From a technology push to a market pull

EUROPE: To make Europe sustainably energy-independent will require a renewable-eneration portfolio built where resources are optimal and not constrained.

(James Fryer)
(James Fryer)

Much of this portfolio will be fuelled by offshore wind, putting an increasing strain on our already congested transmission grids, thus requiring a high-capacity transmission system — the Supergrid.

The Supergrid concept is based on a high-voltage direct-current (HVDC) network connecting offshore and onshore SuperNodes, which collect the renewable energy and deliver it to the high-voltage grid at the load centres.

Technology

Although HVDC is not new, it is the advent of voltage source technology based on the insulated gate bipolar transistor (IGBT) that has allowed us to conceive of an interconnected HVDC grid. Voltage source converters (VSC) allow connection of "weak" electrical networks, such as offshore wind farms. Early versions had relatively high losses (4%), but with an increasing demand, we are moving from a "technology push" from a small number of manufacturers to a "market pull" for better, more economic solutions. The supply chain is responding; the latest VSCs are so-called multi-level devices with losses of less than 1%. So, while the electricity regulators dither, offshore wind has driven the demand for innovation on the grid.

The SuperNode concept is a hybrid AC/DC device that is designed to collect and route power on the HVDC Supergrid. Although much of the technology exists today, a number of challenges need to be overcome, including the need for compact designs suited to offshore, better control systems and HVDC circuit breakers. Once again, the need for innovative, improved, cost-effective solutions is paramount.

Today's control and data monitoring systems are often proprietary and based around technology from a single supplier. In the future, open software platforms will prevail with internet protocol as the norm and plug-and-play technology for devices.

Power cable technology is more than 100 years old, and transport weight, cable tension limits and installation methodologies restrict onshore installation lengths to one kilometre. Offshore, with large ships, the length can be up to 100 kilometres.

New designs for underground transmission are required and innovations such as gas insulated lines, new electric pipelines, such as "elpipes" and, in the longer term perhaps, superconducting devices will make economic sense as power-transfer levels surpass 10,000MW over distances of several hundred kilometres. These new designs must also take installation into account — design for installation should be our mantra.

Standards
Even in Europe the number of HVDC links proposed is increasing with each year and all will one day be part of the European Supergrid. But current new connections are largely single point-to-point with no interconnection facilities. The absence of standards does not help — projects are designed bespoke with different voltages and control interfaces, making it costly to interconnect these links later. The regulators and standards bodies must take the long view, and fast-track processes for standard voltage levels and control interfaces.

As a species we are on a one-off transition to sustainability. The power system will be instrumental in delivering this and the Supergrid will be its backbone. We must create our vision, innovate to deliver and standardise critical items to future-proof our work.

Joe Corbett is head of technology at Mainstream Renewable Power, and on the technical working group of Friends of the Supergrid

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