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Steep learning curve for grid operator

Such is the power wielded by Spain's transmission system operator that despite its threat to disconnect wind plant in the name of grid stability and the limit it has already placed on installed wind power capacity, wind industry representatives feel they have no choice but to sing to REE's tune, even though lessons from other countries suggest the operator is striking severely false notes.

Such is the power wielded by Spain's transmission system operator that despite its threat to disconnect wind plant in the name of grid stability

and the limit it has already placed on installed wind power capacity, wind industry representatives feel they have no choice but to sing to REE's tune, even though lessons from other countries suggest the operator is striking severely false notes

Improve your grid integration technology or die. This is the increasingly loud and clear message to Spain's wind sector from the power establishment, particularly from national grid operator Red Eléctrica de España (REE). What is more, REE's demands for wind to shape up to the power system's needs if it expects to gain access to the grid in future are winning backing from both the national electricity regulator and the government. The wind industry is responding positively -- but it wants to see facts and figures before it is prepared to swallow all of REE's demands as serious technical requirements, rather than politically influenced bullying.

"With over 5000 MW online, wind is no longer an anecdotal drop in the ocean," says Cristina Martínez Vidal of REE's grid development office. In Spain, all wind generation has priority access to the grid, yet "wind can offer no guarantees of supply and it does not contribute to grid security," says Martínez Vidal. "Spain cannot reach its 13,000 MW target if these problems are not solved." Martínez is referring to the government's wind power target for 2011.

She maintains that "grid security is paramount and above any other legal provisos guaranteeing access to the grid for renewables." The darker implication of Martínez's words is that failing improvements in the ability of wind power stations to meet scheduled production forecasts and contribute to grid stability, they could be sporadically denied access to the network. With a draft national law on grid connection in preparation, the wind industry is bracing itself for change.

It is also doing its best to meet REE at least half way. At a wind integration conference organised by the industry in Toledo in October, delegates listened to demands for improved wind forecasting and grid security technology from not only REE and the power regulatory office, the Comisión Nacional de Energía (CNE), but also from the ministries of technology and economics. Just prior to the conference, the organiser, Plataforma Eólica Empresarial (PEE), had shown it too was willing to act by releasing a new program for predicting output from wind power stations to help with scheduling of supplies.

The wind industry's willingness to listen and learn is in stark contrast to a conference two years ago in Madrid, when REE's suggestion that installed wind capacity should be capped at 13,000 MW caused uproar, along with accusations of vested interests in conventional power (Windpower Monthly, July 2002). Nonetheless, the government acceded to REE's request and implemented the cap as part of its energy infrastructure bill for 2002-2011.

Furthermore, the bill gave REE the right to disconnect wind plant at periods of low demand if more than 3000 MW was being supplied from wind power. That limit could increase to 5000 MW if the wind turbines online were state of the art technology capable of contributing to grid stability.

"What REE says goes and if we want to change their way of thinking we need to play ball as far as we can. REE is in charge of grid connection and we need to tread carefully. There's a lot of politics at play here," was the behind-the scenes comment of one wind industry delegate at the Toledo conference. It was greeted by nods of agreement all round. "REE has calculated how much it is prepared to hand out to wind, not how much it can handle. Sure, there have to be limits but we are best going to define those by taking the initiative with our own studies, on the one hand, and sitting down to talk it out with REE on the other. Sticking our heels in will get us nowhere," said another.

What became clear at Toledo was that REE is not backing all its arguments with fact. Grid integration studies in other countries with relatively high levels of wind on the system do not support REE's claims that wind has no capacity credit on a power system, or that the limit on wind generation for a secure Spanish system is 13,000 MW, or about 17% of Spanish generation by 2011. In Denmark, wind generation has today reached spot penetration levels as high as 70% without flickering the lights and the country is aiming for 30% wind penetration by 2010 and 50% by 2030. In Spain, overall wind penetration is about 5% of national generation (peak demand 35,000 MW), while spot penetration has not once reached even 20%.

So why so much fuss? REE argues that it is struggling to cope with a pace of development which this year will add about 1000 MW of wind power capacity to the national total. More specifically, it says Spain is a special case when it comes to wind integration, for three reasons.

