REP Renewable Energy Technologies & Applications 4 — Questions and Answers
Question 1: What is 'net metering' and how does it benefit a PV system owner?
- A method to measure total PV panel degradation annually
- A billing mechanism crediting customers for excess electricity fed to the grid (Correct answer)
- A technique to optimize inverter efficiency at partial loads
- A utility program requiring smart meters on all renewable installations
Correct answer: A billing mechanism crediting customers for excess electricity fed to the grid
Net metering allows PV owners to receive bill credits for surplus electricity exported to the grid, effectively using the grid as a virtual battery.
Question 2: In offshore wind development, what is a key advantage of floating foundation systems over fixed monopile foundations?
- Lower manufacturing cost per unit
- Ability to access deeper water sites (>60 m) with strong wind resources (Correct answer)
- Faster installation requiring no specialized vessels
- Reduced environmental permitting requirements
Correct answer: Ability to access deeper water sites (>60 m) with strong wind resources
Floating foundations unlock wind resources in water depths exceeding ~60 meters where fixed-bottom structures become uneconomical, opening vast new offshore areas.
Question 3: Which pumped hydro storage characteristic makes it the dominant form of utility-scale energy storage globally?
- Fastest discharge rate among all storage technologies
- Highest round-trip efficiency of any storage medium (~99%)
- Lowest cost per MWh of stored energy at large scale and long lifespan (Correct answer)
- Smallest land footprint per MWh of capacity
Correct answer: Lowest cost per MWh of stored energy at large scale and long lifespan
Pumped hydro dominates grid storage because of its very low cost per MWh at scale and extremely long asset life (50+ years), despite moderate round-trip efficiency (~70–85%).
Question 4: What does the 'specific yield' metric represent for a wind turbine installation?
- Cost per kW of installed capacity
- Annual energy production divided by rotor swept area
- Power output per unit of tower height
- Annual energy production per kW of rated capacity (Correct answer)
Correct answer: Annual energy production per kW of rated capacity
Specific yield (kWh/kW/year) equals the annual energy generation divided by the rated capacity, indicating how effectively the site's wind resource is utilized — equivalent to annual capacity factor hours.
Question 5: In a solar resource assessment, what does a 'P90' energy estimate mean for project financing?
- 90% of panels will perform at rated efficiency
- There is a 90% probability that actual energy production will meet or exceed this estimate (Correct answer)
- The project will reach 90% capacity factor in its first year
- 90% of capital costs will be recovered in the first decade
Correct answer: There is a 90% probability that actual energy production will meet or exceed this estimate
P90 means there is a 90% probability that actual energy production will equal or exceed the estimated value, representing a conservative scenario used by lenders to assess project risk.
Question 6: Which renewable energy application best describes 'agrivoltaics'?
- Using agricultural waste biomass to generate biogas
- Co-locating solar PV panels with crops or livestock on the same land (Correct answer)
- Applying solar thermal energy to greenhouse heating systems
- Irrigating crops using wind-powered water pumps
Correct answer: Co-locating solar PV panels with crops or livestock on the same land
Agrivoltaics (agrophotovoltaics) involves installing elevated solar panels above farmland so crops, livestock, or beekeeping can continue beneath, maximizing dual land use.
Question 7: What is the primary purpose of a 'power purchase agreement' (PPA) in renewable energy project development?
- To obtain construction permits from local authorities
- To secure long-term revenue by locking in the price a buyer pays for electricity (Correct answer)
- To negotiate equipment warranties with turbine manufacturers
- To register renewable energy certificates with a tracking system
Correct answer: To secure long-term revenue by locking in the price a buyer pays for electricity
A PPA is a long-term contract between a generator and a buyer that specifies the price, volume, and duration of electricity sales, providing revenue certainty needed to secure project financing.
REP Renewable Energy Technologies & Applications 4
What is 'net metering' and how does it benefit a PV system owner?