Comprehensive photovoltaics system (600 W) with battery based energy spreading, control and visualization.

The complete system consists of the following subsystems:

1. 600 W photovoltaic system: two 400 W panels, one Hoymiles HM-600 inverter
2. OpenDTU: Really awesome ESP32 based WiFi frontend for the HM-600
3. Volkszaehler SmartMeter EHZ: Another awesome ESP8266 Wifi frontend to gather energy information from an EHZ energy meter via its infrared interface
4. Data logging and visualization: Dockerized MQTT data brokerage and Grafana visualization with the support of InfluxDB and Telegraf
5. Battery extension of the PV system: Two Victron SmartSolar and two Renogy 24 V / 25 Ah batteries for spreading the daytime solar energy over night
6. Optimizing PV yield by energy spreading: Dockerized Python script optimizes the yield by battery energy spreading targeting basic load coverage

I started step by step with 1. - 4. and then decided to extend the little photovoltaic system by batteries (5.) and programmed a python script for optimizing (6.).

• Two monocristalline solar panels TrinaSolar VertexS TSM-405 DE09.08

• One dual-DC/single AC 600 W inverter Hoymiles HM-600

I mounted some bracket stands

As the Hoymiles HM-600 inverter is not equipped with a general WiFi interfacee but instead with a proprietrary wireless interface you'd need for remote access to the inverter a so called Data Transer Unit (DTU) from Hoymiles which you'd get on the market for appr. 50 € - 100 €. It only works via a Hoymiles server where you'd have to register etc.

Contrary to the commercial solution there are two open source solutions available which cost you ca. 30 €:

• Ahoy-DTU
• OpenDTU

A really good comparison of both projects (...sorry, German ;-) https://blog.helmutkarger.de/balkonkraftwerk-teil-8-opendtu-und-ahoydtu-fuer-hoymiles-wechselrichter/ Both projects are really awesome. The story of development reads quite exciting here.

However, I decided for OpenDTU and followed the instructions on OpenDTU and ordered four basic components:

• NodeMCU-ESP32 Development Board @ 11 €
• nRF24L01 Wireless Transceiver Module @ 2 €
• 100-240 VAC to 5 VDC / 600 mA converter @ 9 €
• ABS Housing 83x58x33 mm @ 10 €
• breadboard, cable, solder tin @ ca. 5 €