Tham khảo tài liệu 'wind power impact on power system dynamic part 17', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Wind-Solar Driven Natural Electric Hybrid Ventilators 541 Fig. 4. Spherical centrifugal ventilators at the University of New South Wales These ventilators operate as drag devices and hence the angular velocity of the device cannot exceed the ambient wind speed. The difference in the coefficient of drag_on the convex and concave sides of the blades causes the device to rotate Fig 4 . This rotation forces exhaust air to be drawn into the centre of the pump where it is subsequently centrifuged out of the device. iv. Solar Ventilator The fourth type of ventilation method uses solar power exclusively to operate an air extraction fan . This fan is usually of the axial type. Fig. 5. External and internal views of solar powered ventilator Image For many commercial buildings Australian Standards demand a minimum flow rate of fresh air and a minimum number of air-changes per hour. Such requirements are usually met with mains-powered air extraction fans. 542 Wind Power Such fans are usually axial types and are very similar in concept and construction to the solar ventilator of figure 4. The main difference between the two lies in the absence of the solar panel and the requirement for hard-wiring to a mains power source. v. Mains powered ventilators They include various forms of ventilation devices that are powered by mains electricity supply. These are essentially dependent on the non-renewable powered systems. Although they are the most reliable systems they come at a cost to environment and hence the push to seek greener alternatives. vi. Hybrid ventilators If human comfort convenience and reliability are sought with equal concern for environmental impact it appears that a compromise solution may be the most effective. Thus some form of hybrid solution may be explored that will provide air extraction capacity at all times and operate in all conditions. This would make it useful for applications that require a continuous flow rate of air. The hybrid
