Germany is bidding farewell to nuclear energy, expanding renewable energy resources and working to make its economy virtually climate-neutral by the mid-century. The plan is known as the Energy Transition.
The project will rely on renewable energy, energy efficiency, and energy demand management. By 2022, nuclear reactors and coal-fired generators will need to be retired.
The Energiewende makes it necessary to extend the transmission grid. Therefore, Karlsruhe Institute of Technology (KIT) and the grid operator TenneT are studying the way to use superconductor technology instead of conventional power cable for short grid sections within the framework of the ENSURE Kopernikus Project. The new superconductor cables designed for this purpose are efficient and powerful.
The length of the transmission grid in Germany is about 35,000 km. In order to make sure the power from renewable energy gets everywhere it needs, the grid will have to be extended by about 5,300 km. According to the project’s plan, underground cables will be located near cities and villages.
In order to achieve maximum benefits from the project, superconductor cables could be used. They might allow a more compact construction of power transmission lines in the three-phase grid.
The cable is designed for a continuous power of 2,300 megawatts. It has smaller losses than conventional cable with copper conductors. This technology can also be used in transmission line construction. It can transmit the same power like a regular cable but by using six three-phase power cables instead of twelve. This will significantly reduce the width of the line.
Superconductors are materials which have an electrical resistance of zero at a temperature below a certain point (transition temperature). The new cable concept uses high-temperature ceramic superconductors. They have transition temperatures of about minus 196°C (compared to conventional low-temperature ones with transition temperatures below minus 250°C). Therefore, it is possible to cool down the cable with liquid nitrogen and achieve zero loss of power with lower costs (less energy is needed for cooling).
Another advantage is that the setup of the new cable compensates current flow in the electrical shielding layer, so no magnetic field exists outside of it and it is operated without any emissions.
Right now, the cable and cooling concept specially designed for the voltage of 380 kilovolts are used in the feasibility study carried out by KIT and TenneT. The study will be completed by the end of this year. By now, it has shown that superconductors can be technically feasible to be used with this voltage level.
After the study, the cable, including the necessary coupling sleeves and terminations, will have to be produced first. Then, it will have to be tested extensively together with a cooling system. In addition, the lead time necessary to cool the cable has to be addressed.
Experience and results gained by Karlsruhe Institute of Technology in the “AmpaCity” cable project show that superconductors can be used in energy infrastructure. Now, the AmpaCity has the longest high-temperature superconductors cable in the world(it is more than one kilometer long). Since 2014, it is an efficient and stable power supply of about 10,000 households in the city of Essen with a voltage of 11 kV.