Researchers show how cli­mate-neu­tral ener­gy sup­ply is pos­si­ble even under extreme weath­er conditions

In a cli­mate-neu­tral ener­gy sys­tem, in which oil and gas heat­ing sys­tems are replaced by heat pumps, among oth­er things, sig­nif­i­cant­ly more elec­tric­i­ty is need­ed, espe­cial­ly at low tem­per­a­tures. At the same time, elec­tric­i­ty gen­er­a­tion is increas­ing­ly depen­dent on the weath­er, as a sig­nif­i­cant­ly high­er pro­por­tion of elec­tric­i­ty is pro­duced from renew­able ener­gies (RE). In a recent study, researchers at the Uni­ver­si­ty of Cologne have shown how secu­ri­ty of sup­ply can still be guar­an­teed in such a cli­mate-neu­tral ener­gy sys­tem — even in extreme weath­er sit­u­a­tions. With the help of weath­er and pow­er plant deploy­ment mod­els, the two doc­tor­al stu­dents Linh Ho and Berit Han­na Czock as well as junior pro­fes­sor Dr. Stephanie Fiedler inves­ti­gat­ed the reli­a­bil­i­ty of the pow­er sup­ply with increas­ing RE shares in par­tic­u­lar­ly extreme weath­er periods.

The results have been pub­lished in the expert report “Cli­mate Neu­tral­i­ty 2045 — Trans­for­ma­tion of the Con­sump­tion Sec­tors and the Ener­gy Sys­tem” as part of the “dena Lead Study Towards Cli­mate Neu­tral­i­ty”, which was pre­sent­ed by the Insti­tute of Ener­gy Eco­nom­ics at the Uni­ver­si­ty of Cologne (EWI) at the begin­ning of Octo­ber. The study describes a sce­nario for the trans­for­ma­tion of the Ger­man ener­gy sys­tem towards cli­mate neu­tral­i­ty in 2045. Accord­ing to the report, although final ener­gy con­sump­tion will fall by about 41 per­cent by 2045 com­pared to 2018. Final ener­gy is the ener­gy obtained from pri­ma­ry ener­gy sources such as lig­nite, hard coal, crude oil, nat­ur­al gas, water or wind through con­ver­sion. How­ev­er, the gross demand for elec­tric­i­ty will increase sig­nif­i­cant­ly from today’s 580 ter­awatt hours (TWh) to 910 TWh. This is because trans­port, build­ings and indus­try are increas­ing­ly elec­tri­fied and elec­tric­i­ty is also need­ed to pro­duce hydro­gen. In par­tic­u­lar, the nine mil­lion elec­tric heat pumps in 2045 dri­ve simul­ta­ne­ous peak demand in the sce­nario, which must be met by the avail­able pow­er plants.

At the same time, con­ven­tion­al elec­tric­i­ty gen­er­a­tion from nuclear pow­er and coal is declin­ing, while elec­tric­i­ty gen­er­a­tion from wind and solar ener­gy con­tin­ues to gain impor­tance in the long term and will cov­er 85 per­cent of gross elec­tric­i­ty demand in 2045. How­ev­er, because the wind does not always blow and the sun does not always shine, so-called flex­i­bil­i­ties play an impor­tant role. Ide­al­ly, they absorb demand or RE feed-in peaks and thus sta­bilise the ener­gy sys­tem. As part of an excur­sus in the “dena lead study”, the Cologne researchers looked at extreme weath­er sit­u­a­tions in which it was par­tic­u­lar­ly cold through­out Europe and, in addi­tion, wind­less in Ger­many for sev­er­al days. “So-called cold dark spells are par­tic­u­lar­ly crit­i­cal for the pow­er sup­ply,” says junior pro­fes­sor Dr. Stephanie Fiedler, who, in addi­tion to her work at the Insti­tute of Geo­physics and Mete­o­rol­o­gy, is also Chief Ener­gy Mete­o­rol­o­gist at the EWI and works togeth­er with Ho and Czock in the Cli­mate Mon­i­tor­ing and Diag­nos­tics research area of the Hans Ertel Cen­tre for Weath­er Research, a vir­tu­al cen­tre for mete­o­ro­log­i­cal research in Ger­many. “These are sit­u­a­tions of low tem­per­a­tures and result­ing high elec­tric­i­ty demand cou­pled with low solar radi­a­tion and low wind speeds, which in turn lead to low­er renew­able ener­gy generation.”

With the help of a mod­el­ling of pow­er plant use and elec­tric­i­ty trade, the sci­en­tists show that in the cli­mate neu­tral­i­ty sce­nario, even in two exem­plar­i­ly select­ed “cold dark slack peri­ods” of the his­tor­i­cal weath­er years 1997 and 2007, the entire elec­tric­i­ty demand can just about be cov­ered, among oth­er things by elec­tric­i­ty imports from oth­er Euro­pean coun­tries. This is because in the extreme weath­er sit­u­a­tions con­sid­ered, Euro­pean neigh­bours are less affect­ed by extreme weath­er and can export elec­tric­i­ty to Ger­many, for exam­ple from North­ern Europe, France and Switzer­land. To achieve this, how­ev­er, the pow­er lines between Ger­many and its neigh­bour­ing coun­tries (inter­con­nec­tors) must be sig­nif­i­cant­ly expanded.

On the Ger­man side, flex­i­ble gas-fired pow­er plants — which in the medi­um term can be (par­tial­ly) oper­at­ed with cli­mate-neu­tral hydro­gen — as well as flex­i­bly deploy­able large-scale bat­ter­ies and pumped stor­age are the main options. The demand side could also con­tribute to the avoid­ance of sup­ply gaps through its flex­i­bil­i­ty, for exam­ple by down-reg­u­lat­ing flex­i­ble indus­tri­al process­es at short notice. Pri­vate house­holds could also use their heat stor­age units and the bat­ter­ies of their e‑vehicles to bridge par­tic­u­lar­ly crit­i­cal hours. Such flex­i­bil­i­ty options are already tech­ni­cal­ly pos­si­ble. How­ev­er, before house­holds and oth­er con­sumers become flex­i­bil­i­ty providers, appro­pri­ate incen­tives, for exam­ple through remu­ner­a­tion for flex­i­bil­i­ty, and the tech­ni­cal inter­faces must be created.

The top­ic of sup­ply secu­ri­ty in cli­mate-neu­tral ener­gy sys­tems will remain a research focus of the Cologne researchers in the future. Although it was pos­si­ble to avoid sup­ply gaps in the elec­tric­i­ty sup­ply in the two case stud­ies. Nev­er­the­less, the role of extreme weath­er events in weath­er-depen­dent ener­gy sys­tems needs fur­ther inves­ti­ga­tion. This is because an increase in extreme events is expect­ed in the con­text of cli­mate change. How­ev­er, the impact on the ener­gy sys­tem has not yet been sys­tem­at­i­cal­ly studied.

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