Municipal Energy TransitionWhen the current flows backwards

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Decoupled, self-sufficient DC grids — how energy transition works in distribution grids

When peo­ple say ener­gy tran­si­tion, they often mean iso­lat­ed grids, decou­pled low-volt­age, and DC grids. Because: With their grow­ing gen­er­a­tion capac­i­ties, local grids are to become increas­ing­ly inde­pen­dent of upstream grids. Or renew­ables are fed direct­ly into the high­er grid lev­els with­out sig­nif­i­cant con­ver­sion loss­es.

The ener­gy tran­si­tion is almost inevitably more dynam­ic in rur­al areas than in met­ro­pol­i­tan areas because only there is suf­fi­cient space avail­able to build up a sta­ble mix of renew­able gen­er­a­tors. In Cen­tral Euro­pean lat­i­tudes, fifty square meters of area is enough to sup­ply an aver­age house­hold with solar ener­gy and new heat­ing tech­nolo­gies. How­ev­er, the respon­si­bil­i­ty for this can­not real­is­ti­cal­ly lie with indi­vid­u­als. Munic­i­pal projects that com­bine wind and solar ener­gy with stor­age tech­nolo­gies and oth­er, more land-inten­sive renew­ables can help rur­al com­mu­ni­ties in par­tic­u­lar move toward self-suf­fi­cien­cy and ener­gy tran­si­tion.

Decen­tral­iza­tion is the mag­ic word. Feed­ing solar pow­er into the pub­lic grid at mid­day will con­tin­ue to make no eco­nom­ic sense in the future due to low demand and low prices. As a result, more and more house­holds are already mov­ing toward stor­ing their own solar pow­er and becom­ing increas­ing­ly inde­pen­dent from elec­tric­i­ty sup­pli­ers. Before this can hap­pen, how­ev­er, leg­is­la­tures must set the reg­u­la­to­ry course.

For com­mu­ni­ties and munic­i­pal­i­ties, this devel­op­ment offers even greater oppor­tu­ni­ties: they can con­sume their own elec­tric­i­ty in a coop­er­a­tive while feed­ing sur­plus­es into the upstream grid. While the bat­tery stor­age and con­vert­er sys­tems or pow­er-elec­tron­ic grid cou­plings required for decou­pling or even self-suf­fi­cien­cy are cost­ly for indi­vid­ual house­holds, they rep­re­sent sen­si­ble invest­ments for munic­i­pal­i­ties. They also pay for them­selves quick­ly — not least because they allow DC grids to be imple­ment­ed and con­ver­sion loss­es to be min­i­mized. 

A tech­ni­cal alterna­tive for net­work oper­ators to har­mo­nize fluctuat­ing loads and gen­er­a­tion between local net­works and medi­um volt­age are volt­age reg­u­la­tion dis­tri­b­u­tion trans­form­ers. With these so-called VRDTs, the per­for­mance of the net­works can be increased with­out the need for cost-inten­sive line expan­sion.

Experts agree that bat­tery stor­age at all grid lev­els is the linch­pin for the suc­cess of the ener­gy tran­si­tion. By 2030, 250 GWh of stor­age capac­i­ty will be need­ed for Ger­many alone. This was cal­cu­lat­ed by spe­cial­ists from Europe’s largest solar re­search insti­tute, Fraun­hofer ISE. As of today, Ger­many only has 4 GWh.

So there is a lot to do.
But a look behind the scenes reveals: Much of the ground­work has already been laid.

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