I am an energy hog - Going Solar with 5 Aircon, 2 UF Heating, 2 stoves, 2 hobs, 2 geysers and a pool

richardimorserichardimorse Registered Users Posts: 98 ✭✭
My design for this 230V Single Phase SYSTEM is an AC coupled system which grid parallels 1 geyser, 1 stove, 1 Hob and 3 UF Heating which are discarded on grid failure.

So that leaves 5 Aircon 1 stove 1 hob 1 geyser and a pool which is to be on the AC coupled part of the system.

The system is in a hot country South Africa (10 months of the year) with heating required at night 8 weeks of the year, the grid fails once a week so it has to have the ability to work off Battery Inverters at night, which is where I want to look at minimising the battery inverter capacity, lets say to cut it down from 15kVA to preferably 10kVA but that might not be so easy.  Here the system proposed will be Fronious / Victron ESS with colour control and lithium battery.  Looking at either 2 or 3 Multiplus II 5000VA units with an 8.2kW Fronius on AC Output 1.

A 10 AMP Energy Control Unit (LOAD SHEDDING DEVICE) can manage the Stove/Geyser situation (NOT ALLOWED ON AT SAME TIME).

My energy baseline would be 1 kW + 2kW Aircon = 3kW plus Aircon spikes and Geyser spikes I can use load shedding on the baseline with an ECU and only allow the geyser to heat when that baseline remains under 15.25 Amps (3.6kW) I guess I can do the same for aircon by splitting it into 2 groups 1 group of 2 aircon (master bedroom and lounge = essential) and 1 group of 3 aircon (kids rooms and so on) then I could load shed the non essential aircon which may get the requirement down to 10kVA, hmm, I guess it is what it is and may be worthwhile just getting the 3rd 5000VA Multiplus II battery inverter to be used for headroom only in case of simultaneous demand. 

So it comes down to managing Aircon on solar, 5 units in this case all independent and also brand new, one approach is to use an IFTTT energy monitor (Smappee, Nuerio, Sense), coupled with some native aircon or tuya / broadlink IR/WiFi controllers, the basic problem is that the 5 * aircon will use say an average of 2kW but will have some large peaks lets say all 5 are on at the same time = 7.5kW.  

At night 10kVA of battery inverter is enough to manage this but UNLIKELY to do the same in peak periods (4pm to 8pm for example), then 10kVA may not be enough headroom with the power utility out and the fronius not generating power, hence some more sophisticated method (other than load shedding) of simultaneous power limit control is what I am looking for in this peak period.

Some form of round robin on the aircon units to prevent them heating or cooling simultaneously is preferred instead of load shedding the aircon units which will cause them boot up again making loads of beeps waking everyone up and all that, would rather put them on some kind of rotating energy pause which only allows 2 units to perform cooling compressor operations simultaneously, this might need some more sophisticated aircon wifi controllers which can do more than on/off and can interact with the aircon functions or aircon inverter controls.

Any ideas or should I just buy the 3rd Multiplus II even though it will hardly ever be used ?



  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited August 2019 #2
    Consider an air to water heat pump + tank which will allow you to accumulate cold water while the sun shines and then use it for cooling later.  Similar for hot water (geyser).

    I am available for custom hardware/firmware development

  • richardimorserichardimorse Registered Users Posts: 98 ✭✭
    Thats why I pointed out the the 5 split unit air conditioners are all fairly new, and they are independent not part of a multi system, so it is a bit hard to tell someone to replace the new air conditioning units that they just bought.
  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    They could still be used during sun hours.  Run the numbers - battery costs for running them at night might exceed the cost of replacement with a hydronic system.

    I am available for custom hardware/firmware development

  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    How about using heat recovery with the existing units to heat domestic water rather than wasting it to atmosphere. https://www.hotspotenergy.com/commercial-heat-recovery/HRU-specs.php

    Ps. I'm not a refrigeration engineer or tech, but have seen this used on split systems.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Sign In or Register to comment.