Image: Next2Sun GmbH

Ver­ti­cal solar sys­tems reduce need for gas imports and elec­tric­i­ty storage

Leipzig researchers show in new study: Ver­ti­cal solar plants on agri­cul­tur­al land offer enor­mous poten­tial for ener­gy transition

Solar ener­gy is not sub­ject to sup­ply bot­tle­necks, is cheap and CO₂-neu­tral. In order to achieve max­i­mum ener­gy yield, solar plants are usu­al­ly installed fac­ing south with an angle of incli­na­tion of 20 to 35 degrees. This gen­er­ates a lot of elec­tric­i­ty pri­mar­i­ly in sum­mer and at mid­day. In the future, renew­able ener­gies are to com­plete­ly replace fos­sil fuels — a major chal­lenge. If solar mod­ules con­tin­ue to be installed pri­mar­i­ly in a south­ern ori­en­ta­tion in the future, addi­tion­al elec­tric­i­ty stor­age sys­tems will be need­ed to com­pen­sate for fluc­tu­a­tions depend­ing on the day and sea­son. In a new study pub­lished in the spe­cial­ist jour­nal “Smart Ener­gy”, a Leipzig research team shows that it would make sense in the future to install bifa­cial solar mod­ules ver­ti­cal­ly as a mat­ter of pri­or­i­ty and to use agri­cul­tur­al land for this pur­pose, for example.

“Bifa­cial solar mod­ules can use solar ener­gy from both sides. Installed in an east-west ori­en­ta­tion, most elec­tric­i­ty is gen­er­at­ed in the morn­ing and evening. This would reduce the need for elec­tric­i­ty stor­age while at the same time keep­ing the amount of land required for elec­tric­i­ty gen­er­a­tion low,” says Sophia Rek­er from the Leipzig Uni­ver­si­ty of Applied Sci­ences (HTWK Leipzig) and lead author of the study “Inte­gra­tion of ver­ti­cal solar pow­er plants into a future Ger­man ener­gy sys­tem”. The researchers base their argu­ment on a sim­u­la­tion of the Ger­man ener­gy sys­tem using the Ener­gy­plan software.

New leg­isla­tive pack­age to accel­er­ate expan­sion of renew­able energies

In order to become inde­pen­dent of ener­gy imports and reduce CO₂ emis­sions, the Bun­destag passed a com­pre­hen­sive pack­age of leg­is­la­tion at the begin­ning of July to expand renew­able ener­gies in Ger­many. Accord­ing to this, the share of renew­able ener­gies in total elec­tric­i­ty con­sump­tion is to be increased from just under 50 per­cent at present to at least 80 per­cent by 2030. To achieve the goal, the frame­work con­di­tions for new solar plants are to be improved, among oth­er things.

“Bifa­cial solar mod­ules are some­what more expen­sive than con­ven­tion­al solar sys­tems. But because they increase the num­ber of hours of avail­able solar ener­gy, oth­er elec­tric­i­ty needs, such as at gas-fired pow­er plants, are reduced. Installed ver­ti­cal­ly, solar arrays can be well sit­ed on agri­cul­tur­al land. This cre­ates addi­tion­al income oppor­tu­ni­ties for farm­ers and increas­es the land poten­tial for renew­able ener­gy in Ger­many to such an extent that we would only need to import a small amount of addi­tion­al ener­gy,” says Jens Schnei­der, Pro­fes­sor of Net­worked Ener­gy Sys­tems at HTWK Leipzig and co-author of the study. Solar pan­els installed on agri­cul­tur­al land can sup­port the growth of cer­tain crops by pro­tect­ing the plants from wind and heat. Flow­er­ing strips for more bio­di­ver­si­ty are pos­si­ble direct­ly under the mod­ules. The Ger­man gov­ern­men­t’s new leg­isla­tive pack­age is intend­ed to pro­vide spe­cial sup­port for so-called agri-pho­to­voltaics in the future.

Mod­el­ing of the ener­gy sys­tem in 2030 as a basis

For their study, Sophia Rek­er, Jens Schnei­der and Christoph Ger­hards used Ener­gy­plan soft­ware to mod­el an ener­gy sys­tem for Ger­many that, in line with Ger­many’s cli­mate pro­tec­tion tar­gets, would pro­duce a total of 80 per­cent few­er CO₂ emis­sions in 2030 com­pared to 1990. For this, the researchers assume an increase from cur­rent­ly 64 to 195 gigawatts of wind ener­gy capac­i­ty and from cur­rent­ly 58 to 400 gigawatts of solar ener­gy capac­i­ty. In order to actu­al­ly use this installed pow­er, elec­tric­i­ty stor­age is need­ed. In their study, the researchers show that the need for elec­tric­i­ty stor­age decreas­es when most of the added solar capac­i­ty is installed ver­ti­cal­ly in an east-west ori­en­ta­tion. For exam­ple, in a sce­nario with­out addi­tion­al elec­tric­i­ty stor­age, more than 10 mega­tons of CO₂ per year can be saved sim­ply by installing 70 to 90 per­cent of the added solar mod­ules ver­ti­cal­ly in an east-west ori­en­ta­tion rather than tilt­ed to the south.

Sophia Rek­er stud­ied ener­gy, build­ing and envi­ron­men­tal tech­nol­o­gy in her mas­ter’s degree at the HTWK Leipzig. The paper is based on her 2021 mas­ter’s the­sis. Rek­er works as a research asso­ciate in the research group of Prof. Jens Schnei­der. Sus­tain­abil­i­ty and cli­mate neu­tral­i­ty are a cross-cut­ting issue in research and teach­ing at HTWK Leipzig.