Safe storage: Precaution is better than cure

Safety first. Burning electric cars and aviation batteries reported in the media have caused skepticism about energy storage technology. However the use of the technology can be both safe and manageable if the correct safety precautions are taken.

 

By Stephan Wild, and Stefan Karl, Freelance Journalists

Green energy must be stored in order to bridge the time when the wind has died or the sky has clouded over. Storage technology has made great strides in the last few years, yet a few incidents have caused damage to its reputation. Nonetheless, one thing is clear: the technology can be both safe and manageable if the correct safety precautions are taken.

A glance at the press, be it trade, industry, or the daily newspapers, would deter the less technically aware readership: Burning electric cars and aviation batteries have cast a shadow over energy storage technology.

A recent investigation by the German Karlsruhe Institute for Technology (KIT) into stationary energy storage systems for domestic usage seems, at face value, to have added to the gloom – spicing up its report with a certain audience appeal, the piece was entitled, ‘Single Family Homes will Go up in Flames’. If you take a look at the content of the analysis the central message of the KIT investigation is clear: only non-certified safety systems represent a danger.

This verdict is correct and is hardly surprising – otherwise the existing certifications would be worthless. Franz-Josef Feilmeier, Managing Director of German energy storage provider FENECON, also sees it this way: “The safety of storage systems utilizing Lithium-ion technology is a critical issue. But we can learn a great deal from the electric vehicle manufacturers, who have succeeded in ensuring system safety in what are significantly more testing circumstances.

The manufacturers have committed themselves to stringent and wide-reaching safety standards which also cover stationary storage, with the result that the systems now available on the market are thoroughly safe.” Here is the basic problem: in the case of damage to the separators – which divide the positive and negative electrodes from one another – short-circuits within the battery cells can burn within a very short space of time, perhaps even explode.

Feilmeier and his team, together with partner firms and cell suppliers such as BYD, ascribe safety the highest priority in three central areas: thermal, mechanical, and electrical stresses, to the lithium-ion batteries. In this sense, the company does not differ from other serious suppliers.

Safety with batteries and accumulators – what really counts?

Residential storage systems usually ensure mechanical safety. This is due to their stationary application, which is in general not related to major physical stresses. However, inappropriate transportation can damage the systems and in some cases even lead to fires.

Systems that pass safety tests such as the well-known nail-penetration test – in which a battery should not ignite when a nail is driven through it – can, against this backdrop, be applied without risk. More difficult is the question of electrical stress (and the associated thermal stress), which can arise as a result of overloading for example.

Ceramic separators, or those made from other fire-resistant materials, are an option here to prevent short circuits. “Lithium-titanate and Lithium-Iron-Phosphate electrodes have an advantage when compared to Lithium-mixed oxides such as Lithium Cobalt Dioxide.

When overheated they do not release flammable oxygen”, continues Feilmeier. Andreas Niederholz, Application Engineer for Industrial Storage at Leclanché, continues on the theme of safety: “Because of the fact that titanate can no longer react with oxides from the cathode, the battery’s so-called ‘thermal runaway’ is avoided, even in the case of mechanical damage.”

Beyond this, a corresponding battery management system is able to prevent the undesired overload conditions or, in the event of damage, to disable the affected cells. Such systems also measure important core electrical data such as temperature, however, those who seek salvation in the physical attributes of lead batteries – such as charge/discharge performance, or capacity – should consider the fact that the overloading of these cells can cause the production of hydrogen, which is highly explosive.

Better safe than sorry: Certified Safety

It is important that energy storage systems, together with a management system, have the appropriate safety certificates. Examples, amongst others, are the QC/T 743, ISO 12405, IEC 62660, SAND 2005, UL 1642 and UL 2580 certifications which are required by the electromobility sector.

That said, it is not enough to simply make the use of the battery safe: Manufacturers and distributers must look at further issues, such as the use of legally compliant packaging and the correct transportation of the systems, where a transport certification under UN38.3 is required. The aforementioned certifications are the key to the safe deployment of energy storage systems in both the domestic and industrial sectors.

Those currently reading the literature provided by the manufacturers on material components, the transport and installation instructions etc. can plan for a safe and worry-free future of selfsupply. But one rule applies, even in the case of the headline grabbing examples from the vehicle and aviation sectors mentioned at the start of this article: The technology is safe when it is used correctly.

 

Author Stephan Wild Stefan is a freelance journalist and regularly contributes articles on renewable energies and energy storage to trade magazines and public media.
Author Stefan Karl writes articles for different magazines and media in the field of renewable energy.

Image Source: © tashatuvango | fotolia.com

 

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