© Brett Sayles

Pho­to­volta­ic bat­ter­ies to sta­bi­lize pow­er grid

Trans­mis­sion sys­tem oper­a­tor TransnetBW is test­ing pow­er grid sta­bi­liza­tion using “Pow­er­wall” pho­to­volta­ic home stor­age sys­tems from U.S. ener­gy and mobil­i­ty com­pa­ny Tes­la. Dur­ing peri­ods of high load or low feed-in, the pow­er grid is relieved by post­pon­ing the charg­ing of the bat­ter­ies, with the solar plants feed­ing pow­er into the pub­lic grid as need­ed and as instruct­ed by TransnetBW. This helps to sta­bi­lize the pow­er grid in a cost-effi­cient, resource-con­serv­ing and cli­mate-neu­tral way.

“Our goal is to sup­port the move away from fos­sil fuels as quick­ly as pos­si­ble and at a rea­son­able cost to pow­er grid oper­a­tions by intel­li­gent­ly inte­grat­ing decen­tral­ized flex­i­bil­i­ties into the grid,” explains Dr. Rain­er Pflaum, CFO of TransnetBW and respon­si­ble, among oth­er things, for the Grid Busi­ness unit, which is home to the pilot project. The field tri­al, which will ini­tial­ly run for six months, also aims to gath­er expe­ri­ence on the avail­abil­i­ty and pre­dictabil­i­ty of flex­i­bil­i­ty poten­tial, which will be used in the prepa­ra­tion of a stan­dard­ized mech­a­nism, known as Redis­patch 3.0. Through the coop­er­a­tion of con­sumers and grid oper­a­tors, renew­able ener­gies are effi­cient­ly inte­grat­ed into the pow­er grid and cli­mate neu­tral­i­ty is fur­ther advanced.

For this pur­pose, TransnetBW took a clos­er look at the charg­ing cycles of Tes­la Pow­er­walls and found that PV home stor­age sys­tems have degrees of free­dom for flex­i­ble charg­ing from the PV sys­tem in some months. This time mar­gin between gen­er­a­tion and load, the so-called flex­i­bil­i­ty, can be used by intel­li­gent con­trol: By selec­tive­ly post­pon­ing the bat­tery charg­ing process, house­hold­ers do not suf­fer any dis­ad­van­tages. For par­tic­i­pat­ing PV home stor­age own­ers, this shift could even mean addi­tion­al finan­cial reward in the future. In turn, the grid oper­a­tor can poten­tial­ly use the gen­er­at­ed PV pow­er to reduce grid con­ges­tion (pos­i­tive redis­patch). Up to now, fos­sil-fired pow­er plants have been used pri­mar­i­ly for the latter.

“With PV Shift, we are enter­ing new ter­ri­to­ry, which we are open­ing up step by step. The elim­i­na­tion of con­ven­tion­al pow­er plants is off­set by the enor­mous demand for e‑cars, heat pumps and solar sys­tems with bat­tery stor­age. Prac­ti­cal expe­ri­ence in the inter­ac­tion between grid oper­a­tors, sys­tem providers and end con­sumers is of cen­tral impor­tance for the devel­op­ment of the elec­tric­i­ty sys­tem of the future,” says Dr. Sab­ri­na Ried, project man­ag­er of PV-Shift. For the field test, TransnetBW receives free flex­i­bil­i­ty poten­tial from a lim­it­ed num­ber of sta­tion­ary pow­er­walls. Tes­la acts as an aggre­ga­tor here and forms the inter­face between home stor­age own­ers and TransnetBW, which uses the pow­er to sta­bi­lize the pow­er grid when needed.

TransnetBW already had the eco­nom­ic poten­tial for using decen­tral­ized flex­i­bil­i­ty for redis­patch in Baden-Würt­tem­berg exam­ined last year by a short study con­duct­ed by the Uni­ver­si­ty of Stuttgart. The result: In Baden-Würt­tem­berg alone, there is poten­tial in the triple-dig­it mil­lion euro range. The com­pa­ny now intends to grad­u­al­ly raise these. The launch of the PV Shift project is an impor­tant build­ing block for this. By the end of the year, the project is expect­ed to pro­duce its first results.