Photo: Stadtwerke Konstanz

Car fer­ry: Wire­less pow­er sup­ply via induction

At the sug­ges­tion of the Con­stance pub­lic util­i­ty com­pa­ny, stu­dents at the HTWG Uni­ver­si­ty of Applied Sci­ences Con­stance Tech­nol­o­gy, Eco­nom­ics and Design have devel­oped a con­cept for sup­ply­ing the Lake Con­stance car fer­ries between Con­stance and Meers­burg with local emis­sion-free pow­er via induc­tion over the fer­ry bridge. This can poten­tial­ly save up to 20 tonnes of CO2 per fer­ry per year. Stadtwerke Kon­stanz wants to imple­ment the concept.

Car fer­ries shut­tle across Lake Con­stance between Con­stance and Meers­burg around the clock, sev­en days a week. Dur­ing rush hour, they are in the port of Meers­burg or Con­stance-Staad for eight min­utes, and at night for up to 45 min­utes. Even dur­ing this time, the ships need ener­gy, after all, all the mea­sur­ing instru­ments on the bridge, the light­ing on deck, the WLAN sup­ply and the cof­fee machine for the on-board cater­ing are to remain in oper­a­tion. Cur­rent­ly, the required elec­tric­i­ty is gen­er­at­ed by a diesel gen­er­a­tor on board. At the sug­ges­tion of the Stadtwerke Kon­stanz (Con­stance pub­lic util­i­ty com­pa­ny), HTWG stu­dents have devel­oped a con­cept for an emis­sion-free on-board pow­er sup­ply via induc­tion over the fer­ry bridge.

“It’s well thought out, smart and absolute­ly con­vinced us,” says Christoph Witte, tech­ni­cal man­ag­er of Stadtwerke fer­ries. He announces his inten­tion to imple­ment the con­cept with a first fer­ry. At present the sub­si­dies for this are still being applied for. “It will be a first com­po­nent of our mea­sures to save CO2 emis­sions in fer­ry oper­a­tions,” he explains. “The big idea behind this is to devel­op auto­mat­ic charg­ing tech­nol­o­gy for the fer­ries of the future, which means all-elec­tric ships where the bat­ter­ies are auto­mat­i­cal­ly recharged dur­ing the short turn­around times.”

Every time the fer­ries enter the har­bour, they have docked accu­rate­ly at the land­ing stage for decades, so that vehi­cles and pedes­tri­ans can dri­ve or walk ashore com­fort­ably. In the process, the land­ing stage low­ers onto the deck of the fer­ry. If an induc­tion plate is now installed on the fer­ry bridge and on the deck respec­tive­ly, the con­tact­less pow­er sup­ply to the fer­ry can be pro­vid­ed direct­ly via the jet­ty itself from land­ing to departure.

High secu­ri­ty in the spe­cial fer­ry environment

“The pro­ce­dure is impres­sive­ly sim­ple and con­vinces with its high lev­el of secu­ri­ty,” says Daniel Kirch, project man­ag­er at Stadtwerke Kon­stanz. The pow­er sup­ply with­out exposed elec­tri­cal con­tacts is the ide­al solu­tion in an envi­ron­ment exposed to the ele­ments. “There are no open con­tacts, no sparkover, no short cir­cuit with­out plugs and sock­ets,” lists mechan­i­cal engi­neer­ing stu­dent Tarek Sadek.
The posi­tion­ing is opti­mal regard­less of the water lev­el, as the fer­ry bridge adapts to the water lev­el. In addi­tion, the induc­tion device is robust and has a long ser­vice life, and the main­te­nance effort and the prob­a­bil­i­ty of fail­ure are low, empha­sizes mechan­i­cal engi­neer­ing pro­fes­sor Dr. Peter Stein. This would be dif­fer­ent, for exam­ple, with a robot­ic arm that makes a con­nec­tion to the fer­ry after each entry: it would be prone to fail­ure and, in the case of a plug-in con­nec­tion, high wear and tear would occur on the sock­ets due to the repeat­ed plug­ging in and unplug­ging sev­er­al times a day. In addi­tion, water, dirt and air could pen­e­trate. Prof. Dr. Heinz Reb­holz, Fac­ul­ty of Elec­tri­cal Engi­neer­ing and Infor­ma­tion Tech­nol­o­gy, adds: “The pow­er sup­ply by induc­tion meets the legal require­ments, so that health haz­ards are excluded.”

