Review of benefits and challenges of vehicle-to-grid technology

Plug-in electric vehicles (PEVs) can behave either as loads or as distributed energy sources in a concept known as vehicle-to-grid (V2G). The V2G concept can improve the performance of the electricity grid in areas such as efficiency, stability, and reliability. A V2G-capable vehicle offers reactive power support, active power regulation, tracking of variable renewable energy sources, load balancing, and current harmonic filtering. These technologies can enable ancillary services, such as voltage and frequency control and spinning reserve. Costs of V2G include battery degradation, the need for intensive communication between the vehicles and the grid, effects on grid distribution equipment, infrastructure changes, and social, political, cultural and technical obstacles. Although V2G operation can reduce the lifetime of PEVs, it is projected to be more economical for vehicle owners and grid operators. This paper reviews these benefits and challenges of V2G technology for both individual vehicles and vehicle fleets.

I. Introduction

With environmental and climate change issues and legislation, rising energy costs, concerns about energy security and fossil energy reserves, and growing consumer expectations, plug-in electric vehicles (PEVs) are appearing worldwide [1], [2]. Although PEVs have not been widely adopted in part because of technical limitations, social obstacles, and cost premiums compared to conventional internal combustion engine (ICE) vehicles [3], based on moderate expectations, by 2020 up to 35% of the vehicles on the market in the US will be PEVs [4]. Convenient recharging, and available electricity supplies are necessary to realize the benefits of vehicle-to-grid (V2G) capabilities.. V2G/G2V interfaces can reflect any possible charging rates, but industry has defined three typical rates as summarized in Table I. This paper reviews V2G technology and its economic costs and benefits. The context is PEVs - whetherpurely electric or hybrid. A range of proposed V2G concepts, services, costs, and benefits is discussed. It will be shown that V2G concepts that allow benefits to be shared among grid operators and vehicle owners are likely to accelerate PEV deployment. TABLE I. C<sc>harging</sc> P<sc>ower</sc> L<sc>evels</sc>

Level Types	Description	Power Level
Level 1	Opportunity charger (any available outlet)	1.4kW (12A) 1.9kW (20A)
Level 2	Primary dedicated charger	4kW (17A) 19.2kW (80A)
Level 3	Commercial fast charger	Up to 100kW