Off grid solar router

[cristof]

With the help of a French technician, we created a solar router, capable of heating water thanks to the excess solar power supplied by the solar panels.
When the hybrid inverter is near the end of charging the batteries, and the inverter load is not at its maximum, if there is still the possibility of drawing energy from the solar panels, this energy is sent to the water heater, step by step, without discharging the batteries. We monitor the charging voltage of the batteries as well as the charging / discharging current of the batteries with a DC clamp . We use for this an ESP32 micro controller, a 40 amperes triac, a DC clamp .HST016L
the system has a web interface to access settings and controls. It is open source available to everyone. The project is in French language, the system works in 110V-240V 50/60 hertz. We have 2 version, "La Mini" with 1 triac output, and "La Maxi", with 2 triac output and one SSR output

 

[Hedges]

Are you able to vary the power draw rather than just turning the heating element on/off, so it consumes just the surplus PV power but doesn't draw from battery?
Using the triac like a light dimmer would be one way. Better but more expensive is a switcher - MOSFET with an inductor, controlled with PWM so it has a sinusoidal current draw.

What I would like are controls which respond to SMA Sunny Island's signal: Up to one frequency (e.g. 60.5 Hz), draw zero power. Linearly increase power draw up to maximum at a second frequency (e.g. 61 Hz.) That would let the load, in this case water heater, consume any surplus power up to it's maximum draw. Then from 61 Hz to 62 Hz, the Sunny Boy inverters linearly decrease their production because no loads are available to use it.

Does your device deliver AC, DC, or rectified AC?
Safety devices in water heaters are designed for AC, would likely arc and fail to turn off current for DC. Rectified AC might work OK because current drops to zero, but that should be verified experimentally. Perhaps polarity reversal not just zero crossing is necessary to extinguish the arc.

 

[cristof]

The system works as a dimer in AC 0 to 240V. Only for resistive loads. when starting the system, the dimer send a 1st step of 1W. if the DC clamp does not detect a discharge current, then an additional step is sent. And so on. As soon as the clamp begins to sense a discharge current in the battery, then we take a step back. it is very fast, and we studied different cases, like a fast cloud passage. I have been using this system for over 8 months, and every day, if the weather permits, I heat 200 liters of water, on average from 40 ° C to 65 ° C without ever discharging the batteries. At the end of the day, my batteries are fully charged and I have 200 liters of hot water at 65 ° C

 

[Hedges]

OK, that provides some of the possible benefits, but not all. In fact I think it delays and could for some systems prevent battery recharging.

During bulk charging, perhaps we want 100% of PV to charge the battery, so no need to divert power to the water heater. Although in my case, PV produces considerably more power than maximum charge current. My inverter is set for 85A (at 48V) charge current, about 4.2 kW. My PV could be producing 12 kW, so about 8 kW is available for house loads or water heating. Does your device draw all it can at this point, since no discharge of battery will occur (assuming water heater < 8 kW)?

During absorption, current to battery tapers off but doesn't drop to zero. Most systems (at least lead-acid, not sure about lithium) apply a regulated voltage to battery and current flow is reduced. So charge controller lets PV voltage drift above Vmp. During this time your device sees battery charge current, so it remains off. (or does it take all power it can without discharging battery? So making hot water is a higher priority than recharging the battery?)

Once battery is full and charging moves to the "float" phase, then your device uses any available PV (not used by other loads) to heat water, but avoids discharging the battery. This portion of the operation is as desired.

 

[cristof]

This system at home works on lithium ion batteries. But it works the same elsewhere with lead batteries. For the system to start, 2 conditions are necessary, the 1st is the battery voltage. You can adjust this value according to your system. The second is that the battery must not be discharged, so the router can start before the end of the batteries charge using the current that the batteries do not use. The router gives priority to charging the batteries.

 

[Sparky]

Have you set a consumer price yet?

 

[Henrysangret]

With the help of a French technician, we created a solar router, capable of heating water thanks to the excess solar power supplied by the solar panels.
When the hybrid inverter is near the end of charging the batteries, and the inverter load is not at its maximum, if there is still the possibility of drawing energy from the solar panels, this energy is sent to the water heater, step by step, without discharging the batteries. We monitor the charging voltage of the batteries as well as the charging / discharging current of the batteries with a DC clamp . We use for this an ESP32 micro controller, a 40 amperes triac, a DC clamp .HST016L
the system has a web interface to access settings and controls. It is open source available to everyone. The project is in French language, the system works in 110V-240V 50/60 hertz. We have 2 version, "La Mini" with 1 triac output, and "La Maxi", with 2 triac output and one SSR output

Hey guys, fantastic , I have been looking for this fo a while, is a developed product for sal or can you share the details or design

 

[cristof]

Hey guys, fantastic , I have been looking for this fo a while, is a developed product for sal or can you share the details or design

Hello, it's an open source projet :https://github.com/bidouilleurs/routeur_solaire

 

[Henrysangret]

Thank you Cristof and members. I have been working on a simple design using low cost industrial PLC’s and monitoring the input and output current From the MPP controllers . I set a operating current window to not drop below a certain value and maintain a constant voltage at battery potential. As the battery obtains charge the PLC senses the charge level and redirects part of the energy to a 300 L hot water heater. I use that as a water preheater into my home system 150L hot water heater. That is a simplified version of what I am working on.