Vertical Axis Wind Turbines

In the last two decades, an increase in large rotary machines/systems has been witnessed. To ensure safe operation of these systems especially due to extreme stress caused by centrifugal forces as well as the wind or water loadings, regular structural health monitoring (SHM) of the unbalanced parameters, particularly at the blade tips is necessary. For this, the use of non-contact sensors provides the most appropriate approach; however, millimetric out-of-plane deflection monitoring using non-contact sensors at distances >1 m has not been comprehensively addressed for rotary systems, like wind turbines. This study presents a modelling environment to simulate radar returns to analyse rotary systems. Employing Sammon mapping as a dimensionality reduction procedure in conjunction with 2D visualisation, the study demonstrates the characterisation of dynamic deflection parameters using a fast, portable ground-based interferometric radar (GBR). Comparisons between the GBR results with those of a Leica AR20 GPS indicate a divergence ±12.79 mm. The study utilises SHM framework to acquire, normalise, extract, and validate GBR signals within an SHM framework for structures under test or for deflection validation of the new system. Further, it contributes to the non-contact structural fatigue damage detection during design, testing, and operating stages of rotary structures blade tips.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/joe.2019.0503

Deflection characterisation of rotary systems using ground-based radar

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Wind turbines for irrigation pumping

Studies indicate that vertical axis wind turbines provide a more reliable energy conversion technology, as compared to horizontal axis wind turbines, especially in areas of lowly rated and/or uncertain wind speeds. The challenge however is the development of an efficient Savonius rotor blade which is affordable to low income earners in Kenya. The author researched on different technical design solutions and their advantages in terms of noise, shadows and impacts on birds and wildlife. The objectives of this research were thus to design and develop a Savonius rotor blade locally and compare its performance and production cost with the existing blades. From the developed blade, a laboratory test was conducted using a domestic fan and a torque of 15.46NM at a wind speed of 6.94 m/s was obtained which led to a conclusion that it was possible to locally develop a wind conversion technology that is affordable, efficient and adaptable for Kenya’s average wind speed of 4m/s.

Design and field testing of a Savonius wind pump’s rotor blade for pumping water in rural areas

Studies indicate that vertical axis wind turbines provide a more reliable energy conversion technology as compared to horizontal axis wind turbines, especially in areas of lowly rated and/or uncertain wind speeds. The challenge however is the development of an efficient Savonius rotor blade which is affordable to low income earners in Kenya. The different technical designs available in the local market were studied and their effects in terms of noise, shadows and impacts on birds and wildlife analyzed. The objectives of this research were thus to design and develop a Savonius rotor blade with locally available materials and compare its performance and production cost with the existing blades. The blades were made using glass reinforced fibre because of the material's light weight. This factor enabled the rotor to rotate at very low wind speeds, it is also long lasting and does not rot hence can survive in all weather conditions. A prototype rotor blade was fabricated, tested and an efficiency of 29% was achieved. Further modification was done and a more efficient rotor blade was fabricated which achieved an efficiency of 45%. A maximum power output of 111.64 W at a wind speed of 8.57 m/s with line voltages of 75 V, 85 V, 81 V and currents of 0.68 A, 0.88 A and 0.85 A respectively for line L1, L2 and L3 were obtained when the blade was connected to a three phase generator. The line voltages and currents obtained were with a torque of 143.8 N-m. A field test was also done at Ngong hills at a height of 2460m (8070 ft) above the sea level and a maximum wind speed of 6.44 m/s was reached at the time of testing. Voltage and current linesof 57.6 V, 57.98 V, 57.60 V and 0.88 A, 0.90 A and 0.80 A were recorded for each line giving a maximum output power of 85.95 W. The Vac from the generator was then rectified by a bridge rectifier and a maximum voltage obtained was 10.5 Vdc which was then used to charge a 12 V dc lead battery. The battery was fully charged after 11 hours and 36 minutes and used to light a 12Vdc bulb for 7 hours. The total cost of developing the rotor blade was Kshs 79,800 which was found to be 58.5 % cheaper than rotor blades in the local market of the similar rating. The above tests led to a conclusion that it is possible to locally develop a wind conversion technology that is affordable, efficient and adaptable for Kenya's average wind speed of 4 m/s.

Design and Testing of a Low Cost and Higher Efficient Savonius Wind Turbine's Rotor Blade for Low Wind Speed Applications

Studies indicate that vertical axis wind turbines provide a more reliable energy conversion technology, as compared to horizontal axis wind turbines, especially in areas of lowly rated and/or uncertain wind speeds. The challenge however is the development of an efficient Savonius rotor blade which is affordable to low income earners in Kenya. The author researched on different technical design solutions and their advantages in terms of noise, shadows and impacts on birds and wildlife. The objectives of this research were thus to design and develop a Savonius rotor blade locally with locally availlable materials and compare its performance and production cost with the existing blades. The blades were made using glass reinforced fibre because of the light weight of the material which enables it to rotate at very low wind speed, it is also long lasting and does not rot hence can survive in all weather conditions. A prototype was made and after testing and understanding it, a more efficient rotor blade was made. Laboratory and field tests were then done. From the developed blade, a laboratory test was conducted using an industrial fan which could go at a maximum speed of 960 revolutions per minute (RPM) which was calibrated to generate an equivalent wind speed of 15 m/s (meters per second). A torque of 367.57 NM (Newton-metre) at a wind speed of 13.7 m/s was obtained. When the blade was connected to a three phase generator, the line voltages obtained were: 7.5, 8.5, and 8.1 V for line L1, L2 and L3 respectively. The Vac from the generator was then rectified by a bridge rectifier and a maximum voltage obtained was 10.5 Vdc which was then used to charge a 12 V dc lead battery. The battery was fully charged after 11 hours, 36 minutes and used to light a 12Vdc bulb for 7 hours. A field test was also done at Ngong hills at a height above the sea level of 2460m (8070 ft) and a maximum wind speed of 6.44 m/s was reached at the time of testing. The angular velocity obtained was 13.58rads/sec, voltage of 5.63V, 6.2V and 5.93V was recorded for each line. The above laboratory test led to a conclusion that it was possible to locally develop a wind conversion technology that is affordable, efficient and adaptable for Kenya’s average wind speed of 4m/s.

Alice A. Kasera

Papers

Design and field testing of a Savonius wind pump’s rotor blade for pumping water in rural areas

Design and Testing of a Low Cost and Higher Efficient Savonius Wind Turbine's Rotor Blade for Low Wind Speed Applications

Design and testing of an efficient savonius wind turbine’s rotor blade for low wind speed applications.