آنالیز سود هزینه اجتماعی پروژه های ذخیره انرژی الکتریکی با مقیاس شبکه A social cost benefit analysis of grid-scale electrical energy storage projects: A case study

1. Introduction Electrical energy storage (EES) can support the transition toward a low-carbon economy (decarbonisation) by helping to integrate higher levels of variable renewable resources, by allowing for a more resilient, reliable, and flexible electricity grid and promoting greater production of energy where it is consumed, among others [1]. In addition to decarbonisation, EES promotes lower generation costs by increasing the utilisation of installed resources and encouraging greater penetration rates of lower cost, carbon-free resources [2]. EES plays an important role supporting distributed generation and distribution planning processes for future power systems. Different jurisdictions are evaluating the value of EES (and other Distributed Energy Resources) for planning purposes related to the next generation of electric distribution utilities [3–5]. The global electrical energy storage market is expanding rapidly with over 50 GW expected by 2026 of utility-connected energy storage and distributed energy storage systems.1 In the United States alone, deployment is expected to be over 35 GW by 2025 [6]. This upward trend is mainly explained by favourable policy environments and the declining cost of EES, especially batteries [7]. Market structures that support its deployment are also observed (i.e. California Public Utility Commission – CPUC and the goal is to install 1.3 GW of EES by 2020) [8]. The declining costs of EES combined with cost optimisation models show an increase in the number of applications and use-cases of storage technologies [9,10]. There are different types of EES technologies with specific technical characteristics (i.e. response time, number of cycles, discharge time, storage duration), that make them more or less suitable for a different range of EES applications (i.e. peak shaving, voltage control, frequency regulation) [11,12]. Depending on the market, EES technologies and their applications can be subject to different regulatory context and policies [13–15]. Even though there are a large number of EES technologies, not all of them are exposed to the same level of development. This reflects the different size of capital and/or operational costs among them. In fact many of them are still in a research or development stage. While pumped hydro storage is among the most mature and cheapest storage technologies for short-term and longterm storage [16], battery storage is the one with the most commercial interest and growth potential [17]. EES can be used for multiple applications and can therefore generate different revenues streams whose value depends on the type of technology2 [18] and the place where the EES facility is located, at generation sites, on the transmission or distribution grid or behind the end consumer’s meter [19]. Different studies have evaluated the cost and benefits of EES however few of them take into account the multiproduct nature in agreement with the diverse EES revenues streams and the uncertainty component. Idlbi et al. [20], estimate the net benefits of battery storage systems – BSS (connected at medium voltages (MV)) in the provision of reactive power versus other options such as conventional reinforcement.