SHI Research Methods & Evidence-Based Practice 3 — Questions and Answers
Question 1: A solar installer is evaluating a research paper on drain-back system performance. Which section of the paper should be reviewed first to quickly assess overall quality and relevance?
- Acknowledgments
- Abstract (Correct answer)
- Appendix
- References
Correct answer: Abstract
The abstract summarizes the study's purpose, methods, findings, and conclusions, enabling rapid assessment of relevance and quality.
Question 2: When using Solar Fraction (SF) as a performance metric, an SF value of 0.70 means:
- 70% of collector area is shaded annually
- 70% of the annual load is met by solar energy (Correct answer)
- The system loses 30% efficiency due to pipe heat loss
- The glycol mixture is 70% propylene glycol
Correct answer: 70% of the annual load is met by solar energy
Solar Fraction represents the proportion of total annual energy demand supplied by the solar system, with 0.70 meaning 70% solar coverage.
Question 3: In a field study comparing evacuated tube vs. flat-plate collectors in a cold climate, which confounding variable must be controlled to ensure valid comparison?
- Tank color
- Collector tilt angle and azimuth (Correct answer)
- Pipe thread type
- Number of panels per array
Correct answer: Collector tilt angle and azimuth
Tilt angle and azimuth directly affect irradiance received, so they must be held constant or accounted for when comparing collector types.
Question 4: An evidence-based installer uses the Solar Energy Factor (SEF) from an ENERGY STAR rating to compare water heaters. A higher SEF indicates:
- Higher standby heat loss from the storage tank
- Greater combined solar and backup energy efficiency (Correct answer)
- A larger collector area relative to tank volume
- Lower solar irradiance requirement for operation
Correct answer: Greater combined solar and backup energy efficiency
SEF accounts for total energy input including backup, so a higher SEF means the combined system delivers more hot water per unit of total energy consumed.
Question 5: A researcher measures collector stagnation temperature under zero-flow conditions. Why is this data important for evidence-based installer practice?
- It determines the collector's optical efficiency at peak output
- It identifies material and fluid degradation risks during power outages or pump failures (Correct answer)
- It sets the minimum ambient temperature for installation
- It predicts the freeze protection temperature threshold
Correct answer: It identifies material and fluid degradation risks during power outages or pump failures
Stagnation temperature defines the maximum thermal stress the system experiences without fluid flow, informing fluid and material selection to prevent degradation.
Question 6: Which data source is most appropriate for obtaining peer-reviewed solar thermal performance research in the United States?
- Manufacturer product brochures
- DOE Office of Scientific and Technical Information (OSTI) or ASHRAE journals (Correct answer)
- Social media installer forums
- Local utility company billing statements
Correct answer: DOE Office of Scientific and Technical Information (OSTI) or ASHRAE journals
DOE OSTI and ASHRAE journals publish peer-reviewed, scientifically validated research, making them authoritative sources for technical solar thermal data.
Question 7: In a long-term solar water heating study, researchers use 'degree-days' as a climate variable. How does heating degree-day (HDD) data help interpret system performance results?
- It calculates the daily collector flow rate
- It normalizes performance data across different climates so results are comparable (Correct answer)
- It measures the number of daylight hours available per month
- It determines the glycol freeze point for the region
Correct answer: It normalizes performance data across different climates so results are comparable
HDD data characterizes a region's heating demand, allowing researchers to normalize and compare system performance findings across climates with different heating requirements.
SHI Research Methods & Evidence-Based Practice 3
A solar installer is evaluating a research paper on drain-back system performance.
Which section of the paper should be reviewed first to quickly assess overall quality and relevance?