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High Efficiency Hybrid Systems

October 2, 2017

High Efficiency Hybrid Systems: Exploring New Ways to Move with Drs. Chris Atkinson and Grigorii Soloveichik

Drs. Atkinson and Soloveichik discuss their backgrounds, why they came to ARPA-E, and how a new approach to powertrains could boost transportation efficiency.

  Drs. Chris Atkinson and Grigorii Soloveichik

1. Tell us a little about your backgrounds. How does your previous experience provide insight into your work at ARPA-E?

Chris:
My position at ARPA-E represents a third career for me—over the past 26 years, I have been an academic, a consultant and now a Program Director at ARPA-E. I specialize in increasing the efficiency of energy conversion systems, ranging from engines, to vehicles, to HVAC systems. My educational background is in both mechanical engineering, with a Sc.D. from MIT, and chemical engineering, as an undergraduate in South Africa. Through my experience in the development of advanced engine controls and hybrid-electric vehicles, I have come to realize the complexity—and urgency—of building highly fuel-efficient propulsion systems for a range of automotive applications. Our nation’s energy security and economic success depends critically on improving the energy efficiency of the transportation sector while also reducing emissions.

Grigorii:
I am an inorganic/organometallic chemist by training, but I have worked mostly in the areas of catalysis and electrochemistry, which I find endlessly fascinating. After graduating from Moscow State University with my Ph.D., I joined the Institute of Chemical Physics of the Russian Academy of Sciences. I moved to the United States in 1993, and worked in academia (Boston College), a small business (Moltech Corp., now Sion Power) and a large company (GE), where I became a U.S. citizen. All of these experiences were extremely interesting, but only at GE Global Research did I have the opportunity to work on a true multitude of projects—homogeneous catalysis, heterogeneous catalysis, electrosynthesis, hydrogen production and storage, batteries, fuel cells and flow batteries. It’s during this time that I completed my move from classic chemistry to electrochemical energy storage and conversion. 

2. Why did you decide to come to ARPA-E?

Chris:
I attended the first ARPA-E Energy Innovation Summit in 2010 as an interested outside observer and was immediately struck by how confidently ARPA-E tackled thorny energy problems head-on. I saw first-hand how well regarded ARPA-E was, both within the United States and internationally, as a developer of highly innovative and uniquely important energy technologies. It was only after attending the GENSETS workshop some four years later that I finally decided to apply for the post of Program Director. Being at ARPA-E has been the highlight of my professional career, and I continue to be impressed by the successes of the teams we fund in developing a wide portfolio of energy technologies.

Grigorii:
It feels like I became a Program Director by chance. Working as a principal investigator on an ARPA-E-funded project, I attended the agency’s annual Summit, where another Program Director with whom I worked together at GE encouraged me to apply. At ARPA-E, I feel I can make a much bigger impact on the energy landscape by developing and launching multi-million-dollar programs, realizing my vision while improving U.S. energy security and competitiveness through the work of many highly motivated, bright and talented teams. It also helps that I immediately liked the friendly ARPA-E team and its supportive atmosphere. 

3. You’re working on combining some of the technologies in battery-electric vehicles (BEV) with those powered by fuel cells (FC) and more traditional internal combustion engines (ICE)—why is ARPA-E potentially interested in this technology area? 

Grigorii:
ARPA-E’s primary mission is the advancement of early-stage energy technologies with potentially huge benefits for America’s economy, security and environment. We’re interested, on one hand, in supporting a potential fusion between battery-electric powertrains and fuel cells, because we believe it’s possible to combine these technologies to address their respective challenges of total on-board energy and power presented. We also think it’s possible to develop long-range vehicles with efficiencies substantially exceeding the current state of the art. 

Chris:
The same applies for BEV-ICE combinations. As on-board battery chargers or range extenders, fuel cells and combustion engines can both be designed to perform at optimal conditions, thus reaching maximum possible efficiencies. Some of these configurations exist today in various forms, but both also present significant opportunities to create a better experience for the user while saving large amounts of energy.

Grigorii:
For the BEV-FC component, we’re looking at using liquid fuels—which can be stored more easily and safely than pressurized gaseous fuels—to power a fuel cell stack capable of recharging a battery. The battery would then power an electric motor to move the vehicle. Today’s hydrogen fuel cell vehicles use smaller batteries to assist the FC stack, and this doesn’t fully capitalize on the power and performance characteristics of the battery. There are also challenges with hydrogen infrastructure that have limited adoption of FC vehicles. By enlarging the battery and using a liquid-fueled fuel cell capable of meeting or exceeding performance of a hydrogen cell, it’s possible we could open up this hybrid combination to many more applications, including auxiliary power units for aircraft or heavy trucks, unmanned vehicles, or high-performance primary propulsion for consumer vehicles.

Chris:
The story is similar for internal combustion engines, where we’re looking at taking conventional hybrid powertrains to the next level by pairing a relatively small battery with an ultra-high-efficiency engine capable of extending the vehicle’s range far beyond that of hybrids or BEVs today. We are interested in novel engine architectures, engine configurations and emerging technologies such as integral engine and electric machine design.

4. What gaps currently exist in this technology, and what are some areas for advancement? 

Grigorii:
Highly efficient hydrogen fuel cells have struggled due to their limited power output per cell area and the absence of hydrogen refueling infrastructure. It’s hard to imagine something like a sports car powered by hydrogen, as it would require an enormous cell stack and have few places to refuel. On the other hand, batteries, especially lithium-ion cells, are capable of releasing large amounts of power on demand, but with limited energy storage ability. With internal combustion engines, energy is limited only by the size of the fuel tank, but high power output typically comes at the expense of reduced efficiency. 

We’re looking at taking the best aspects of BEVs—the high power output and good round-trip efficiency—and combining those with the complementary benefits of liquid-fueled fuel cells or advanced combustion engines, for which the vehicle driving range is defined only by the size of the fuel tank. By having these hybrid systems (either battery and fuel cell, or engine and battery) highly integrated and closely controlled to deliver the best power and performance characteristics, overall vehicle energy consumption can be significantly reduced.

To realize this vision, it is necessary to develop novel fuel cell stack designs capable of starting up quickly and delivering high power using liquid fuels, as well as advanced, highly capable internal combustion engines with efficiencies well above present-day levels.

5. Where would these solutions fit into a broader or longer-term solution? 

Chris:
Transportation consumes over a quarter of the energy and most of the petroleum used in the United States, so it has long been an area of intense interest for ARPA-E. While batteries, fuel cells, and internal combustion engines have all made impressive leaps in efficiency and performance in recent years, developing new energy efficient, low-emissions technologies to leverage their greatest advantages in a combined or hybrid configuration presents a huge opportunity to generate significant energy savings across our current transportation system, while potentially using existing refueling infrastructure.

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