energies Article Advantages of Applying Large-Scale Energy Storage for Load-Generation Balancing Dawid Chudy * and Adam Le´sniak Institute of Electrical Power Engineering, Lodz University of Technology, Stefanowskiego Str. 18/22, PL 90-924 Lodz, Poland; [email protected] * Correspondence: [email protected] Abstract: The continuous development of energy storage (ES) technologies and their wider utiliza- tion in modern power systems are becoming more and more visible. ES is used for a variety of applications ranging from price arbitrage, voltage and frequency regulation, reserves provision, black-starting and renewable energy sources (RESs), supporting load-generation balancing. The cost of ES technologies remains high; nevertheless, future decreases are expected. As the most profitable and technically effective solutions are continuously sought, this article presents the results of the analyses which through the created unit commitment and dispatch optimization model examines the use of ES as support for load-generation balancing. The performed simulations based on various scenarios show a possibility to reduce the number of starting-up centrally dispatched generating units (CDGUs) required to satisfy the electricity demand, which results in the facilitation of load-generation balancing for transmission system operators (TSOs). The barriers that should be encountered to improving the proposed use of ES were also identified. The presented solution may be suitable for further development of renewables and, in light of strict climate and energy policies, may lead to lower utilization of large-scale power generating units required to maintain proper operation of power systems. Citation: Chudy, D.; Le´sniak,A. Keywords: load-generation balancing; large-scale energy storage; power system services modeling; Advantages of Applying Large-Scale power system operation; power system optimization Energy Storage for Load-Generation Balancing. Energies 2021, 14, 3093. https://doi.org/10.3390/en14113093 Academic Editor: Egwu Eric Kalu 1. Introduction Nowadays, the cost of most energy storage (ES) technologies remains high, making Received: 9 March 2021 it impossible to ensure return on investment for many grid applications [1]. This claim Accepted: 21 May 2021 applies, inter alia, to battery technologies [2–4]. The profitability of a given technology and Published: 26 May 2021 application is also dependent on additional factors, such as specific market conditions and installation site [5]. On the one hand, only the most profitable and technically effective Publisher’s Note: MDPI stays neutral solutions are currently chosen by new investors, but on the other, further reduction of ES with regard to jurisdictional claims in costs can increase their profitability and scope of application [6–8]. It is therefore expected published maps and institutional affil- that new ways of ES exploiting will emerge shortly. iations. The most popular applications of ES in the power system include price arbitrage, voltage and frequency regulation, reserves provision, black-starting, renewable energy sources (RESs) supporting and load-generation balancing [9,10]. The use of ES for grid balancing was analysed mainly in the scope of distribution networks (medium voltage Copyright: © 2021 by the authors. (MV) and low voltage (LV) networks). The battery ES intended to provide balancing Licensee MDPI, Basel, Switzerland. services at MV distribution feeder was presented, inter alia, in [11,12]. The ES technologies This article is an open access article may also perform balancing services compensating renewables energy fluctuations, as distributed under the terms and shown in [13,14]. The current research covered multiple services which combine balancing conditions of the Creative Commons with reactive power compensation [15] and power loss minimization [16]. Illustrative Attribution (CC BY) license (https:// applications in LV networks cover the balancing performed by centrally located and creativecommons.org/licenses/by/ dispersed ES [17], services performed by multiple ES cooperating with smart buildings [18], 4.0/). Energies 2021, 14, 3093. https://doi.org/10.3390/en14113093 https://www.mdpi.com/journal/energies Energies 2021, 14, x FOR PEER REVIEW 2 of 17 Energies 2021, 14, 3093 2 of 17 and dispersed ES [17], services performed by multiple ES cooperating with smart build- andings residential [18], and photovoltaicresidential photovoltaic (PV) installations (PV) [installations19]. A high potential[19]. A high is also potential demonstrated is also bydemonstrated vehicle-to-grid by (V2G) vehicle technologies-to-grid (V2G) and utilizationtechnologies of reusedand utilization vehicle batteries of reused which vehicle lead tobatteries better performance which lead to of better renewables, performance reducing of theirrenewables curtailment, reducing and better their utilizingcurtailment excess and energybetter utilizing [20–22]. excess energy [20–22]. ToTo thethe bestbest knowledgeknowledge ofof thethe authors,authors, onlyonly aa littlelittle attentionattention hashas beenbeen paidpaid toto thethe balancingbalancing services services performed performed by by large-scale large-scale ES ES which which allow allow not not only only for thefor compensationthe compensa- oftion load-generation of load-generation fluctuations fluctuations but also but for also the for reduction the reduction of the of number the number of starting-up of start- centrallying-up centrally dispatched dispatch generatinged generating units (CDGUs) units (CDGUs) required required to satisfy to satisfy the peak the electricitypeak elec- consumption.tricity consumption. Consequently, Consequently, the remainder the remainder of the of article the article will focuswill focus on this on particularthis partic- ESular application. ES application. 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During the start-up, the start a- givenup, a unitgiven cannot unit cannot be controlled be controlled and does and not does take activenot take participation active par- inticipation the load-generation in the load-generation balancing. balancing. The start-up The of start a power-up of generating a power generating unit lasts untilunit lasts the unituntil reaches the unit its reaches required its minimum required minimum output power, output and power from that, and point from it that can point be controlled it can be bycontrolled the power by system the power operator system [26 operato]. r [26]. Energies 2021, 14, x 3093 FOR PEER REVIEW 33 of of 17 17 FigureFigure 2. AnAn exampleexample ofof the the start-up start-up characteristic, characteristic, where: where: tstart-up—the tstart-up—the time time point point when when the start- the startup begins;-up begins; t1–t6—characteristic t1–t6—characteristic times relatedtimes torelated the warming to the up processes;warming Pup1–P 3processes;—characteristic P1– P3values—characteristic of output power values relatedof output to thepower warming related up to processes;the warming PMIN—minimum up processes; PMIN technical—minimum output technicalpower after output start-up power process; after PDIS—minimum start-up process; output PDIS power—minimum available output for the power system available operator for taking the systeminto account operator power taking reserved into account for the provisionpower reserved of the additionalfor the provision services. of Own the additional development services. based Ownon [26 development,27]. based on [26,27]. DuringDuring the the morning morning ramp ramp of of demand, demand, many many generating generating units units perform perform start start-ups-ups and dodo not provide load-generationload-generation balancing balancing services. services.