Supergrid: Why it is not a series of point to point connections
The original high voltage direct current (HVDC) cables and transformation stations were national grid to other national grid connections. The HVDC arrangements were invented by the entrepreneurial ASEA company to carry Scandinavian hydroelectricity from where it was generated to where it could be consumed by customers. The HVDC link presupposed that the structure of the transmission grids was a permanent feature. In this regard, and at this time in the mid 1950s this was a good assumption to make.
The world was in full throttle dependence on hydrocarbons then. Fuel could be transported; power stations could be located at any suitable location; most governments encouraged electricity monopolies and used the electricity system to further social aims such as development of local coal mines, lignite and peat. The grid of the day was adequate for this generation arrangement. It was built almost entirely within national boundaries, in a Europe dominated by national interests.
The original HVDC connected these national grids together.
The Supergrid is a very different proposition. It takes into account that 50% of Europe’s generation will probably come from wind by 2050. It recognises the fact that only 250,000MW will be able to be built on land, with 1,000,000MW to 1,500,000MW being built at sea. In concept the Supergrid is designed to facilitate pan European trading in electricity, in the context of a single market. The Supergrid has to be able to provide bulk electricity as reliably across Europe as the current AC transmission grids do now. Obviously it must, by design, integrate with current grids.
So at this design stage there has to be built into the Supergrid a certain amount of redundancy. Just in fact like the transmission grids of today. It has to address the issue of failure of a part of the system, and come up with a cost effective design that ensures that the customer is not affected. Those promoting the Supergrid are like the “stout Cortez, standing on a peak in Darien, beholding the Pacific ocean for the first time”. We who promote the Supergrid are equipped with a table raza, and are given a severe test of our imaginations.
As we studied the issue it became clear that a series of meshed nodes was the simplest and therefore the cheapest way to achieve the reliability goal. Such a node would be a collector of power generated from offshore wind, wave or ocean current devices; it would be able to route power to where the demand was greatest; it would contain a number of switches to allow maintenance work to be done on various components; there would be as many information cables as needed to allow the node to be the central piece of equipment used in the trading of electricity.
Such a node is called the Supernode.
Tomorrow we will deal with the issue of how the Europe of 2050 will cope with an electricity supply entirely composed of renewables and nuclear.