SHI Site Assessment & Solar Resource Evaluation 2 — Questions and Answers
Question 1: Which database provides historical solar radiation data most commonly used for solar site assessments in the United States?
- NOAA Weather Service Database
- NASA Surface Meteorology and Solar Energy (SSE)
- NREL's National Solar Radiation Database (NSRDB) (Correct answer)
- USGS Topographic Survey Data
Correct answer: NREL's National Solar Radiation Database (NSRDB)
NREL's National Solar Radiation Database (NSRDB) is the primary resource used by solar installers in the US for accessing historical solar radiation data for site assessments.
Question 2: What is the primary purpose of a shading analysis during a solar site assessment?
- To determine the best time of day to perform the installation
- To identify obstructions that will reduce collector performance throughout the year (Correct answer)
- To calculate the required distance between collector rows
- To determine the optimal pipe insulation thickness
Correct answer: To identify obstructions that will reduce collector performance throughout the year
A shading analysis identifies trees, buildings, and other obstructions that will cast shadows on collectors, quantifying the reduction in system performance across different times of year.
Question 3: What time range defines the 'solar window' that solar thermal installers typically aim to keep unobstructed for optimal system performance?
- Sunrise to sunset
- 9 AM to 3 PM solar time (Correct answer)
- 10 AM to 2 PM solar time
- 8 AM to 4 PM solar time
Correct answer: 9 AM to 3 PM solar time
The solar window from 9 AM to 3 PM solar time captures the majority of daily solar energy and is the critical period to keep free from shading obstructions.
Question 4: Which instrument measures global horizontal irradiance (GHI), capturing both direct and diffuse solar radiation on a horizontal surface?
- Pyrheliometer
- Pyranometer (Correct answer)
- Actinometer
- Spectroradiometer
Correct answer: Pyranometer
A pyranometer measures global horizontal irradiance (GHI), which includes both direct beam and diffuse solar radiation falling on a horizontal surface.
Question 5: What does the acronym 'GHI' stand for in solar resource measurement?
- General Heat Index
- Ground Heating Intensity
- Global Horizontal Irradiance (Correct answer)
- Gradient Heat Insolation
Correct answer: Global Horizontal Irradiance
GHI stands for Global Horizontal Irradiance, the total solar radiation received on a horizontal surface including both direct and diffuse components.
Question 6: How does increasing collector tilt angle above the local latitude value typically affect seasonal performance of a solar thermal system?
- Improves summer performance while reducing winter performance
- Improves winter performance while reducing summer performance (Correct answer)
- Improves performance equally in all seasons
- Has no effect on seasonal performance distribution
Correct answer: Improves winter performance while reducing summer performance
Increasing tilt above latitude favors winter collection when the sun is lower in the sky, while reducing the advantage in summer when the sun is higher.
Question 7: What is a 'solar path diagram' (sun chart) primarily used for during a solar site assessment?
- Measuring the intensity of solar radiation at a site
- Visualizing the sun's position throughout the day and year to identify shading periods (Correct answer)
- Calculating the annual energy output of a solar thermal system
- Determining the optimal pipe routing for a solar thermal system
Correct answer: Visualizing the sun's position throughout the day and year to identify shading periods
A solar path diagram plots the sun's altitude and azimuth at all hours and months of the year, allowing installers to identify when shading obstructions will impact collector performance.
SHI Site Assessment & Solar Resource Evaluation 2
Which database provides historical solar radiation data most commonly used for solar site assessments in the United States?