Sustainable and efficient

Without energy, nothing works. That's why it is so important to get our energy from sustainable sources and make sure they operate as efficiently as possible. Model-based control concepts now enable small and medium sized biomass combustion plants to get the most out of their equipment.

Energy is one of our most valuable commodities, but the past few months have made it clear just how broad of an impact it has on our everyday lives. As we seek solutions to skyrocketing costs and fossil fuel dependency, all eyes are on renewable energy. Not only does sustainable energy protect our environment, it is also readily available in a variety of forms around the world.

In addition to the big three – wind, water and solar – biomass combustion is an eco-friendly option for generating power. One of the biggest concerns for operators of biomass power plants is efficiency: How much of what goes into their process comes out in the form of useful energy? On top of that, they are under pressure to reduce their plants' emissions. To achieve both of these goals, the combustion process must be perfectly tailored to the materials being used.

This is precisely where Seamtec, an Austrian specialist in innovative control technology, comes in. "We help the operators of district heating plants optimize their systems and improve efficiency," explains Seamtec founder and CEO Peter Reiter. "We do that through a holistic approach that incorporates the electrical and control system, the boiler and also combustion and mains control. And we integrate consumer systems into the mains via custom telecontrol technology."

Particularly in smaller biomass plants, the conventional approach is still to regulate parameters like pressure and temperature using PID controllers, which rely heavily on assumptions and general rules of thumb for parameter settings. "That results in control loops that are generally stable, but not optimal," explains Reiter. "The combustion process is influenced by many different interdependent variables. There's simply no way to represent that complexity with a PID controller."

In the search for new solutions to further increase the efficiency of small and midsized biomass combustion plants, Seamtec therefore looked to their larger counterparts for inspiration. "There, model-based control control is already being used with great success," says Reiter.

In a multivariate system like a combustion plant, classic PID controllers deliver mediocre results at best. "The actual values fluctuate strongly, and can deviate significantly from the desired target values," explains Reiter. "That forces you to set very conservative target values." With model-based control, there is very little deviation between the target values and the actual values. "You can set your targets much closer to the system limits and make the overall process much more efficient," says Reiter.

Model-based plant control typically takes considerably more time and effort to implement than a solution with PID controllers. Until now, smaller plants didn't get enough return on this added investment in development to make it profitable. "Our goal was to find a way to implement model-based control cost-effectively for smaller operations ranging from a few hundred kilowatts to a few megawatts of power," Reiter says.

As its partner for implementing this idea, Seamtec chose B&R. "We've enjoyed a lot of success through our close cooperation with B&R, which began in 2009. When we first approached them with this project, it quickly became clear that the MATLAB/Simulink tool integrated in their development environment was exactly what we needed," explains Reiter. "We knew right away that B&R would be our partner of choice for this project as well."

Using a test system, developers from the two companies worked together to develop the control concept for Seamtec. "The path to the final design wasn't always a straight line, but with B&R's support we were able to clear all the stumbling blocks that came up along the way. Even with the relatively small size of our company, we received first-class support that always got us to a solution quickly," says Reiter.

The control solution based on MATLAB/Simulink comprises modules for each of the processes involved in a biomass combustion plant. Seamtec's developers begin by diving deep into a plant's process behavior and mapping it as realistically as possible in Simulink. That allows them to design a control algorithm that is tailored to the plant and can be tested and tuned in a simulation.

Seamtec's modular control system is based on B&R hardware and software. B&R's Automation Studio engineering tool features B&R Simulink Target, an integrated interface that makes it easy for developers to import the control algorithm with just a few clicks.

One of the biggest benefits of model-based control is that all the testing can be performed in a simulation to detect errors early, when they are cheaper and easier to fix. It's no longer necessary to run tests on the real system and risk damaging expensive equipment. The same approach can be used to tune all the process parameters. Automatic code generation considerably reduces the programming effort.

Seamtec has demonstrated the potential of model-based control for smaller heating plants – for example a district heating plant with three parallel pumps: "We implemented an interconnection strategy for the pumps that turns on one, two or all three pumps depending on the optimal operating point," Reiter explains. "That allowed us to maximize the efficiency of the plant in the corresponding range, while minimizing energy losses."

Seamtec sees potential benefits of model-based control in other sustainable methods of energy generation as well. "We've received a number of interesting inquiries from the hydropower sector," notes Reiter. "That's another area where model-based control would be right at home."

The topic of sustainability and solutions for more conscientious use of resources have been top priorities for Seamtec since its founding in 2009. "Earth, nature, region, people – these things are close to our hearts. Improving wellbeing through sustainability calls for intelligence and know-how. These values are our constant motivation to find ways to optimize plants for sustainable energy generation," says Reiter.

Author: Carola Schwankner, Corporate Communications Editor, B&R