Abstract
Horizontal axis wind turbines are an attractive renewable energy source due to their very low carbon emission during their life cycle. In this study the effect of pitching the rotor blades of the NREL Phase VI rotor has been investigated in detail using CFD in order to allow a detailed torque analysis. Initial investigations have shown that at low rotational speeds the inboard section of the blade is responsible for the majority of the power generation. As the rotational speed increases the power producing section is shifted towards the blade tip. These trends are less pronounced when the blade is pitched which allows the blade to generate significantly more power at low rotational speeds. The improved low speed performance however comes at the cost of a significantly lower maximum power output. These findings are particularly relevant for turbines operating in unfavourable wind environments and for small scale turbines which solely rely on their aerodynamic torque for starting.
Highlights
These findings are relevant for turbines operating in unfavourable wind environments and for small scale turbines which solely rely on their aerodynamic torque for starting
Wind turbines have experienced a significant increase in their number over the last years as they have a very low carbon footprint of only 4.64 g of CO2 equivalent per kWh over their life cycle, most of which occur during their manufacturing and construction [1]
After having established relevant criteria influencing the performance of the National Renewable Energy Laboratory (NREL) Phase VI rotor, the blade pitch has been analysed by pitching the NREL Phase VI rotor by 10° into the wind, reducing the angle of attack
Summary
Wind turbines have experienced a significant increase in their number over the last years as they have a very low carbon footprint of only 4.64 g of CO2 equivalent per kWh over their life cycle, most of which occur during their manufacturing and construction [1]. Several studies, such as those of the WKA-60 rotor [2], have been conducted to investigate the effect of blade pitch These studies typically only address their torque and power characteristics but not the underlying physical phenomenon, fully understanding relevant characteristics could aid in the design process of blades that perform well over a wide range of different wind environments. This could help designing more efficient large scale rotors and more efficient small scale rotors as they often operate in unfavourable wind environments and solely rely on their aerodynamic torque for rotor starting. Due to the availability of extensive experimental data, the two-bladed upwind rotor with a radius of 5.029 m shown in Figure 1 served for validating the CFD model
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