Life’s roads often involve unexpected turns. Take the journey of Mehdi Ferdowsi, example. A single “random selection” during his master’s work led him into the field of power electronics. “I was considering who I should work with,” recalls the assistant professor of electrical and computer engineering at Missouri University of Science and Technology. “The advisor I picked happened to be a power electronics person, so that’s how I got into it, and I really liked it.”
Part of the appeal was the subject’s contradictory nature. “From one point, it is very simple—the elements are only inductors, capacitors, and switches—but in other aspects it’s very multidisciplinary,” Ferdowsi says. “You need to know a little bit about magnetics, circuits, control, digital signal processing—all of these come together in power electronics.”
Also complex are the situations that power engineering considers. Ferdowsi looks for ways to transform and control energy in systems that are constantly changing. For instance, how can the temperature of a room be maintained inspite of disturbances? “You open the door, you close the door, you open the window, [or] somebody walks in,” he says, listing some causes of temperature disturbances. “In electric systems, what if there is a sudden change in the load? How are you going to accommodate that and, at the same time, regulate the output voltage?”
Power engineering has applications anywhere there is electricity: televisions, computers, cell phones, power plants, even wall outlets. The field has been growing rapidly since Ferdowsi chose his path years ago. One particular application of power engineering has captured the attention of the public, investors, and even politicians: hybrid vehicles. As concern about climate change and greenhouse gas emissions has grown, more investments have been made in energy. Ferdowsi’s random choice has proven lucky; as he admits, “I happened to be at the right time and the right place to put proposals together.”
One of those proposals was to the University of Missouri Research Board, which provided the researcher with crucial support last year. “It was my first grant. Once I got it, I realized that now I can be relaxed, explore some other possibilities.” The award also eased much of the tension in Ferdowsi’s life: “Believe it or not, receiving a grant eliminates a lot of nightmares, especially as a young faculty member,” he admits. Two graduate students worked with Ferdowsi for nine months on this particular project—without the UMRB, there would not have been funds to sustain them. “Most of these students are international students," he explains, "so their visa status depends on the support and that depends on the proposal. Their life kind of depends on me.”
Just as important as the researcher here is the actual research. For years, engineers have been torn over the future of automobiles. Work on more efficient, environmentally responsible cars has been underway for decades, but researchers disagree on which energy source will lead the way.
“Batteries are good in terms of energy density,” says Ferdowsi of the amount of energy that can be stored in them, "but when it comes to power density, batteries are not so good. You cannot dump a huge amount of energy in them in a short period of time, so you would want to go after ultracapacitors or super-caps.” Traditional batteries use chemical reactions to create electricity. When the positive and negative terminals are connected through a circuit, electrons flow from the negative side to the positive, and trigger the chemical reaction. Electric double-layer capacitors, often called ultra- or supercapacitors, use two metal plates to separate positive and negative charges and store energy. This design makes a supercapacitor more efficient in releasing energy, since no chemical reaction needs to take place; it also allows the storage unit to charge and recharge very quickly.
Rather than choosing one storage system over the other, Ferdowsi’s work focuses on integrating batteries and ultracapacitors into a single system. This kind of hybrid would be effective in terms of energy density as well as power density. It could hold a large amount of power and also recharge very quickly—even on-the-go. This is vital in an energy-intensive system. For instance, an automobile’s needs are constantly changing, and if it runs out of power on the road the driver may be miles from the nearest filling station or outlet.
Ferdowsi explains the sequence as follows: “When the vehicle is accelerating, you need a huge amount of energy in a short period of time, and that’s where you are going to use your ultra-cap; when the vehicle is in cruising mode, there’s not much energy needed, so you can use your battery energy storage system." These new composite designs could not only change the way power is stored and used, but also modify the way it's gathered: “We have three or four seconds of braking—there’s a huge amount of kinetic energy of the mass of the vehicle that has to be returned to the energy storage system. You may want to recharge your ultracaps that you are discharging during the acceleration.”
One of Ferdowsi's goals is figuring out how to regulate the load of a hybrid motor and control the system, but there are limitations to his work. Research is currently in a model-heavy phase because the battery technology to run physical experiments is still being developed. “When it comes to batteries or ultracaps, we assume they are kind of ideal blocks. You can do whatever you want with them, just draw them on the board, and say ‘this is how much current you can draw out of it,’ and that’s fine. And to this date, there is not a very good, accurate model for these kinds of chemical devices,” he notes. To fill in these “ideal blocks,” many different specialties must converge.
“The whole campus is pursuing a battery-testing center, which will develop different battery models,” Ferdowsi says. This center is bringing together representatives from many different departments: material science, electrochemistry, and, of course, Ferdowsi’s field of electrical engineering. Even students have a chance to get in on the fun; Ferdowsi teaches a class on electric and hybrid vehicles, focusing a good portion of the course on batteries. As he puts it, “whatever our outcomes have been throughout this particular project or similar projects will be directly offered to students as course material, and vice versa: we push them to see what else is there and what else could be explored.”
Any research on energy storage completed at the center also stands to improve research throughout the university: “Simulations are sometimes not very realistic, and we don’t even realize they aren't realistic,” Ferdowsi explains. “Sometimes, if there’s a real battery, instead of a simulation block, your battery could get too hot, or there might be packaging issues.” More research and development of storage devices will help avoid these problems and benefit the general public with greener, more efficient, and less expensive electric systems in automobiles.
Benefits of electric or hybrid electric vehicles are already well known. Improved fuel economy, diminished greenhouse gas emissions, and reduced need for expensive fuel imports are prominent among them. Ferdowsi thinks the benefits of plug-in hybrids could stretch beyond these environmental and financial concerns, changing the way we use our power grid: “on average, we only use our vehicles one hour a day. For the remaining time, the vehicle could be plugged in, and could actually be sharing its energy storage capability with the power grid.” The larger ultracapacitor storage systems have power to share, and they gather their own electricity during braking. Sharing that electricity could improve the stability of a local power grid; it might also make vehicle owners “shareholders in the energy market,” able to buy power before driving to work or school, then selling it back when everyone is home for the evening.
Finding a pathway to this vision is not easy, as Ferdowsi himself points out: “We are talking about millions of vehicles, which are not only basically independent systems when they are unplugged but also part of a larger system when they are plugged in. So there are many control and stability issues.” Those issues have been the focus of his work since 2007, when he wrote about them in a National Science Foundation CAREER proposal—one that resulted in an award that stretched through January 2010. This kind of support is necessary: “It’s quite a challenge--how to evolve from the legacy of infrastructures we have had and to move towards combined and interacting infrastructures.”
These vehicles and infrastructures are the stuff of dreams, but Ferdowsi and his colleagues are advancing confidently towards them. Someday soon, the rest of the world may see their dreams come true.