All You Need to Know About an Energy Storage System (ESS)

Published on 16th December 2022

An energy storage system (ESS) is a device or group of devices used to store energy and supply it for later use. Battery, chemical, electrochemical, mechanical, and thermal are some of the popular energy storage systems available to meet everyday energy needs.


Energy storage systems make it easier to store and deliver energy where and when needed to create a more resilient energy infrastructure and provide cost savings to consumers and utilities. Furthermore, these ensure system reliability and stability by responding rapidly to power fluctuations.


The variable supply from renewable sources and a surge in demand for electricity are posing challenges for energy grids worldwide in addition to the rising energy cost scenario, which demands more flexibility in our energy mix to make clean energy accessible and affordable to all.


Delivering energy reliably at the flip of a switch is achievable with current and emerging energy storage technologies.


Even when the sun does not shine or the wind does not blow, grid-based energy storage makes it possible to address solar or wind intermittency and make clean energy available consistently for residential, commercial, and industrial applications.


Keep reading to learn more about an ESS and the global energy storage systems market.


Components of an Energy Storage System (ESS)

A typical energy storage system includes two main components:


The power conversion system (PCS) handles AC-to-DC and DC-to-AC conversions (AC – Alternating Current and DC – Direct Current are types of electric power), with energy flowing into the batteries for charging them or being converted from battery storage into AC power and fed into the grid.


The battery management system (BMS) is responsible for cell charging, balancing, and health monitoring, along with a microcontroller that provides system control and communication. 


Drivers of Energy Storage Systems

In the rapidly evolving power industry, more and more companies are choosing renewable energy sources to meet varied needs, such as:


  • Generate power off-grid
  • Improve sustainability
  • Increase energy efficiency
  • Manage risk
  • Reduce emissions
  • Reduce energy spending
  • Save money


However, renewables such as solar and wind are subject to weather changes. An ESS system can complement and mitigate the intermittency of solar or wind power by storing energy for later use.


For example, when solar panels are affected due to cloud cover or rain, ESS technology helps maintain a reliable power supply source and utilize stored energy when required.


Furthermore, energy storage helps electricity grids, including microgrids, operate more cost effectively and efficiently because the system runs at average load rather than peak load. ESS technologies can also generate substantial savings annually.


According to an estimate by Imperial College London’s Energy Futures Lab, “energy storage technologies could generate savings of £10bn a year by 2050 in the UK.”


As the energy storage industry continues to evolve, adapt, and innovate in response to changing energy requirements, let us look at the main drivers of the surge in energy storage systems:


  • A growing number of grid stability ESS projects
  • Growth of energy-intensive industries (such as data centers)
  • Increasing demand for uninterruptible power supply 
  • Increasing popularity of solar plus storage in the residential market
  • Rise of wind and solar PV power generation technologies
  • Time shifting


Front-of-the-Meter (FTM) and Behind-the-Meter (BTM)

The growing adoption of energy storage as a service (ESaaS) enables energy storage companies to deliver reliable power and potential cost savings to commercial and industrial (C&I) users.


Front-of-the-meter (FTM) and behind-the-meter (BTM) are commonly used terms in the context of energy storage.


Front-of-the-meter: Utilities use energy storage to relieve congestion on aging grid infrastructure and generating plants. Energy storage enables utilities to balance grid loads and extend infrastructure life while progressing toward a distributed energy future.


Behind-the-meter-storage systems: BTMS systems directly supply electricity to buildings and homes and help minimize grid impact, integrate EV charging, and more.


Researchers are working on developing energy storage technologies for BTMS stationary applications as the BTMS market is expected to see strong growth driven by consumer awareness and cost reductions coupled with EV adoption and solar hybridization.


FTM and BTM BESS Applications


Source: https://www.integrasources.com/blog/energy-management-and-energy-saving-bess/


Benefits of Energy Storage Systems

There are definitive advantages when it comes to energy storage systems—from actively managing mismatches between electricity supply and demand to enhancing grid resilience.


ESS benefits include but are not limited to the following:


  • Ensure reliability of critical services
  • Increase facility flexibility
  • Increase interdependent network resilience
  • Meet load during periods of peak demand
  • Prepare the grid for EV charging (fast)
  • Serve remote communities


In recent years, there has been a stronger focus on energy storage solutions like stationary storage to enhance grid reliability, resilience, and demand management.


