Reaching the Betz limit via the Newton's method for one (1)-dimensional optimisation

The $Betz$ theory states that a horizontal axis wind turbine can only extract less than $\frac{16}{27}$ ($59.3\%$) of the kinetic energy of the wind. The value $\frac{16}{27}$ ($0.\overline{592}$) is called the $Betz$ limit. In $1919$, $Albert$ $Betz$ used a method that is analytic to derive the $Betz$ theory and henceforth finding the $Betz$ limit. In the theory, he derived momentum equations of an actuator disc ($AD$) in the stream of wind. In this research, a $Newton's$ method scheme is used to reach the $Betz$ limit. For the axial induction factor denoted by either $a$ or $a_{*}$ we used a reasonable initial point guess of $0.259$. The results agree well with the analytical results of the $Betz$ theory. From the $Newton's$ method scheme results corresponding to $a$ and $a_{*}$, the relative errors in comparison with the $Betz$ limit are $4\%$ and $0.9\%$, respectively. The small amount of errors shows the possibility of reaching the $Betz$ limit using the $Newton's$ method scheme. If alternate power coefficients [$C_{p}(a)$ or $C_{p_{*}}(a_{*})$] are found where the (exact) value ($a$ or $a_{*}$) cannot exactly be found analytically, the $Newton's$ method scheme would be an ideal way of estimating (or calculating) other proposed limits or the $Betz$ limit. This method yields extremely accurate results. Furthermore, for a quadratic equation, the quadratic formula would do. However, if the quadratic equation has floating-point numbers, the $Newton's$ method would be more appropriate.

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Publication Details

Journal
Applied Mathematical Sciences
Published
2025-01-01
DOI
https://doi.org/10.12988/ams.2025.919237
Primary Topic
Matrix Theory and Algorithms
Type
article
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article

Reaching the Betz limit via the Newton's method for one (1)-dimensional optimisation

Rodrick V. Chima, Reccab O. Manyala, Timothy Oreta, Vernon M. Chisapi
Applied Mathematical Sciences
Matrix Theory and Algorithms
article

Reaching the Betz limit via the Newton's method for one (1)-dimensional optimisation

Rodrick V. Chima, Reccab O. Manyala, Timothy Oreta, Vernon M. Chisapi
article en

Abstract

The $Betz$ theory states that a horizontal axis wind turbine can only extract less than $\frac{16}{27}$ ($59.3\%$) of the kinetic energy of the wind. The value $\frac{16}{27}$ ($0.\overline{592}$) is called the $Betz$ limit. In $1919$, $Albert$ $Betz$ used a method that is analytic to derive the $Betz$ theory and henceforth finding the $Betz$ limit. In the theory, he derived momentum equations of an actuator disc ($AD$) in the stream of wind. In this research, a $Newton's$ method scheme is used to reach the $Betz$ limit. For the axial induction factor denoted by either $a$ or $a_{*}$ we used a reasonable initial point guess of $0.259$. The results agree well with the analytical results of the $Betz$ theory. From the $Newton's$ method scheme results corresponding to $a$ and $a_{*}$, the relative errors in comparison with the $Betz$ limit are $4\%$ and $0.9\%$, respectively. The small amount of errors shows the possibility of reaching the $Betz$ limit using the $Newton's$ method scheme. If alternate power coefficients [$C_{p}(a)$ or $C_{p_{*}}(a_{*})$] are found where the (exact) value ($a$ or $a_{*}$) cannot exactly be found analytically, the $Newton's$ method scheme would be an ideal way of estimating (or calculating) other proposed limits or the $Betz$ limit. This method yields extremely accurate results. Furthermore, for a quadratic equation, the quadratic formula would do. However, if the quadratic equation has floating-point numbers, the $Newton's$ method would be more appropriate.

Applied Mathematical SciencesVol. 19(4)
Openalex Percentile: Top 82%
Matrix Theory and Algorithms
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