Boost­ing so­lar mod­ule ef­fi­ciency

Fo­cus is now shift­ing to­wards in­creas­ing the ef­fi­ciency of so­lar con­ver­sion to elec­tric­ity and cost re­duc­tion

Utilities Middle East - - SPECIAL REPORT - Baset As­aba, Edi­tor Email:­[email protected]

If you were to walk into a so­lar store and pur­chase some of their best-sell­ing PV pan­els, it is likely that their so­lar ir­ra­di­ance-to-elec­tric­ity con­ver­sion ef­fi­ciency would be around 17%. This is the typ­i­cal ef­fi­ciency of the top-sell­ing PV prod­uct, a mul­ticrys­talline sil­i­con panel. This means that for a typ­i­cal panel, 17% of all in­ci­dent so­lar en­ergy is con­verted di­rectly to us­able elec­tric­ity.

This is quite im­pres­sive for a de­vice that has no mov­ing parts and can gen­er­ate power at the lo­ca­tion where the elec­tric­ity is re­quired and no trans­mis­sion losses. It is no won­der that PV is al­ready one of the cheap­est power tech­nolo­gies avail­able.

How­ever, the ques­tion arises: more than 60 years af­ter the first demon­stra­tion of a prac­ti­cal so­lar cell by Bell Labs, have PV re­searchers al­ready reached the prac­ti­cal ef­fi­ciency limit for the tech­nol­ogy? Ac­cord­ing to pre­dic­tions made in a re­cent pub­li­ca­tion the an­swer seems to be very much a re­sound­ing “No.”

Var­i­ous man­u­fac­tur­ing trends that will lead to fur­ther ma­jor im­prove­ments in ef­fi­ciency over the next decade are al­ready be­ing im­ple­mented by in­dus­try.

Cur­rently, multi- and mono-crys­talline sil­i­con ac­count for more than 90% of the world mar­ket. Both multi- and mono- pan­els are con­structed with in­di­vid­ual sil­i­con wafer cells. The pri­mary dis­tinc­tion is the crys­tal struc­ture of the sil­i­con wafers them­selves, with mono-crys­talline hav­ing a higher qual­ity crys­tal struc­ture than multi-crys­talline. The typ­i­cal ef­fi­ciency of the most com­monly in­stalled pan­els (multi-crys­talline sil­i­con) is around 17%. For the high end of the mar­ket (pre­mium mono-crys­talline), the value is around 21%.

Boost­ing so­lar panel ef­fi­ciency is very much on the minds of pho­to­voltaic man­u­fac­tur­ers. Im­prov­ing the ef­fi­ciency of pho­to­voltaic mo­d­ules helps in­crease sales and boosts the bot­tom line. For in­stance, China head­quar­tered JinkoSo­lar, which is our Knowl­edge Part­ner in this Spe­cial Re­port (p36), re­cently re­leased its Chee­tah mod­ule, a com­mer­cially mass-pro­duced mono­fa­cial mod­ule, bring­ing the in­dus­try into the new age of PV 4.0.

JinkoSo­lar Chee­tah se­ries has cre­ated a new bench­mark for ul­tra-high per­form­ing mo­d­ules with its in­dus­try lead­ing per­for­mance in met­rics such as out­put, lim­ited degra­da­tion, shade tol­er­ance, and dura­bil­ity.

As man­u­fac­tur­ers con­tin­u­ally work on bet­ter­ing their prod­ucts, con­sumers win, as their PV sys­tems pro­duce more free en­ergy by har­ness­ing the sun’s power. Pho­to­voltaic mo­d­ules are made of sev­eral com­po­nents, each of which gives man­u­fac­tur­ers more op­por­tu­nity to im­prove ef­fi­ciency.

Pho­to­voltaic man­u­fac­tur­ers are work­ing to re­fine the man­u­fac­tur­ing process to im­prove pro­duc­tion ef­fi­ciency. They are also work­ing to iden­tify bet­ter ma­te­ri­als for use in panel fabri­ca­tion.

Specif­i­cally, man­u­fac­tur­ers are im­prov­ing the anti-re­flec­tive coat­ings and tex­ture lay­ers, with the goal of im­prov­ing panel ef­fi­ciency.

You may have also no­ticed that most pho­to­voltaic pan­els fea­ture dis­tinc­tive grid lines. These are ac­tu­ally tiny metal wires called bus­bars, and they help with elec­tric­ity flow from the mod­ule. Be­cause the bus­bars re­flect some sun­light, man­u­fac­tur­ers are re­search­ing ways to elim­i­nate the wires, or to make them thin­ner to re­duce the en­ergy lost due to this re­flec­tion.

Pho­to­voltaic mo­d­ules also have small white spa­ces be­tween the so­lar cells, as well as along their edges. By get­ting rid of these gaps, or find­ing a way to over­lap the cells, man­u­fac­tur­ers be­lieve they can boost PV panel ef­fi­ciency even fur­ther.

Most pho­to­voltaic panel designs have so­lar cells at­tached to a sturdy back­sheet, which means only one side of the mod­ule can cap­ture en­ergy from the sun. Man­u­fac­tur­ers are ex­plor­ing the use of bi­fa­cial tech­nol­ogy, cre­at­ing clear pan­els that can ab­sorb light from both sides.

Although this ef­fi­ciency im­prove­ment may not be use­ful for all pho­to­voltaic applications, it could sig­nif­i­cantly im­prove the ef­fi­ciency of some PV sys­tem in­stal­la­tions.

But can we ex­pect fur­ther in­no­va­tions to emerge, which will raise the record efficiencies and drag the typ­i­cal val­ues along with them? Ac­cord­ing to the In­ter­na­tional Tech­nol­ogy Roadmap for Pho­to­voltaics, there are al­ready some key de­vel­op­ments that will do ex­actly that.

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