Polarised debate on best approach -- Wind forecasting in Spain

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The current focus on forecasting output and scheduling production from each separate wind power station is "ineffective" and is "taking the Spanish wind sector down the wrong road," warns national renewables association Asociación de Productores de Energía Renovable (APPA). It is calling for centralised broad-based wind forecasting and scheduling, preferably through the creation of a new secondary operator entirely dedicated to renewables or, alternatively, by existing grid operator Red Eléctrica de España (REE). APPA has lodged its concerns as part of a government consultation on a new energy white paper.

xJust over a year ago, Royal Decree 436 established a blanket obligation for individual wind stations to forecast and schedule their daily production. The obligation is supported by the Plataforma Eólica Empresarial (PEE), a wind industry lobby group and APPA rival representing the interests of 85% of Spain's installed wind capacity. PEE sees individual scheduling as a necessary burden to bear if wind penetration is to increase substantially and if the industry is to mature as a main professional player within Spain's electricity sector. "But watch out," says APPA's José María Vélez. "Not only is plant-by-plant forecasting expensive, it is also mainly useless to the [grid] operator."

xxNo help at all

xRD 436 gives new wind producers two options for selling their generation. The first is to schedule and trade production on the daily wholesale electricity market, receiving the market price for generation plus an incentive. The second is a feed-in tariff guaranteeing the level of earnings over a plant's life cycle. Operators opting for the fixed tariff must also schedule production individually from January 2006.

x"Around 33% of wind capacity now trades on the wholesale market," says Vélez. But while the option brings better earnings, it has done nothing to help REE integrate wind, he argues. By buying and selling on the six openings on the daily electricity market, wind producers can smooth out any imbalances between scheduled production and that actually delivered. "In fact, it is technically possible to schedule 100 MW when you know you're going to produce 2 MW, or vice versa, and still come out winning," says Vélez.

x"This clearly does nothing to help REE balance the system and REE still ignores wind in its daily balancing calculations," he argues. Far from helping the integration of wind, the scheduling requirement could be a restriction on wind power's growth, he argues.


xWhen the forecasting obligation comes into force for wind plant signed up for the fixed tariff, the sum of wind plant forecasts might offer a more accurate tool for balancing the grid, Vélez concedes, as there will be no fiddling with market mechanisms. But even so, he says it is "absurd" to force all developers into buying expensive forecasting technologies. "It is cheaper and more effective to determine centrally how much wind power will be produced at key grid points," says Vélez.

xMoreover, operators on the fixed tariff face penalties of around EUR 7/MWh for deviations between scheduled and delivered production. Vélez points out that the maximum average accuracy so far attainable for hourly scheduling is around 30-40% for just six hours ahead of delivery. "We need the same percentages for 30 hours ahead if forecasting [under the fixed tariff] is to be viable." If results fail to improve, it will be unfair to burden operators under the fixed tariff with these extra costs. "The method is inherently defective," argues Vélez.

xxWait and see

xPEE's Alberto Ceña is confident that results will improve. PEE members are currently participating in an exercise which compares six different forecasting models across seven wind plants.

x"Improvements will now be thick and fast as we have compiled a lot of historic data which we didn't have when we started," he says. Ceña also justifies the plant-by-plant approach. "If forecasting is centralised and divorced from individual operators, where are the incentives for optimising models?" He is confident that fine-tuning will produce viable forecasting by autumn and that REE will then bring wind into its daily load management.

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