☀️ Solar Energy: Advantages, Disadvantages & Efficiency
Advantages: Renewable, reduces bills, diverse applications, low maintenance, advancing technology.
Disadvantages: Expensive storage, weather dependent, no night use, large area, low conversion rate.
Efficiency: Typical solar cell η ≈ 15%, overall 15–20%. Surface irradiance ≈ 1 kW/m² on a sunny day.
Disadvantages: Expensive storage, weather dependent, no night use, large area, low conversion rate.
Efficiency: Typical solar cell η ≈ 15%, overall 15–20%. Surface irradiance ≈ 1 kW/m² on a sunny day.
$$\boxed{\eta_{solar,overall} = 15\text{ to }20\%}$$
$$G_{surface} \approx 1\,\text{kW/m}^2 \quad \text{(normal sunny day)}$$
$$E_{daily} = 120\times10^{15}\,\text{W}$$
$$\text{Demand} = 5\%\text{ of total world energy demand}$$
EM Radiation from Sun:
$$\text{IR: }\lambda > 700\,\text{nm} \quad|\quad \text{Visible: }400\text{-}700\,\text{nm} \quad|\quad \text{UV: }\lambda < 400\,\text{nm}$$
Sunlight Recording Instruments:
$$G_{total} = G_{direct} + G_{diffuse} \quad\text{(Pyranometer)}$$
⚖️ Advantages vs Disadvantages
⚖️
Storage cost = key challenge
Electromagnetic Spectrum
γ
X
UV
Vis
IR
μW
Radio
0.01nm10nm400nm700nm1mm1m
Solar output zone: UV + Visible + IR
Sunshine Recorder
Campbell-Stokes glass sphere focuses sun onto paper strip → burn marks = hours of sunshine per day
Pyranometer
Dome-shaped sensor measures Gtotal = Gdirect + Gdiffuse (all-sky radiation)
Pyrheliometer
Narrow tube pointed at sun → measures Direct Normal Irradiance (DNI) only
Efficiency Gauge
15%
S-Q 33.7%
Carnot 93%
0%Practical: 15-20%100%
🌞 Surface Irradiance Calculator
🌞 Types of Solar Collectors
Non-Tracking (T < 100°C): Flat Plate, Evacuated Tube, CPC — stationary collectors.
Tracking (T > 100°C): 1-axis (Fresnel, Parabolic Trough, Cylindrical) and 2-axis (Solar Tower, Dish Stirling, Circular Fresnel).
CR = Aaperture/Areceiver. Higher CR → higher temperature → higher Carnot efficiency.
Tracking (T > 100°C): 1-axis (Fresnel, Parabolic Trough, Cylindrical) and 2-axis (Solar Tower, Dish Stirling, Circular Fresnel).
CR = Aaperture/Areceiver. Higher CR → higher temperature → higher Carnot efficiency.
$$Q_u = \dot{m}c_p(T_{out}-T_{in}) = F_R[G\alpha - U_L(T_{in}-T_a)]\cdot A_c$$
$$\boxed{\eta_c = \frac{Q_u}{G\cdot A_c} = F_R\left[\alpha - \frac{U_L(T_{in}-T_a)}{G}\right]}$$
$$CR = \frac{A_{aperture}}{A_{receiver}} \qquad T_{max} = T_a + \frac{G\cdot CR\cdot\alpha}{U_L}$$
☀️ Solar Collectors
↙ ↘
❄️ Non-Tracking
T < 100°C
T < 100°C
🔥 Tracking
T > 100°C
T > 100°C
🌡️ Temperature Comparison
📐 Collector Efficiency Calculator
🌡️ Concentration Ratio & Tmax
🏭 Solar Thermal Power Plant
CSP (Concentrating Solar Power): Uses mirrors/lenses to concentrate sunlight → heat HTF → steam → turbine → generator.
Types: Parabolic Trough, Solar Tower, Dish/Stirling, Fresnel.
Thermal Storage: Molten salt (285–565°C) enables 6–15 hours of power after sunset.
Types: Parabolic Trough, Solar Tower, Dish/Stirling, Fresnel.
