taylortops avatar image
taylortops suggested

Hot Water Heater Opportunity Load

A little something I'm cooking up...

I have a Raspberry Pi that is receiving MQTT data. I use that data to determine if there is spare power available in my system. The Pi is driving a buck converter into a hot water heating element and modulating drive current according to present conditions. I've provided the circuit diagram previously. Here's my dashboard:


MQTTdashboard displayHot Water Diversion
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matejs avatar image
matejs commented


This is exactly what I am looking for. I do not want to feed-in and I want to use spare power to heat water. I have started looking how to determine there is surplus power available (solar charger MppOperationMode, etc.), but I see you already have it all done.

Can you share more?

Thanks, Matej

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taylortops avatar image taylortops commented ·

For sure, I assume you saw this-> Design. Key idea is to monitor battery amps and gradually step up current to the heater. If the battery current goes negative, you step down the heater current. It rides conditions.

Happy to assist, just ask.

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frankmsc68 avatar image frankmsc68 taylortops commented ·
Hi taylortops,i am looking as well to switch axcess pv power to a hot water heater from the Multi RS Solar which i'm planing to buy.You have done grat work on this,thanks for sharing!Have you ever thought of selling a kit for people like me who don't want to mess about with programming?Would be great!Thanks again,Frank
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runout avatar image
runout commented

Interesting! I'm experimenting with something similar: 3-phase island-setup with an additional PV-inverter (SolarEdge SE5k) on AC-OUT of MP2 and did run into a few problems.

- determining the maximum possible energy harvest at the actual time

- dispatching power equally to the phases (not overloading one of the MP2).

- do use the harvested energy primarly for charging the battery.

I use an ESP32 and MCP23017 for switching loads (Heaters: 150W, 300W, 600W, 1200W; Boiler: 600W, 2000W).

ESP32 gets data from Cerbo via MPPT and runs a logic on that.

My logic tries to figure out how much energy is produced an used by various components. Then add some more (expected possible by the frequency of MP2-L1) energy and distribute that to the consumers (preferred the akku, then the boiler and last the heaters.)

There is some more logic involved to determine if the boiler is fully heated or if the room temperature is high enough. Still not sure what to do with all the excess energy in summer as I'm not on the grid.

- Accu is on DC 48V

- Boiler is 2kW on one phase, 600W on one other phase

- Heaters are symmetric on 3-phases. (Via a 3-phase rectifier and switched by opto-isolated IGBTs - 538V DC! - You might not want to do this if you are not an electrician!)

Interesting would be if it is possible to use the MPPT-algotithm of the Victron chargers in some way to determine the possible energy harvest because MPPT is limiting the power and might know by how much it reduces it. Does anybody knows more?

I did not publish the code yet as it is part of a monitoring system and would not run without that. The whole system is not documented well right now.

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