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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - Eco-Solar (Eco-Solar Factory - 40%plus eco-efficiency gains in the photovoltaic value chain with minimised resource and energy consumption by closed loop systems)

Teaser

Summary

Eco-Solar envisions an integrated value chain to manufacture and implement solar panels in the most ecologic way by maximising resource efficiency, taking into account reuse of materials during production and repurposing solar panel components at end of life stage. Eco-Solar will demonstrate that during the lifetime of a solar electricity producing field, individual panels can be monitored, allowing to identify defaulting panels at an early stage, replacing or repairing them and thus to increase the overall energy yield.
Even though solar power is pollution-free during use, production of PV-modules consumes considerable energy and natural resources. Moreover, recycling is hardly considered during module production, and therefore still cumbersome and inefficient. Considering that the fast growth of the PV-industry entails similarly fast growth in resource consumption with growing production capacity: currently modest amounts of use can become very high.
The Eco-Solar project aims to maximise resource productivity and reduce pollution in PV, through minimising use of critical resources like energy, water, chemicals, aluminium, silver and lead, while simultaneously maximising recycling possibilities, by introducing design for recovery, reuse and recycling in this sector, and collaborating over the value chain for improvements in waste reduction.

Work performed

Crystallisation:
Argon recycling has been implemented for monocrystalline ingot growth and a recycling rate of 96% was achieved. The method is based on a chemical looping combustion process to convert combustible species in the exhaust gas stream to carbon dioxide and water, followed by efficient of carbon dioxide and water in regenerable reactor beds. First results from crystals grown with argon recycling show similar material performance as grown by standard process without recycling.
Reusable crucibles based on advanced silicon nitride ceramics have been tested for crystallisation of multicrystalline silicon ingots. The silicon nitride crucible has been used so far in five subsequent crystallisation runs. Material performance is similar to material grown from conventional silica crucibles.
Wafering:
Silicon kerf loss from wafer sawing has been recycled and cleaned. Transition metals were reduced down to ppm level, but oxygen remained in the range of some percent. Thermal treatment of silicon kerf loss below melting temperature of silicon has been carried out and the oxygen amount could be reduced significantly. Furthermore it has been demonstrated that silicon kerf loss has the potential to be used as anode material in lithium ion batteries.
Solar cell:
A Solar cell process using only one etching and cleaning step was developed by ISC. Solar cells were produced from p-type (single crystalline) wafers. First results show superior performance of a phosphorus diffusion process for the formation of the pn junction that does not require subsequent phosphosilicate glass (PSG) removal. Thus, the PSG etching step, commonly performed in diluted HF can be left out. In addition a phosphorus diffusion process for the formation of the pn-junction was developed that allows excellent passivation quality without the necessity to remove the phosphorus silicate glass.
Optical system for the labelling of solar cell defects and self-learning software were programmed.
Module:
A first set of two industrial size (60 cells) modules have been manufactured with Glass/Glass lamination technique. The module is based on solar cells manufactured from material crystallised under argon recycling.
Recovery of glass sheets as an entire piece has been demonstrated. This presents an important innovation compared to state-of-the-art recycling of standard laminated PV modules, where glass is recovered in form of secondary grade granules. A second component that has been successfully recovered as entire piece from discarded NICE modules that also presents an innovation, is the copper wire that can be easily detached from the front of the cells since there is no physical link as in standard modules by soldering.

Final results

All project developments: reduction of waste and resource consumption per production of 1 mono-Si based PV-module (60 6-inch solar cells) envisaged at the beginning of the project and the current degrees of achievement after implementing of all project developments from the project partners and an overview on the reduction potential for greenhouse gas emissions of the current processing status of the individual work packages (multi-Si based PV module) are shown.