Thermal Storage: Molten salt (285–565°C) enables 6–15 hours of power after sunset.
$$Q_u = \dot{m}c_p(T_{out}-T_{in})$$
$$Q_{HX} = U\cdot A_{HX}\cdot LMTD \qquad LMTD = \frac{\Delta T_1 - \Delta T_2}{\ln(\Delta T_1/\Delta T_2)}$$
$$E_{stored} = \dot{m}_{salt}c_p\Delta T_{salt}$$
$$\boxed{\eta_{CSP} = \eta_{collector}\times\eta_{HTF}\times\eta_{thermal}\times\eta_{electrical} \approx 15\text{-}20\%}$$
Parabolic Trough CSP — Complete Flow
☀️/🌙 Thermal Storage — Day vs Night
Hot 565°C
→
Day: Charging ☀️
HTF heats molten salt
→
Cold 285°C
CSP vs PV Comparison
| Parameter | CSP | PV Solar |
|---|---|---|
| Principle | Heat → Steam → Elec | Light → Direct Elec |
| Storage | Thermal (cheap) ✓ | Battery (expensive) |
| Efficiency | 15–20% | 15–22% |
| Water Need | High (cooling) | Minimal ✓ |
| Best Location | DNI > 2000 kWh/m² | Any sunny area |
| Load Following | Good (storage) ✓ | Poor (night) |
| Scale | Utility only | Any scale ✓ |
🌡️ LMTD & CSP Power Calculator
⚡ CSP Power Output
🪞 Heliostats & Solar Tower
Heliostats: Flat or slightly curved mirrors with 2-axis tracking (azimuth + elevation) that reflect sunlight onto a central tower receiver.
Aheliostat ≈ 20–150 m². Large plants use hundreds to thousands of heliostats.
Tower receiver: 200–300m height, T ≈ 500–1000°C. CR ≈ 300–1500.
1 kW peak power requires 8 m² area (at G = 1000 W/m², η = 12.5%).
Aheliostat ≈ 20–150 m². Large plants use hundreds to thousands of heliostats.
Tower receiver: 200–300m height, T ≈ 500–1000°C. CR ≈ 300–1500.
1 kW peak power requires 8 m² area (at G = 1000 W/m², η = 12.5%).
$$P_{tower} = G_{DNI}\times A_{total}\times\eta_{optical} \qquad \eta_{optical} \approx 50\text{-}70\%$$
$$\eta_{tower,Carnot} = 1 - \frac{T_{cold}}{T_{hot}} = 1 - \frac{300}{800} = 0.625$$
$$CR_{tower} = \frac{\text{Total heliostat area}}{\text{Receiver area}} \approx 300\text{-}1500$$
$$\boxed{1\,\text{kW peak} = 8\,\text{m}^2 \text{ (PV at } \eta=12.5\%\text{)}}$$
Drawbacks of Solar Energy:
$$G_{avg} \approx 0.1\text{-}0.3\,\text{kW/m}^2 \text{ (24hr avg)} \quad\text{| Available only sunrise to sunset}$$
$$G_{cloudy} \approx 0.1\text{-}0.3 \quad vs \quad G_{clear} \approx 0.8\text{-}1.0\,\text{kW/m}^2$$
Solar Tower with Heliostat Field
⚠️ Solar Drawbacks
🪞 Heliostat Field Calculator
☀️ Panel Area Calculator (1kW = 8m²)
📋 Solar Remember Points Summary
Key Facts: η ≈ 15%, 90% Si cells, Mono = octagonal, 1 kW = 8 m², Eg(Si) = 1.12 eV, S-Q limit = 33.7%, Solar constant = 1367 W/m², Edaily = 120×10¹⁵ W.
$$\eta_{typical} \approx 15\% \quad|\quad E_g(\text{Si}) = 1.12\,\text{eV} \quad|\quad \text{S-Q limit} = 33.7\%$$
$$G_{sc} = 1367\,\text{W/m}^2 \quad|\quad G_{surface} \approx 1000\,\text{W/m}^2 \quad|\quad E_{daily} = 120\times10^{15}\,\text{W}$$
$$1\,\text{kW peak} = 8\,\text{m}^2 \quad|\quad 1\,\text{MW} = 8000\,\text{m}^2 = 0.8\,\text{ha}$$
$$\text{90\% of cells: Silicon} \quad|\quad \text{Mono shape: Octagonal} \quad|\quad \text{Bypass diode: protection}$$
Complete Solar Quick Reference
| Parameter | Value |
|---|---|
| Solar constant | 1367 W/m² |
| Surface irradiance (peak) | ≈ 1000 W/m² |
| Earth solar energy/day | 120 × 10¹⁵ W |
| Silicon band gap | 1.12 eV |
| S-Q efficiency limit | 33.7% |
| Typical cell η | 15% |
| Mono Si shape | Octagonal |
| 90% material | Silicon |
| 1 kW peak area | 8 m² |
| Area per MW | 8000 m² = 0.8 ha |
| CSP overall η | 15–20% |
| FPC temperature | < 100°C |
| Parabolic trough temp | 300–550°C |
| Solar tower temp | 500–1000°C |
| Dish Stirling temp | 750–1000°C |
| Best concentration ratio | Dish (1000–3000) |
🃏 Flashcard Quiz — 10 Key Solar Facts
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Cell Shapes
Octagonal
Square
Rectangle
🌡️ Collector Temperature Ladder
☀️ Area Calculator (1kW = 8m²)
Module 10 — Geothermal & MHD