The doomed Apollo 13 space mission was one of the first instances where the public understood that performing experiments in a simulation model could save a system. The three astronauts on board would never have survived if not for engineers who ran simulations and predicted a course of action that rescued the mission.
Carolina Distinguished Professor Roger Dougal recently embarked on research to develop new technologies for digitally replicating the process of delivering power and energy to mission systems.
Dougal and his team were recently awarded a three-year, $10 million contract from the Office of Naval Research (ONR) for his project, “Digital Twins for Navy Power and Energy Systems.” Columbia-based Integer Technologies will serve as subcontractor.
“Our group has been developing tools for the simulation and design of advanced power systems for many years, and digital twins are a logical next step beyond simulation models. You could think of digital twins as simulation models that are always up-to-date relative to the corresponding real system,” Dougal says.
Digital twins are virtual replicas of real systems that experience all of the same operating conditions as the real system. Dougal’s research will focus on developing a ship-like electrical grid testbed for developing and evaluating component and system-level digital twins. It is a natural progression of the expertise developed over many years in modeling and simulation tools for advanced power electronics systems.
“Our first research project on simulation tools for electric ships was funded by the ONR in 1996. The tools and technologies have evolved, and as the world’s capability to use these tools has evolved, we’ve discovered new opportunities to stay on the leading edge,” Dougal says.
Predicting the maintenance needs to improve the availability (“up time”) and reliability of systems is a primary use of digital twins in industry today. Dougal says the next interesting use case will be improving the performance of systems by managing the delivery of power and energy in real time.
“This involves answering two questions,” Dougal says. “Given a particular set of equipment, how can we operate it to best effect, sometimes in extreme ways? And, if we have digital twins that can predict operational limits, how close to the boundary can we get without stepping over the edge?”
Dougal’s digital twin technologies address the management of power and energy in all forms. This includes the transformation of energy from one form to another, delivery of electric power to equipment when and where it is needed, and the management of associated waste heat. Today’s deeply integrated energy systems benefit from management via digital twins.
“The transformation from mechanically propelled ships to electrically propelled ships are a bit like the transformation from gas-powered cars to electric cars. In the old cars, if you had a problem with the brakes, other parts probably still worked. But if an electric car’s battery doesn't work, it actually affects the braking system. Everything depends on the power and energy system, and a problem in one area likely affects the entire car,” Dougal says.
The electric ship’s benefits are comparable to an electric car. Instead of separate power sources for different functions, an electric ship can simply shift power back and forth between propulsion and mission systems, such as radar. The use of digital twins can improve the way that power is shared between systems to improve their performance and minimize competition between the systems. “Part of our purpose is to build tools to look ahead and make wise choices in the way we configure the power and energy components of the system to meet all of the mission requirements,” Dougal says.
Dougal and other researchers who have studied electric ship systems for years have developed design concepts that will be replicated in an on-site reduced-scale power and energy testbed for digital twins. He will use the testbed to evaluate the performance of digital twins and the degree to which digital twins will be useful in improving the management of power and energy delivery.
“We will configure our power and energy testbed so it’s similar to some of those ship systems but at a smaller scale,” Dougal says. “Instead of 100 megawatts for a real ship, our testbed will be more like 100 kilowatts. But that is big enough to involve interesting power and thermal problems that are representative of the physics and complexity of a ship system without actually operating at the higher power level.”
According to Dougal, a naval ship can consume as much electric power as a small city and produce a significant amount of waste heat that must be removed to maintain the system’s operation. If a fluid pump responsible for cooling a power converter fails, functions such as the propulsion motor cannot achieve full power, or the radar system will not operate. Digital twins can be used to understand the operational limits of the system in its compromised state, and then operate the system close to its current limits.
“It’s different than the old way of operating. In the past, if a part was overheating, it simply had to be shut down. You didn’t have any way to know what else you could do about the problem,” Dougal says. “But with new reconfigurable power systems, and the use of digital twins to understand what is possible, there will be opportunities to operate with reduced capability and to route power around a trouble area and still execute a successful mission.”
Dougal says the digital twins development will be incremental, with some benefits realized quickly and others over many years. The process will be similar to how consumer electronics and apps constantly improve. There will be plenty of opportunities for upgrades since Navy ships typically see service for 30 or 40 years.
“There will be many other applications of the digital twin technologies, not just naval applications. For example, the same approaches can be used to manage residential or industrial microgrids,” Dougal says. “Success will be measured in how these digital twins improve the effectiveness of power and energy delivery.”