---
title: "Solar generation and wind power characteristics"
subject: "Power Plant Design"
chapter: 1
key: "semester_8/power_plant_design:solar-generation-wind-characteristics"
source: https://www.bctengineer.com/q/semester_8/power_plant_design/solar-generation-wind-characteristics
site: BCT Engineering
---

# Solar generation and wind power characteristics

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

- Asked in: 2074 Magh, 6 marks
- Video: [How do solar plants work? | solar plant explained | on grid solar power system](https://www.youtube.com/watch?v=FQXkMt0Zm1A) — Let's Grow Up
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/power_plant_design/solar-generation-wind-characteristics
- Whole chapter: https://www.bctengineer.com/md/semester_8/power_plant_design/chapter-1

## Question

Explain how the electricity can be generated from solar with suitable sketch. Explain the characteristics of wind power on the basis of turbine efficiency, energy cost, capacity and annual energy output.

## Short answer

Solar electricity is generated by PV cells (silicon p-n junction produces DC, modules/arrays with inverters for AC). Wind turbine efficiency is limited by Betz limit (59.3%), practical 35-45%; energy cost is mainly capital, no fuel; capacity ranges from small to multi-MW; annual output E = P_rated × 8760 × CF, CF 20-40%, strongly dependent on wind speed.

## Answer

#### Electricity generation from solar
Solar energy is converted mainly by **photovoltaic (PV) cells**. A PV cell is a silicon p–n junction; sunlight creates electron–hole pairs, which the junction field separates, producing DC voltage (about 0.5–0.6 V per cell). Cells form modules and arrays.

```text
 Sun -> PV array -> MPPT/charge ctrl -> Battery
                         |
                     Inverter -> AC loads / grid
```
- Off-grid systems store energy in batteries.
- Grid-tied systems feed AC directly to the grid through an inverter.
- Solar thermal plants use mirrors to make steam for a turbine (less common).

#### Characteristics of wind power
| Basis | Characteristic |
|---|---|
| Turbine efficiency | $C_p$ cannot exceed 59.3% (Betz limit); practical modern turbines 35–45%; overall wind-to-wire about 30–40% |
| Energy cost | No fuel cost; cost is mainly capital (turbine, tower, foundation, grid). Large onshore wind is among the cheapest new sources; small turbines cost much more per kWh |
| Capacity | From a few hundred watts (small) to 3–15 MW per modern unit; output $\propto v^3$, so capacity rating is at rated wind speed (about 12–15 m/s) |
| Annual energy output | Depends on wind speed distribution; capacity factor typically 20–40%, so $E = P_{rated}\times 8760 \times CF$ |

- Since $P = \frac{1}{2}\rho A v^3 C_p$, a site with 10% higher mean wind speed gives about 33% more energy, so site selection is critical.
- Output is variable and must be backed by storage, hydro or other plants.

## Check yourself

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

1. In an off-grid PV system, the energy path is
   A. PV array, MPPT/charge controller, battery, inverter to AC loads
   B. Inverter first, then PV
   C. Battery to PV
   D. Grid to PV
   Answer: A. The array gives DC, charged into the battery and inverted for AC loads. (Key point: Solar PV chain)

2. Maximum theoretical Cp is
   A. 100%
   B. 35%
   C. 59.3%
   D. 80%
   Answer: C. Betz limit; practical turbines reach 35-45%. (Key point: Turbine efficiency)

3. Annual energy output is estimated by
   A. P x 24
   B. P_rated x 8760 x capacity factor
   C. P / 8760
   D. v^3 x CF
   Answer: B. E = P_rated x 8760 x CF, with CF typically 20-40%. (Key point: Annual energy)

4. A 10% higher mean wind speed gives about how much more energy?
   A. 10%
   B. 20%
   C. 50%
   D. 33%
   Answer: D. P is proportional to v^3: 1.1^3 = 1.33. (Key point: Site selection)

## Related in Power Plant Design

- [Wind energy conversion options and characteristics](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Awind-conversion-options) — Power Plant Design, chapter 1
- [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
- [Energy sources and solar power generation](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aenergy-sources-solar-power) — Power Plant Design, chapter 1
- [Wind turbine output: 12 m blade, 18 m/s](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Awind-numerical-12m-18ms) — Power Plant Design, chapter 1, asked 3×
- [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×
- [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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- [Full regulation: reservoir, capacity, annual energy](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Astorage-full-regulation-monthly-hydrograph) — Hydropower Engineering, chapter 3
- [Gas turbine 6:1: power output and efficiency](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Agt-6-1-power-efficiency) — Power Plant Equipment, chapter 6, asked 2×
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