Photo: Fraunhofer IFAM

For small vehi­cles: Ger­man researchers devel­op a paste as a hydro­gen stor­age tank

Hydro­gen is seen as the dri­ving force of the future. While the first hydro­gen cars are already dri­ving over Ger­man roads, the usu­al pres­sure tank for e‑scooters is not man­age­able. The POWERPASTE pro­vides an alter­na­tive: Hydro­gen can be safe­ly stored chem­i­cal­ly, eas­i­ly trans­port­ed and refu­elled with­out expen­sive fill­ing sta­tion infra­struc­ture. A team of researchers at the Fraun­hofer Insti­tute for Man­u­fac­tur­ing Tech­nol­o­gy and Applied Mate­ri­als Research IFAM in Dres­den has devel­oped the paste, which is based on mag­ne­sium hydride.

Gaso­line and diesel engines pow­ered by fos­sil fuels are becom­ing phase-out mod­els due to cli­mate change – instead, new propul­sion options are being launched. One of the fuel hope­fuls is hydro­gen. It is usu­al­ly pressed into the pres­sure tanks of the vehi­cles at 700 times the atmos­pher­ic pres­sure. From there, it flows into a fuel cell, where it is con­vert­ed into elec­tric­i­ty. The cur­rent, in turn, feeds an elec­tric motor that dri­ves the vehi­cle. For cars, this approach is already quite mature: sev­er­al hun­dred hydro­gen cars are already dri­ving on Ger­many’s roads. And the Ger­man hydro­gen fill­ing sta­tion net­work is to be expand­ed from the cur­rent 100 to 400 fill­ing sta­tions over the next three years. How­ev­er, small vehi­cles such as e‑scooters, scoot­ers and the like do not use this very much: the pres­sure shock dur­ing refu­elling would be too great. So is this the “off” of hydro­gen tech­nol­o­gy for e‑scooters and co.?

POWERPASTE: The hydro­gen response for small vehicles

Absolute­ly not! Researchers at the Fraun­hofer Insti­tute for Man­u­fac­tur­ing Tech­nol­o­gy and Applied Mate­ri­als Research IFAM in Dres­den have devel­oped a hydro­gen solu­tion that is per­fect for small vehi­cles: the POWERPASTE, which is based on the sol­id mag­ne­sium hydride. “With POWERPASTE, hydro­gen can be chem­i­cal­ly stored at room tem­per­a­ture and ambi­ent pres­sure and released as need­ed,” says Dr. Mar­cus Vogt, a sci­en­tist at Fraun­hofer IFAM. This is uncrit­i­cal even if the scoot­er is in the sun for hours in the sum­mer heat, because the POWERPASTE only decom­pos­es above about 250 degrees Cel­sius. The refu­elling process is very sim­ple: instead of head­ing to a gas sta­tion, the scoot­er dri­ver sim­ply changes a car­tridge and addi­tion­al­ly fills tap water into a water tank – ready. He can also do this com­fort­ably at home or on the go.

The start­ing mate­r­i­al of the POWERPASTE is pow­dered mag­ne­sium – one of the most com­mon ele­ments and thus an read­i­ly avail­able raw mate­r­i­al. At 350 degrees Cel­sius and five to six times the atmos­pher­ic pres­sure, this is con­vert­ed into mag­ne­sium hydride with hydro­gen. Now esters and met­al salt are added – and the POWERPASTE is ready. To dri­ve the vehi­cle, a stamp trans­ports the POWERPASTE out of the car­tridge. Water is added from the water tank, result­ing in gaseous hydro­gen. The quan­ti­ty is adjust­ed high­ly dynam­i­cal­ly to the hydro­gen demand of the fuel cell. The high­light: Only half of the hydro­gen comes from the POWERPASTE, the oth­er half sup­plies the water. »The ener­gy stor­age den­si­ty of the POWERPASTE is there­fore enor­mous: it is sig­nif­i­cant­ly high­er than with a 700 bar pres­sure tank. Com­pared to bat­ter­ies, it even has ten times the ener­gy stor­age den­si­ty,” says Vogt. For the dri­ver, this means that the POWERPASTE achieves a sim­i­lar range to the same amount of gaso­line, if not a larg­er one. The POWERPASTE also per­forms bet­ter when com­par­ing ranges with hydro­gen com­pressed to 700 bar.

Only suit­able for e‑scooters? Because of…

This also makes the POWERPASTE inter­est­ing for cars, deliv­ery vehi­cles or range exten­ders – which increase the range of elec­tric cars. Yes, even large drones could sig­nif­i­cant­ly increase their range with the hydro­gen paste, leav­ing them in the air for sev­er­al hours instead of twen­ty min­utes. This is par­tic­u­lar­ly help­ful for inspec­tion tasks, such as the inspec­tion of for­est areas or pow­er lines. A slight­ly dif­fer­ent kind of appli­ca­tion is offered when camp­ing: Here, the POWERPASTE can pro­vide elec­tric­i­ty for cof­fee mak­er and toast­er via fuel cell.

Lack of infra­struc­ture? Here, too, the POWERPASTE scores.

In addi­tion to the long range, there is anoth­er point that speaks for the POWERPASTE: While gaseous hydro­gen requires a cost-inten­sive infra­struc­ture, the POWERPASTE can also be used where such an infra­struc­ture is lack­ing. In oth­er words, where there are no hydro­gen fill­ing sta­tions. Instead, any gas sta­tion could offer POWERPASTE in car­tridges or can­is­ters. This is because the paste is flow­able and pumpable – it can there­fore also be refu­elled via a nor­mal refu­elling process and com­par­a­tive­ly cost-effec­tive fill­ing lines. Petrol sta­tions could ini­tial­ly offer the POWERPASTE in small­er quan­ti­ties, for exam­ple from a met­al bar­rel, and expand the sup­ply accord­ing to demand – with invest­ment costs of sev­er­al tens of thou­sands of euros. By way of com­par­i­son, fill­ing sta­tions for gaseous hydro­gen at high pres­sure are cur­rent­ly cost­ing around one to two mil­lion euros per pump. The trans­port of the paste is also cost-effec­tive: after all, com­plex pres­sure tanks or very cold liq­uid hydro­gen are not necessary.

Pilot cen­tre planned for 2021
At the Fraun­hofer Project Cen­ter for Ener­gy Stor­age and Sys­tems ZESS, Fraun­hofer IFAM is cur­rent­ly set­ting up a pro­duc­tion plant for POWERPASTE. It is sched­uled to go into oper­a­tion at the end of 2021 and then pro­duce up to four tons of POWERPASTE per year. Not just for e‑scooters, of course.