I’ve finally gotten my stuff setup on my Sunsynk to feed into Home Assistant and starting to automate things. One of my issues is that you have to guess how much solar power is available particularly when you need to know. While battery is charging or there is load you kind of know what PV power is available but once the battery is charged you cannot know this as the PV power drops to match the demand.
At the moment my automation turns on the geyser when the batteries are full and the house is running off solar fully. If after turning on the geyser we start running of grid/batteries I switch it off again. The idea being to heat the geyser to high levels when excess PV to avoid using grid/batteries later or the next morning. I.e. an extra “battery”.
I’m thinking it will be useful to have an irradiance sensor. The fancy ones are very expenseive R5k to R10k+. So I’m looking for a cheap one or a easier self build.
With such a sensor one can see that you have Solar PV Power of 5kW available now even if the house is drawing 500W only or whatever. You can then activate geyser, pool pump, pool heating, etc. until you match the available power.
Anybody doing this? Anyone have experience?
Here is an example of a R11k one:
This says low cost but doesn’t show the price. I’ve checked. Will give feedback if interest.
There also seems to be the option of building your own. Seems a cheap solar panel plus somethign arduino can do the job. My fear with this is durability on the roof. Maybe too fidgetty for me.
Other thought is to get a weather station of some sort. Another item on my project list and get one with irradiance measurment in…
It’s on an old server. I conveniently alread have ether cable from the roof to the server (from an old project of mine). So I could easily get it connected. So that’s not a problem. I was thinking if it’s RS485 based sensor it will be easy with one of those RS485 to usb converters for example. And then a script to get it on MQTT or similar.
In my industrial automation past there was a stand-off between industrial controllers (PLCs, DSC’s etc) and PC based control systems. PCs were perceived to be not solid enough.
I still kind of think like that.
However I was amazed to discover that the Geyserwise display has the TOD clock built into it. This means that the display has to be plugged in to the relay control unit to function.
Case if:
Panels are generating > 3500w, Eskom draw is <500w, switch geyser on.
Wait 5 min.
If condition remains true, take another 5 min beak.
If the batts are full:
Within pre-set time frame, switch geyser on.
Wait 5 min.
If Eskom draw remains under <500w, keep on for another 5 minutes.
Batt will be charged after geyser is hot.
… or something like that.
5 min delay also takes care of clouds.
Also takes care of kettle or MW going on in that time.
Less relay swiches too.
The above the simplest answer I found over the last few years, to draw max from panels.
Yeah have something like that. But what if you knew how much kW your PV could put out.
Logic is something like if pv capacity less pv output > 2kw the turn on geyser or pool. Probably put some 5 min time or so to not switch it too quickly.
Think I’m going to try one of the cheaper ones on AliExpress. Not too expensive and worst case if it’s not very accurate you can apply some adjustment factor to match observed PV output.
Interesting. What is the SCR in that discussion? Might be useful in scaling the plunge pool heating element back as it’s 4kW. Which is probably needed.
I have a similar setup to @TheTerribleTriplet , which simply switches the geyser on if the load is low enough. But I only do it with the one geyser (the less critical one that won’t affect the WiQ state). But then also, despite making the system bigger over the years, I always have a substantial grid component each day, and in the end it doesn’t really matter where the energy comes from at any particular period in time as long as all the PV is used and the battery is fairly well charged by the end of the day. So a simple peak-shaver is sufficient in my case. I can well see that if I had more PV, I’d want even more sophisticated ways of putting it into places (and delaying putting it in those places).
Add an EV to the mix and see how interesting that gets! It is 2PM, the sun is shining nicely, the pool pump has switched off, and the batteries are full. Your wife is at the shops for a quick 2-hour errand.
Set Geysermax temperature to a high value on the device.
I’ve then replicated the Geyser Max schedule and logic in Home Assistant. It switches on when schedule hits (early morning pre shower) and late evening. This switches off when a lower temperature is reached (55). This ensure I have warm water in the monring and evening. This only switches off when the grid disconnects.
I have a Excess PV Power binary sensor which switches on when PV is running covering the house load, the grid is not being used and the battery is full (SOC > 98%).
If this excess PV sensor is on for 5 min I then switch on the GeyserMax which will then turn on the element (because high temp setting) and run it.
If the excess PV sensor remains on the geyser stays on.
If running the geyser causes the excess PV sensor to switch off for more than 5 min (battery SOC starts dropping or the grid is being used) I switch the GeyserMax off.
This is a geyser with hot water panels on the roof too so this is an additional boost. As soon as these require maintenance / repairs I’d probably remove them and swap for PV panels.
The goal of all this is to reduce the chances of the Geyser being switched on in the evening or the next morning. This chows battery/grid if it happens.
It’s working for today for the first time really (Cape Town clouds have limited it). I had set the element heating to 75 max but wondering if I should shift it down to 70? Do I shorten my geyser’s lifetime if too high?
