NABCEP NABCEP Solar Heating Installation Professional 1 — Questions and Answers
Question 1: What is the primary difference between a solar thermal collector and a photovoltaic (PV) module?
- Solar thermal collectors generate electricity directly
- Solar thermal collectors convert sunlight into heat, while PV modules convert sunlight into electricity (Correct answer)
- Solar thermal collectors require no maintenance
- PV modules produce more energy per square foot in all climates
Correct answer: Solar thermal collectors convert sunlight into heat, while PV modules convert sunlight into electricity
Solar thermal collectors capture solar radiation and transfer that energy as heat to a fluid, whereas PV modules use the photovoltaic effect to generate direct current electricity.
Question 2: Which type of solar thermal collector is most efficient in cold climates with high heat demand?
- Unglazed flat-plate collector
- Evacuated tube collector (Correct answer)
- Batch (ICS) collector
- Open-loop thermosiphon collector
Correct answer: Evacuated tube collector
Evacuated tube collectors use vacuum insulation to minimize heat loss, making them highly efficient in cold climates where flat-plate collectors lose significant heat to the environment.
Question 3: What is the function of a differential controller in an active solar thermal system?
- It converts DC power to AC for the pump
- It turns the circulator pump on when the collector is hotter than the storage tank and off when it is not (Correct answer)
- It measures solar irradiance only
- It controls the backup electric heater only
Correct answer: It turns the circulator pump on when the collector is hotter than the storage tank and off when it is not
The differential controller compares temperatures at the collector and storage tank and activates the pump when the collector temperature exceeds the tank by a set threshold, preventing reverse circulation.
Question 4: Which heat transfer fluid is commonly used in closed-loop solar thermal systems to prevent freezing?
- Distilled water only
- Propylene glycol-water mixture (Correct answer)
- Gasoline
- Ammonia
Correct answer: Propylene glycol-water mixture
Propylene glycol mixed with water is the standard non-toxic antifreeze heat transfer fluid for closed-loop solar thermal systems, providing freeze protection without plumbing contamination risk.
Question 5: What is the purpose of a pressure relief valve in a solar thermal system?
- To regulate pump speed
- To release excess pressure and prevent damage to collectors or storage tanks from thermal expansion (Correct answer)
- To control collector tilt angle
- To measure flow rate
Correct answer: To release excess pressure and prevent damage to collectors or storage tanks from thermal expansion
Thermal expansion during stagnation (when the pump is off but collectors are hot) can create very high pressures, and the relief valve opens to prevent system damage or rupture.
Question 6: What is 'stagnation' in a solar thermal system and why is it a concern?
- When the pump runs continuously without stopping
- When no fluid flows through the collectors while they are receiving full solar radiation, causing extreme temperatures and potential fluid degradation (Correct answer)
- When collectors are shaded for extended periods
- When the storage tank is fully charged
Correct answer: When no fluid flows through the collectors while they are receiving full solar radiation, causing extreme temperatures and potential fluid degradation
Stagnation occurs when circulation stops while collectors are in full sun, causing fluid temperatures to spike well above 300°F, which can degrade glycol, damage seals, and create steam.
NABCEP NABCEP Solar Heating Installation Professional 1
What is the primary difference between a solar thermal collector and a photovoltaic (PV) module?