Opportunity Load Control

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taylortops asked Sep 20, '22

Opportunity Load Control

Here's my current setup. I'm getting ready for summer (Australia) and will soon have more solar than I can store, as well as hibernating the wood heater till next winter.

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.

This Raspberry Pi setup responds to MQTT data to drive a buck converter which will sink spare power into my water heater. It positions itself as lowest priority, modulating the buck current against: MPPT state, PV voltage, battery current, AC draw and so on. It never consumes battery power for heating purposes.

You could implement this idea without the Sorel TDC but you'll need sense water tank temp using a cheap analogue or digital temp probe.

Here's a pic:

And remote dashboard for same here: https://community.victronenergy.com/idea/160811/hot-water-heater-opportunity-load.html

Here's the mini TFT display giving me a summary of what's going on:

MQTT Hot Water Diversion

whoswhointhezoo-new-dhw-tt-adacdrawio-3.png (201.5 KiB)

pxl-20221130-032521029.jpg (679.7 KiB)

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Modifications Space

Node Red Space

Answer 1 · 2023-03-27T08:25:22Z

usernamepasswordbs answered · Mar 27, 2023 at 08:25 AM

Very interesting. The fire symbol on the bottom left; I'm guessing it's an alternative heat source for the water tank? If I have no other heat source can I simplify the circuit?

I would like to do something similar using the existing AC steatite element in my tank or do i need a DC heater element?

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taylortops commented · Sep 11, 2023 at 06:21 AM

You can do either DC or AC. I chose DC so I didn't unnecessarily load up the Inverter and also I can avoid come conversion losses. A 48V/24V element is not expensive.

Yes the fire symbol is Wood Stove. The controller shunts water through a water jacket and then the hot water through a coil in the hot water tank. This mode dominates in winter. In summer, when there's more power than the batteries can hold, I shunt current through the tank's 48V element. My circuit really just focuses on that second source.

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Answer 2 · 2023-09-11T06:29:35Z

taylortops answered · Sep 11, 2023 at 06:29 AM

This is the Buck Converter I used:

https://www.aliexpress.com/item/4000353761772.html

screenshot-2023-09-11-at-162821.png (759.2 KiB)

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Answer 3 · 2023-09-14T07:07:29Z

usernamepasswordbs answered · Sep 14, 2023 at 07:07 AM

Thanks for the details. However, I have now installed a 3 element 230v heater which is combined with a Dingtian relay box. The relays switch on element by element via node red and all is working pretty well thanks to a couple of members on here and on NodeRed.org.

I know there are more losses and more load on the inverter using an AC heater with a DC source but then in the winter not enough solar panels so I will be using mostly AC directly from the grid to heat the water, so swings and roundabouts for me.

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