|European grid vision|
Gunnar Lorenz, Head of Networks, Eurelectric
Europe's power system will undoubtedly need to undergo a major transformation in order to cope with additional pressure on the grid, resulting from a rapid expansion of renewables or demand-side technologies like electric vehicles. An additional layer of infrastructure, i.e. a supergrid, could play a part in achieving tomorrow's integrated power system. But existing networks will also need to become 'smarter': both in terms of their embedded technology and in the way they are operated and managed. Such issues are currently being assessed within the e-Highway2050 project, which aims to develop a top-down methodology to plan a future pan-European system of 'electricity highways' between 2020 and 2050. The project, co-funded by the European Commission, will last for over three years.
Whether the future grid will really build on a supergrid remains open. In any case, though, Eurelectric believes that the development of electricity highways - and grid planning in general - will depend on many other factors, including demand response, the increased development and use of storage technologies, and the implementation of smart grid functionalities. Fostering such developments, many of these happening at the distribution level, will require a well-functioning interface with distribution system operators, to make Europe's networks smarter and more flexible.
Joe Corbett, Head of Technology, Mainstream Renewable Power
Although HVDC technology has been around for some time, it is the advent of voltage source technology, based on the insulated gate bi-polar transistor, that has allowed us to conceive of an interconnected HVDC grid. In parallel, the development of offshore wind farms has meant an increasing demand for the technology; so much so that we are moving from a 'technology push' from a small number of manufacturers to a 'market pull' for better and more economic solutions.
There are no technology barriers to deliver a supergrid today: however, innovation will be required to ensure economic solutions delivering the reliability that TSOs expect.
Even in Europe the number of HVDC links proposed is increasing each year. Many of these are stand-alone point-point connections. And yet all studies that address interconnection conclude that meshed designs are better in the long term.
The absence of standards also does not help. Projects are designed bespoke with no standard voltages. It will be costly to interconnect these links later. Thus, regulators and standards bodies must take the long view and allow future proofing of designs.
Dr Norman MacLeod, Technical Director, HVDC, Parsons Brinckeroff
In many respects the development of a European-wide HVDC supergrid is an inevitable outcome of the many schemes presently in operation, in planning or under construction.
This is despite a current institutional and regulatory framework that is not structured to deliver a centrally planned and funded supergrid. All evidence suggests that development of the DC grid will mirror development of the AC grid, i.e. piecemeal development, which is ultimately interconnected to create a continental-wide transmission system.
Many visions serve to illustrate the concept of the supergrid. Realistically it will evolve organically from the many disparate schemes which were never planned to form a unified grid, but which will become integrated into a grid, driven by the operational and societal benefits that can be achieved by interconnecting these systems.
Crucial technological advances have already been announced, but further improvements are necessary to achieve the vision.
National governments and regulators also need to create a sustainable policy framework which does not discriminate against renewable energy sources and provides a stable platform for long-term investment in grid infrastructure. Along with industry, they also need to inform society about the economic benefits of the supergrid, whilst demonstrating how technology can alleviate concerns about environmental impacts.
Peter Vaessen, Principal Consultant, Super Grids, DNV KEMA
The dynamics of the energy flows are rapidly growing. The increase in electricity demand, sustainable generation and cross-border transmission on the one hand, and a decrease of controllable conventional power plants one the other, make their presence felt.We have a hard time keeping up, but we have little choice.
First of all, capacity management needs to be addressed: maintaining the real-time balance between demand and generation. Just as crucial is voltage control: keeping the grid energised requires reactive power. The higher the AC-voltage and the longer the distance, the more reactive power is required.
To face up to these challenges, the development of supergrids will contribute to a better capacity management because they integrate regions and therefore improve the balancing of a mix of controllable and fluctuating sources.
A solution for the reactive power issue is to switch from AC to DC. The conversion to a HVDC grid is relatively simple, without new line routes being required. Moreover, HVDC connections can transport up to 200 per cent more energy over the same route. The drawback is that complex and costly converter stations are needed. Building a meshed DC grid is also a challenge. Therefore, it is best to start with small pockets of a hybrid grid.
Another major challenge is being able to realise supergrids while the current grid infrastructure is still operational. Thus more research is required to enable us to make the right choices.
Professor Ronnie Belmans, KU Leuven & CEO, EnergyVille
The development of HVDC grids is the next logical step in the development of grids to accommodate greater international trade, wider than the former UCTE and NORDEL synchronous zones, and the integration of far distant and offshore renewable energy resources. The technology for this type of electricity highway therefore requires the use of DC technology rather than AC.
For the next generation overlay grid, redundancy and reliability are crucial elements requiring a meshed layout and thus DC circuit breakers. The latter has become available recently.
Therefore, all technical elements for building this next generation VSC HVDC-based overlay grid to serve society on the road to a sustainable energy system are available now.
Gunnar Asplund, Vice President, GBA Consulting AB
Back 1992, ABB developed a vision of an HVDC supergrid that could enable Europe to be supplied solely by renewable energy - hydro from the north, wind power from the Atlantic coast and solar from the south.
However, one big problem with HVDC at the time was that the current only flowed in one direction and a change of power direction required a change in polarity, which would not be possible if several stations were connected in a grid. In 1997, HVDC Light arrived, a new kind of converter, which changes power direction by changing the direction of the current. With this converter, ABB removed one of the big obstacles to building an HVDC grid.
The next challenge was to be able to isolate a fault very quickly to prevent the whole grid going down. An HVDC breaker was needed that had to be extremely fast and last year ABB developed such a breaker using a hybrid technology. This device fulfills the requirements from an HVDC grid and has almost no losses as the current pass though the mechanical switch.
Thus, technically there is no big obstacle left to prevent the building of a supergrid. So when could it take place? Actually it is probably already happening. Several of the exisitng HVDC schemes could feasibly form part of a future European supergrid.
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