Risks of Energy Storage Systems

Energy storage systems do pose some risks, such as:


  • Electrical fires
  • Overheating
  • Short circuit
  • Thermal runaway


For instance, lithium-ion batteries combine flammable electrolytes with highly energetic materials, which can lead to a fire hazard if there is damage to the separator. Therefore, an integrated fire protection system must be in place for early and reliable fire detection in Li-ion battery energy storage systems.


Moreover, the widespread, grid-based adoption of lithium batteries does have certain challenges related to cost, limited lifespan, and safety.


An ESS technology roadmap is incomplete without proper guidelines on planning, risk assessment, performance assessment, and safety considerations for the deployment and maintenance of energy storage systems.


In addition, economic and technical factors make commercial viability challenging for ESS deployment. Consequently, ESS technologies are at different stages of adoption worldwide.


Types of ESS Technologies

Based on the form in which energy is stored (storage principle), energy storage technologies are commonly classified into five categories, including:


Chemical energy storage

  • Ammonia
  • Hydrogen
  • Methanol
  • Synthetic natural gas
  • Synthetic fuels


Chemical energy storage uses electricity to produce a chemical that can be used as a fuel for electricity generation, transportation, or thermal load support.


Chemical energy storage includes hydrogen and other hydrogen-rich chemical energy carriers produced from diverse domestic energy sources (such as fossil, nuclear, and renewables) for use in various energy storage applications, including:


  • Heavy duty vehicles
  • Power-to-gas
  • Power-to-liquids
  • Steel manufacturing


Hydrogen can be stored as a gas in high-pressure tanks or large underground caverns (compressed gaseous H2), as a liquid in cryogenic tanks (cryogenic liquid H2), or as liquid or solid hydrides (such as ammonia and magnesium).


Electrical energy storage

  • Capacitors
  • Supercapacitors
  • Superconducting magnetic energy storage (SMES)


Also known as “electrochemical double-layer capacitors” or “ultra-capacitors,” supercapacitors are high-power, low-energy devices that use an electrochemical double-layer of charge to store energy.


Supercapacitors are scalable and can withstand a high number of cycles (up to 100,000) due to the absence of a chemical reaction.


A SMES system stores electricity as a magnetic field created by current flow through superconducting coils (cooled to below a critical temperature point) and releases energy by discharging the coils. This energy storage system is capable of instantaneous discharge with the added benefit of easy maintenance of the electromagnetic field.


Electrochemical energy storage/Battery energy storage systems (BESSs)

From the invention of the first battery by Alessandro Volta in 1800, batteries have evolved into multiple forms. Several rechargeable batteries are available to meet specific power and duration requirements.


Rechargeable batteries


ESS batteries are based on the concept of storing energy through reversible electrochemical reactions in one or more electrochemical cells and converting stored energy into electrical energy.


While battery cells are single-unit devices, battery modules refer to cells connected in parallel or series, and a battery pack consists of a series of individual modules and protection systems organized together.


Traditional battery systems consisted of deep-cycle lead-acid batteries. However, lightweight, highly efficient, and scalable lithium-ion batteries started dominating in recent years and began to be widely used for a variety of applications, including mobile phones, electric vehicles, and stationary energy storage in smart grids.


Furthermore, Li-ion batteries are suitable for larger systems that store multiple megawatt hours (MWh) with a small footprint and can support the entire electric grid. For instance, a utility-scale 100 MWh system could fit on less than 0.5 acres.


Flow battery technology is based on the circulation of liquid electrolytes to charge or discharge electrons via redox (reduction and oxidation) reactions and generate electricity. Flow batteries are designed with recyclable components, last longer, and provide cost-efficient, reliable power.


ESS Inc., a leading provider of long-duration energy storage solutions, specializes in iron flow battery technology that uses earth-abundant iron, salt, and water to deliver environmentally safe energy storage solutions for commercial- and utility-scale applications.


ESS Inc’s Energy Warehouse (EW) is an environmentally sustainable battery with no capacity fade or degradation. The EW is ideal for traditional renewable energy and utility projects requiring long life and unlimited cycling capability.


