Design and testing of a novel exhaust air energy recovery wind turbine generator / Ahmad Fazlizan Abdullah

An innovative system to recover part of the energy from man-made wind resources (exhaust air systems) is introduced. A vertical axis wind turbine (VAWT) in cross-wind orientation, with diffuser-plates is mounted above a cooling tower’s exhaust fan to harness the wind energy for producing electricity. The diffuser-plates are designed as a power-augmentation device to improve the performance of the VAWT as well as the cooling tower airflow performance. The performance of the VAWT and its effects on the cooling tower were investigated by experiment. A small scale of cooling tower is fabricated to mimic the actual counter-flow induced draft cooling tower. The supporting structure to hold the VAWT and dynamometer where turbine the position can be moved vertically and horizontally to study the performance in various configurations. The wind from the discharge outlet is generated by fan which is not in uniform profile. From the experiment, it is determined that the best horizontal position of the VAWT with a diameter of 300 mm at the outlet of the cooling tower with the outlet diameter of 730 mm is when the center of the turbine is at a distance of 250 mm to the center of the outlet. The distance is about 2/3 of the outlet radius. However, the vertical distance of the VAWT to the outlet is different depending on the fan speed. Based on the evaluation on the VAWT performance as well as the cooling tower performance, the best configuration of the system at fan speed of 708 rpm is when the VAWT is at horizontal position of 250 mm and vertical position of 350 mm. At this configuration, the cooling tower’s flow rate improved by 9.55%, the fan motor power consumption reduced by 2.07% while the turbine generating energy. For the fan speed of 910 rpm, the best VAWT position at the outlet of the cooling tower is at horizontal position of 250 mm and vertical position of 400 mm with the air flow rate of the cooling tower and fan motor consumption showed a 9.09% increase and 3.92% decrease respectively. The double multiple stream tube analysis produced similar pattern of graphs to the experimental result which indicates an v agreement between these two analyses. Theoretical analysis explains the wind turbine behavior in the not uniform wind stream as acquired from the experiment. For the selected wind turbine, it is the best to match the highest wind velocity region to the wind turbine at the range of 45° to 115° azimuth angle. This is as shown by the wind turbine at the positions of X = 250 mm and -250 mm. At this range of azimuth angle, the turbine produces higher instantaneous torque and better angle of attack compared to the other azimuth angle. The dual rotor exhaust air energy recovery turbine generator experiments found that the system produced the best performance at the VAWT vertical distance of 300 mm to the outlet plane. The integration of diffuser-plates further improved the VAWT performance with 20% and 27% for the fan speed of 708 rpm and 910 rpm respectively. At 910 rpm, with the diffuser-plates, the cooling tower air flow rate improved by 10.05% and the fan consumption decreased by 2.68% compared to the bare cooling tower. It also improved the energy recovery by 27.03% compare to the VAWT without diffuser-plates. For the actual size of cooling tower, it is estimated that 13% of the energy from the common cooling tower with the outlet size of 2.4 m and rated motor consumption of 7.5 kW is recovered. For the cooling tower that operates for 20 hours per day, every day throughout the year, a sum of 7,300 kWh/year is expected to be recovered. The payback period for the system of this size is 7 years while the net present value of the system at the end of the life cycle of the analysis is RM 25,437. The cumulative recovered energy value at the end of the life cycle of the system is RM 179,786. This system is retrofit-able to the existing cooling towers and has very high market potential due to abundant cooling towers and other unnatural exhaust air resources globally. In addition, the energy output is predictable and consistent, allowing simpler design of the downstream system

The design and testing of an exhaust air energy recovery wind turbine generator / Ahmad Fazlizan Abdullah