First, unlike Denmark, Spain has poor interconnection to its neighbours, amounting to just 3% of its entire capacity. Wind fluctuations have to be absorbed within its thermal, nuclear and large-hydro generating base. Forecasts of expected wind production help with this balancing act -- and REE says the forecasts are getting more accurate.

Second, Spain's weather is different from other areas of the world with relatively high levels of wind generation, says REE. Anticyclone conditions often last for days or even weeks, with high pressure resulting in periods of low winds and cold weather in the winter and low winds and high temperatures in the summer -- just when demand for electricity for heating or cooling soars. This year's low, so far, came on April 9, when with a noon-time peak demand of 34,000 MW, REE registered a total wind output of 9 MW. But anticyclone wind conditions are predictable and give plenty of warning for scheduling of alternative generation sources. PEE's Alberto Ceña argues that wind lows are easily covered by the rest of Spain's 58,000 MW mix, especially its huge hydroelectric resource. Moreover, there is plenty of reserve, also to cover an expected historic demand peak this winter of 35,000 MW. REE is more concerned with the future, fearing that when wind penetration reaches 17% in 2011, a drought coupled with a dearth of wind would become very expensive.

security risk

Third, Spain arguably has the world's highest geographical concentrations of wind generation, particularly compared with the more thinly distributed plants in Denmark and Germany. Martínez claims the concentration is a security risk should grid faults occur. She cites lightening strikes on power lines or power station failures as an example. "Wind is highly sensitive to such drops [in voltage] in a very short space of time," says Martínez. "Existing legislation establishes that wind turbines disconnect [for self protection] in such conditions. Yet the law dates back to 1985 when wind's penetration was negligible; now we have large wind clusters of 100, 200 or 300 MW."

Martínez insists that such large amounts of capacity should be called upon to stabilise the grid rather than "suddenly disappearing" and "aggravating the problem." She says the bulk of wind turbines operating in Spain cannot ride through grid faults without retrofits. "Possible solutions are being investigated by manufacturers." she says. Martínez recognises that newer more sophisticated wind turbines do not aggravate problems of grid instability. But REE cannot prescribe turbine design or technology," she says. "What we can do though is demand technological specifications for [wind] operators to meet, either through the turbines they choose or via components installed in the wind plant or substation."

Lack of data

REE says that grid fault ride-through capability and improved wind production forecasts would both reduce the amount of spinning reserve it needs on a daily basis. But it is unable to state how much reserve is required to typically cover wind plant dropping off the net due to grid faults, or to cover deviations in scheduled output. Neither can the system operator give an approximation of how much extra reserve is needed on the system to counteract the problems it claims wind's intermittent production causes it.

At the Toledo conference, utility Iberdrola, Spain's largest wind operator with over 1700 MW online, had more at stake than most. The utility's Angeles Santamaria's main criticism of REE was the urgency with which it is pressing for action on scheduling and ride-through issues. "REE's 13,000 MW ceiling and wind dispatching rights were justified on the basis of existing technology," she said, meaning that any extra technological obligations should not be forced on the wind industry before then.

Under Spain's fixed rates of pay for wind output, wind plant operators fear that REE is imposing unexpected costs on them which they have no chance of recouping. "Any extra costs and effort assumed by wind developers and operators from forecasting and grid security technology have to be reimbursed via the wind tariff," says PEE's Alberto Ceña. Yet while calling for incentives to improve wind output forecasts and decrease the costs of scheduling imbalances, Spain's electricity market regulator, the Comisión Nacional de Energía (CNE), is arguing for a possible reduction in the wind tariff to slow wind's rapid growth. One delegate pointed out that losing on the production incentive swing, while gaining on a forecasting incentive roundabout, would make life hard for smaller developers lacking the administrative capacity to run prediction programs.

The general wind industry feeling is that incentives for improved technology will appear tentatively over the next two or three years without a radical change to the production incentive. After that, much will depend on how well the wind sector has been able to negotiate with REE, which controls grid permits, and CNE and the ministries, which control the purse strings.

All agreed that eventual integration solutions are essential for the future of wind and that voluntary attempts to solve them should start immediately. Both PEE and Santamaria called for the creation of developer-operator offices to jointly evaluate the requirements and handling capacity of the 50 or so major grid nodes in Spain.

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