The plant is owned and operated by KODELA, the state utility company, and consists of 12 Nedwind 250-kW turbines. KODELA is now studying plans for a second phase of development in which another 6 MW of wind capacity would be installed.
The Tera Kora facility began supplying power to the island grid in July 1993. In the succeeding 12 months it supplied 1.1 percent of Curacao's power needs, and the turbines' average availability was 94 percent. Based on an evaluation completed in July, 1994, KODELA's figures for the turbines' performance indicate a 38 percent capacity factor.
Since those evaluations, the Tera Kora windfarm has continued to exceed performance expectations. "We have improved performance somewhat by adjusting blade pitch," Karel Tujeehut of KODELA told Wind Energy Weekly in an interview. "Up to now the measures we have taken have given us good results. There have been no major breakdowns. We had a problem with a single turbine's cables twisting, but we do not know why."
Tujeehut expressed optimism that the plans for the second phase will proceed. "We would like to have a second phase operating by 1998 at Tera Kora," he said. Additionally, KODELA is looking at another site, at Paiya Canoa, a location with nearly the same wind characteristics as Tera Kora. The utility is building a grid connection nearby. "This second phase will use 500 MW machines," Tujeehut said. Eventually, the Curacao utility would like to develop a 20-MW wind farm on the island. KODELA's monitoring period at the Tera Kora plant will end in July 1995.
"I have seen very few windfarms doing better in the world," said Margo Guda of Fundashon Antiyano Pa Energia (FAPE), a nongovernmental organization which supports renewable energy. The turbines are installed on the windward coast of the island, on the San Pedro plain. "They capture a nearly undisturbed sea breeze," Guda said. "In fact this windfarm is the only one in the world that is actually operating as a baseload plant."
Asked to comment on this assertion, Tujeehut said, "There is very little diurnal variation at Tera Kora. Because of this the turbines generate constant power. If you look only at production, we may have a basis to call Tera Kora a fixed, baseload unit. This was one of our goals, and we are continuing to study it."
Windmills have been used for decades to pump water on the small island in the Dutch Antilles. Hundreds of them are still in use irrigating orchards and providing water at remote sites, according to a KODELA report. Among the first modern wind turbines on Curacao is a 300-kW Dutch NEWECS machine, which Guda called an "unsung success story," adding, "It is just upwind from the Tera Kora, and it is quite well maintained. This year will mark 10 years of operation." The NEWECS 300 was installed in 1985 and, despite some dire maintenance projections, has been in nearly continuous operation since.
KODELA began construction of the Tera Kora plant in 1992 after extensive wind measurements and site planning. Construction was completed in July, 1993. In initial projections, based on wind speeds of 8.5 m/s (19 mph), the expected output was 7.5 million kWh (625,000 kWh/year per turbine, or 1,243 kWh per square meter of rotor area. The measured output in the first full year of operation was 9.2 million kWh, or 1,525 kWh/sq-m. The annual wind speed was 8.8 m/s (19.7 mph).
Included in planning were some necessary and innovative adaptations to the corrosive Caribbean climatic conditions. It was known that the turbines would be exposed to salt air and perhaps sea spray. Engineers made the nacelle and cone airtight and installed yaw-control bearings inside the nacelle. All exposed nuts and bolts were coated, and the aerodynamic brakes on the blade tips were removed.
The site on the San Pedro plain was selected for its excellent wind regime. The 12 turbines stand on simple reinforced concrete foundations, spaced 125 meters apart in a line following the natural contour of the land. The three-bladed rotors have a diameter of 25.3 meters; the hub height is 30 meters.
Control systems were tested in a total blackout of the Curacao system in November, 1993, and the wind turbine protection systems automatically switched off all turbines as designed.
Curacao's annual electricity consumption is 530 million kWh. The grid has to serve a peak of 84 MW.