Shoulder to shoulder on wind integration

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Encouraged by the government, Spain's power system operator is working closely with the wind industry on finding solutions to integrating large volumes of wind power into the national grid while maintaining security of supply. By some accounts, Spain is now leading the world on wind integration

With is sights firmly set on integrating another 10 GW of wind into its power system by 2010, Spain is rising to the challenge of how best to manage a more variable supply of electricity flowing into the national network. "Spain is clearly at the forefront of wind integration and is an example of where we would like other markets to go," says Christian Kjaer of the European Wind Energy Association (EWEA). If the target is reached, 20 GW of wind power will be covering just over 13% of annual electricity demand in 2011, according to the government's national renewable energy plan, or about 40 TWh of the 298 TWh expected production.

The Spanish approach to wind integration is pro-active. A series of rules and regulations have been mutually developed by the system operator and the wind industry. Wind stations, like other power plant, are expected to technically contribute to the smooth operation of the grid, also in times of trouble. A national grid code, Procedimiento Operativo 12.3 (PO 12.3), specifying grid support rules, is pending government approval (Windpower Monthly, September 2005). And under a more recently formulated and complimentary set of rules, PO 3.7, all wind output will be subject to centralised dispatch and control from next year, allowing for optimum management of electricity supply (box).

Kjær says the key to Spain's rapid progress on wind integration is the spirit of co-operation between power system operator Red Eléctrica de España (REE) and the wind industry, represented by national wind group Asociación Empresarial Eólica (AEE). The shoulder-to-shoulder approach that started two years ago is partly explained by political appointments at the head of REE, following the 2004 electoral victory by the PSOE socialist party, which has Kyoto high on its agenda. But the wind industry has also been willing to meet REE half way. "For optimum wind penetration, agreement on integration is vital and each party must offer expertise from its own specialist field," says AEE's Alberto Ceña.

International focus

The positive attitude was never more apparent than at a recent conference on integrating wind into the existing power system, organised in Madrid's Royal Opera Theatre by AEE with the collaboration of EWEA and the participation of the association of European Transmission System Operators. "A unique event, drawing together all the people involved in the day to day work of European wind integration," was Kjaer's description of the initiative. Throughout the event, the focus shifted from platform to floor and back again as grid and wind experts tossed ideas back and forth -- along with much praise for the Spanish way.

"Just on the practical front of collecting and analysing data, Spain is miles ahead of Germany," said Karsten Burgen of German wind consultancy Ecofys. In Germany, he says, "There is no online information on system balancing at all." The reason is partly historical. The Spanish market structure has stimulated the connection of large wind farms to the transmission network, whereas in Germany, "ninety-eight percent of wind power, most of it from small wind farms, is connected to distribution networks," said Burgen.

He also pointed out that 91% of Spanish wind capacity now trades its production on the national wholesale market, requiring day-ahead programming of hourly output. As a result, the system can be managed much more effectively than in Germany, where little attempt is made to reduce or increase generation from other plant to dovetail with the ups and downs of wind output.

Sweet talking

REE's boss of operations, Alberto Carbajo, praised the Spanish wind sector's efforts towards more accurate forecasts of its output, together with the "professionalism" of AEE's contribution to analysis of grid management issues and the "broad sector acceptance of dispatch control centres." Of the integration challenges associated with the 20 GW target, "none are insurmountable," he added; thanks to Spain's complex topography, if the wind is not blowing in one part of the country it is likely to be blowing somewhere else.

It was all a far cry from just over a year earlier when Carbajo publicly branded wind as "unmanageable," "problematic" and "a supply security risk" with increased penetration. These days Carbajo highlights "the security advantages of an indigenous source like wind," against the backdrop of cross-border gas cuts in Eastern Europe. Wind covered 11% of Spanish demand for electricity last year, becoming the fourth biggest supplier to Spain's mix. As REE's Miguel Duvisón points out, apart from combined cycle gas, wind is the only other source covering soaring national demand for energy, growing at an annual average of 5-6%.

Three conditions

Only time will tell if the current happy state affairs will last once the honeymoon days for REE and wind power are over. At the Madrid conference, AEE's Fernando Ferrando pointed out that the government has historically continued to raise the wind target for 2010, having started with just 9 GW in 1999. "Now it's 20 GW. Who knows what the future has in store?" Carbajo, however, instantly raised a warning hand, insisting that even reaching 20 GW is not a foregone conclusion.

The 2010 target depends on three main factors, he said. First, at least 75% of all installed wind capacity must meet the demands of PO 12.3, which requires wind stations to ride through grid faults and deliver network support when necessary.

Second, all wind power production must go through dispatch centres, which will ensure that maximum production at peak demand in any single hour does not exceed 14 GW, based on the national wind turbine fleet not producing at more than 72% of capacity during periods of peak electricity consumption. The production cap for wind power will be correspondingly lower in times of less demand.

So far so good, says AEE. Only rarely will wind power production exceed 72% of its total capacity -- and even then REE will only intervene if necessary. Discussions of maximum allowable wind production in periods of low demand are still to be concluded, but in practice REE has not found it necessary to curtail wind on more than a few isolated occasions.

Carbajo's third condition, however, improved interconnection with France is demanding more than is necessary, says Ceña. According to Carbajo, more interconnection is needed to absorb 20 GW of wind. As an "energy island," Spain's international connections (mainly with France) are equivalent to less than 3% of national installed capacity, providing REE with limited potential for balancing swings in supply and demand by exporting or importing power to and from its neighbours. But AEE argues that the whole point of the agreed grid code and generation cap was to compensate for Spain's poor interconnection with the rest of Europe. "Any extension in interconnection would help raise the wind target, not keep it where it is," says Ceña.

Meanwhile, all turbine manufacturers in Spain are offering technology that allows wind stations to ride-through grid faults, meeting the grid code requirement. Speaking at the conference, Eckard Quitmann of German manufacturer Enercon said the inherent design of the company's turbines meets PO 12.3 demands. Spanish turbine suppliers, Gamesa Eólica and Ecotècnia, together with GE Energy, Germany's Repower and Siemens also all claimed to be up to date with PO 12.3 or to be fine-tuning solutions.

But how does a potential investor in a new project know that the ride-through technology will meet the legal requirements? One commercial solution was presented by Spanish company Energy to Quality (E2Q) with a hi-tech mobile unit called Ulises. Mounted on a lorry trailer, Ulises trundles from wind plant to wind plant simulating onsite a wide range of voltage drop conditions within and beyond those set in PO 12.3. The system was designed in conjunction with national electronic certifying agency Laboratorio Central Oficial de Electrotecnia. E2Q expects Ulises to be certified shortly as a means by which owners can be assured the hardware is meeting requirements.

Ecotècnia has already signed up for E2Q services. "There's really nobody else yet providing a ready verification solution," says E2Q's Ana Morales. It may not have the market to itself for long. E2Q arose from AEE's dedicated working group on ride-through verification. Other solutions are expected to appear. National renewables centre Centro Nacional de Energías Renovables, which is aiming to become an international turbine certification body, said its work on verification was advanced.

For older wind stations using conventional induction generators, French engineering giants Alstom and Areva, and Swiss counterpart ABB, are offering an alternative to retrofitting turbines. They presented the so-called FACTS solutions (Flexible AC Transmission Systems) at the conference, which provide advanced power electronics and capacitor packs for installation at wind plant substations. "They work fine but they're very expensive," whispered one turbine manufacturer. "Still, the alternative is failure to adapt to PO 12.3. That means you'll be at the top of the list for curtailment -- and that's even more expensive. We all want to stay online and generate earnings."

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