Optimized power lines
In the past, Germany’s electricity was mainly produced in large power plants located close to the main consumers in urban areas. Nowadays electrical power systems (and energy distribution systems in general) are facing one of the largest technological change ever. Due to the increasing renewable energy percentage in the energy mix, large amounts of electrical energy have to be transported over long distances. Large offshore wind parks in the North Sea are more efficient than wind farms in southern Germany, whereas there are areas with high electricity consumption.
With an “electricity highway”, an optimized transmission grid which can efficiently and reliably transport the energy over long distances, it is much easier to balance electricity generation and demand than relying on regional grids. Less wind farms and solar plants need to be installed in order to keep a sustainable power supply reliable.
However the planning of new transmission lines is often difficult due to opposition of the citizens in the affected areas. Underground cables could be an alternative to overhead lines. However, today’s AC technology is not suitable for an economic long-distance transmission underground. Therefore new technologies have to be developed in order to secure our future energy supply.
• Development of technological components systems and operating strategies for an efficient power transmission (AC and DC)
• Concepts for the stabilization of the electrical power system with an increasing amount of renewable energy from volatile, decentralized sources, facing new consumers such as electric mobility and electricity-based heat supply for the building sector.
• Optimization of the energy management for an efficient and economic usage of operating resources
LOEWE project FLAME
Fermi Level Engineering of Antiferroelectric Materials for Energy Storage and Insulation Systems
The LOEWE project “FLAME” investigates how the properties of functional materials can be adjusted via their electronic structure. Twelve research groups from the fields of materials science, geosciences, chemistry, electrical engineering and information technology will develop lead-free antiferroelectrics for capacitors with high energy and power density and for high-voltage insulators. These enable more efficient conversion and transmission of electrical energy from renewable sources and in electromobility. The Tongji University in Shanghai is also involved in the project.
The research approach, which can be transferred to other materials and fields of application, is based on the adjustment of optimized electronic structures (“Fermi Level Engineering”), which can be predicted with computer simulations and realized experimentally. This enables a precise adjustment of the properties along with shorter development periods.
The project is being funded from January 2019 to December 2022 by the State of Hesse within the 11th season of the LOEWE Initiative.
Real-Scale Field Experiment Cable Test Site
A field experiment facility was built at TU Darmstadt in 2013 to study the ampacity of directly buried energy cable systems under environmental conditions. The test field was established by a collaborative research alliance by the Department of Geothermal Science and Technology and the High Voltage Laboratories at the TU Darmstadt in addition to a Bavarian distribution grid operator.
This experimental set-up allows for investigations on various cables and cable arrangements in different bedding materials and soils under natural conditions. The overall dimension of the test site is 14 m by 6 m, divided into four sections of 3.5 m length that are hydraulically and thermally decoupled by each other. The changes of the thermal and hydraulic conditions within the test site are monitored by numerous sensors
When electrical energy is transmitted via buried cables, electrical losses are dissipated to the environment in the form of heat. This leads to an increase of temperature of the conductor of the cable. As the latter is limited and directly proportional to the current, the so called thermal current rating represents one important limit of the cable capacity.
At present, the cable ampacity ratings are established based on standardized consumption patterns and conservative assumptions regarding the thermal properties of the bedding. Thereby, values below the actual limit are derived. The influence of natural water content changes of the surrounding soil on the thermal properties of the bedding is not taken into consideration.
By adopting the ratings to the actual thermal limit, the need in grid reinforcements – that arouse due to the connection of more and more dispersed power injection to distribution networks – is lowered an therefore the costs of the German energy transformation may be reduced.
Test Site for Gas-insulated High Voltage Transmission Lines
An on-site test laboratory for direct buried gas-insulated transmission lines is under construction. In the laboratory, transmission lines for 500-kV high voltage direct current (HVDC-GIL) can be tested in long-term-experiments up to one year under realistic environmental conditions.
This new technology demonstrates a further and compact alternative to overhead lines and cables for the transport of electrical energy. It makes a signifcant contribution for a safe energy supply with renewable energies, e.g. the electricity transport between North and South Germany.
Participating researcher: Volker Hinrichsen