xBut while the episodes underline wind as a significant contributor to the mix, it also opens the question of whether grid operator Red Eléctrica de España (REE) is handling wind production properly and fairly. Peak wind output was just over 6000 MW -- equivalent to six nuclear power stations working at full capacity. It met 14% of the mainland electricity demand at the time, which was around 42 GW. Furthermore, average wind production was at 3000 MW for each of the cold spells, according to wind association Plataforma Eólica Empresarial (PEE).
xUnlike Denmark and Germany, Spain's interconnection with the rest of Europe is weak with a maximum import capacity of just 2500 MW, mainly from France. Most supply-demand balancing is done internally. With Spain's thermal plant working flat out during the cold spell, the high wind production saved REE from having to cut supplies to so-called "interruptible" industry clients, even though the grid operator broke its own rules to do so. REE has consistently argued that wind penetration must never rise above 12% if system security is to be maintained. Indeed, it has applied this rule in the past to curtail large amounts of wind production during periods of low demand in 2004 (Windpower Monthly, November 2004).
xREE's response to having its cake and eating it is that the 12% limit was not breached. But to arrive at that conclusion, REE is only taking account of the 80% of wind production that transmits real time data to the operator. Extrapolating from that 80% puts wind's actual contribution at 14% of demand.
x"The important thing is that wind was there when it was needed most," says PEE's Alberto Ceña. True, wind dropped from around 4000 MW to 800 MW over seven hours during a fourth Arctic spell on March 1, he concedes. But this merely underlines the need for REE to take wind forecasting seriously in its daily scheduling of electricity supply, argues PEE. "REE still never includes wind power in its programming," says Ceña. He explains that REE programs conventional production as if wind power did not exist. So if wind fails to produce, it makes no difference to balancing the grid. If it does produce, the excess thermal capacity REE scheduled either goes on standby or shuts down completely.
xThe grid operator says wind forecasting is not good enough to help it maintain its supply guarantees to customers. Initial results from the first three months of PEE's own forecasting exercise (next story) have done little to dispel this belief. PEE is confident, however, that over a year it can improve forecasting accuracy to the extent that REE can include wind in its scheduling of power supplies.