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Forum Index : Solar : Poor mans PV Diverter.
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| Mulver Senior Member  Joined: 27/02/2017 Location: AustraliaPosts: 160 |
As was I so I got this to get me started. Bit pricey but it was a birthday gift. Arduino Starter Kit As previously mentioned using open energy monitor information if you can get voltage and current measurement your well on your way to automated control. I highly recommend giving it a go! Once you get it working just a bit of advice from here and you'll have it turning things on and off. Oz, you have mentioned feeding a GTI with rectified AC from a generator using Motor run Caps to limit current. Could this same setup be throttled by your PWM controller on the DC side of the rectifier? So you set up the max current with the Caps then limit it down with the PWM controller? |
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oztules Guru  Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Yes, but I have not done it to see how robust it would be. I guess you could do without the series caps, and just have filter caps, and control it from there. I found the caps work just fine really, but it is something else to consider, and may give it a go too. ........oztules Village idiot...or... just another hack out of his depth |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
One of these sensors on your grid connection would allow you to sense current being exported, feeding this signal into an Arduino you could send a PWM signal to a SSR on your HW. This could be setup so you divert excess power to your HW. https://www.aliexpress.com/item/Free-Shipping-1pc-hall-current-sensor-module-WCS1700-70A-short-circuit-Overcurrent-prote ction-modul-hall-effect/32770750311.html?traffic_analysisId=recommend_3035_null_null_null&scm=1007.13338.80878.000000000 000000&pvid=1875e9c4-4fb3-4a9a-8385-5ae02fa0ae4a&tpp=1 However the open energy monitor is a tried and tested solution, all you need to do is put it together. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Can't get the slightest bit excited about the open energy monitor. The aliexpress unit is worth consideration though...... I wouldn't bother personally. I rather home grown stuff... and the sensors in the aerosharps and the inspires will do the same thing just fine for simple current measurement, which is what we are really wanting for the hot water part, however the aliexpress part would do just as well. The open energy thing is lots of piffle, and offers little else, for a lot of expenditure. We need only current flow... not all the other wall paper. If it offered current direction, then it would be worth a very quick look, but a 4 channel comparator for 10 cents would do that with an xor chip ( 10 cents again). So no... not for me anyway. If we thought like that, we wouldn't have an inverter that blows the doors of your original commercial ones, and you would not be able to control your GTI's as you now can... I have never seen or heard of that being done before.. but we can. There is something to be said for experimentation. .........oztules Village idiot...or... just another hack out of his depth |
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| Mulver Senior Member Joined: 27/02/2017 Location: AustraliaPosts: 160 |
Just to clarify when i say the "open energy monitor" I am only referring to the information provided in this bunch of web pages to get started. https://learn.openenergymonitor.org/electricity-monitoring/ctac/how-to-build-an-arduino-energy-monitor I used it to help me get started on measuring power usage. On my PV diverter "thats still in testing" once the power starts to flow back to the grid it starts loading up a SSR with the HWS on it. Right now the house is using 1500w (evap AC is on) and 600w into the HWS. The Inverter is generating approx 2100w. The Arduino is basically trying to hold the RearPower at 0. With this running my Smart meter reads zero export and very minor import, probably a calibration thing. |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
George, the article Mulver points to pretty much solves the hot water problem, with little effort, and full explanation.... good learning tool. After you build that it is a simple matter of putting in a new subroutine to control a fet from the arduino outputs, and your away.... then add temp etc etc. But the bare bones are there. The feedback problem is different in that we need current direction and amplitude, which is still simple, but a step I have not taken, but perhaps Warp has. Get the hot water under control first... then you will gleam the tools for the next stage. .........oztules Village idiot...or... just another hack out of his depth |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
Thanks all. Have been reading up on the open energy monitor and ordering Ct's and bits and Pieces. I'll go ahead with the voltage monitor idea and with the energy monitor as well as a learning exercise for Arduino. Initially I might be able to use a Ct to monitor the 3rd leg of the AC input and just switch in a GTI to that phase. Bought a 1500W GTI cheap so that can be the test module. Have to get the clamp meter out today and measure the draw of the AC on that leg at the fusebox which will be the easiest way to get it's power consumption. Got an idea it will be around 2 KW ( nameplate on the unit is very non specific with only Locked rotor amps) so I'll see what will be the closest size inverter I can use or see if a PMW motor speed controller will work for fine tuning an over size unit. |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
Voltage monitor relays arrived a couple of days ago and were put straight into service. All seems to be working well and as expected. Did take a little fiddling with the controllers to get the settings right, mainly the hysteresis as the line voltage variation from the main circuit is not nearly as much as where the inverters are in the shed. I made up a box with a 10A breaker, Volt/watt/ KW meter, a PWM speed controller, 25A Ac/AC SSR and the voltage monitor. I used the PWM as I am just running this off a power circuit for the time being for testing and obviously can't drive the 3800W heater element from a normal socket. I'm putting in 1500W which everything seems very happy with. Once I have verified it all works and found any bugs/ tweaks, I'll run the thing to a 25A relay as the voltage switch is only rated to 6A. Seems to work very well and even more effective than I thought. I notice boiling the kettle tends to drop the line voltage a surprising amount. If the solar is backing off a bit say in the afternoon, the Relay may pick up on this in it's threshold and turn off the water heater. once the kettle is done or the solar comes up, it kicks in again. I'm really pleased with this and reckon it's a bargain controller for those that don't have the knowledge of electronics or arduino to put one together themselves. Lot easier for me to wire up a box of components than work out electronics or write/ troubleshoot Code. That may be different for a lot of the boffins here but I think there are a lot more electronic Dummies like me out there than there are the geniuses here. The thing could be simplified down to a relay/ contractor and the Voltage monitor if it were installed in the fuse box permanently making knowledge required to set it up zero if a licensed person were doing it. One could leave the off peak supply as it were and hook this into the line to the heater with the relay. The solar kicks in when available and if there is not enough to bring the tank to full temp, you have saved whatever it has contributed. Certainly these controllers would beat the cost of anything else commercially available I have seen to do the same job. |
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