Remote Monitoring and Control
Rezin reports that USEMCO's Bi-gester uses two PLCs to control temperature, level and pressure reported by sensors, as well as manage timers and logic settings. However, as more farms put in more tanks, the sensor inputs and PLCs that users and USEMCO must monitor and manage is likely to multiply quickly, and personally visiting all these small, far-flung farms will become impractical.
To solve this challenge, USEMCO is linking the PLCs on its digesters to 2005CD industrial, virtual private network (VPN) routers from eWon, which provide secure, encrypted, remote access via cellular modem or via a local Ethernet connection, as well as monitoring, alerts and alarms, data logging and control. USEMCO and its client also use eWon's Talk2M Free cloud-based infrastructure to connect to the remote routers. Talk2M is also designed to manage and simplify documentation, device management and user authentication, and kick out any unauthorized entities. Enhanced data collection is achieved by several flexible options, such as exporting comma-separated-values (CSV) software files to an application programming interface (API). As a result, 2005CD's remote login capability allows users to monitor, adjust and reprogram Bi-gester's PLCs at a distance, which means USEMCO's technicians don't have to visit each local site to monitor, troubleshoot, maintain and adjust a digester's operations. And, besides only allowing access to predetermined devices, eWon's onsite routers can also be equipped with a physical key switch, so users can turn their VPN on and allow remote access when desired.
"Now, when any of the digester's temperature, level or pressure sensors goes out of whack, the router sends a text message or email to the user's smart phone, tablet or PC and to USEMCO's office as well," says Rezin. "This also means the farmer can control equipment in the tank building and digester and in the control and generator rooms from his laptop and smart phones, and we can do it as needed."
Likewise, eWon's routers are combined with the virtual network computing (VNC) capability of the digester's operator interfaces, and this allows remote users to log into the display and navigate the screens to see how the digester is performing (Figure 3). Collecting data to build a database helps evaluate critical digester operations and determine necessary changes. Digester temperatures, biogas flows, biogas pressures, generator status, power generated, tank levels, water temperatures, pumping totals and room temperatures are just some of the data files being collected.
Next, the routers are programmed to email status updates eight times a day, and send email and text messages if alarm conditions exist. These messages are sent to multiple individuals, depending on the type of alarm. Along with the data-collection and alarm functions, other software polls the digester's electric meters and posts data to the web. This allows the farmer, generator-service technician or other users to view the generator's kilowatt output and other data.
"Our engineer, Mike Harris, wrote the code, so our PLCs could run through eWon's routers, and this gives us the access to tweak parameters and troubleshoot remotely," adds Rezin. "The routers talk to eWon's server, and this allows us to establish a VPN between each digester and our PCs at USEMCO. In the future, we'll be able to monitor the temperature, pressure, flow and other key parameters of all our customers' digesters from our office. We also want to add eWon's routers and remote monitoring capabilities to the 8,000 pump stations we already have installed in the field.
"Where we previously visited a user's site every couple of days, we can now go just couple of times per month. And all those former two-hour roundtrips each become five-minute jobs. We estimate that remote access will save about 80% on our visits, which also means we can grow USEMCO faster because we don't need as much new staff. In the past, where we might need one full-time technician per farm, we can now have one monitor and manage 10 or 20 digesters."