Building Your Dream in America
(Written by Andrey Gunawan and Pourya Shamsi, editors of IEEE TEI Newsletter)
This article is based on an edited transcript of the IEEE Transportation Electrification Initiative and Arizona State University’s (ASU) LightWorks Lecture Series given by Micheal Austin on October 28, 2013 at the ASU SkySong in Scottsdale, AZ.
BYD stands for Build Your Dreams. It is a company founded in 1995 by a research scientist, Chuanfu Wang, who is now the Chairman of the company. In 2002-2003, BYD acquired a Chinese State-owned auto manufacturer (and thus the manufacturing license) and launched vehicle development. Their vision was to electrify transportation. In 2008, they launched the world’s first mass-produced, plug-in electric vehicle, the F3DM, and has since launched solar panel development and manufacturing, electric buses, electric taxis and other high-utility, long-range electric vehicles.
|Figure 1 - 40-foot Z-bus, the zero emissions electric bus solution (used with BYD permission)|
Figure 1 shows the first electric bus that the company launched. It has two in-wheel hub electric motors; no transmission; no engine; and it has 324 kWh of environmentally-friendly, fire-safe, BYD Iron-phosphate batteries. The bus drives 155 to 200 miles depending on the route profiles, driver behaviors, air-conditioning/heating and other parasitic loads, which equals about 24-hours of service if operated in an LAX (Los Angeles International Airport) duty cycle or as similarly reported at the New York Transit Manhattan bus lines. The buses would then be charged only-at-night in 3-5 hours depending on the state-of-charge when the bus pulled into the garage.
News releases state that, Los Angeles’ MTA ordered 25 of these 40-foot, zero-emission, silent buses. Long Beach also ordered 10 similar 40’ buses for their Long Beach Port, Passport route, which will also have inductive charging at the Queen Mary stop and Port passenger loading areas. This means that there will be an inductive pad embedded in the asphalt at the Queen Mary stop, and a secondary coupling pad mounted on the bottom of the bus which is separated by a fixed 11 inch gap (and no mechanical parts are needed to reduce the coupling gap). The inductive couplers transfer 50 kW of power at ~90-91% efficiency.
The BYD e6 electric car (in Figure 2 below), was launched in 2010 and has been qualified in the U.S. as is a high-utility, long-range electric fleet vehicle. This five passenger vehicle has up to a 187 mile range, top speed of 90 mph, and again, it is zero-emissions and uses the same size BYD Iron-phosphate batteries modules that the buses use.
|Figure 2 - Zero emissions car/taxi solution, the BYD e6 (used with BYD permissions)|
All vehicles mentioned have integrated chargers on-board and the operators just deliver AC directly to the vehicle, which makes for very low infrastructure costs. Transit companies have been evaluating these electric buses from frigid Montreal (presently) to Hot-Miami, from sprawling Los Angeles to heavy-dense Manhattan traffic. The New York’s Metro results showed 0.3 hours per % SOC, translating to 30 hours of operation per full charge. These uninterrupted operational hours are more meaningful in a busy city like New York, as routes and speeds travelled tend to be short in distance but long in duration. When contrasted to diesel bus technology, electric buses are far more efficient in energy consumption because diesel engines are still idling when in heavy or stopped traffic.
The inverters on-board the buses and taxis are also bi-directional, which means that not only can they charge from the AC, but they can be energized to discharge 220V AC with 30 to 40 Amps, so the cars and buses can become a mobile generators (see Figure 3). One can charge the bus literally with a taxi, or charge a bus with a bus (e.g., “stranded vehicle assist”). Vehicle-to-load is also very simple, but vehicle-to-grid is more complex because a partner utility company is required to send control signals for the remote asset. This technology is bi-directional, so it is capable of doing it with the proper SCADA controls.
|Figure 3 - Bi-directional charging (used with BYD permission)|
The life cycle and specifically the longevity of the BYD Iron-phosphate battery is really the key to BYD’s successful EV’s, because it addresses barriers acknowledged for renewables attached to the grid. This concern grows higher when saturation levels of renewables are increased (that are perceived as non-firm), and these are perceived to destabilize the grid. Storing the energy (energy storage) solves the concern. The problem then becomes the price of storage. BYD envisions that vehicle energy sources would be repurposed at the end of vehicle life. Therefore, the battery systems are oversized on purpose for more than the average range needed and are fully depreciated in the first-purpose. For example, in Shenzhen in 2010, 300 electric buses were launched with three different transit companies and about the same number of electric taxis a year earlier in 2009. The company recently began analyzing energy modules from those early taxis, and discovered that they were still 92% of their original capacity after 250,000 miles traveled. Meanwhile, the electric buses are predicted to, at most, consume half of the battery capacity in their life-time—that is, the battery’s “first-purpose”. Because of this available overhead in the remaining capacity of the modules, these batteries are able to be repurposed into home energy storage applications, community energy storage, and fixed energy storage stations for renewable balancing on the smart grid.
BYD’s vision is truly a zero-emission ecosystem. The (first) dream is to deliver affordable solar power, but make that renewable source relevant to the grid by adding battery storage and making it firm and “dispatch-able.” The company also believes that the path to a “low-cost” energy storage is by fully depreciating the value of those batteries in the first purpose, the vehicles. And then, repurpose these very low-cost assets into large-scale energy storage, finally making commercial and residential ecosystems relevant and cost effective.
Pourya Shamsi received his BSc and PhD from University of Tehran, Iran, and The University of Texas at Dallas, Texas, respectively. He was the chief R&D engineer of PSP Co., Iran, for six years. He was a post-doctoral research associate at the University of Texas at Dallas. Currently, he is an assistant professor of Electrical Engineering at Missouri University of Science and Technology.
He is mainly focused on applications of power electronic converters in smart micro-grids. Moreover, he has worked on modern drive systems for transportation electrification. His research interests include but are not limited to smart grids, distributed generation, modeling and stability analysis of power electronic converters, V2G, motor drives, and high frequency power conversion. He has several patents and publications in peer reviewed journals and conferences. He is also a reviewer for many journals in the area of power electronics and energy systems.