To transition to a world powered by renewable energy, efficient long-distance transport of electricity is essential, since the supply — renewable energy sources such as wind and solar farms, as well as hydroelectric dams — is often located far from cities, where most of the demand exists.
High-voltage direct current (HVDC) cables are the most efficient means of transporting electricity over long distances. HVDC cables with an insulation layer can be buried underground or on the seabed, allowing for considerable expansion of networks. During transport, as little energy as possible should be lost. One way to reduce transmission losses is by increasing the direct current voltage level.
However, an increase in the transmission voltage adversely affects the insulation of a HVDC cable. The resulting higher electric field stresses could be handled if the electrical conductivity of the insulation material was reduced sufficiently. Researchers have developed a new insulation material up to three times less conductive, offering significant improvements to the properties and performance of such cables.
The basis of the new material is polyethylene, which is already used for insulation in existing HVDC cables. Now, by adding very small amounts — 5 parts per million — of the conjugated polymer known as poly(3-hexylthiophene), the researchers were able to lower the electrical conductivity by up to three times
The additive, also known as P3HT, is a widely studied material and given the tiny amounts required, opens up new possibilities for manufacturers. Other possible substances that have previously been used to reduce the conductivity are nanoparticles of various metal oxides and other polyolefins but these require significantly higher quantities.
Conjugated polymers, such as P3HT, have been used in the past to design flexible and printed electronics. However, this is the first time they have been used and tested as an additive to modify the properties of a commodity plastic. The researchers therefore believe that their discovery could lead to numerous new applications and directions for research.