Ulrich Spizig's Smart Wall Switch Wants to Help You Stop Wasting Your Solar Generation
Living in a country where excess generation is sent to the grid for free, Spizig built a tool for making full use of it locally instead.
Electrical engineer Ulrich Spizig has built a smart wall switch which is designed to trigger devices only when local solar generation is online — offering an easy way to run devices only when sufficient power is available and make full use of harvested energy.
"In Germany small solar power plants (balcony PV [Photovoltaic]) [have] become more and more popular. With this small power plants you can generate 600-800 Watt and use the power you created on your own home grid," Spizig explains. "The downside is: whenever your solar PV generates more than you consume you will give the power away to your electricity company for free. There ought to be a better way than giving away power for free to the energy companies. How about measuring electric current consumption of several devices and switch them ON/OFF based on the power of your solar power plant."
That's exactly what Spizig's smart wall switch is designed to do. built around an Espressif ESP32-S3 microcontroller module, the board includes an ePaper touchscreen display as its primary interface, a Bosh SensorTec BME680 environmental monitoring sensor with equivalent carbon dioxide (eCO₂), temperature, humidity, and pressure monitoring, a real-time clock, bistable relays for powering mains devices on and off, and even a MEMS-based gyroscope and accelerometer — the latter offering earthquake detection as an added bonus.
"With this HW specs you can think about your possibilities," Spizig writes. "Switching certain power consumption devices based on external data. Measuring the current of certain power devices. Air quality monitoring. Display latest news/temp graphs. Display weather forecast received over Wi-Fi." An on-board HopeRF RFM95 transceiver further increases the device's capabilities, offering low-power long-range communication over a LoRa network.
Its key feature, though, is the ability to track energy generation and use that information to automatically switch relays to power mains devices on and off. For nations where excess micro-generation is sold back to the grid at a reasonable rate, such functionality may not be so tempting — but when it's a choice between sending your generated energy to the grid for no compensation or making use of it yourself, by topping up batteries or running storage heaters or the like, it's an easier sell.
Spizig's project is detailed on Hackaday.io, with limited design files available on GitHub under the reciprocal GNU General Public License 3.