5 Key Safety Considerations for Battery Energy Storage Systems

HSE considerations on Battery Energy Storage Systems (BESS) sites.

A BESS is a battery energy storage system (BESS) that captures energy from different sources, accumulates this energy, and stores it in rechargeable batteries for later use. Should the need arise, the electrochemical energy is discharged from the battery and supplied to homes, electric vehicles, industrial and commercial facilities.

A BESS is a compound system comprising hardware components along with low-level and high-level software. The main BESS parts include:

• A battery system. It contains individual battery cells that convert chemical energy into electrical energy. The cells are arranged in modules that, in their turn, form battery packs.
• A battery management system (BMS). A BMS ensures the safety of the battery system. It monitors the condition of battery cells, measures their parameters and states, such as state-of-charge (SOC) and state-of-health (SOH), and protects batteries from fires and other hazards.
• An inverter or a power conversion system (PCS). This converts direct current (DC) produced by batteries into alternating current (AC) supplied to facilities. Battery energy storage systems have bi-directional inverters that allow for both charging and discharging.
• An energy management system (EMS). This is responsible for monitoring and control of the energy flow within a battery storage system.  An EMS coordinates the work of a BMS, a PCS, and other components of a BESS. By collecting and analysing energy data, an EMS can efficiently manage the power resources of the system.

Depending on its functionality and operating conditions, a  BESS can also include a range of safety systems, such as a fire control system, a smoke detector, a temperature control system, cooling, heating, ventilation, and air conditioning systems. The safety systems have their own monitoring and control units that provide conditions necessary for the safe operation of a BESS by monitoring its parameters and responding to emergencies.

Five key safety considerations when working on BESS systems and sites

1. Invest in the right battery management system and energy management software

Using safe and standard compliant components is the mandatory first step to ensure the highest possible safety level; however, how the battery is used is key too. That’s why the battery management system (BMS) should ensure that the battery is not pushed beyond its limits. To provide this functional safety, the BMS must be certified according to IEC61508, the standard for functional safety of electrical/electronic/programmable electronic safety-related systems.

The BMS generates a huge amount of data that are read by the energy management software (EMS), saved locally and regularly backed-up to a secure cloud system. All this data can be used for analytic purposes to detect possible battery misbehaviour or deviations at an early stage as well as optimise system operation.

2. Thermal Runaway, Fires, and Explosions

In addition to standard fires, which require fuel, heat, and oxygen to continue burning, lithium-ion (Li-ion) battery cells can experience a chemical reaction known as thermal runaway, which does not require oxygen or a visible flame, if it occurs within a tightly packed cell assembly.

If not addressed by system protection devices, this process can continue to drive up temperature and pressure until the battery cell ruptures, which in turn can release explosive gases. If thermal runaway propagates through a module, flammable gases may build up within the BESS, creating the conditions for an explosion to occur. Thermal runaway can also be caused by exposure to overheating from traditional fires.

It is important to note that a standard approach to minimizing conventional fires—turning off ventilation and using clean fire suppression agents to cool or starve a fire of oxygen— may worsen the threat of an explosion by allowing explosive gas concentrations to increase. Thus, emergency systems and emergency response protocols shall be designed to extinguish fires and ventilate enclosures, as needed, before entry.

3. Ergonomics and Emergency stops (E-Stops)
Battery systems must shut down immediately for a controlled shutdown if a safety issue or battery anomaly is detected by the EMS, the BMS or any other safety device. It is also important to have a manual ‘emergency stop’ that can be performed by operators or first responders.

Due to this technology and BESS systems being in their infancy, design flaws can and do occur when constructing such sites. Some sites may have two BESS containers stacked two high and each BESS container has an E-stop which, if all on one level are perfectly accessible. However, when these are stacked, the E-stop for the top tier of containers is then inaccessible which could prove to be catastrophic in the event of a fire or incident that requires the system to be isolated and shut down.

4. Cybersecurity

Computer security, cybersecurity, or information technology security (IT security) is the protection of computer systems and networks from information disclosure, theft of, or damage to their hardware, software, or electronic data, as well as from the disruption or misdirection of the services they provide.

BESS developers should rely on experienced suppliers who can ensure the integrity of all equipment and routinely update security software.

Only vetted, trained personnel should have access to the BESS. Likewise, connections between the BESS and other web-based systems should be kept at a minimum.

5. Decommissioning
Decommissioning is especially important for Li-ion batteries, given that they contain hazardous materials. Used Li-ion batteries are considered hazardous waste that must be disposed of. Damaged Li-ion batteries that have not been fully discharged present a stranded energy hazard and are still considered batteries. The decommissioning process must take into consideration the full discharge of all power prior to being considered hazardous waste.

As Greensolver currently provides HSE services and assistance to battery storage projects in the UK and manages storage assets across Europe, it makes us an unrivalled partner for your storage projects.

Our team of experts have experience throughout various points of a BESS life, from HSE and construction considerations to operational management.

For more information regarding battery energy storage systems services, contact us and a member of the team will be happy to assist.