WindEnergy 2018

•••8••• Innovationen Graphic representation of the superconducting cable studied by KIT for partial underground cabling Photo: ITEP / KIT Superconductor for the grid Researchers design cable for high-voltage electricity transmission T he German energy transition makes it necessary to extend the transmis- sion grid. Karlsruhe Institute of Technol- ogy (KIT), together with a grid operator, now studies the use of supercon- ductor technology as an alterna- tive to conventional power cables for short grid sections within the Kopernikus project ENSURE. The superconductor cables designed by KIT for this purpose are ef- ficient and powerful. After suc- cessful testing, they might allow for a more compact construction of power transmission lines in the three-phase grid. The length of the transmis- sion grid in Germany totals about 35,000 km. To ensure that the power produced from renewable ener g y sources gets to the locations where it is needed, it is planned to ex tend the g r id by about 5,300 km in the course of the energiewende. Within the framework of pilot projects, underground cables are planned to be used near cities and villages in particular. Major advantages could be achieved if they would be re- placed partly by superconducting cable systems. This is the result of a feasibil- ity study carried out by KIT in coop- eration with a grid operator under the Kopernikus project ENSURE. The study is planned to be completed by the end of this year and will also cover ecological and economic aspects. The feasibility study is based on cable and cooling concepts specially designed for the voltage of 380 kilovolts (kV) of the German transmission grid. “This is a big technical challenge, because super- conductor technology has never been used before on this voltage level,” says Professor Mathias Noe of KIT’s Institute for Technical Physics, who coordinates the development project. “We have now demonstrated that this is technically fea- sible with our new cable concepts.” The cable system is designed for a continu- ous power of 2,300 MW. Losses under a high current load are significantly small- er than those of a comparable above- ground line or conventional cables with a copper conductor. Superconductor technology might also be advantageous in transmission line construction, ex- plains Hanno Stagge, who manages the project at the grid operator: “A conven- tional cable system in the transmission grid requires twelve three-phase power cables. A superconducting cable sys- tem can transmit the same power with six cables.” As a result, grid operators could significantly reduce the width of a line. Another advantage is that the setup of the cable compensates cur- rent flow in the electrical shielding layer. Consequently, no magnetic field exists outside of the cable and the cable is op- erated without any emissions. But it is still a long way to maturity. “After the study, the cable, including the nec- essary coupling sleeves and termi- nations, will have to be produced first. Then, it will have to be tested extensively together with a cool- ing system,” Hanno Stagge says. Also the lead time necessary to cool the cable has to be adressed. Superconductors are materials, whose electrical resistance drops to zero when the temperature decreases below a certain point, the so-called transition tempera- ture. As a result, these materials conduct current with hardly any losses. The new superconductor cable concepts for the transmis- sion grid are based on so-called high-temperature ceramic super- conductors. While conventional low-temperature superconductors have transition temperatures below 23 kelvin (-250 °C), high-temperature supercon- ductors have comparably high transition temperatures. With liquid nitrogen, they are cooled down to an operation tem- perature of 77 kelvin (-196 °C), and can be operated at comparably low costs, for less energy is needed for cooling. Experience gained by KIT in the “Am- paCity” cable project shows that use of superconductor technology in energy infrastructure really works. With more than one kilometre length, the Ampa- City cable is the longest high-tempera- ture superconductor cable in the world. Since 2014, it has guaranteed efficient and stable power supply of about 10,000 households in the city of Essen with a voltage of eleven kV. High-voltage power grid Photo: Mike Wilson on Unsplash Leise Rotorbl tter für Windparks Bei der Genehmigung von Wind- parks spielen die zu erwartenden Lärmemissionen und der dadurch erforderliche Abstand zur Wohn- bebauung eine große Rolle. Wis- senschaftler vom Institut für Aero- dynamik und Strömungstechnik des Deutschen Zentrums für Luft- und Raumfahrt (DLR) in Braun- schweig haben ein gleichermaßen lärmarmes wie leistungsfähiges Rotorblattprofil entworfen und dessen Potenzial zur Lärmminde- rung erprobt. Die gewonnenen Messdaten helfen Simulations- tools so zu verbessern, dass Ent- wickler mögliche Varianten bereits am PC vergleichen können. Um komplexe, innovative Geo- metrien zur Lärmminderung zu entwickeln und verbesserte Blatt- spitzen zu bewerten, werden physikbasierte, weitgehend nicht empirische 3D-Simulationsverfah- ren benötigt. Die Wissenschaftler haben das aeroakustisch verbes- serte Profil in Windkanälen unter charakteristischen Strömungs- bedingungen getestet. Hauptziel der Messungen war, präzise Va- lidierungsdaten für vorhandene 2D- und neu entwickelte 3D-Simu- lationsansätze zu erhalten. Dazu wurden auch passive Technolo- gien zur Lärmminderung getestet. Lärmarme Rotorblätter können beim Repowering in Windparks neue Möglichkeiten eröffnen. Eine Reduktion der Schallemissionen um nur zwei Dezibel vergrößert rechnerisch die mögliche Anlagen- zahl im Park um 58 Prozent. Impressum WindEnergy Hamburg Verlag: CONNEX Print & Multimedia AG Große Packhofstraße 27/28 30159 Hannover Telefon: +49 511 830936 Telefax: +49 511 56364608 E-Mail: connex@die-messe.de Internet: www.die-messe.de Auflage IVW-geprüft. Auflagengruppe: G Redaktion: Cyrus Salimi-Asl Verantwortlich für den Anzeigenteil: Tina Wedekind Druck: Berliner Zeitungsdruck GmbH, 10365 Berlin MESSEJOURNAL DIE MESSE