The Paris Agreement on climate change holds nations accountable for reducing their greenhouse emissions and reliance on fossil fuels, thus driving them to invest and use renewable energies, such as solar and wind. However, the sun doesn’t always shine and it’s not always windy – or it might be very sunny or windy, leading to over-supply of the grid. To ensure that renewables are used for maximum benefit, any excess energy they produce (i.e., that isn’t needed for the grid at that time) is stored in local storage facilities, which take the form of large batteries. These release energy later – when the grid requires more power, or when there is less sun or wind, such as overcast nights or calmer, duller days. However, these batteries can only release energy for a few (between 1 and 12) hours, so their use is limited to short-term, energy-on-demand requirements.
Batteries are effective at reducing power outages since they can also store excess traditional grid energy. The energy stored within batteries can be released whenever a large volume of power is needed, such as during a power failure at a data centre to prevent data being lost, or as a back-up power supply to a hospital or military application to ensure the continuity of vital services. Large scale batteries can also be used to plug short-term gaps in demand from the grid. These battery compositions can also be used in smaller sizes to power electric cars and may be further scaled down to power commercial products, such as phones, tablets, laptops, speakers and – of course – personal gas detectors.
Battery technologies can be segregated into four main categories:
Chemical – e.g. ammonia, hydrogen, methanol and synthetic fuel
Electrochemical – lead acid, lithium ion, Na-Cd, Na-ion
Electrical – supercapacitors, superconductive magnetic storage
Mechanical – compressed air, pumped hydro, gravity
Typical processes and associated gas detection issues
A major concern arises when static electricity or a faulty charger has destroyed the battery’s protection circuit. Such damage can permanently fuse the solid-state switches into the ON position, without the user knowing. A battery with a faulty protection circuit may function normally, but it does not provide protection from short circuit.
At this point, a gas detection system can establish if there is a fault and may be used in a feedback loop to shut off power, seal the space and release an inert gas (such as nitrogen) into the area to prevent any fire or explosion.
Thermal runaway of lithium-metal and lithium-ion cells has caused numerous fires. Studies have found the fires to be fuelled by the flammable gases that are vented from the batteries during thermal runaway.
The electrolyte in a lithium-ion battery is flammable and generally contains lithium hexafluorophosphate (LiPF6) or other Li-salts containing fluorine. In the event of overheating, the electrolyte will evaporate and eventually be vented out from the battery cells. Researchers have found that commercial lithium-ion batteries can emit considerable amounts of hydrogen fluoride (HF) during a fire, and that emission rates vary for different types of battery and stateof-charge (SOC) levels. Hydrogen fluoride can penetrate skin to affect deep skin tissue and even bone and blood. Even with minimal exposure, pain and symptoms may not present for several hours, by which time damage is extreme.
With hydrogen fuel cells gaining popularity as alternatives to fossil fuel, it is important to be aware of the dangers of hydrogen. Like all fuels, hydrogen is highly flammable and if it leaks there is real risk of fire.
Traditional lead acid batteries produce hydrogen when they are being charged. These batteries are normally charged together, sometimes in the same room or area, which can generate an explosion risk, especially if the room is not properly ventilated.
Most hydrogen applications cannot use odorants for safety, as hydrogen disperses faster than odorants do. There are applicable safety standards for hydrogen fuelling stations, whereby appropriate protective gear is required for all workers. This includes personal detectors, capable of detecting ppm level hydrogen as well as %LEL level. The default alarm levels are set at 20% and 40% LEL which is 4% volume, but some applications may wish to have a custom PPM range and alarm levels to pick up hydrogen accumulations quickly.