Mw Scale Battery Energy Storage For Grid Application

BY D Geethalakshmi
MW scale Battery Energy storage will become a critical element of the future electrical grid. Energy storage will play a significant role in not only improving the operating capabilities of the grid but also defer the infrastructure investments. Recent developments in battery storage technologies and power electronics have expanded opportunity for electric storage as a cost effective electric energy resource.

Several types of energy storage systems like Pumped storage, Batteries, Fly wheel, Compressed air, Super capacitors etc. are currently available in different stages of maturity levels. Pumped storage, the traditional storage system had dominated energy storage for over many decades. However the need for renewable power integration and grid enhancement are driving huge investment and development of battery energy storage technologies. Battery energy storage offer a great potential to store and dispatch energy when needed enabling a more flexible and responsive energy infrastructure for grid application.

There are several different types of battery technologies available in the market for MW scale grid application. Among them Lithium Ion, Flow batteries, Sodium sulfur and Advanced Lead acid battery technologies are more prominent, proven and leading at present for the grid applications. There are also a number of battery technologies that are under development.

Lithium-Ion (Li-Ion) batteries were first commercialized in 1991. They have experienced tremendous research & development investment and gained the popularity in the last few years due to their high energy density, high voltage, better cycle life and higher efficiency. Lithium Ion batteries have demonstrated suitability for many grid applications, particularly in conjunction with renewable.

Sodium Sulfur (NaS) : Commercialized in 2002, Sodium Sulfur is termed as high temperature battery as the operating temperatures of these batteries are in the range of 300 deg C to 360 def. C. NaS battery is designed for long duration and bulk storage application. Many NaS batteries have been used for grid applications, majority of them being in Japan.

Flow batteries are unique in their design when compared to both Li-ion and high temperature batteries because of the cell construction. In this battery, the electrolyte is stored in tanks external to the electrodes. During discharge and charge cycles, electrolyte is pumped from the tank into the cell stack to interact with the electrodes. Flow batteries are well suited for long discharge duration application and have been proven for MW scale installations.

Advanced Lead Acid Battery is an improvised version of conventional lead acid battery. It is a hybrid energy storage device that combines the characteristics of a super capacitor and conventional lead acid battery at the material level within the cell. Though lead acid battery technology is existing for many decades, Advanced lead acid batteries are yet to penetrate the market in a large scale.
Energy storage benefits the entire power value chain, from generation, transmission and distribution, all the way to users. Battery energy storage system will have many potential benefits to power grid operation and load balancing, such as:

(i) Support in smoothening the grid voltage and frequency variation

(ii) meeting peak electrical load demands through electrical energy time of shift

(iii) mitigate the intermittence of renewable power generation by means of load leveling

(iv) helping in the management of spinning reserve and standby power generation

(v) Transmission and distribution congestion relief and upgrade deferral

(vi) Meeting the end user requirement such as energy cost management, demand charge management and electric service power quality

The potential benefits of battery energy storage installation to power system operation have been widely recognized. However some major challenges in the deployment of battery energy storage systems still exist, such as;

(i) choosing the appropriate battery energy storage technology to meet the power system application requirements

(ii) cost competitiveness of battery technology– Capital Cost and life cycle cost

(iii) lack of International Codes & Standards

(iv) limited engineering standards and evaluation tools

(v) mitigation of safety risks associated with fire and explosion

The selection of appropriate battery technology for an application mainly depends on the performance characteristics of the batteries. The key performance characteristics that are to be considered in the selection of battery technology are

(i) Power and Energy capacity
(ii) Energy density and Power density
(iii) Discharge rates
(iv) Depth of discharge
(v) Roundtrip Efficiency
(vi) Discharge duration
(vii) Cycle Life and Life span
(viii) Environmental impact upon disposal
(ix) Degradation

Tata Consulting Engineers Ltd (TCE) can offer full-fledged engineering services to the Industry. The services include selection of appropriate battery technology, optimum sizing of the battery capacity, feasibility studies, basic and detailed design and engineering of complete Battery Energy Storage system (BESS) Project and its integration with power grid. The services would also include procurement assistance, Vendor drawing/document reviews, factory/site inspection and construction and commissioning supervision.

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