Enhanced Electrical and Thermal Rating Power Cables for Renewables Connections in Developing Countries

The world faces a major challenge, namely, how to supply energy to a growing population reliably, economically and without causing severe environmental damage. Looking forward, it is inevitable that our reliance on electricity will increase, as transport and heating become increasingly electrified, and that this increase will be largely met by renewable sources. Such facilities will be constructed at locations where prevailing conditions are appropriate and, in the UK, an example relates to plans to develop major offshore wind resources in the North Sea. However, the construction of large offshore facilities and the transmission of the resulting electricity back to shore is still very expensive and, therefore, it is imperative that this is done efficiently.
All electrical plant relies upon electrical insulation and, today, this is primarily based upon polymers. While these materials are excellent electrical insulators, they are also poor conductors of heat, such that heat dissipation is a major issue. There would therefore be massive technological, environmental and societal benefits from the availability of commercially viable material systems that were excellent electrical insulators and good thermal conductors. Although it is intuitively appealing to think that thermal conductivity can be increased by adding a good thermal conductor to a thermally insulating material, this is not generally true, because the resulting boundaries give rise to phonon scattering which, effectively, offsets the anticipated gains. While this can be overcome if the thermally conducting additives form percolating paths through the material, the consequences of this have inevitably been an unacceptable reduction in the electrical breakdown strength of the material. However, recent results obtained at the University of Southampton appear to overthrow this paradigm. Specifically, a 20% INCREASE in breakdown strength has been accompanied by a 60% INCREASE in thermal conductivity in a system based upon hexagonal boron nitride (h-BN) dispersed in a polyethylene matrix. Since these preliminary results were obtained from a totally non-optimised system, we believe that further improvements in both technical performance and economic attractiveness (i.e. reduced cost from adding less h-BN) are attainable.
The results of our preliminary work are contrary to accepted understanding, so the PROJECT AIM is to determine how simultaneous improvement can be optimised for use in two key materials that are particularly relevant to power cable applications. The key challenges are: to understand how to optimse the exfoliation of h-BN particles into their constituent layers and, subsequently, to disperse them within the matrix, such that the required combination of electrical and thermal characteristics result; to ensure scale-ability, such that laboratory results are technologically viable. In this project, we will consider two matrix systems, due to their technological relevance. First, we will examine crosslinked polyethylene (XLPE), since this is currently the most important cable insulation material. The work programme will progressively build from improving solvent dispersion, polymer blending methods and surface functionalisation, to scale-up with masterbatch production through combined solution and melt-process methods. Characterisation of the microstructure and dielectric testing will ensure consistent dispersion and distribution of the hBN filler, as well as optimal electrical properties. In this way, quantitative structure-property-process relationships will be established that will enable the resulting material systems to be used reliably in the electrical cable industry. While the focus of this project is on electrical properties, the knowledge about structure-property-process relationships will affect much wider technology areas, which employ advanced materials for improved mechanical or thermal properties.

Economic: This project will bring economic benefits to both developed and developing economies. In Europe, some 1.5 Mton per annum of polymeric materials are used for electrical insulation, with an estimated value of ~£2bn. The "UK Renewable Energy Roadmap" published in 2013 indicates that DECC recorded announcements of private sector investment in renewable generation worth £31bn between January 2010 and September 2013, with the potential to support over 35,000 jobs. According to DECC's April 2014 "Energy Investment Report", the pipeline of UK energy sector investment projects is worth £218bn; thousands of associated supply-chain jobs are being produced across the UK. The 2014 "IEA Renewables Report" indicates a similar position worldwide, with global investment of around $250bn in new renewable power capacity in 2014 alone. We therefore believe that the technology that results from this work will lead to increased global sales of UK manufactured advanced materials and high technology equipment and, consequently, will enhance the provision of UK high technology jobs. The Sub-Saharan Africa (SSA) power outlook, as conducted by KPMG in 2016, estimates a short-term increase of ~70 GW in the need for electricity and that investments of $120bn to $160bn are required, per annum, in order to provide electricity access to the entire Sub-Saharan region by 2030. Cross border projects, as exemplified by the MoZiSa and ZiZaBoNa transmission schemes, are needed to significantly upgrade the regional transmission network between the respective countries. Several energy initiatives amongst ASEAN countries show
the increased momentum towards enhancing and expanding interconnections throughout the region. There has been particular interest in tapping the hydropower potential in Cambodia, Lao PDR and Myanmar for domestic use and cross-border interconnections, to supply growing demand in Thailand, Malaysia, Singapore and Viet Nam, as a means of facilitating trade and underpinning development of a regional power market. For example, Lao PDR more than quadrupled electricity exports from 2.8 TWh in 2000 to 12.5 TWh in 2013 and expects to quadruple again by 2025.

Social and Environmental: The provision of improved cable systems for the efficient connection of renewable resources to national networks and for the interconnection of neighbouring power systems will bring social and environmental benefits to both developing and developed economies. This includes contributing to the provision of electricity access the entire Sub-Saharan region through increased access to energy, by optimising the exploitation of renewable generation resources and realising more affordable tariffs. This will, then, lead to more reliably energy supply to the population and subsequently provide the basis for improved water management and supply, and drive improved social, agricultural and industrial development, as part of primary infrastructure development. Similar benefits are expected in South East Asia, with the growth of hydropower, wind and solar-based renewables. In UK, the technology developed in this project will help the UK government to meet its post-2020 cost target of <£100/MWh, and will grow UK on- and offshore wind energy employment (currently 18,300 and 17,100 employees respectively). We anticipate the development of the Custom Material Supply chain by GnoSys will help protect >3,000 jobs in the UK electronics, automotive and aerospace industries, where optimised high performance materials are crucial for competitiveness. HM government has estimated that UK materials-related industries have a yearly turnover of £197bn. The result of this project will be integrated into the University of Southampton's EPSRC funded public engagement activities activities (POLYMAT EP/N002199/1), which include Café Scientifique lectures, school visits and supporting web-based materials that demonstrate the societal benefits that stem from materials and energy research.