Because turning around and going back is always helpful, Reverion GmbH reports it’s developed a compact, fuel-call-based, biogas power plant that can remove tons of atmospheric CO2 and bottle it, use surplus solar and wind energy, and operate in reverse to store biogas or green hydrogen, as well as generate power. Its high-temperature fuel cell technology converts biogas or hydrogen into electricity, and switches to electrolysis mode to make green hydrogen or methane (Figure 1).
The company’s solid-oxide fuel cells (SOFC) electrochemically convert energy stored in fuel gas into electricity, while in reversible operation, they act as solid-oxide electrolyzer cells (SOEC). Its containerized, transportable, biogas units are reported to achieve 80% electrical efficiency during well-insulated operations at approximately 600-750 °C by employing a high level of system integration, which lets it exploit all potential optimization from interactions among its different process sequences. Reverion reports its first biogas power plant prototypes achieved 100 kW output. It adds that series production was expected to start in 2024, and that larger 500-kW output systems are already in development.
To coordinate its sensors, monitoring and control functions, Reverion relies on PC-based control from Beckhoff and its TwinCAT software, networking, communications and visualization technologies. The modular biogas plants use two computers, including CX2043 embedded PC as its main control computer, and C6930 control-cabinet, industrial PC (IPC), or C6030 compact IPC in the future.
“The idea of using two IPCs to communicate with each other came up during system development as the biogas plant’s complexity increased. This approach made it easy to scale up controller performance, and adapt it to our platform,” says Sven Bettendorf, application engineer at Reverion. “Its redundancy also improves operating reliability.”
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The biogas plant’s hardware consists of more than 450 EtherCAT terminals serving approximately 1,200 sensors and 300 actuators. These include more than 220 analog terminals, such as EL3024 (4-20 mA), EL3064 (0-10 V), EL3208 (Pt100), EL3255 (potentiometer) and EL3318 (thermocouple) analog input terminals. Data from all of these I/O is evaluated via TwinCAT, which can also map complex systems. In addition, TwinCAT’s communications allows sensor data to be easily and flexibly transferred to higher-level databases via TwinCAT 3 IoT communication (TF6701) and MQTT protocol.
“TwinCAT supports object-oriented programming, automatic unit testing, and a modular software architecture, which are advantageous for extensive and continuously developed control programs,” adds Julian Schauseil, senior software developer at Reverion. “This makes it easy to introduce changes without creating errors in the rest of the program. Necessary abstractions can also be implemented, which makes structuring easier by encapsulating functions, such as controller and analog value processing.”
To monitor data for control, as well as development and billing metrics, Reverion also developed its own HMI extension that’s supported by TwinCAT. “TwinCAT 3 HMI engineering (TF2000) facilitates rapid application development, and results in an easily expandable HMI,” adds Bettendorf. “What’s more, TwinCAT PLC’s openness and Beckhoff’s training were huge help.”
