π Energy π Planet π Industry
Energy transition: recycling materials to preserve resources

How recycling solar panels will help preserve energy security in Europe

Daniel Bajolet, Member of SAGSI (China) and Co-founder of ROSI
On March 22nd, 2023 |
3 min reading time
Daniel Bajolet
Member of SAGSI (China) and Co-founder of ROSI
Key takeaways
  • Of the 3.5 million tonnes of silicon manufactured worldwide, Europe as much as 17%, while China produces as much as 75%.
  • It takes about 6 tonnes of scarce natural resources to produce one tonne of photovoltaic silicon or “polysilicon”.
  • This chain generates a lot of CO2 – for a standard 60-cell module manufactured in China, 77 kg of CO2is emitted compared to 13 kg in France.
  • The technologies developed today make it possible to recycle solar panels in their entirety with the exception of the polymers.
  • The wave of panels at the end of their life combined with recycling should make it possible to build a new virtuous and almost autonomous value chain in Europe.

In the pho­to­volta­ic indus­tri­al chain – from quartz to elec­tron – it is often said that sil­i­con is abun­dant­ly avail­able on our plan­et. But, con­trary to the com­mon­ly used expres­sion, this abun­dance in the Earth’s crust has noth­ing to do with its indus­tri­al avail­abil­i­ty. To extract so-called ‘met­al­lur­gi­cal’ sil­i­con (99.8% pure), very spe­cial qual­i­ty quartz, low-ash reac­tive coal, wood and elec­tri­cal ener­gy are required. Of the 3.5 mil­lion tonnes man­u­fac­tured world­wide, Chi­na pro­duces around 75%, while Europe pro­duces only as much as 17% of its own consumption.

Val­ue chain for pho­to­volta­ic pan­els. Cred­it: ROSI.

This sil­i­con must be puri­fied to a puri­ty of 9N (99.9999999) in order to be processed into pho­to­volta­ic “grade”. How­ev­er, Europe and the Unit­ed States, which were lead­ers in the 2010s, have become mar­gin­al in the pro­duc­tion of this mate­r­i­al. Only the Ger­man com­pa­ny, Wack­er, has man­aged to remain a major play­er, thanks to its qual­i­ty, even if the pres­sure exert­ed on prices and anti-dump­ing mea­sures have been enabling Chi­nese pro­duc­ers to obtain a cur­rent mar­ket share of more than 90%. The fol­low­ing two tables illus­trate this*:

In 2022, 827,000* tonnes of PV sil­i­con were man­u­fac­tured in Chi­na com­pared to about 40,000 tonnes in Ger­many. Giv­en the pro­cess­ing yields, it takes about 6 tonnes of scarce nat­ur­al resources to pro­duce one tonne of pho­to­volta­ic sil­i­con or “poly­sil­i­con” (5.8 T/T to pro­duce Mg-Si, and then a min­i­mum of 5% loss in the con­ver­sion of Mg-Si to PV-Si).

Pro­duc­tion of raw mate­ri­als for pho­to­volta­ic pan­els in 2019*.

From polysilicon to electron

The next step is to trans­form this pure mate­r­i­al into ingots, which are in fact more than 83% monocrys­talline. The search for high pho­to-elec­tric yields is turn­ing play­ers away from poly­crys­talline ingots, while the ‘semi-mono’, a French curios­i­ty, is non-exis­tent. At this stage, about 35 to 40% of the sil­i­con is lost, trans­formed into kerf – a nano­met­ric sus­pen­sion of chips that is very dif­fi­cult to use. Wafers are then obtained. Here again, Chi­na has cap­tured most of the world’s pro­duc­tion with 357 GW equiv­a­lent. Only one Euro­pean pro­duc­er is still oper­at­ing (NORSUN in Norway).

The wafers are then trans­formed into cells, a process that requires 7–12 steps depend­ing on whether PERC, TOPCON or HETEROJONCTION tech­nolo­gies are used. It is at this stage that the sil­ver col­lec­tors are put in place. In 2020, PV was already con­sum­ing 3000 T/year or 10% of the world’s avail­able sil­ver. This has increased to 13% by 2022. Chi­na pro­duced 318 GW equiv­a­lent in 2022 and fore­casts to 2030 make sil­ver extrac­tion unten­able with­out recycling.

Final­ly, the assem­bly of cells, inter­con­nect­ed by cop­per-based col­lec­tors, is encap­su­lat­ed between two sheets of EVA to with­stand about 20 years of weath­er­ing, and then glued under a sheet of glass, with an alu­mini­um frame, to become a mod­ule. There is a strong trend towards increas­ing the num­ber of cell for­mats, both whole and half cells, to opti­mise the effi­cien­cy and capac­i­ty per mod­ule. From the 150 WattC of the 2010s, we are now mov­ing to mod­ules deliv­er­ing 500 WattC1. Chi­na has pro­duced the equiv­a­lent of 288 GW of mod­ules by 2022. 

This chain is high­ly ener­gy con­sum­ing and gen­er­ates CO2 emis­sions. If we cal­cu­late these two indices, for a stan­dard 60-cell mod­ule man­u­fac­tured in Chi­na, deliv­er­ing 350 WattC, we obtain respec­tive­ly 120 KWH con­sumed and 77 kg of CO2 reject­ed. The same mod­ule man­u­fac­tured entire­ly in France would have required 118 KWH and released 13 kg of CO2. 

Panel recycling

We can now mea­sure what it means to recre­ate a sov­er­eign PV chain in Europe, where only basic sil­i­con met­al and PV grade sil­i­con are avail­able. The inclu­sion of recy­cling of loss­es in this val­ue chain is essen­tial for the sus­tain­abil­i­ty of a new indus­tri­al mod­el to avoid the waste of scarce nat­ur­al resources.

Recy­cling of pho­to­volta­ic pan­el com­po­nents. Cred­it: ROSI. 

The tech­nolo­gies devel­oped today now make it pos­si­ble to recy­cle solar pan­els in their entire­ty – with the excep­tion of poly­mers – includ­ing ker­f’s (ROSI has devel­oped tech­nolo­gies to recy­cle them as a replace­ment for fresh sil­i­con), the alu­mini­um frame (the cir­cuits and tech­nolo­gies already exist), the glass (which has to be per­fect­ly clean in order to be recy­cled by glass­mak­ers), the cop­per (the cir­cuits and tech­nolo­gies already exist) and the silver.

But most impor­tant­ly, and this was the most dif­fi­cult part, we are now able to recy­cle these dif­fer­ent sources of sil­i­con to 5N qual­i­ty: recov­ery effi­cien­cies are around 90% of a pan­el’s con­tent. The wave of end-of-life pan­els com­bined with the recy­cling of ker­f’s should make it pos­si­ble to build a new vir­tu­ous and almost autonomous val­ue chain in Europe.

1The watt-peak (WattC) cor­re­sponds to the deliv­ery of an elec­tri­cal pow­er of 1 watt, under stan­dard ref­er­ence con­di­tions. Def­i­n­i­tion by EDF: https://​www​.edfenr​.com/​l​e​x​i​q​u​e​/​w​a​t​t​-​c​rete/

Our world explained with science. Every week, in your inbox.

Get the newsletter