A retired French electronics and telecommunications engineer, André Buhart, has released comprehensive open-source plans and software for a 'solar router' designed to optimize residential photovoltaic (PV) self-consumption. This innovative do-it-yourself (DIY) system, dubbed F1ATB, allows homeowners to direct surplus solar power to various electrical devices, significantly reducing their reliance on grid electricity and enhancing the economic viability of their PV installations.

The F1ATB system, detailed on Buhart's website, provides a shopping list of components and step-by-step manufacturing instructions, making it accessible even to non-expert DIY enthusiasts. "DIYers will have no problem," Buhart told pv magazine France, emphasizing the straightforward electrical wiring and assembly. The modular architecture is a key feature, allowing measurement units to be placed near the electricity meter while control modules can be situated remotely next to the appliances they power, communicating via Wi-Fi. This flexibility has contributed to a burgeoning online community, with some 4,400 Facebook group members, 20,000 YouTube subscribers, and 1,700 forum participants actively engaging with the project.

Component costs for the F1ATB system are remarkably low, ranging from approximately €100 ($117.7) for a basic kit accessible to non-technical users, down to about €30 for experienced builders. The system relies on standard, readily available parts such as Shelly modules and ESP32 microcontrollers. In France, no special authorization is required for its installation. The router's core functionality involves real-time power measurement at the individual meter, data processing, and precise control of devices absorbing excess solar power. It supports both single- and three-phase configurations.

Buhart has developed seven distinct measurement methods, including reading data from Linky smart meters, using current probes, or interfacing directly with solar inverters like those from Enphase. This data is then transmitted to an inexpensive ESP32 microcontroller, which hosts a web server for historical data logging. Device control is managed through electrical components like triacs or solid-state relays (SSRs), with careful attention to oversizing for optimal performance and heat dissipation. For instance, a 3 kW water heater would typically use a 60-amp SSR. The system employs 'multi-sine' and 'sine train' approaches for power control, avoiding traditional sinusoidal slicing that can cause network interference.

Users access real-time data, including injected power, consumption, and historical trends, via a web interface accessible from any device, without requiring a dedicated smartphone app. Buhart has also developed a 3D-printable local display unit that provides immediate visual feedback on power status. The management software is freely downloadable from the F1ATB website. The project originated from Buhart's personal need to optimize his own PV self-consumption, recognizing the water heater's potential as a 'super battery' for daytime energy storage. User requests and ongoing development continue to shape the system, though industrial production and certification are not currently planned.