Suc­cess­ful inter­dis­ci­pli­nary cooperation

Eight HTWG stu­dents, Bach­e­lor and Mas­ter stu­dents from the Fac­ul­ty of Mechan­i­cal Engi­neer­ing and the Fac­ul­ty of Elec­tri­cal Engi­neer­ing and Infor­ma­tion Tech­nol­o­gy, devel­oped the con­cept. “The project demon­strates the inno­v­a­tive pow­er of HTWG. It is an exem­plary com­bi­na­tion of prac­tice-ori­ent­ed teach­ing, applied research and trans­fer for the ben­e­fit of region­al com­pa­nies and a resource-con­serv­ing soci­ety,” says Prof. Dr. Gun­nar Schu­bert, Vice Pres­i­dent for Research, Trans­fer and Sus­tain­abil­i­ty. The pow­er sup­ply via induc­tion was not the only focus of the stu­dents’ work at the begin­ning. Among oth­er things, they had con­sid­ered sup­ply­ing elec­tric­i­ty via pho­to­volta­ic cells on the fer­ry roof — which is still con­ceiv­able as a sup­ple­ment to the pow­er supply.

Onboard gas­tron­o­my closed due to Coro­na pandemic

“The stu­dents first mea­sured the pow­er con­sump­tion on the fer­ry dur­ing a few cross­ings and cal­cu­lat­ed the ener­gy con­sump­tion from this,” explains elec­tri­cal engi­neer­ing pro­fes­sor Dr. Heinz Reb­holz. Since the on-board cater­ing remains closed due to the pan­dem­ic restric­tions, the stu­dents had to addi­tion­al­ly esti­mate the con­sump­tion of the refrig­er­a­tors, cof­fee machine and cash reg­is­ter sys­tems. Then it was a mat­ter of defin­ing the require­ments for the induc­tive charg­ing sys­tem and design­ing it with all its para­me­ters. Trans­mis­sion loss­es also had to be esti­mat­ed. In par­al­lel, the stu­dents researched offers on the mar­ket. “The inter­dis­ci­pli­nary col­lab­o­ra­tion as well as the coop­er­a­tion with the employ­ees of the munic­i­pal util­i­ties was enrich­ing for every­one involved. The stu­dents learned to see the top­ic through dif­fer­ent lens­es,” says Prof. Dr. Heinz Rebholz.

The Meers­burg car fer­ry will be the test vehicle

“It was a great project. If our idea is now imple­ment­ed, I’m incred­i­bly hap­py,” says mechan­i­cal engi­neer­ing stu­dent Tarek Sadek, who wrote his bach­e­lor’s the­sis on the top­ic. The car fer­ry FS Meers­burg is suit­able as a test vehi­cle for the endurance test. The ener­gy sup­ply of this fer­ry is mod­u­lar. It has two sep­a­rate pow­er cir­cuits or diesel gen­er­a­tors. In this way, the gen­er­a­tor, which is not con­nect­ed to the main dri­ve, can be switched off while the ship is at berth.

Sav­ings poten­tial: 20 tons of CO2

The next step is to devel­op a suit­able induc­tion plate in coop­er­a­tion with an indus­tri­al part­ner. It could ini­tial­ly be attached to a fer­ry bridge in Staad, and lat­er anoth­er one in Meers­burg. “If we replace the use of the pow­er gen­er­a­tor with shore pow­er while the fer­ry is moored at the jet­ty, we can save up to about 50 per­cent of the diesel con­sump­tion need­ed to pow­er the fer­ry dur­ing day­time course oper­a­tions,” Daniel Kirch cal­cu­lates. With the now mea­sured con­sump­tion of 25kW and two cross­ings per hour with a lay­time of 15 min­utes each, this would be approx. 20 litres of diesel per fer­ry and day, which in turn would cor­re­spond to up to 20 tonnes of CO2 per fer­ry per year.

Fur­ther expan­sion stages possible

The con­cept can be fur­ther expand­ed, says Christoph Witte: “For exam­ple, a bat­tery on board could com­plete­ly replace the diesel gen­er­a­tor for the on-board pow­er sup­ply. “A bat­tery of the size installed in the Renault Zoe would suf­fice for this,” says mechan­i­cal engi­neer­ing pro­fes­sor Dr. Peter Stein. The next stage of devel­op­ment would be the load­ing of a fer­ry­boat pow­ered entire­ly by electricity.

And the research ves­sel of the HTWG also ben­e­fits from the concept

The HTWG research ves­sel “Sol­ge­nia” will also ben­e­fit from the devel­oped con­cept. The induc­tive charg­ing sys­tem will ini­tial­ly be test­ed on the ship with a pho­to­volta­ic-hydro­gen hybrid drive.