SE Engr. Solar Resource Assessment and Meteorology 1 — Questions and Answers
Question 1: What is the standard unit of measurement for solar irradiance?
- kWh/m²
- W/m² (Correct answer)
- W/m³
- kWh/kWp
Correct answer: W/m²
Solar irradiance is the instantaneous power of solar radiation per unit area, measured in watts per square meter (W/m²).
Question 2: How is Global Horizontal Irradiance (GHI) mathematically defined?
- DNI + DHI
- DNI × cos(θz) + DHI (Correct answer)
- DNI × cos(θz) + DHI + reflected irradiance
- DNI + DHI + GTI
Correct answer: DNI × cos(θz) + DHI
GHI equals the direct normal irradiance projected onto the horizontal plane (DNI × cosine of the solar zenith angle) plus the diffuse horizontal irradiance (DHI).
Question 3: What does DNI stand for in solar resource assessment?
- Diffuse Normal Irradiance
- Direct Normal Irradiance (Correct answer)
- Daily Net Irradiance
- Diurnal Normalized Index
Correct answer: Direct Normal Irradiance
DNI stands for Direct Normal Irradiance, the solar radiation received per unit area by a surface always held perpendicular to the sun's rays.
Question 4: Which instrument is specifically designed to measure Direct Normal Irradiance (DNI)?
- Pyranometer
- Pyrheliometer (Correct answer)
- Spectroradiometer
- Luxmeter
Correct answer: Pyrheliometer
A pyrheliometer, mounted on a solar tracker to continuously point at the sun, measures the direct beam (DNI) component of solar radiation.
Question 5: What is the clearness index (Kt) in solar resource characterization?
- Ratio of GHI to extraterrestrial horizontal irradiance (Correct answer)
- Ratio of DNI to GHI
- Ratio of actual to maximum possible sunshine hours
- Ratio of DHI to GHI
Correct answer: Ratio of GHI to extraterrestrial horizontal irradiance
The clearness index (Kt) is the ratio of GHI measured at the surface to the extraterrestrial horizontal irradiance, indicating how much solar radiation is transmitted through the atmosphere.
Question 6: What is the approximate solar declination angle at the summer solstice in the Northern Hemisphere?
- 0°
- +23.45° (Correct answer)
- -23.45°
- +45°
Correct answer: +23.45°
At the summer solstice (around June 21), the solar declination reaches its maximum positive value of approximately +23.45°, corresponding to the axial tilt of Earth.
Question 7: Which U.S. dataset is most widely used for solar resource assessment and long-term energy modeling?
- ASHRAE Fundamentals Handbook
- National Solar Radiation Database (NSRDB) (Correct answer)
- EPA Clean Air Status and Trends Network
- NOAA Coastal Weather Buoy Archive
Correct answer: National Solar Radiation Database (NSRDB)
The National Solar Radiation Database (NSRDB), maintained by NREL, provides long-term hourly solar radiation data for the U.S. and is the standard resource for solar project assessments.
SE Engr. Solar Resource Assessment and Meteorology 1
What is the standard unit of measurement for solar irradiance?