 yrs. My POV

    I dont like autostart gen systems anyway as Im normally home24/7 365 as I moved to my holiday local on retirement so im always on Holiday .I like to make the decision when to run the generator depending on local weather conditions and next day forecast .

    Internet access and off grid properties dont usually mix but its improving all the time

    If I did require auto gen start say i had to leave the house unoccupied for a week then the simple load/voltage levels autogen start stop offered by most offgrid inverter charges are more than adequate .

    I could live with the ocasional genny coming on at 6am charging the batteries to 90% and then see the charge controller blow a full days solar output . For the times this may happen in the week Im away then I could live with that.

    I wouldnt say this is a solution looking for a problem, because there is always a problem seeking a solution, but I fear your solution seekers will be low.

    Trying to get people to invest in a Battery Monitor at $200 is hard work.

    Plus if your not home and you can switch everything off, then the solar even in real poor weather should keep the batteries topped up if only self discharge is all you have to cope with. If I was leaveing my property unattended for more than a couple of week I would consider running the fridge freezer content down dfrost and power down the inverter.
  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    Re: Weather compensated control system

    Plus for those that needed remote monitoring I think a cheaper solution could be fabbed quite easily by using a cheap GSM Burglar Alarm Unit. Trigger the alarm when the battery voltage gets to a set point, easy if you have a Battery Monitor like the XBM or a MPPT CC like FM or XW, it sends you a SMS to your mobile , you check the weather forecast on line then you ring the burglar alarm unit to start your genny. If necessary. Simple GSM alarms are less than $150. I have a simple single zone GSM alarm that could do this easily ish.
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    Re: Weather compensated control system

    Thanks for all the comments - useful stuff! I work in IT and write programs quite fequently, so I'm naturally biased towards automating almost everything :D
    Good points raised, and it confirms what I was suspecting. I'll definitely build a little system for my own off-grid kit (when it's finally installed), but will hold off on trying to make it a commercial product.

    Thanks again!
  • SolarJohn
    SolarJohn Solar Expert Posts: 202 ✭✭
    Re: Weather compensated control system

    I've been thinking about doing something similar to what you've suggested, since I have experience with microprocessors, but I agree with the others that it would have limited appeal as a commercial product. I've automated my own system with a Morningstar Relay Driver, at a cost of about $160.00. It doesn't facilitate remote monitoring, but it does help to protect my batteries from over-discharging. The relay driver has 4 channels, so you could get creative with it. As an example: If solar panel current is less than 5 amps, and it has been less than 5 amps for more than 1 hour then it must be a cloudy day, or it must be night time. If that is true, and battery voltage is less than XX.XX, then start the generator. (You get the idea). I've considered putting together a system for data logging, but that task could easily be accomplished with free software available for my charge controller.