Smart Grid - Battery Energy Storage Systems

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Written by Sandhya Sundararagavan1, Harsh Thacker2, and Deepak Krishnan3

As one of India’s leading renewable energy (RE) states, Tamil Nadu needs to decide how to grow its energy generation capacities to meet future growth in demand. High RE penetration for Tamil Nadu is likely to bring its own set of challenges for the state grid operator and the state utility especially since the state’s wind power plants have been facing curtailment issues. These grid balancing challenges are expected to exacerbate with the must-run status of RE plants and the limited flexibility of thermal power plants. In this context, it becomes critical to examine how much more RE can be added in this decade in Tamil Nadu and at what cost of flexibility in the grid. Can coal addition be minimized and Tamil Nadu become a model state to mitigate the impacts of climate change in India? With an increase in the percentage of renewables in the grid, the need for a storage system to store excess energy increases. This paper shares requirements of a battery energy storage system to seamlessly integrate RE into Tamil Nadu’s grid for different RE trajectories using an optimization model - Python for Power System Analysis (PyPSA) for 2025 and 2030 timeframe.


Written by Gopinath Subramani and Vigna K. Ramachandaramurthy

Maximum Demand (MD) charges were established to encourage the commercial and industrial users to alter their electricity use pattern to decrease the peak demand and lower the requirement for costly peaking plants. Many energy users are opting for solar photovoltaic (PV) system to be installed on their building’s rooftop for self-consumption purposes, thus reducing the electricity bill. However, atmospheric conditions such as temperature, and irradiance influence the solar PV power. Hence, it is likely that the peak solar PV output does not coincide with the instant of maximum demand. This is where batteries can play a crucial role. So, what should be the threshold above which the maximum demand will be shaved to ensure the highest Return-of-Investment (ROI)?

Written by Ram Krishan and Er. Alekhya Datta

With increasing penetration of Distributed Energy Resources (DERs), in-particular solar PV and wind energy, and the intervention of smart monitoring & control devices, the modern electricity grid is undergoing a paradigm shift wherein effective and reliable operation of the electricity network has become imperative. Distribution utilities have a challenging task at-hand in terms of managing the peak-loading and ensuring reliable and high quality power supply alongside addressing the operational challenges posed by DERs including Electric Vehicle (EV) chargers. The situation becomes more pronounced in the case of metropolitan areas facing increasing load and space constraints and extreme weather variations such as those in New Delhi. Hence, the need for controllable balancing fleets at the distribution system level is being felt to maintain reliability and avoiding periodic distribution network augmentation. Battery Energy Storage System (BESS) is being considered to be one of the most prominent technological solutions to manage the electricity supply and demand gap in an efficient way, courtesy the rapid technological advancements and falling prices of Li-ion batteries in addition to their quick response feature. Several types of BESS technologies are being deployed at different levels within the electricity network for a variety of applications such as energy arbitrage, peak shaving, power back-up, power ramp control, frequency regulation, avoiding power scheduling mismatch penalties (known as ‘deviation settlement mechanism’ control in India) etc., based on their technological advantages and limitations. However, appropriate sizing and siting of BESS is imperative for any application so as to optimize the overall system operation. Few pilot demonstrations of BESS within the urban distribution network in the National Capital Territory (NCT) of Delhi are being undertaken under the US-India Collaborative for Smart Distribution System with Storage (UI-ASSIST) for three different applications (serving three distinct consumer categories) that have been identified after carrying out the pre-feasibility assessment. A preliminary study comprising of techno-economic analysis of different BESS technologies, load research, identification of plausible revenue streams and development of operational strategy was performed accordingly. The battery size and operational control scheme for these applications were determined to ensure system operation within the technical constraints of the selected battery technology which include the state of charge (SoC) operating window, battery degradation and charge/discharge rate limitations (either by technology or by regulations).

Written by Ram Krishan, Er. Alekhya Datta, and Ashish Kumar Sharma

With increasing share of renewable energy (RE) in the power system, the resource adequacy planning exercise for power distribution utilities or Distribution Companies (DISCOMs) is bound to change. The role of balancing fleets such as Battery Energy Storage Systems (BESS) will become important and gain prominence with falling battery prices and more arbitrage opportunities in power markets. Flexibility and system reliability will be important attributes for any electricity distribution system operator and thus micro-grids will have a crucial role to play in both urban and rural set-ups. In an urban setting, micro-grids will help in synchronizing demand and supply and aid in improving quality & reliability of power supply. Such 'urban micro-grids' have gained relevance in congested Indian cities such as New Delhi, Kolkata, Mumbai where power distribution equipment augmentation becomes a tedious task due to underground cabling, space constraints and right of way challenges. Recent examples of distribution grid failures in major metropolitan cities have established the need for black-start support at the distribution-level. However, operational use cases at the distribution network-level can be unique and can change dynamically with time depending on demand & supply patterns, power purchase portfolio of the utility, customer-service obligations, etc. One such operational use case was found to exist for a Delhi based distribution utility wherein an urban micro-grid can be utilized to redeem energy arbitrage benefits, providing black-start support, meeting RPO targets and improving quality and reliability of power supply. A pre-feasibility study was carried out in this context which envisaged 8 MWp of solar PV potential along with 4 MWh of AC coupled BESS. The power evacuation for system integration at the utility power grid level was proposed through an 11 kV distribution line that emanates from a 66/11 kV distribution sub-station that serves the area. An operational control strategy for BESS was defined so as to maximize the benefits earned from the system in terms of peak power purchase cost saving while operating under Energy Arbitrage mode.

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