CCP Solar, Wind & Storage Technologies 3 — Questions and Answers
Question 1: What is 'perovskite' in the context of next-generation solar cells?
- A silicon-doping technique to improve carrier mobility
- A class of crystal-structured materials used as light-absorbing layers in emerging PV cells (Correct answer)
- An anti-reflective coating applied to conventional solar panels
- A type of concentrated solar power heat transfer fluid
Correct answer: A class of crystal-structured materials used as light-absorbing layers in emerging PV cells
Perovskite solar cells use a crystal structure (ABX₃) as the photoactive layer and have rapidly achieved lab efficiencies exceeding 25%, rivaling crystalline silicon.
Question 2: Which grid service do battery energy storage systems (BESS) provide when they respond to frequency deviations within milliseconds?
- Peak shaving
- Frequency regulation (Primary Frequency Response) (Correct answer)
- Reactive power compensation
- Voltage ride-through
Correct answer: Frequency regulation (Primary Frequency Response)
BESS can inject or absorb power within milliseconds to respond to grid frequency deviations, providing primary frequency regulation faster than any thermal generator.
Question 3: In a utility-scale solar project, what does 'bifacial gain' refer to?
- Extra revenue from selling RECs on two separate markets
- Additional power generation from light captured on the rear side of bifacial panels (Correct answer)
- Efficiency improvement from dual-axis tracking systems
- Power boost from combining solar and wind generation on the same site
Correct answer: Additional power generation from light captured on the rear side of bifacial panels
Bifacial solar panels generate electricity from both front and rear surfaces; the bifacial gain is the additional energy yield from rear-side irradiance, typically 5–30% extra.
Question 4: What is the primary purpose of 'repowering' an existing wind farm?
- Adding battery storage to smooth wind intermittency
- Replacing older turbines with larger, more efficient models to increase energy output (Correct answer)
- Connecting wind farms to offshore HVDC transmission lines
- Installing met masts to improve wind resource assessment
Correct answer: Replacing older turbines with larger, more efficient models to increase energy output
Repowering replaces aging turbines with modern, higher-capacity machines on the same site, often doubling or tripling energy output while using the existing land permits and grid connections.
Question 5: What does the 'duck curve' illustrate in power grid management?
- The seasonal variation in wind energy production over a year
- The mismatch between daytime solar generation and evening demand peaks (Correct answer)
- The cost reduction curve of utility-scale battery storage over time
- The relationship between carbon price and renewable deployment rates
Correct answer: The mismatch between daytime solar generation and evening demand peaks
The duck curve (named for its shape) shows how high midday solar generation creates a steep ramp requirement in the evening when solar drops and demand peaks, straining grid operators.
Question 6: In concentrating solar power (CSP) plants, what material is most commonly used as the thermal energy storage medium?
- Pressurized steam
- Molten salt (sodium-potassium nitrate mixture) (Correct answer)
- Phase-change paraffin wax
- Compressed air in underground caverns
Correct answer: Molten salt (sodium-potassium nitrate mixture)
Molten salt (a mixture of sodium nitrate and potassium nitrate) is the dominant CSP thermal storage medium, storing heat at 565°C and enabling dispatchable solar generation.
Question 7: What is the 'capacity factor' of a wind turbine, and what is a typical onshore value?
- Ratio of actual output to rated capacity over time; typically 25–35% (Correct answer)
- Efficiency of converting wind kinetic energy to electricity; typically 45–59%
- Percentage of time turbine blades spin at rated speed; typically 60–70%
- Ratio of turbine lifetime output to construction energy; typically 15–20%
Correct answer: Ratio of actual output to rated capacity over time; typically 25–35%
Capacity factor is actual energy generated divided by maximum possible generation at rated capacity over a period; onshore wind typically achieves 25–35%, while offshore wind reaches 40–50%.
CCP Solar, Wind & Storage Technologies 3
What is 'perovskite' in the context of next-generation solar cells?