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The electricity grid: the greatest machine ever created by ma nkind

The electricity grid: the greatest machine ever created by mankind The electricity grid is the biggest machine mankind has ever built. It operates on a supply model that tries to balance supply and demand to maintain stability. When supply becomes insufficient, frequency and/or voltage drops and the supply can be interrupted.  These are the emergencies that the electricity grid tries to avoid.

  • The power grid is made up of many components, including:
  • Power generators running on hydro, thermal, nuclear, gas, oil, coal, solar, wind, tidal and other forms of energy.Voltage step-up transformers, which raise the voltage of the electricity to the level of the transmission grid.Long transmission lines.
  • Voltage step-down transformers (substations) which reduce the voltage to the level of the local transmission grid.Street transformers, supplying the required voltage (240V, 110V, 400V three-phase) to consumers.

However, traditionally, the electricity grid does not have the energy storage capability to balance sudden  spikes in demand. This means that in a grid without battery energy storage systems (BESS), any surplus has to be consumed immediately. Generators must be kept in a state of operation ("spinning reserve") so that additional supply can be quickly switched on when demand exceeds existing supply. In a well-managed grid, the spinning reserve can be as high as 15-30% of the total capacity.


What is BESS?

Battery Energy Storage Systems (BESS) are becoming essential tools for stabilising the electricity grid, integrating renewable energy sources and storing and using electricity efficiently. BESS work by storing electricity in rechargeable batteries and discharging it when needed. Most importantly, these battery systems can be quickly integrated into the grid - as soon as demand or frequency/voltage instability signals it.BESS principle and operationThe main purpose of BESS is to support the operation of "behind the meter" (beyond the customer's boundary) systems and to integrate BESS into grid management systems. These systems are suitable for both on-site integration of renewable energy and for ensuring the stability of electricity supply in regions where the grid is unreliable.These storage systems require investment, but their advantages are significant. One of the main advantages is the extremely fast response time. Batteries can provide grid-synchronised alternating current (AC) in just a few grid cycles (50-60 Hz). As fast-response electricity is the most expensive, the commercial value of the stored energy can be 10-100 times higher than conventional electricity prices.

How does BESS work?

Energy storage starts with a charging system that charges the batteries with surplus grid AC or solar DC current. Depending on the settings, charging can be fast or slow.Most BESS use lithium battery technology, where energy is stored electrochemically and released as direct current (DC). Since the grid operates on alternating current (AC), converters are required to convert DC to AC and to ensure synchronisation with the grid frequency.

The BESS system consists of:

  • Power electronics - for controlling the power flow, voltage conversion and synchronisation with the grid.
  • Thermal management system - to optimise battery performance and longevity.Safety mechanisms - to protect against overheating, overcharging and other system failures.When charging the batteries, the energy conversion efficiency is around 80-85%, meaning that out of 100 kWh of grid surplus energy, only 80-85 kWh will be stored in the batteries and the rest will be dissipated as heat.

BESS types

BESS can be of different types depending on the battery technology used:

Lithium batteries are the most popular due to their high energy density, long lifetime and low maintenance costs. Different versions of lithium batteries: LiCoO2, NCA, NMC, LiFePO4, LTO, solid state.

Flow batteries - energy is stored in liquid electrolytes and the system is easily expandable. Ideal for long-term energy storage.

Lead-acid batteries - the oldest and cheapest energy storage technology, used for emergency UPS power supplies and small remote systems.

Sodium-sulphur batteries - operate at high temperatures and have a high energy capacity. Used for grid stabilisation and renewable energy integration.

Supercapacitors - store energy electrostatically and are very efficient for fast charge/discharge cycles, but have lower energy density than batteries.

Performance of lithium batteries

Lithium batteries work through electrochemical processes whereby lithium ions move between the anode (negative electrode) and cathode (positive electrode).

The cathode is usually composed of lithium compounds (LiCoO2, NCA, NMC, LiFePO4, LTO).The anode is usually graphite or graphene.

The electrolyte is an ionic conductor that ensures the movement of lithium ions between the electrodes. It can be liquid, gel or solid.

