To harness the wind

July 25 - If the morning wind in Tshimasham is like blowing from a fan, Wangduephodrang is called Windy Phodrang because of the strong winds, which many believe come from a “wind hole” behind the dzong.

But speed alone is not enough, if Bhutan is to harness wind energy, an alternate source, to enhance the country’s energy security.

Officials from the renewal energy division of the energy department have erected a wind mast in Tsimasham and two more will be erected at the Chelela pass (between Ha and Paro), and in Rubesa, Wangduephodrang, to see if Bhutan’s wind could be tapped to produce electricity.

The 20-metre long wind mast, with wind sensors and other equipment to measure humidity, solar radiation, pressure and temperature, will be erected soon, according to engineer Nar Bahadur from the renewal energy division. The data will be recorded every 10 minutes and saved to a data logger; and downloaded every three months for analysis.

But it is not soon before any conclusion could be drawn on the alternative energy source. Nar Bahadur said that at least two years’ data is required for feasibility and development study. “Ideally, at least 10 years’ data is required to forecast the potential of wind energy,” he said.

The department has earlier studied wind speed in six places across the country – Bhur, Damphu, Bajo, Semtokha, Tsimasham and near the power substation at Charkilo, near Chuzom. But the data couldn’t be analysed because of the lack of a data analyser. The department, however, is purchasing a data analyser.

Nar Bahadur said that, of the six sites, Damphu in Tsirang revealed some potential. “But we are still hunting for better sites. We’re yet to come up with a actual generation capacity,” he said. Actual generation capacity depends on the velocity of the wind.

Although Wangduephodrang is strong, Nar Bahadur said that through his own observation, it was too gusty and not constant. “There’s a lot of fluctuation throughout the day. Too strong winds are also not good for the windmills,” he said.

The engineer said that studying wind profile in Bhutan is difficult because of the topography. “We need steady wind for wind power generation, but our wind path is different,” he said. “Winds in Bhutan have a funneling effect, it is only in the valleys.” While the ideal terrain should not be less than 10-degree slope, our terrains are complicated, said the engineer.

There are other challenges in tapping this free source of energy. Even if there is enough wind to rotate the turbines, bringing in windmill equipment is another identified challenge. “Our roads are too narrow, and there are too many bends, making it difficult for transporting windmills, especially the blades,” said Nar Bahadur.

At least a 10-metre long blade is needed for a 180 kW wind turbine, which is enough to light 90 rural households. “Bigger is better,” said Nar Bahadur, explaining that, if the blades are bigger, the generation is bigger too. A 330kW wind turbine would need blades measuring not less than 16 m. Another impediment is the grid connectivity, said Nar Bahadur. “Connecting the power to transmission lines would be expensive and mightn’t be economically viable,” he said.

A minimum wind speed of 3 m/s is required to generate power. Although preliminary studies indicate that the Wangdue and Tsirang winds fulfil the speed condition, it is not constant. “It’s windy only for a few hours a day,” said Nar Bahadur. “To get constant power generated from wind, the wind speed should be at least 12 m/s and should be continuous.”

source: kuensel