Fire Protection for Residential Solar Battery Storage Systems

Many UK homes have solar PV panels which generate electricity during daylight. By adding a battery to the system, you can now use this energy in the evenings.

And it’s good to know that when you add a battery to your solar PV any existing Feed-in Tariff or Smart Export Guarantee payments are unaffected.

The use of Lithium-ion batteries is expanding rapidly in domestic applications.

This innovative technology poses specific potential threats represented by the battery’s thermal “runaway” as a consequence of battery mismanagement / battery abuse and /or defects in battery manufacturing.

The battery runaway may result in serious fires and explosions that may lead to a catastrophe, if the accident is not contained/controlled and the consequent fire is allowed to spread.

Today there are a number of different Lithium-ion battery technologies in the market.

Some technologies are promoted as safer, but experience demonstrated that all the Lithium-ion batteries show the same behaviour/sensitivity versus the adverse effects or battery mismanagement that may lead to a runaway.

Battery thermal runaway.

The battery thermal runaway is a consequence of the battery being subjected to “adverse effects”. It will generate a heavy increase in the battery’s temperature, which will cause the electrolyte gasification and a subsequent rupture of the cells’ metal casing, or in case of lithium-polymers the rupture of the plastic pouch releasing the electrolyte gas.

These vapors, when in contact with the atmosphere, burn (flash fire) at a very high temperature (in excess of 800⁰C). Solarfire Systems also offer a detection system that senses these vapours, you can find our blog post on the off gas system here.

When subject to heating - thermal runaway - the battery cells’ burst suddenly.

The fire will involve in sequence the battery cells and the runaway may last for hours. Experience shows that batteries react for hours after the first incident, even when they are apparently under control.

Through tests performed, it is reported that 120⁰C is the critical temperature since the electrolyte will start to gasify.

The battery shall be cooled down to 40⁰C to interrupt the runaway sequence, however the remaining power stored in the damaged battery poses an additional potential threat.

The electrolyte fire will generate substantial amount of HCl, HF, CO, HCN, and potentially SO2 and H2S, depending on the battery technology and the electrolyte technology.

The release of toxic and/or combustible or explosive substances during a fire can evolve forming an explosive mixture.

Battery Storage Fire Protection www solarfiresystems com

Battery electrolyte leakage.

The wrong handling and mismanagement of batteries may result primarily in a battery internal pressure increase, which will lead to the electrolyte leakage.

The pouch/prismatic batteries (wrapping/casing cells made of polymers) are more sensitive to this phenomenon.

The electrolyte leakage poses a potential human hazard in case of exposure/contact, moreover it may cause short circuit of the battery cells and electronics protecting the battery.

Battery anodes and cathodes.

The self-heating of lithium-ion anodes/cathodes, in the presence of electrolyte, initiates at temperatures in the range of 70 to 90°C (158 to 194°F). If a cell is brought to the initiating temperature, it will self-heat to the point where a thermal runaway initiate. For a typical cylindrical metallic body cell, the thermal runaway will occur after approximately two days, if the cell is well-insulated.

The common architecture of Lithium-ion batteries with a cylindrical body is a metallic casing cell. In case of “flat cells”, the cells are wrapped by a “polymer envelop”, defined as a “plastic pouch” battery architecture.

In both cases the “battery” is formed by cell aggregates connected together. The number of “cells” and “cell aggregates” depend on the battery total power to be delivered.

The Solution

An Automatic fire detection and alarm system is fitted into or besides the battery storage enclosure to extinguish the battery fire and notifity the home owner of a discharge.


Why use a SolarFire System?

As the UK’s market leader in fire suppression, we understand the importance of protecting your home.

Our systems are certified to the highest standards, fully automatic and tailored to meet your needs and give you complete protection day or night.

Call us on 01628 902107 or email [email protected] for a free quote.

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