Separation of organic components from crystalline silicon solar cells by supercritical fluid technology
Typ
Examensarbete för masterexamen
Program
Applied physics (MPAPP), MSc
Publicerad
2020
Författare
Zachmann, Nils
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Photovoltaic solar cells are a safe, efficient, reliable, and non-polluting sustainable
alternative to fossil-fuel based energy source. However, decommission of solar modules
become gradually an environmental issue themselves. Untreated disposal of the
end-of-life modules provokes enormous environmental pollution by the enhancement
of leaching of hazardous constituents plus the loss of valuable raw materials. Hence,
efficient sustainable and feasible recycling of spent photovoltaic modules becomes
crucial to fulfil their sustainability purpose.
The biggest challenge in the recycling of the spent modules is associated with the
complete removal of the organic compounds from the solar cell. The current available
waste photovoltaic module recycling procedures rely either on high temperature
pyrolysis, leaching agents or a combination of both. Although, pyrolysis provides
the successful delamination of the encapsulant of the solar cell and the separation of
the glass in environmental perspective, it is not the most sustainable solution. First
of all the demand in energy during the pyrolysis process is rather high. In addition,
greenhouse gases such as carbon dioxide, carbon monoxide and hydrogen fluoride
are produced during the process and lead to environmental pollution. Thus, a more
sustainable and simultaneous economically feasible technique for the separation of
the solar cell from the encapsulation and the glass layer has to be developed. Supercritical
fluid technology is proposed to be a sustainable approach as a replacement
of incineration or pyrolysis methods.
In this work the effects of supercritical carbon dioxide (scCO2) with and without a
co-solvent on organic separation from crystalline silicon solar cell samples were investigated.
Apart from pure scCO2, the solvent power combination of scCO2+DMSO
and scCO2+Ethyl lactate at various pressure conditions were tested. The analysis
of the FTIR-spectra of the exhaust gas as well as SEM images of the samples are
leading to the conclusion that the combination of scCO2 and DMSO partly dissolves
the organic layerr from the cell.
The results were compared with those of the common incineration techniques on
the same type. For this, FTIR-spectra from previous as well as new experiments
were used to determine the exhaust gas emission of incineration system depending
of temperature and high temperature reactor design. Acetic acid, carbon dioxide,
carbon monoxide and hydrogen fluoride were detected in the exhaust gas.
Beskrivning
Ämne/nyckelord
Photovoltaic , c-Si solar cell , Recycling , Supercritical scCO2 , Incineration , Separation , EVA , Backsheet , FTIR , SEM