Keywords

10.1 Introduction

The majority of the conventional solar panels being deployed are conventional solar panels made from the silicon as silicon is easily available in nature and in abundance but the problem is high cost of manufacturing [1]. Hence there is a gradual shift towards generating solar energy from nanomaterials such as nanofiber, nanowires, nanoparticles and other various active nanotemplates [2] which will not only help in increasing the efficiency but will also reduce the manufacturing cost. When the conventional panels will reach their end use there will be great inflow of silicon waste but this waste will get reduced by using nano solar panels [3]. For protection of the environment, recycling of solar panels can be done but the limitation is that when these panels are recycled, it utilizes much more amount of energy as compared to recycling of nano solar panels. According to the researcher’s the amount of E-silicon that can be recovered from used solar panels is 90% but the equipment’s used for manufacturing as well as recycling the panels also contribute to E-waste [4]. The paper presents a comparison between the recycling of silicon solar panels and nanomaterial (perovskite) based solar panels and analyzes amount of waste generated.

10.2 Conventional Solar Cells

10.2.1 Manufacturing of the Silicon Solar Panels

Elements used in making the solar includes silicon, carbon, boron, alluminium, zinc, pottasium, silver etc. with average silicon cell diameter ranging from 6 to 15 cm and thickness of 200–250 µm. An average module contains around 36 numbers of cells [5].

The composition and thickness of the cell varies according to the type of cell. The technology requires a number of thermal or chemical processing steps such as diffusion, doping, drying, firing, annealing, deposition, and coating of the solar cell [6] and hence the required machinery. This green technology is being manufactured in developing countries like China [7] and India but they not have proper provision of protecting the environment as well the workers employed. Once the panels will complete their life cycle, if not properly disposed, will add to the silicon waste.

The below table compares the physical parameters for Single Silicon and Cadmium Telluride solar cells based on three scenarios [8]

  • Business as usual (BAU)

  • Realistic improvement (REAL)

  • Optimistic improvement (OPT)

It is estimated that the cumulative global deployment of solar panels will reach approximately 1,632 GW in 2030 and about 4,512 GW in 2050 [9]. Depending upon the increase in number of panels deployed for generation of electricity there will be subsequent rise in the amount of materials like silicon, silver, cadmium, telluride, glass etc. required for manufacturing (Table 10.1).

Table 10.1 Physical parameters of Single Si and CdTe solar cell based upon business as usual, optimistic and realistic improvement [12]
Full size table

10.2.2 Recycling of Solar Panels

The panels contain hazardous as well as valuable materials. The process of recycling is necessary for recovering, reusing materials in order to reduce the cost of per peak of new panels as well as the dependence on the natural resources. Process of recycling requires the process of recycling requires the panel to be dismantled after which the methods such as mechanical separation, chemical dissolution and electrodeposition are used to recover the metal [10]. After layer by layer stripping the elements can be recovered parts per billion during recycling [11]. Hence, after an operational life time of 25–40 years based on early and regular loss scenario the panel waste is estimated to be 60–78 million tons globally respectively [9]. Depending upon the waste generated the great amount of elements like silver, glass and silicon recovered can be used again reducing the cost of new panels without compromising the efficiency [12].

10.2.3 Synthesizing Nano Based Solar Panels

Nano material is the future technology in solar energy. Synthesis of nanosolar panels or dye synthesized solar panels can be done using materials like ZnO, perovskite, graphene, carbon nanotubes/rods, Copper-Indium-Diselenide semiconductor ink, Silicon nanocrystalline ink, “Nano-cables” which are grown on a thin film material [13]. Recently nano cells made from lead Iodide have emerged as strong competitor to the conventional solar cells [14]. Efficiency of perovskite based solar cells is 20% more than the power conversion efficiency of the commercially available solar panels [15].

10.2.4 Recycling of Nano Based Solar Panels

The recycling of nano cells have been performed at laboratory level till date, hence it challenging to estimate the cost as well the difficulties in recycling at industrial level. The elements of the Perovskite based solar cells which contain Methylammonium lead iodide (MAPbI3), the conductive glass, gold electrodes [4] all layers when stripped which includes toxic lead as well as Fluorine doped tin oxide glass which forms the most expensive part of the cell can be reused without effecting the performance of the device as such devices gives the performance efficiency of 13.5% [16]. Recycling process of nanosolar includes technology which requires low temperature solution. Devices used for recycling at laboratory level are chemicals like dimethylformamide, chlorobenzene, ethyl acetate etc. which are easily available [4].

10.3 Limitations

Research is being done to overcome the following limitations.

  • The operational lifetime for silicon solar panels is almost two decades hence more focus is on installation and generation of electricity rather than

  • The manufacturing and use of nanosolar panels is still at research and laboratory stage

  • There is no sufficient data available on amount of each metal recovered from nanosolar panels.

  • Polysilicon is being used with ethanol instead of chlorine-based chemicals, in order to avoid the creation of silicon tetrachloride.

10.4 Conclusion

Attempt is being made to bring change in technology for recycling of solar panels. It is also observed that though there is limited data available, the recycling of 3rd generation solar cells is simpler as compared to the energy intensive equipment’s required for conventional solar panels. The manufacturing cost is reduced as well as the rate of conversion of solar energy to electricity is high. The dyes used can be manufactured locally and easily. Use of nanomaterials if recycled and disposed in environmental friendly manner will not only protect the environment but also help us sustain the goal of establishing green energy.