An innovative system to recover part of the energy from man-made wind resources (exhaust air systems) is introduced. A vertical axis wind turbine (VAWT) in cross-wind orientation, with an enclosure is mounted above a cooling tower’s exhaust fan to harness the wind energy for producing electricity. The enclosure is designed with several guide-vanes to create a venturi effect (to increase the wind speed) and guide the wind to the optimum angle-of-attack of the turbine blades. Another feature of the enclosure is the diffuser-plates that are mounted at a specific angle to accelerate the airflow. Moreover, safety concerns due to blade failure or maintenance activities are tackled by the design of the enclosure. The performance of the VAWT and its effects on the cooling tower were investigated. Laboratory test conducted on a scaled model (with a 5-bladed H-rotor with 0.3 meter rotor diameter) shows no measureable difference on the air intake speed (1.6~1.8 m/s) and current consumption of the power-driven fan (0.39 ampere) when the turbine was spinning on top of the scaled model of the cooling tower. Field test on the actual induced-draft cross flow cooling tower with 2 meters outlet diameter and powered by a 7.5 kW motor was performed using a 3-bladed Darrieus wind turbine with 1.24 meter rotor diameter. There were no significant differences on the outlet air speed of the cooling tower, i.e. the outlet speed of the cooling tower without and with wind turbine was 10.63 m/s and 10.67 m/s respectively (the rotational speed of the turbine was 881 rpm). No measureable difference was observed on the power consumption which was recorded between 7.0 to 7.1 kW for both cases. This system is retrofit-able to the existing cooling towers and has very high market potential due to abundant cooling towers and other unnatural exhaust air resources globally. In addition, the energy output is predictable and consistent, allowing simpler design of the downstream system

Thermal comfort assessment of naturally ventilated public hospital wards in the tropics

Natural ventilation, which is a common method used in tropical climate countries, can provide a high rate of airflow to maintain good indoor air quality and thermal comfort. However, the use of natural ventilation alone as passive cooling strategy is insufficient to improve indoor thermal environment. Thus, this study aims to deter�mine the existing thermal comfort conditions in a naturally ventilated public hospital ward by using three methods: simulation works, objective measurements and field surveys. The combination of all these methods in measuring thermal comfort is essential in acquiring the most accurate results and has yet to be implemented in any public hospital in the tropics on the basis of the literature review conducted. The simulation results presented that more than half of the total occupants in the ward feel discomfort, with a predicted mean vote (PMV) be�tween 1.0 and 1.6 and a predicted percentage of dissatisfied between 40% and 56%. On-site measurements recorded the same PMV reading, indicating slightly warm and warm, on the basis of the ASHRAE Standard 55 assessment scale. By contrast, the results of the survey questionnaire showed a different perception of the oc�cupants, with 82% of the respondents voting in the range of warm to hot scale. The thermal conditions in the naturally ventilated ward studied for two months in 2020 were found to be uncomfortable and required further improvement. Knowledge of the climatic characteristics and the current state of the indoor thermal environment will help the building owners strategise an appropriate bioclimatic design approac

Review Of Desiccant In The Drying And Air-Conditioning Application

Desiccant is a hygroscopic substance generally used in the dryer and air-conditioning system as a drying agent. The function of desiccant is to remove moisture from the air to reduce the humidity of the surrounding air been conditioned. This paper presents several works on the performance of desiccant material in the drying and air-conditioning application. It puts focus on the various advantages and disadvantages of the use of desiccant as a drying agent. There are some advantages of using desiccant include consistent drying and low energy usage. However, there are several disadvantages of using desiccants which are low capacity for moisture absorption and pressure drop in solid desiccant. Solar drying applications have some advantages such as being comparatively cheaper than other methods and less risk of spoiling the product. On the contrary, drying applications have disadvantages include being lower in comparison to the original foodstuff and drying foods eventually leads to shrinkage. The advantages of using desiccant in air-conditioning applications offer dehumidified fresh air to keep the building's temperature in a comfortable range and enhances water recovery efficiency. There are disadvantages such as desiccant will substantially impact the system's performance and desiccant should be cooled after completely dried