Study sug­gests gen­er­at­ing so­lar en­ergy from snow­cov­ered moun­tains


The Daily News Egypt - - Front Page - By Mo­hammed El-Said

A re­cent study sug­gests that so­lar power can be gen­er­ated not just sum­mer but in win­ter as well, by plac­ing so­lar pan­els on snow-cov­ered moun­tains with steep tilt an­gles.The study aims to trans­form the sea­sonal pro­duc­tion of so­lar en­ergy through pho­to­voltaic (PV) cells into PV pan­els from tem­po­rary—in the sum­mer months only—to per­ma­nent in or­der to keep up with the in­creas­ing de­mand for elec­tric­ity.

Ac­cord­ing to the re­sults of the study which was pub­lished on Mon­day in the Pro­ceed­ings of the Na­tional Academy of Sciences Jour­nal, plac­ing the so­lar pan­els on the snow-cov­ered moun­tains in this po­si­tion can gen­er­ate sim­i­lar amounts of en­ergy, com­pared with the place­ment of so­lar pan­els in cities and flat lands-which have a lower sur­face area-and can con­vert a large amount of elec­tric­ity pro­duced from sum­mer to win­ter,and bal­ance the re­la­tion be­tween elec­tric­ity de­mand and pro­duc­tion dur­ing win­ter and sum­mer.

Elec­tric­ity must be pro­duced when it is needed, be­cause it is dif­fi­cult to store large amounts of it. So­lar pan­els pro­duce elec­tric­ity when it is sunny, but not nec­es­sar­ily when the de­mand for it is high­est. In coun­tries which use a great ex­tent of elec­tric­ity for cool­ing pur­poses, de­mand and PV pro­duc­tion might be well aligned, but in mid-lat­i­tude coun­tries the need for elec­tric­ity is high­est in win­ter when it is cold and dark. Con­se­quently, de­mand and pro­duc­tion do not cor­re­late, ac­cord­ing to the lead au­thor of the study,An­ne­len Kahl, from L’École Polytech­nique Fédérale de Lau­sanne (EPFL), Switzer­land.

Kahl in­formed Daily News Egypt that the higher the con­tri­bu­tion of so­lar PV to a coun­try’s elec­tric­ity bud­get, the more crit­i­cal this dis­crepen­cancy will be­come.“It is not just im­por­tant to pro­duce as much re­new­able elec­tric­ity as pos­si­ble, it is also im­por­tant to pro­vide it at the right time. Our re­sults show that we can sig­nif­i­cantly im­prove from the con­ven­tional setting,” she said.

She noted that she started work­ing with the re­new­able en­er­gies group at the EPFL in Fe­bru­ary 2015, but this spe­cific study took prob­a­bly about 1.5 years.

Achiev­ing the study’s goals can be done by plac­ing PV pan­els un­der steep tilt an­gles in a moun­tain­ous en­vi­ron­ment.The re­sult­ing ef­fect of boost­ing win­ter elec­tric­ity pro­duc­tion is three­fold: in the moun­tains there is less fog and cloud cover in win­ter than in the val­leys (the typ­i­cal ur­ban in­stal­la­tion sites), hence the in­com­ing ra­di­a­tion that reaches the ground is al­ready higher in win­ter.

Also, by in­stalling the pan­els with a steeper in­cli­na­tion an­gle than pos­si­ble in con­ven­tional ur­ban set­tings (in Switzer­land the law re­quires PV pan­els to flush with the roof sur­face), win­ter pro­duc­tion is fur­ther in­creased be­cause the PV sur­face is more per­pen­dic­u­lar to the in­com­ing ra­di­a­tion, tak­ing into con­sid­er­a­tion that the sun is closer to the hori­zon in win­ter than in sum­mer.The snow cover in the moun­tains in­creases the re­flec­tion of so­lar ra­di­a­tion onto the sur­face of the PV panel.This is due to the high re­flec­tion of snow in com­par­i­son to all other sur­face cover types such as soil, grass, or con­crete.

The cost of the process de­pends on which PV tech­nol­ogy you de­cide to in­stall, and that is in­de­pen­dent of whether it is in­stalled on the roof of a house in a big city, on a build­ing in a ski re­sort, or on a slope in the moun­tains.The cost of the as­so­ci­ated in­fra­struc­ture how­ever can vary, ac­cord­ing to sup­port struc­tures,ca­bling, and the con­nec­tion to the elec­tric­ity grid, and pos­si­bly road ac­cess for easy main­te­nance.

Ex­plain­ing the process and tech­niques of gen­er­at­ing en­ergy from snow-cov­ered moun­tains with steep tilt an­gles, Kahl said that there are three rea­sons why elec­tric­ity pro­duc­tion in the moun­tains is ad­van­ta­geous over pro­duc­tion in ur­ban ar­eas.

The first rea­son is that there is less sun­shine in win­ter, as clouds ob­struct the sun, there­fore less en­ergy will reach the so­lar pan­els and they will pro­duce less elec­tric­ity. Hence, it is bet­ter to place them in lo­ca­tions with lit­tle cloud cover, such as the moun­tains. Gen­er­ally, there is less cloud cover and fog at high el­e­va­tions dur­ing the win­ter months.

The sec­ond rea­son is that with steep panel tilts, PV pan­els will gen­er­ate the ut­most amount of elec­tric­ity when the sun rays hit the sur­face ver­ti­cally. In win­ter the sun stays are very close to the hori­zon,and in or­der to re­ceive sun rays ver­ti­cally the PV pan­els needs to be very steep. In ur­ban ar­eas the panel in­cli­na­tion is of­ten dic­tated by the roof’s slope, which is more ori­ented to­wards sum­mer sun than to­ward win­ter sun. In moun­tain lo­ca­tions the tilt could be op­ti­mised for win­ter pro­duc­tion.

The third rea­son is the ex­tra ra­di­a­tion re­flected from the snow-since the snow is white-be­cause it re­flects light at all vis­i­ble wave­lengths, which in­cludes most of the en­ergy that comes from the sun. Clean snow can re­flect as much as 85% of the in­com­ing en­ergy from the sun.That is al­most as if there was sun­shine com­ing from the ground, and it also reaches the sur­face of the so­lar panel. How much of it reaches the panel de­pends again on the in­cli­na­tion. Sub­se­quently, the panel col­lects ex­tra en­ergy, and can pro­duce ad­di­tional elec­tric­ity if there is snow on the ground.


So­lar power can be gen­er­ated not just sum­mer but in win­ter as well, by plac­ing so­lar pan­els on snow-cov­ered moun­tains with steep tilt an­gles

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