The frequency control service is an ancillary service that Transmission System Operators (TSO) provide to keep grid’s frequency within a strict band around the nominal frequency (Fabozzi, Thornhill and Pal, 2013). Even though frequency control is not a new task to the energy system, the growth of Distributed Energy Resources (DER) – especially Distributed Generation (DG) – increase the challenges to maintain the frequency of the power system (Black and Ilic, 2002; IRENA, 2017). Thus, traditional generation-based frequency regulation may not be the best way to deal with the increasing need of frequency control services, and we should think on new strategies.
In this sense, Electric Vehicles (EV) can bring positive externalities for the power systems and provide a bundle of services, including the enhancement of flexibility of grid’s frequency control.The way to use these services and monetize it can be central to implement EV policies. In this post, we discuss the potential introduction of bi-directional Electrical Vehicles as non-conventional solution to provide frequency flexibility services.
New technologies, new challenges
The share of DER in the energy matrix is increasing in many regions (IRENA, 2017). However, with the boom also emerge new challenges to coordinate the grid (Eid et al, 2016), such as frequency and voltage control, which are critical for system’s stability and security (Borne et al, 2018).
Renewable electricity generation “are subject to forecast error which increase the need for holding and deploying balancing reserves”, as pointed out by Hirth and Ziegenhagen (2015). Even though Transmission System Operator’s grid controlling can lead to efficient balancing of the system (Ocker and Ehrhart, 2017), the relevant volume of DERs can demand substantial amount of ancillary services (Eftekharnejad et al, 2013). Nevertheless, while some technologies of Distributed Generation impose a new challenge to the grid, other DERs technologies like Smart Controlling and Electric Vehicles can also provide a solution to frequency control, in special EV. According to Borne et al (2018),
“Electric vehicles (EV) have technical characteristics that enable them to provide very short-term flexibility services, when the charging system allows for the variation of charging power or the flows of electricity from the Vehicle to the Grid (V2G).”
New challenges, new solutions
Codani (2016) defines flexibility product by five attributes: (a) direction, (b) electrical composition in power, (c) starting time, (d) duration and (e) location (Figure 1). Electric Vehicles have the technical requirements to provide this kind of service (Eid et al, 2016; Borne et al, 2018).
First, EV can provide bi-directional flexibility, taking or charging energy from the grid. Second, at the aggregated level it can be highly predictable once grid’s coordinator knows the pattern of use (for mobility) and charge. Third, EVs can provide a quick response time within seconds. In a few words, EVs can offer “power adjustmentsustained at a given momentfor a given durationfrom a specific location within the network” (Eid et al, 2016).
Figure 1. The attributes of an electric flexibility product
Source: Codani (2016)
Once is clear that Electric Vehicles can be used to enhance the flexibility of grid’s frequency control, we should assess how to implement this solution efficiently. Borne et al(2018) developed a framework to organize the decision process of whether agents would use DERs – specifically Electric Vehicles – to provide frequency services. The framework is divided in three modules (Aggregation, Product Definition and Payment Scheme) with simple yes and noprocedures. Each step must have a “yes” answer for the optimal market-design that allow efficient participation of players. First, rules should allow aggregators (of DER’s reserved power) to provide the reserve to the network. Second, rules should allow aggregators to define the flexibility product itself, including the minimum level of aggregation (bid granularity), the period of provision and the bidirectionality of the service. And third, rules should remunerate the reserve provision. The payment scheme must be designed to “incentivize actors to reveal true costs in order to have clear price signals” (Borne et al, 2018).
Figure 2. Decision tree for participation of DERs in Frequency Restauration Reserve provision.
Source: Borne et al(2018)
Thus, on the policy side, current rules need to be adapted. In this sense, Codani, Perez and Petit (2016) suggest that TSOs’ rules should consider a formal status for distributed storage units that recognize flexibility as a service to be provided. This would help to follow a complete path of yesanswers. Vazquez et al. (2018) the development of the electrical vehicle depends on the coevolution between rules and technologies, it should impact not just in the amount but also the way the industry will evolve.
New solutions, more challenges
The effective provision of frequency services using Electric Vehicles depends on… Electric Vehicles. Even though the number of Electric Vehicles around the world has increased in the last decade – with over 2 million vehicles in 2016 – and keeps rising, we still need to have a larger fleet to provide an efficient flexibility service. IRENA (2016) mentions four elements that are necessary to have a larger EV fleet, including the integration between the fleet and the grid. The other three are: (1) electrification of all vehicles, (2) creation of an infrastructure of chargers and (3) decarbonization of the generation sector.
Overall, the use of Electric Vehicles to create new flexibility services should be considered in policymaking. The adaptation of current rules can (1) create clear price signals to incentive the decarbonization of personal vehicles and impact on automobile industry organization, (2) diminish the challenges introduced by the penetration of distributed generation technologies, and (3) increase the efficiency and the smart use of the distribution grid with a decrease in the needs of new investments.
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