Selection of electrolytic capacitors is mainly based on their reliability. Beside this property, the evaluation of environmental performances of such devices is crucial due to their wide dissemination and utilization of critical raw materials for their production. Starting from the environmental analysis of the stages of selection and supply of raw materials, it is possible to improve the sustainability of the manufacturing process of a capacitor. In addition, the use stage and end-of-life of the devices can be analyzed to evaluate their entire life cycle. In this study, LCA (Life Cycle Assessment) methodology is applied to perform a comparative analysis between two types of aluminum electrolytic capacitors. These products can be applied in different sectors as industrial, inverter and UPS, solar, medical and tractions systems. The aim of this study is to compare the environmental impact due to the stages of production (from the raw materials supply to the assembly) and end-of-life (recycle or disposal of wastes) of two aluminum electrolytic capacitors, which are characterized by different internal designs but are manufactured by the same producer.
The paper was presented by Chiara Moletti, Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, Italy at the 3rd PCNS 7-10th September 2021, Milano, Italy as paper No.1.8.
INTRODUCTION
Modern life lays its foundations on the smart use of functional materials that are increasingly present in everyday life products and devices. The growth of the last decades is based on the wide application of semiconductor and passive components. Capacitors are one of the most common passive components and several types of capacitors are nowadays produced worldwide, like array capacitors (ACs), aluminum electrolytic capacitors (AECs), aluminum organic polymer capacitors (AOPCs), ceramic capacitors (CCs), multilayer ceramic capacitors (MLCCs), tantalum electrolytic capacitors (TECs), and supercapacitors [1].
Climate change is one of the main issues of our times. In the last decade, Europe and most of the countries worldwide introduced in their development programs the energy efficiency and independence, limiting the use of fossil fuel and rare earth [2], [3]. The growth of producers and users’ awareness about the environmental issue, together with the spread of policies aimed at the reduction of the human activities impacts on the environment, led to the necessity to manage the resources exploitation during design and manufacturing of products, and to use devices as much efficient as possible. This goal can be reached converting traditional systems into energy efficient systems and capacitors play an important role in this game [4]–[6]. One of the main fields of application of capacitors is the automotive sector, that requires an extensive use of these devices due to the rise of alternative propulsion technologies, where a proper electric management is crucial [7], [8]. For example, AECs are typically employed for small systems like for example air conditioning, automatic windows and engine controls [9].
Capacitors can help the efficient use of energy, nevertheless they trend to reduce the power factor of systems using harmonics that may decrease the overall efficiency.
Aluminum electrolytic capacitors have many applications in a wide range of sectors (e.g. industrial, medical, UPS). This type of capacitors is the most common thanks to their low price, high volumetric efficiency, and the possibility to select a proper voltage range and capacity depending on their application [10]. They are used when attenuation of voltage ripple, electric energy storage, and a large capacitance are required. Typical values of capacitance range from 0.1 μF to 2.7 F in these devices, and leakage current is not a crucial factor [11]. Their generally short lifetime respect to the other components of a device usually determines the service life of the system, for aluminum electrolytic capacitors this span of life ranges from 5000 to 25000 hours [12].
The selection of materials is crucial to produce capacitors, the AECs have the same internal structure but the specific materials which constitute them can vary. The positive pole is formed by an anodized aluminum foil that constitutes the anodic surface, which is in contact with a liquid electrolyte, that acts as cathode, in which a set of paper spacer is soaked. The electrolyte main components are a solvent and a solute, typically ethylene glycol and ammonium borate. This group of components is contained in an aluminum can and sealed in a polymeric case [13]. The assembly is composed to limit as much as possible the evaporation of the electrolyte that is one of the main causes of the decrease of the capacitance and the device wear-out.
The Life Cycle Assessment (LCA) is a standardized methodology through which it is possible to quantify and evaluate the environmental performances of a product or of a process [14], [15]. This study consists in an LCA of the manufacturing stage of two types of aluminum electrolytic capacitors having different internal design and manufactured by the same producer. The stage of production of the component is crucial since the selection of materials and assembly strategies influences the environmental performances of the capacitor. LCA is an important tool to evaluate the environmental impacts of capacitors, especially during the design phase of the devices. The growing production of these components is reflected in a tangled network of suppliers and manufacturers [16], [17].
