Solar Export Limiting

Backyard solar

Cheap solar project to offset quiescent energy use when the house is unoccupied and there are no other useful options for using the energy.

e.g. hot water good, no car charging, no lights, towel rails, washing, drying etc

Hardware

Node-Red flow (See Kick Dump.js)is kicked to regulate the Dump Load Dimmer switch.
var absdp = Math.abs(ShellyEM - DumpDeadBand);
DumpPower += (absdp * DumpPgain);

Solar Dump Power HTTP client 25-08-2025

  • Two Hubitat Elevation C7 hubs
    You can see the hacked driver for the Zigbee Tuya Dimmer Hacked a Hubitat community driver by "Matt Hammond" to get it working with the _TZ3000_kvwrdf47 from AliExpress

  • eWeLink CUBE running Node-Red in Docker. Seems quite good at more math intensive cyclical workloads. Keeps Hubitat load low and more responsive.

  • Dual 100W channel dimmer both in parallel driving a 280W heat lamp. Stays perfectly cool at full power with heat sink added to Triac's

  • AliExpress part Tuya Dimmer Hacked a Hubitat community driver by "Matt Hammond" to get it working with the _TZ3000_kvwrdf47
    def cfg = [" _TZ3000_kvwrdf47": [ numEps: 2, joinName: "Tuya Zigbee 2-Gang Dimmer module" ]]
    See Greenway Tuya Zigbee dimmer module.groovy

Function

  • Stop solar export in low load situations, which does happen when the house is unoccupied
  • The 2 second update

You can see below the dump load a $5 lamp regulates the load so I DON"T export hardly any power. While maintaining near peak solar utilization.

We produced 1.119kWh dumping 0.217kWh with a single panel generating 371 Watts so far today we have only exported 2.4 Watt out of 1.119kWh generated

1 Like