Renewable Energy Systems Flashcards
7 cards from real HERS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Renewable Energy Systems flashcards as text
What is the 'solar fraction' in the context of a solar water heating system?
Answer: The proportion of hot water heating load met by solar energy
Solar fraction represents the fraction of the total water heating load provided by the solar system, with the remainder supplied by a backup conventional heater.
In a solar thermal domestic hot water system, what component prevents reverse thermosiphoning that could drain heat from the storage tank at night?
Answer: Check valve or differential controller
A check valve or differential controller prevents reverse flow when the collector is cooler than the tank, which would cause the tank to lose heat.
What distinguishes an active solar thermal system from a passive solar thermal system?
Answer: Active systems use pumps and controls to move the heat transfer fluid
Active solar thermal systems rely on pumps, fans, and controls to circulate the heat transfer fluid, whereas passive systems use natural convection or thermosiphon principles.
Which metric is used to compare the environmental impact of different renewable energy technologies over their full lifecycle?
Answer: Carbon intensity (gCO2/kWh)
Carbon intensity (grams of CO2 per kWh) measures lifecycle greenhouse gas emissions per unit of electricity generated, enabling environmental comparison across technologies.
A home energy rater is evaluating a small wind turbine installation. Which site factor is MOST critical to assess first?
Answer: Average annual wind speed at hub height
Wind power output scales with the cube of wind speed, making average annual wind speed at hub height the most critical factor determining whether a turbine is economically viable.
What is the purpose of a 'combiner box' in a solar PV array?
Answer: Combines multiple PV string circuits into a single DC output to the inverter
A combiner box aggregates the DC output from multiple PV strings, providing overcurrent protection for each string before sending combined DC power to the inverter.
In HERS rating software, which solar PV input parameter most directly affects the modeled annual energy production?
Answer: System DC capacity (kW) and local solar irradiance
System DC capacity combined with location-specific solar irradiance data (from TMY files) are the primary drivers of modeled annual PV energy output.