BESS Applications


A battery energy storage system can be charged by electricity generated from a renewable energy source, like solar or wind energy.


Batteries for solar energy storage help businesses and households become more energy independent while ensuring a reliable electricity supply during prolonged electricity supply disruptions.


BESSs are versatile with flexible energy capacity. Energy security, self-sufficiency, and battery backup power in emergencies are the primary driving factors for home battery storage systems/battery energy storage solutions.


A home energy storage system stores generated heat or electricity to use energy when needed and reduces dependency on the electricity grid.


For example, the Tesla Powerwall Plus is an all-in-one solar energy storage system with an impressive storage capacity, an integrated battery inverter-charger, and an advanced liquid thermal management system.


Many commercial and industrial businesses are also installing BESSs to make energy available on demand, provide backup emergency power sources, manage frequency fluctuations on the grid, reduce harmful emissions, etc.


For instance, the leading utility giant, NextEra Energy, has 1,323 MW of large-scale battery storage projects in various U.S. states, with the majority of the projects being four-hour BESS projects.


Additionally, some BESSs are designed to fit inside shipping containers for utilities and commercial customers. These systems are fully independent and energy efficient with safety and security systems in addition to cooling and operating software.


Mechanical energy storage

Mechanical energy storage systems store energy produced by motion. Examples include:


  • Adiabatic compressed air energy storage (ACAES)
  • Compressed air energy storage (CAES)
  • Fireless locomotive
  • Flywheel energy storage (FES)
  • Pumped hydro energy storage (PHES)/pumped hydro storage (PHS)


Compressed air energy storage draws in air and creates a high-pressure system in an array of large underground chambers/caverns. When the power demand surges or wind speed slows, the pressurized air (generally mixed with some natural gas) is released to generators or power turbines.


A flywheel stores grid energy in a rapidly spinning mechanical rotor and absorbs and typically releases high power for a short duration. A magnetic field holds the wheels in a frictionless vacuum to prevent energy loss. Moreover, spinning can be slowed when power is needed to generate electricity.


Flywheel energy storage systems balance electricity supply and demand fluctuations, recapture braking energy from electric trains, or provide short-term power during power outages. Compared to other energy storage systems, these have a low environmental impact, low maintenance, and long life.


A pumped hydroelectric facility is based on a gravity-based concept, which involves turbines pumping (during off-peak hours) water to an elevated reservoir using excess electricity.


During a period of peak electricity demand, stored water from the upper reservoir is allowed to flow down to a lower reservoir and pass through turbines to generate electricity.


Large-scale energy storage projects use pumped hydro, which provides around 95 percent of the U.S. grid storage, according to the U.S. Department of Energy.


However, factors like long development timelines and the permitting implications of large water-based infrastructure make it challenging to build new pumped hydro storage plants.


Thermal energy storage

  • Brick storage heater
  • Ice storage air conditioning
  • Liquid air energy storage (LAES)
  • Molten salt energy storage (MSES)
  • Phase change materials
  • Solar pond
  • Steam accumulator


Thermal energy storage systems use excess energy to capture heat and cold (heat the molten salts, freeze the water, etc.) and later release energy on demand.


For instance, molten salt stores solar-generated heat for use when sunlight is unavailable. Another example is ice storage in buildings that reduces the need for compressors while providing air conditioning for many hours.


LAES uses excess grid electricity to cool ambient air and convert it into a liquid. Subsequently, the liquid is converted back into a gas by exposure to ambient air or using waste heat, and the expanding gas is used to power turbines for electricity generation.


Phase change materials are used in heat batteries that store spare electricity or heat. A phase change material (PCM) absorbs or releases sufficient energy at phase transition to provide cooling or heat.


For example, a material stores heat when it changes phase from a solid into a liquid and changes again into a solid with heat released to provide hot water, etc.


Sample overview of storage technologies


Sample energy storage technologiesSample overview of storage technologies


Source: https://www.worldenergy.org/assets/downloads/Five_steps_to_energy_storage_v301.pdf?v=1583316514


ESS Applications

The use of energy storage systems spans industries, such as automotive, power generation, and utilities. The most common energy storage applications include:


Black start: Energy storage helps restore a power plant, substation, or system when energy cannot be drawn from the grid after a blackout.


