Renewable energy and safety concerns: the case of secondary batteries

In the framework of the continuous effort in reducing the emissions of greenhouse gases and increasing the amount of renewable energy sources, secondary batteries are playing a more and more significant key role. In fact, on one hand, they allow to make the use of the energy derived from these sources more continuous, in contrast with the intermittent availability which often characterizes them (e.g. wind energy); on the other hand, they allow its adoption in a much wider range of application, such as in the automotive industry, where the number of electric and hybrid electric vehicles is constantly increasing. Consequently, a strong interest is present in the availability of efficient and reliable rechargeable energy storage systems both to be inserted in the main electric network (large stationary systems and off-grid solar PV power systems), and to be installed on mobile electric vehicles. From this point of view, secondary Lithium-ion batteries represent the most promising technology available at the moment. However, despite the wide adoption of these batteries in a number of commonly used technologies (mobile cellular phones, laptops, etc.), a number of past accidents have raised concern about their introduction in the above mentioned larger systems where even much higher powers and energy densities are required (e.g. in the aeronautical and aerospace technologies). In the present paper, an analysis of the causes and of the final consequences of as many as possible of the failures reported in the literature will be carried out. In addition, based on the main characteristics of the energy storage systems and of the specific life cycle under consideration, an efficient risk analysis methodology framework will be suggested, with specific reference to the Li-ion battery technology. This would allow a safer use of this important technology in a wider range of practical applications, thus leading to a more efficient use of renewable energy sources and, at the same time, reducing the risk to the possibly exposed people (either workers or consumers) and to the environment.