What the eclipse will mean for solar power

The Denver Post - - PERSPECTIVE - By Mark Jaffe

The an­cient Greeks thought a to­tal eclipse of the sun was a sign the gods were an­gry and bad things were to come. But for mil­len­nia, it has just been a game of hide-and-seek be­tween the sun and the moon with lit­tle im­pact on Earth’s mor­tals.

Not this time around, as the sun, moon and Earth head to­ward their dark ren­dezvous Aug. 21.

Some­thing has changed on the ground. There are thou­sands and thou­sands of solar pan­els across the coun­try that will sud­denly be switched off as the sun slips be­hind the moon.

The eclipse will cast a 70-mile-wide shadow across the coun­try knock­ing out pho­to­voltaic (PV) solar ar­rays from Ore­gon to South Carolina, briefly turn­ing off as much as 9,000 megawatts (MW) of gen­er­a­tion. That’s equal to 11 of Xcel En­ergy’s big­gest Colorado power plants.

The last time there was a na­tion­wide to­tal eclipse was in 1918, long be­fore solar en­ergy was a thing.

While the eclipse is na­tional, its shadow will fall heav­i­est in the West where solar has been deeply em­braced. Four of the six top states for solar in­stal­la­tions — Cal­i­for­nia, Ari­zona, Ne­vada and Utah — are lo­cated in the re­gion. Some days, Cal­i­for­nia gets as much as 40 per­cent of its elec­tric­ity from solar ar­rays.

The West alone could see the loss of as much as 7,000 MW spread over time, ac­cord­ing to Brett Wan­gen, di­rec­tor of en­gi­neer­ing at Peak Reli­a­bil­ity, the or­ga­ni­za­tion re­spon­si­ble for as­sur­ing the de­pend­able op­er­a­tion of the re­gion’s power grid.

Wan­gen said the “big­gest risk” is in Cal­i­for­nia, where 80 per­cent of the state is served by the Cal­i­for­nia In­de­pen­dent Sys­tem Oper­a­tor (CAISO). The im­pact on Colorado will be lim­ited.

Be­tween about 9 a.m. and noon on the day of the eclipse, CAISO ex­pects to lose 4,194 MW of util­ity-scale solar and 1,365 MW of rooftop solar, ac­cord­ing to Steven Green­lee, a spokesman for the agency.

CAISO is no stranger to solar-power losses on cloudy and rainy days where there can be a drop of 800 MW to 1,200 MW within min­utes. “The dif­fer­ence with the eclipse is the mag­ni­tude,” Green­lee said.

“We’ve been pre­par­ing for sev­eral months, and the best tool in our tool­box has been pre-plan­ning, talk­ing to all the mar­ket par­tic­i­pants,” Green­lee said, re­fer­ring to util­i­ties, in­de­pen­dent power pro­duc­ers, and nat­u­ral gas sup­pli­ers.

The Los An­ge­les De­part­ment of Wa­ter and Power (LADWP) projects it will lose about 605 MW of power from its ar­rays in the Mo­jave Desert, ac­cord­ing to the de­part­ment. “We ex­pect to use the same op­er­at­ing prin­ci­ples we use on cloudy days,” the LADWP said, “car­ry­ing ad­di­tional re­serves with suf­fi­cient ramp ca­pa­bil­ity to keep up.”

Peak has been meet­ing with the top four solar power pro­duc­ers in the re­gion, CAISO, LADPW, Paci­fi­corp and Ari­zona Pub­lic Ser­vice Elec­tric Com­pany, to co­or­di­nate for the eclipse, Wan­gen said. “There is a lot of co­or­di­na­tion going on above and be­yond what we nor­mally do.”

Util­ity of­fi­cials say they have a han­dle on the event, iden­ti­fy­ing po­ten­tial out­age ar­eas and ar­rang­ing for backup gen­er­a­tion. “We know minute to minute when gen­er­a­tion will be fall­ing off and com­ing back,” Wan­gen said.

It will be a test and an im­por­tant one for solar power. The next to­tal eclipse across North Amer­i­can will be in 2024, If the trends con­tinue, there will be a lot more solar ar­rays on the ground. In 2016, there were about 40 gi­gawatts of in­stalled PV ca­pac­ity. By 2024, there could be three times as much, ac­cord­ing the in­dus­try trade group, the Solar En­ergy In­dus­tries As­so­ci­a­tion.

In the fu­ture, man­ag­ing eclipses will be­come a cru­cial ex­er­cise. The an­cient Chi­nese would shoot fire ar­rows to scare off the me­nace to the sun. In some cul­tures, they banged pots and made noise to ward off the threat. Thank­fully, Xcel En­ergy’s plans don’t in­clude such in­dig­ni­ties.

Mark Jaffe, a for­mer Den­ver Post re­porter, writes on Colorado en­vi­ron­ment and en­ergy is­sues.

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