Emergency backup: Distributed generation (DG) refers to generating electricity from sources (such as renewable energy sources) near the point of use. On the other hand, centralized generation consists of sources from power plants.


During a grid failure, energy storage and a local generator provide backup power at several scales—from daily backup for residential customers to second-to-second power quality maintenance for industrial operations.


Energy arbitrage: It is possible to arbitrate electricity prices (buy low and sell high) using the battery as intermediate storage.


Load leveling: Store power during periods of light loading and deliver power during periods of high demand.


Network stabilization: Energy storage improves T&D (Transmission & Distribution) system performance when it compensates for electrical anomalies and disturbances, including sub-synchronous resonance, unstable voltage, and voltage sag.


Peak shaving: The process proactively manages overall demand and levels out peaks in electricity use by commercial and industrial power consumers.


Most electricity storage systems allow consumers to track energy usage online and reduce reliance on more expensive electricity during periods of peak demand.


RES integration: Energy storage is crucial for mitigating rapid output changes from renewable generation due to the shading of solar generation and wind speed variability.


Demand response and storage enhance power system flexibility through better alignment of variable RE (renewable energy) supply with electricity demand patterns.


Seasonal thermal energy storage (SeTES): In a SeTES system, energy is stored for days, weeks, or months during one seasonal condition, such as summer or winter. Depending on the load demand, the stored energy is discharged in the other seasonal condition. 


Time shifting: Time shifting involves storing energy during low-price times and discharging during high-price times. It also avoids high tariffs on electricity by leveraging stored energy at certain times of the day when electricity use is at its peak.


Voltage regulation: Maintaining voltage on the T&D system within an acceptable range ensures continuous and reliable electricity flow across the power grid.


With many countries working toward reducing CO2 emissions and producing green energy by reducing the dependence on fossil fuels, energy storage systems are supporting the energy transition in various ways.


For example, storing surplus energy generated from renewables or intermittent generation sources (IGS) and making it available for use reduces carbon footprint and promotes clean power generation.


In the coming years, fully adopting energy storage and smart grids would be necessary to meet higher electricity demand.


Energy generation and distribution are no longer limited to the national grid—small-scale renewables and energy storage systems for homes and communities ensure control over their own power production as well as the price and the security of supply.


Global Energy Storage Systems Market Outlook to 2028

Do you want to equip yourself with forward-looking insights and be better informed of the global energy storage industry’s competitive landscape?


Blackridge Research & Consulting’s Global Energy Storage Systems Market report provides detailed profiles of key industry players and a rigorous market analysis across multiple regions, including Africa, Asia Pacific, North America, South America, and the Middle East.


Access this report to assess current and future market opportunities, discover the most influential growth drivers, gain a deeper understanding of market trends, and more.


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Wrapping Up

Storing energy reduces imbalances between energy demand and production by providing energy for use at a later time. Energy storage systems enhance grid resilience and help actively manage mismatches between electricity supply and demand.


Other significant energy storage applications include backup power for outage management, load balancing, and power quality management.


As solar and wind compete for capacity additions in various countries across the world, long-duration energy storage is becoming a necessity in places with high concentrations of solar and wind farms.


Decentralization of the power system, growing renewable energy generation, ESS technological improvements, market traction, recent investments, and reduced cost of deployment are accelerating greater market adoption of energy storage systems.


Governments and utility companies, among other organizations, are also upping their targets for clean, safe, and long-lasting energy.


For example, business model and use case promotion is facilitating ESS deployment in countries like Singapore wherein the EMA (Energy Market Authority) launched the ACCESS programme (Accelerating Energy Storage for Singapore).


Another example is American Clean Power (formerly Energy Storage Association), which “unites the power of wind, solar, storage, and transmission companies and their allied industries to enable the transformation of the U.S. power grid to a low-cost, reliable and renewable power system.”


From shifting peak load to providing ancillary services to the market via regulation and reserves, ESS deployment is cost effective and provides a wide range of benefits while promising a more sustainable and cleaner energy future.


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