When talking about commercially producing energy from renewable sources in Malaysia, wind would come last, or even none at all. This is due to the fact that the country has low wind speed.
Malaysia’s mean annual wind speed is not more than 2 metre per second, when minimum 6 metre per second is needed to spin a wind turbine. Plus, wind speed varies according to month and region, making it an unreliable source for energy generation.
However, the lack of good and consistent wind speed are not obstacles to a Universiti Malaya professor.
Dr Chong Wen Tong, who has always been interested in finding a reliable wind source for energy generation, may have found the answer. Around three years ago, he developed a wind energy recovery system from air exhaust outlet – those great fans usually located on top of commercial buildings for air-conditioning.
The system comprised of two vertical axis wind turbines placed above an exhaust outlet in a cross-wind orientation and mounted at a specific height above the exhaust outlet to avoid creating negative performance to the exhaust air system. The system is also equipped with guide vanes to guide the wind to an optimum angle to spin the blades, as well as an augmentation diffuser, which has been shown to improve performance of the wind turbine.
He created the system since air exhaust outlet will give the strong and consistent wind needed, with the aim to recover a portion of the energy generated.
“A good air speed to generate energy is in the range of seven to 13 metres per second and exhaust air creates wind of around 11 metres per second, thus creating a strong and consistent wind,” Chong said.
Testing conducted with the help of the project’s industrial partner, Truwater Cooling Towers Sdn Bhd, which is also a local cooling tower manufacturer, showed that not only the system does not negatively affect the performance of the exhaust, it also re-captures around 13% of the energy created by the motor to spin the exhaust fan.
Chong explained that an air exhaust usually uses a 7.5-kilowatt (kW) motor to spin the exhaust fan and a wind turbine generates around 0.5 kilowatt of energy.
“As the system uses two wind turbines, the energy generated is around 1kW, which shows the system recovers 13% of the energy used to power the motor,” he said.
He added that for the system to work, the wind turbines’ speed has to be faster than the air speed of the exhaust.
And the turbines do spin faster at around 881 revolutions per minute (RPM). In comparison, a 3-blade ceiling fan at your home spins at high speed on average 260 RPM. As a safety measure, the system comes with an enclosure to protect maintenance workers as well as protect others should there be a blade failure.
“The system has a great marketing value since there are many cooling towers as well as other unnatural exhaust air resources around the world,” Chong said.
Plus the capacity factor is quite high, with the exhaust operating in about 16 hours per day (in accordance to operating hours of a building).
The system can be custom-made to fit varying size of exhaust air sources, with the energy generated can be channelled back into the electricity grid or used for commercial purposes.
For the next phase, Chong wants to position the blade into V-shape instead of the current flat-shape… “Much like the wings of an airplane,” he said.
Chong also plans to commercialise the system via Truwater Cooling Towers.