---
title: "Wind power pros/cons and output: 1.5 m blade"
subject: "Power Plant Design"
chapter: 1
key: "semester_8/power_plant_design:wind-pros-cons-1-5m"
source: https://www.bctengineer.com/q/semester_8/power_plant_design/wind-pros-cons-1-5m
site: BCT Engineering
---

# Wind power pros/cons and output: 1.5 m blade

Power Plant Design · Chapter 1: Energy Sources and Electric Power Generation

- Asked in: 2071 Magh, 2+4 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/power_plant_design/wind-pros-cons-1-5m
- Whole chapter: https://www.bctengineer.com/md/semester_8/power_plant_design/chapter-1

## Question

List out the advantages and disadvantages of wind power. Estimate electric power output from a wind turbine that has turbine blade length of 1.5 m and wind speed of 14 m/sec. Assume that air density is 1.23 kg/m³ and power coefficient is 0.35.

## Short answer

Advantages are renewable, clean, free fuel, low running cost, modular sizes, and land use under turbines; disadvantages are intermittency, need for storage, limited sites, high initial cost, noise, and bird deaths. With A = pi r^2 and P = 0.5 rho A v^3 Cp, the output is about 4.18 kW.

## Answer

#### Advantages of wind power
- Renewable, clean, free fuel; no emissions during operation.
- Low running cost; short construction time; modular sizes.
- Land below can be used for agriculture.
- Useful in remote areas and in hybrid systems.

#### Disadvantages of wind power
- Intermittent and variable output; needs storage or backup supply.
- Good sites are limited and often far from load.
- High initial cost; noise, visual impact and bird deaths.
- Output falls at high altitude because of lower air density.

#### Power output
$$
P = \frac{1}{2}\rho A v^3 C_p, \qquad A = \pi r^2
$$
Given: $r = 1.5$ m, $v = 14$ m/s, $\rho = 1.23$ kg/m³, $C_p = 0.35$.

$$
\begin{aligned}
A &= \pi \times 1.5^2 = 7.069\ \text{m}^2 \\
P_w &= 0.5 \times 1.23 \times 7.069 \times 14^3 \\
&= 0.5 \times 1.23 \times 7.069 \times 2744 = 11{,}929\ \text{W} \\
P &= 0.35 \times 11{,}929 = 4{,}175\ \text{W}
\end{aligned}
$$

**Answer:** Electric power output $\approx 4.18$ kW.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Why does wind output fall at high altitude?
   A. Wind speed is always zero
   B. Air density is lower
   C. Blades get longer
   D. Cp becomes 1
   Answer: B. Power is proportional to air density, which falls with altitude. (Key point: Altitude effect)

2. For blade length 1.5 m, the swept area is about
   A. 2.25 m^2
   B. 4.71 m^2
   C. 14.14 m^2
   D. 7.07 m^2
   Answer: D. A = pi x 1.5^2 = 7.069 m^2. (Key point: Swept area)

3. With v = 14 m/s, rho = 1.23 and Cp = 0.35, the output is about
   A. 4.18 kW
   B. 11.9 kW
   C. 41.8 kW
   D. 0.42 kW
   Answer: A. Wind power 11.93 kW x 0.35 = 4.18 kW. (Key point: Power output)

## Close variants set in other exams

- [Wind power pros/cons and output: 1.25 m blade](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Awind-pros-cons-1-25m) — Power Plant Design, chapter 1, asked 2×

## Related in Power Plant Design

- [Wind turbine merits and output: 5.5 m blade](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Awind-merits-numerical-5-5m) — Power Plant Design, chapter 1
- [Wind turbine output: 6.5 m blade, 9 and 18 m/s](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Awind-numerical-6-5m-9ms) — Power Plant Design, chapter 1, asked 3×
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- [Wind turbine output: 6 m blade, 8 and 16 m/s](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Awind-numerical-6m-8ms) — Power Plant Design, chapter 1, asked 3×

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