Just good friends
Without a supergrid the prospect of large scale renewable energy
generation will be impossible. Mike Farish finds out why
For the general public the most obvious difference between an energy supply infrastructure based on fossil fuels and one based on renewable sources is in the sheer number of power generation installations involved. The former model requires a small number of large facilities, the latter a much greater number - literally thousands - of smaller power sources.
The perception is valid but also, quite literally, superficial, because in order for large scale renewable electricity generation to become an effective part of any country’s energy resources something rather less immediately evident is also necessary. This is a grid that can collect the electricity at those multiple, dispersed points of generation and deliver it to its place of consumption. But the type of grid that will be able to do that will be no ordinary grid. It will, instead, have to be a ‘supergrid’.
But just what is a supergrid? Here is a definition: “An electricity transmission system, mainly based on direct current, designed to facilitate large scale sustainable power generation in remote areas for transmission to centres of consumption, one of whose fundamental attributes will be the enhancement of the market in electricity.”
That is the description put forward by a new organisation - Friends of the Supergrid - due to be formally launched early in March, in parallel with a major conference on the subject in London, with a mission to push the message that without a supergrid the prospect of large scale renewable energy generation is a chimera. The organisation currently comprises nine companies with interests in the area of renewable power generation, whether as technology or service providers.
Promotion
One of them is Dublin-based Mainstream Renewable Power, whose founder and CEO Eddie O’Connor is perhaps the highest-profile proponent of the supergrid concept. Someone who works alongside O’Connor, both within Mainstream’s commercial activities and the wider promotion of the supergrid, is Joe Corbett, head of technical services with Mainstream. He points out that until a couple of decades or so ago power generation, certainly in the UK and also in most other developed countries, was dominated by two particular sources - coal-fired power stations and their nuclear counterparts. In both those instances the physical location of the installations was almost invariably remote from the point of use of the energy they generated. In the first case this was because the power stations needed to be close to the coalfields where their fuel was mined because of the cost of transporting the coal over any great distance. In the second it was because nuclear facilities needed to be sited on the coast in order to have easy access to seawater for cooling, though doubtless safety considerations also played a part.
This changed when a new generation of gas-powered stations came on line. In their case it was as easy to pump the gas to the power stations as to transmit the electricity they generated and hence there were few limitations on where they could be sited. But now the economics are moving against gas because of both the finite nature of the resource and the drive to reduce carbon emissions - hence the new emphasis on renewable sources.
With renewable energy, though, the previous distribution pattern for the centres of generation and use will be reinstated. In Europe those two sources of generation are wind power, overwhelmingly offshore and most of that in the North Sea, in northern Europe and solar power in the south. In the first of those instances especially that means that the primary points of generation and consumption could be significantly remote from each other. In the case of the UK Round 3 offshore wind farm developments announced in January, notes Corbett, the distance from wind farms to shore will in some instances be at least 100km.
Sheer distance is therefore a crucial reason why one of the defining features of the proposed supergrid - its use of high voltage direct current (HVDC) - becomes necessary. It is far superior to AC as a means for transmission in bulk.
But given that the electricity is actually generated as AC current there has to be a means of converting it to DC close to the point of generation. This is where an essential technical attribute of the supergrid comes in - that of the ‘super node’, a piece of equipment that can collect AC current from numerous sources, convert it to DC and then funnel the electricity into a single cable for delivery to the existing conventional grid where it can be converted back to AC.
Confident
Nevertheless, Corbett is keen to stress that the super node concept is already far more than a mere aspiration. Mainstream, he confirms, has itself carried out some preliminary development work and is entirely confident that super nodes can become a practical reality. In that respect they exemplify one of the core factors about the wider super grid - that all the necessary technologies either already exist or would be relatively easily achievable developments of existing capabilities.
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