Proven at PJM: Vehicle to Grid (V2G) and Power System/Transportation Synergies
- Nov 17, 2008 12:00 pm GMT
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In his pre-election interview with Rachel Maddow, President Elect Barrack Obama envisioned an enhanced grid whereby plug-in vehicles are able to inject power into the electric power system. The President-Elect has articulated his commitment to create a longer term economy based on environmentally sound energy infrastructure that includes smart grid, renewable energy and the electrification of transportation through plug-in vehicles.
However, the electric power system represents both an aging and a critical infrastructure that is complex and lacks energy storage capacity such that electricity must be simultaneously produced and consumed with the resulting load-frequency control problem (Ref 1). Automobiles are basically distributed energy storage in the form of liquid fuel today but such storage can be transferred to electricity (Ref 2) if adequate public policies are implemented. Such transfer will allow wind power and solar power to be stored as electricity in the cars when parked, drive the cars when needed and give back the power to the grid when called for by the system operators. This scenario has been tested and proven in our study summarized herein.
While the power system is designed to meet peak demands, automobiles are designed to move a limited number of people (one to five) from one point to the other within less than one to four hours a day. In other words, most cars are parked most of the day doing nothing. Hence the actual level of utilization of both assets (power system and automobiles) is less than 100% most of the time especially urban and local commute vehicles. Although the electric power business has undergone restructuring, the fundamental engineering aspects of the power system infrastructure remain the same. The load and the generation in the system must be balanced at all times. To accomplish this real time balancing, several functions have been established to manage the system effectively.
With restructuring, some of the balancing functions - such as spinning reserve and frequency regulation - have become marketed services. Other functions, includes voltage control and reactive power management. Spinning reserve and frequency regulation are termed ancillary services, abbreviated A/S, in well-established power markets such as PJM and other Independent System operators (ISOs). Given the right pricing, A/S can be the most effective market incentive for actualizing the synergetic advantage of re-electrifying transportation.
The biggest challenge with electric vehicles has been the battery that stores the energy needed to drive the vehicle in terms of initial cost and life cycle. However, a drive system has been designed by AC Propulsion of California which uses mass-produced 18650 lithium-ion batteries and patented power electronics with the capability for two way powerflow between the car and the grid. This two-way power flow is termed Vehicle-to-Grid (V2G). This drive train has been used to manufacture all electric vehicles with conversions cars and original cars by an OEM.
Based on the above background, Pepco Holdings, Inc (PHI) co-funded the theoretical analysis of the concept of V2G at the University of Delaware in 2003. This effort was built on the seminal work at the University, published in 1997 (Ref 2), and a burst of activity in 2000-2001 funded jointly by the California Air Resource Board and the LA Department of Water and Power. The results of those analyses were published in international journals between 2002 - 2005 (Ref 3 & 4). In 2007, PHI, University of Delaware, PJM and other partners, established the Mid-Atlantic Grid Interactive Car Consortium (MAGICC) to prove the V2G concept practically. MAGICC activities are funded by awards from the Delaware Green Energy fund, PHI, and Google.org. In October 2007, a team of PHI, PJM and University of Delaware engineers and officials successfully interconnected an AC Propulsion eBox (a converted Toyota Scion xB) to the PJM grid using a direct signal from the PJM control center to dispatch the vehicle as a frequency regulation resource, like other traditional generators. The set-up and key players on the research are captured in Figure 1.
This technical breakthrough was demonstrated publicly for the first time on October 23, 2007 to FERC Commissioners and staff at their Washington offices. Since then it has been tested in several distribution systems. A full report covering this innovative green initiative capable of helping with oil independence, global warming reduction and energy security is due out in the next several weeks. If adequate funding is received, the next phase of the test will included expansion to several vehicles that are dispersed in different parts of the PJM grid performing frequency regulation and storage for renewable but intermittent resources such as wind and solar.
- Udo, Victor E., Adaptive Hierarchical Control Strategy for Large Scale Interconnected Systems, Master Thesis, Howard University, Washington D.C., 1991
- Kempton, W. and Steven Letendre. 1997. "Electric Vehicles as a New Source of Power for Electric Utilities" Transportation Research 2(3): 157-175.
- Letendre, Steven and W. Kempton, 2002. "The V2G Concept: A New Model for Power?" Public Utilities Fortnightly 140(4): 16-26.
- Kempton, W and Tomic, J. 2005. Vehicle to Grid Power Fundamentals: Calculating capacity and net revenue. Journal of Power Sources. Volume 144, Issue 1, pp 268-279.