SINGAPORE - The ventilation units of large buildings and shopping malls could one day be the site of wind farms in Singapore if a local start-up has its way.

Cygnus Power wants to install wind turbines - not the common windmill-like structures, but aerodynamic blades that rotate like a silent, revolving cylinder - next to the vents to harness the energy otherwise wasted.

With just a wind speed of 2.5 metres per second - the speed of an average jogger - needed for a small model to start generating electricity, the company believes wind energy can be introduced here where wind energy is commonly thought unfeasible, given the mild winds that come in multiple directions.

Yet, in October last year, a Taiwanese company tried to find a distributor for a similar vertical axis wind turbine said to be suited for urban use, without making further inroads.

Has anything changed since Today first reported about that pioneer attempt?

Yes, according to a check on the Government's business opportunities portal Gebiz.

Three tenders have been called for wind turbines in the last six months - from the National Parks Board, the Institute of Technical Education and Nanyang Polytechnic (NYP) - suggesting a recent heightened interest in wind power in the public sector.

And NYP could become the first in Singapore to have a vertical axis wind turbine installed.

The turbine order is part of NYP's effort to develop capabilities in clean energy, and is meant for "training and education of students, research and development (and) innovation and support to industry", said a spokesperson.

But the power generated by a 2-kilowatt turbine system - to be supplied by Cygnus Power and installed mid-January - will also be used by the institution, said Mr Chan Yew Meng, Senior Director of NYP's School of Engineering (Electronics).

But whether the turbines take off in a bigger way, he said, will depend on "a matter of economics", such as cost, savings and payback period.

According to Japanese aerodynamics expert Tsuneo Noguchi, who invented the blade design, about 50 to 60 of these turbines are being used atop some streetlights in Ginza, as well as Japan's Ministry of Science and Education.

Efforts began nearly 40 years ago to get vertical axis turbines to start at low wind speeds, but Professor Noguchi, who is also a director of Cygnus Power, said he applied aircraft technology to come up with a breakthrough design. He has patented it in Japan, China and the United States.

Speaking on the sidelines of the Clean Energy Expo Asia, Cygnus Power's chief executive Ong Gin Keat said two major property developers have also expressed interest in the turbines.

"They can be placed not just on top of buildings, but also where buildings form a wind tunnel, or where there's forced draft of ventilation," said Mr Ong.

"Every hotel and shopping centre has chiller and ventilation units, which vent out into the open, and energy is totally lost. It will definitely reduce their cost of operations."

With the adoption of several turbines, "windfarms in large buildings and even shopping centres" can be created.

And while the cost is relatively high - ranging from US$9,000 ($12,500) for a 1kilowatt turbine to US$33,000 for a 5kW one - maintenance is minimal and the payback period is three to 10 years, Mr Ong said.