“You just expect it to be there”, said a Dutchman seated next to us on a flight to Amsterdam. We had already been discussing plastics and their use in electrical applications for a while. The first example of an application of plastics that popped into his mind was mobile telephones, but as our conversation delved deeper into the world of plastics and how they are linked to our daily lives as a way to improve the performance of electricity networks, he came up with the aforementioned conclusion.
We rarely think about how the things we use every day, such as electricity, are produced and made available to us. But we get to enjoy the end result.
Electrical and electronic applications of plastics do not represent great volumes: of the 50 million tonnes of plastics consumed by Europeans, only approximately three million tonnes, or just over 6%, is used to make electrical and electronic applications. In order to function efficiently, modern society needs plastics in electrical and electronic applications to make consumers’ daily lives easier.
Rising demand for electricity storage
Our existing electricity grid is changing. The transformation is due to, for example, an increase in the local production of electricity through wind farms and solar power plants as well as the electrification of transport. The output of wind farms and solar power plants is highly dependent on weather conditions, which increases the need to store electricity locally and to regulate the output whenever a new operator joins the network.
Both the local storage of electricity and connecting new operators to the grid require numerous power capacitors, and the most commonly used insulation material in these capacitors is polypropylene (PP). The plastic is in the form of an extremely thin film typically less than 10 micrometres in thickness, and there are hundreds of metres of film in each capacitor element.
Efforts to improve film capacitors have previously focused on aspects such as crystalline modification by means of catalysts and perfecting the manufacturing process in the hope of creating thinner and more durable plastic films.
Better properties with the help of nanomaterials
VTT is coordinating a project called GRIDABLE–EU, which is aimed at developing better electrical cables and film capacitors. Our goal is to create thinner films for capacitors by mixing silica nanoparticles (nano-SiO2) with polypropylene (PP). Silica has been found, in ideal conditions, to reduce the stress on plastics in an electric field, which can lengthen the life of the components or enable the use of thinner plastic films. The development efforts will also enable the construction of smaller electricity grid components.
The processing of the PP/silica mixture requires specialist expertise and controlled conditions. After the processing stage, the materials are stretched out into thin plastic films, i.e. film capacitor test pieces, using VTT’s biaxial sheet orientation equipment (Picture 1).
Picture 1. Plastic film stretched by means of biaxial sheet orientation equipment
From the laboratory to global markets
We start by demonstrating the performance of the materials by means of test pieces. Our French partners use the results of our cable development efforts to produce a model cable, and our Finnish partners analyse the best new capacitors using a test platform. The best materials are chosen on the basis of the tests, which we can then develop further. Step by step, we get closer to production-scale manufacturing and the ability to use the products in future smart grids.
Picture 2. Illustration of the project’s impact on an individual electricity grid combining several functions by means of VSC and SES units.
In the future, new plastic films in smart grids can be integrated into VSC (voltage source converter) units made up of several capacitors (Picture 2). Their role is to convert the electricity produced by decentralised energy parks to make it compatible with the grid.
Plastic films can also be used in capacitor-containing SES (stationary energy storage) units. Their role is to store electricity locally before it is fed into the grid. Operators as far as a thousand kilometres away can be incorporated into the grid.
The materials’ journey from the laboratory to a real-life electricity grid is a long one but worth it, as new electricity grids cannot exist without more advanced plastics. Perhaps our Dutch travel companion will also get to enjoy the fruits of our labours in the future – in the comfort of his home and happily oblivious to the huge amount of work behind the scenes.
The GRIDABLE–EU project team consists of the following organisations: VTT, Tampere University of Technology / High-Voltage Laboratory, Grid Solutions Ltd, Nexans France SA., Terichem Tervakoski S/A, University of Bologna, University of Twente and Innoexc GmbH.
YouTube: GridAble Project
VTT Technical Research Centre of Finland Ltd
Mika Paajanen, Principal Scientist
GRIDABLE-EU Project Coordinator
VTT Technical Research Centre of Finland Ltd
Satu Pasanen, Research Scientist