Separator - a porous membrane that allows the movement of lithium ions but prevents the electrodes from coming into direct contact and causing a short circuit.

When a lithium battery is charged, lithium ions move from the cathode to the anode and accumulate there. When discharged, they move back to the cathode, releasing electricity.Lithium batteries vary in voltage and capacity depending on the material of the electrodes and the type of electrolyte. Typical voltages are 3.6-3.7 V per cell.

Battery Energy Storage System (BESS) components

Cell raw materials and construction

A Battery Energy Storage System (BESS) is typically composed of the following components:

Lithium-ion batteries come in three main forms:

  • Rigid cylindrical
  • Rigid prismatic (square or rectangular cross-section)
  • Flexible pouch-type cells

The main raw materials used in the production of these batteries are:

Ionic lithium salts - allows charge to move within the cellOrganic solvents - act as charge carriers, allowing current to flow between the electrodes. Depending on the battery technology, they can be liquid, gel or solidCobalt - used in cathodes for stability

Nickel, manganese and aluminium in the cathodes - helps reduce the use of cobaltGraphite - commonly used in the anode structure, but technology is evolving towards silicon for higher capacity and durability

Binders (usually polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) or styrene-butadiene rubber (SBR)) - bind and strengthen the electrode materials

Porous separators made of PE and PP - isolate the electrodes and allow ion movement

Housing materials - steel, aluminium or polymer tubes (for cylindrical and prismatic cells), as well as heat-sealable polymer films (for bag cells). In some cases where thermal insulation is required, ceramic housings may be used, and lightweight carbon fibre composites may be used for aerospace applications.

Other components

A functioning BESS container system or installation shall also include:

  • BESS controller PCS - responsible for power distribution, charge management, operational maintenance and safety control
  • Structural frames and enclosures - used to hold the battery modules
  • Battery management systems - monitor and control the performance of the batteries, ensuring safety and efficiency
  • HVAC cooling systems - regulate the temperature in the container, prevent overheating during charging or discharging, ensure optimal performance
  • Grid-synchronised inverters - converts direct current (DC) from batteries to grid-synchronised alternating current (AC)
  • AC-DC converters (rectifiers) - converts grid AC to DC voltage suitable for charging
  • Transformers - change voltage levels according to the requirements of the grid or local systems
  • Cooling systems - most BESS components require temperature controlFire extinguishing systems - detects and extinguishes fires, ensuring plant safety

BESS applications

BESS systems are widely used in a wide range of applications:

  • Grid stabilisation and frequency regulation - reacting quickly to sudden changes in demand or supply on the grid, absorbing surplus energy during low demand and releasing it during high demand
  • Renewable energy integration - stores surplus solar and wind energy, smoothes generation fluctuations, allows renewable energy to enter the grid more efficiently
  • Peak Shaving and Load Management - stores energy during low tariff periods and releases it when the electricity price is high, reducing the load on the grid and lowering costs
  • Microgrid support - provides backup power, load balancing and grid stability, optimising the use of renewable and thermal energy sourcesSupporting EV charging infrastructure - enables more efficient grid load management and fast charging of EVs
  • Uninterruptible power supply for industrial and commercial facilities - prevents grid disruptions and reduces costs through intelligent power demand management
  • Home energy storage - enables more efficient use of off-grid solar energy, reducing electricity costsRemote or off-grid areas - provides reliable electricity where access to the general grid is not available


Why are energy storage systems important for BESS?

BESS are becoming an increasingly important element in self-contained, resilient power grid systems. They help to integrate renewable energy sources, increase energy efficiency, improve voltage and frequency stability, and increase the reliability of the overall system.

When properly applied, BESS can remove grid constraints that would otherwise hinder the integration of intermittent (solar, wind, tidal, wave) energy sources. Most grids can only accommodate 15-25% of intermittent energy due to rotating reserve requirements. However, BESS can act as this reserve without wasting energy.This flexibility makes BESS indispensable in the transition to a more sustainable and reliable energy future.