The generally acceptance of the impact of fossil fuels fuel on the planet's atmosphere has led to significant investments in renewable generation technologies in both developing and developed economies. For example, in 2015, India dramatically increased its commitment to renewables by setting a target of 175 GW by 2022, while the European Union's 2030 climate and energy framework aims to reduce greenhouse gas emission by 40%, relative to 1990 levels, and exploit 27% of renewable energy. However, renewable sources of electrical generation are generally located far from centres of demand and such changes therefore have major implications for electricity transmission systems. This problem is well demonstrated in Germany, where low public acceptance of overhead power lines means that the Suedlink project will require the installation of a 700 km, 500 kV underground high-voltage direct current (HVDC) link from the northern seaboard to demand centres in the centre and south of the country, in order to integrate offshore wind generation. Indeed, in total, TransnetBW GmbH has estimated that Germany will require new HVDC transmission corridors with a total length of between 2600 and 3100 km and with a total transmission capacity 12 GW.
Ambitious plans such as those outlined above are being facilitated by the development of new generations of cable technologies where advances in insulation systems in general and refinements in polyethylene in particular are critical. For example, in 2014, ABB reported on a new 525 kV HVDC extruded cable system, which was subsequently refined by NKT in 2017 to increase the operating voltage to 640 kV. These advances are fundamentally built upon materials refinements and, in particular, novel strategies to reduce contamination levels within the crosslinked polyethylene (XLPE) insulation, which may arise from both the retention of dicumyl peroxide (DCP) crosslinking residues within the insulation system and the diffusion of labile species from the surrounding semiconductive layers. Both of these sources have been shown to affect charge transport dynamics within the insulation and adversely affect performance.
Project goals:
In this project we will conduct the first experimental investigations relating to recent propositions by which the addition of nanoparticles can modify the electrical behavior of insulating polymers. Since the potential benefits of this strategy were first proposed by Lewis in 1994, understanding of the mechanism have focused on the development of interphase regions located within the polymer matrix. This approach had some early promise, but after two decades of trying to unlock the so-called "interphase region", the suggested volume that is created within the polymer at the interface between nanoparticles and the host polymer, actual evidence is still scarce. As a consequence, more recently, T. Tanaka has suggested a new "Quantum Dot" model, whereby the key regions are located within the nanoparticles themselves. Pioneering work in this regard was performed at the University of Southampton, leading to publication of "Introducing particle interphase model for describing the electrical behaviour of nanodielectrics" in 2018. This work together with Tanaka's original paper lead to the start of an international collaboration of Waseda University, Japan, University of Bologna, Italy and the University of Southampton. This project will consider polymer/quantum dot systems and will explore the influence of pertinent structural parameters on the global electrical characteristics. By controlling the core and shell of core-shell structures independently, and their effect on global electrical properties, we expect to answer the question how nanoparticles affect charge behavior. This will, in turn, allow more reliable dielectrics and higher energy densities.