وسیله نقلیه به شبکه سیستم ها برای توسعه پایدار: تجزیه و تحلیل انرژی یکپارچه

Vehicle-to-grid (V2G) systems represent a means by which power capacity in parked vehicles can be used to generate electricity for the grid. This paper describes the first detailed and global analysis of the potential of V2G technologies over the long-term (to 2100) using a comprehensive energy-systems model. In this analysis we explore the potential for V2G systems to supply a number of electricity submarkets and concomitantly accelerate the diffusion of advanced vehicle technologies, including hybrid-electric and fuel cell drivetrains. We also examine the potential impact of V2G on the global energy system, particularly in terms of investment in conventional capacity, and the possible role of V2G-enabled vehicles in increasing the market penetration of renewable electricity generation technologies. Importantly, however, V2G technologies represent a paradigm shift in how the energy and mobility markets are related, and a number of possible barriers to the widespread adoption of this technology are also discussed.

New technologies represent an important means by which challenges facing the energy system can be overcome. Current global challenges include, among others, the need to reduce greenhouse gas emissions, manage energy security and reduce local and regional pollution, while providing access to cheap and safe energy needed for development [1] and [2]. These challenges are particularly pronounced in the transport sector, where the current dependence on internal combustion engine vehicles (ICEVs) fuelled with petroleum from politically volatile regions remains a major threat to energy security, climate change mitigation and urban air pollution. However, a number of alternative technologies exist that may ameliorate some of the risks emerging in the transport sector through their higher efficiencies and potential to utilize non-petroleum fuels [3]. These technologies include hybrid-electric vehicles (HEVs), fuel cell vehicles (FCVs) and battery electric vehicles (BEVs), although there exists some debate about the suitability of these different options [4], [5] and [6]. Collectively, these options can be categorised as electric-drive vehicles (EDVs), because they all have the capability to produce motive power from electricity, rather than from the internal combustion engine. However, these technologies currently suffer to different degrees from a lack of market experience and high costs. Moreover, even if and when these current barriers are overcome, the transition to EDV technologies may span long periods of time, due to the large inertia resulting from the current dominance of the ICEV and related technologies and social systems [4], [7] and [8]. In this paper we explore whether vehicle-to-grid (V2G) technologies represent a potential opportunity to bring forward and accelerate a transition towards EDVs by improving the commercial viability of new vehicle technologies. The V2G concept involves using parked vehicles to supply generation services to the electricity grid [9], [10], [11], [12] and [13]. In simple terms, vehicles are plugged in to the grid, and then feed in electricity generated from the vehicle engine (in the case of FCVs) or stored in an on-board battery system (HEVs and BEVs).1 However, V2G systems are only likely to change EDV deployment and diffusion patterns if there are benefits associated with providing energy from parked cars. One factor which suggests such benefits may exist relates to the fact that private vehicles are parked on average 93–96% of their lifetime, during which time each represents an idle asset [11] and [14]. Each parked vehicle contains underutilised energy conversion and fuel (or battery) storage capacity, and may actually create negative value due to parking costs. Accordingly, generating V2G power from parked vehicles can better utilise an expensive investment (particularly in the case of new and alternative vehicle technologies), thereby enabling cars to provide both mobility and energy services. Nonetheless, the question remains as to whether vehicles, via V2G, can provide electricity services competitively compared to conventional electricity generation technologies. Electricity services can be characterized according to specific power markets, which differ in terms of control method, response time, duration of the power dispatch, contract terms and price. V2G power generation has already been analysed in several studies [14], [15] and [16] which showed that although EDVs may be less suited to base-load electricity generation, they may be suitable for providing regulation services, spinning reserves and peak power demand. These services are described below: • Peak power is required at times of day when high levels of demand are expected (e.g., hot summer afternoons when air conditioning demands are large). Typically, peak power is generated by power plants that can be switched on relatively quickly, such as gas turbines. However, because these plants are only utilised during the few hundred hours per year (i.e., less than 10% of the time) when demand is high, and are idle otherwise, they represent a relatively inefficient investment. • Spinning reserves refers to generating capacity that is up and running, and synchronized with the electricity grid (but not contributing power). Spinning reserves generators contribute to grid stability, helping to arrest the decay of system frequency when there is a sudden breakdown or loss of another generator. Again, typically, power plants that can provide fast response to the calls of the grid operator are the most suitable, e.g. gas turbines. The capacity required to provide spinning reserves can also be seen as an underutilised investment, although essential for managing market risks. • Regulation services, on the other hand, are used to continuously fine-tune the balance between power generation and demand, in terms of the voltage and the frequency of the grid. In many power markets, this function, called regulation or automatic generation control (AGC), is priced separately from power generation and procured as an ancillary service (another such service is spinning reserves). The grid operator needs to be able to ensure generators ramp output up or down in real time to meet customer reactive power needs, manage customer impact on system voltage, frequency and system losses and ensure that power-factor problems at one customer site do not affect power quality elsewhere in the system [17]. Again, providing regulation services requires electricity generation capacity in excess of demand. V2G may provide a means by which to utilise the spare power capacity available in each parked vehicle and avoid the need to maintain the excess conventional electricity generation capacity currently required to provide regulation, spinning reserves and peak power. The potential economic benefits of V2G systems employing different EDV technologies for providing both electricity and mobility services have been discussed in a related analysis in Moura and Turton [9]. The analysis in [9] represents an important improvement on earlier approaches which examined only the incremental costs or benefits of using EDVs for electricity services—that is, without taking into account the costs associated with using EDVs for mobility services. However, despite the advantages of the approach employed by Moura and Turton [9], the analysis is essentially static and based on a single power market, although they examine the potential of possible future technology and energy system developments. Accordingly, this paper builds and extends upon Moura and Turton [9], and is the first to examine V2G technologies in detail in a long-term, dynamic, bottom–up, global energy systems model which optimizes discounted energy system cost. This analysis framework facilitates the exploration of linkages and competing demands within the energy system, in addition to emulating some features of technological change, including learning-by-doing, that may accelerate the deployment or improve the competitiveness of new technologies. In the remainder of this paper we first describe the energy-systems methodology applied to model and explore the possible future deployment of V2G systems (in Section 2), including details of how these technologies are represented. Section 3 then presents and discusses some of the main findings of the analysis. Other issues related to the diffusion of V2G technologies and important uncertainties are discussed in more detail in Section 4, and the main conclusions presented in Section 5. Readers should refer to [9], for a more detailed discussion of the V2G concept and results of a preliminary analysis.

This study represents the first time that a detailed energy system model has been used to model explicitly V2G technologies and their possible diffusion over long-term. The results indicate that V2G systems may have the potential to transform both energy and transport systems in profound ways, by promoting the deployment of alternative vehicle technologies; reducing inefficient investment in conventional generation; and supporting the installation of renewable electricity sources. On this basis, this technology warrants further analysis to identify how to support the possible diffusion of V2G technologies and, importantly, address some of the key technological and social uncertainties. This will require alternative methodological approaches, particularly since a proper analysis of some of the key social uncertainties—including issues related to consumer, electricity market, and regulatory acceptance—are beyond the scope of the analytical framework applied in this paper, but may well represent some of the most significant challenges to the possible emergence of V2G energy systems.