This paper describes the assessment of potential recovery of secondary raw materials coming from the decommissioning phase of a photovoltaic system, equipped with a storage system made with a battery pack, according to valorisation technologies applicable and market values of recoverable materials. The work is based on the methodology developed within the work done in ENEA in the framework of “Ricerca di sistema elettrico” Report RdS/PAR2017/253 [1]. The work was developed within a master’s thesis in environmental engineering at the University of Bologna and ENEA [2].
Methodology applied is based on four main steps where a clear knowledge of the materials stoked in the PV plant and its storage system is the main premise of the analysis.
To this end, the first step is to collect primary data from suppliers/experts/installers. In case primary data are not available, it is possible to fill the data gaps with in-depth bibliographic research, using scientific papers and database.
The second step consists in identifying all the technologies and all the treatment/disposal scenarios of the components of the system. This analysis also includes the identification of the main suppliers of these technologies available in the recovery/recycling/disposal chain (limited to the technologies available on the market) and the possibility of defining a configuration of the overall valorisation process of the decommissioning scenario, given by the combination of different technologies identified in the above analysis (optimal layout scenario).
The third step consists in the development of a model, in the case of this study, on an excel basis, capable of reproducing all the identified disposal scenarios.
The third step consists in the development of a model, in the case of this study, on an excel basis, capable of reproducing all the identified disposal scenarios. The model uses the plant inventory data, found in the first step, such as input flows to the various treatment scenarios, the efficiencies of separation and recovery of materials (step 2), and generates the material flows in output. These flows, which may have to undergo further treatments in order to be used as secondary raw materials, correspond to the quantities of secondary materials potentially recyclable from the recovery chain. It should be noted that in the study the inventory values are described according to an average value, a minimum value and a maximum value, which makes it possible to manage the high uncertainty present in the characterization of the system, as for example in the case of photovoltaic panels or cables. After identifying the input and output flows, in the fourth step, a Life Cycle Assessment (LCA) study is carried out. It consists in the identification or in the development of the datasets to model the plant and the datasets representative of the disposal and recovery treatments. In the LCA study it is essential to take into account the so-called avoided products (i.e the recovered secondary raw materials), a methodological solution of the LCA methodology to quantify the environmental benefits associated with recycling processes. The results of the LCA study allow both the assessment of the environmental impacts associated with the different scenarios under analysis, and the quantification of the real benefit associated with the treatment.
The last phase of the study provides for a trade-off analysis of the results of the LCA and of the input-ouput analysis described above, to provide a general assessment, both economic and environmental, of the optimal treatment layout. Moreover, based on the results eco-design solutions are defined in order to promote a design of future photovoltaic systems maximizing the recovery efficiency of end-of-life materials and their valorisation as secondary raw materials.
