Q.1 What is the primary purpose of a grid‑connected inverter in a solar photovoltaic system?
To store excess solar energy in batteries
To convert DC generated by panels to AC synchronized with the utility grid
To increase the voltage of the solar array
To protect the panels from lightning strikes
Explanation - A grid‑connected inverter changes the DC output of PV panels to AC that matches the grid’s frequency and voltage, allowing power to be fed directly into the utility network.
Correct answer is: To convert DC generated by panels to AC synchronized with the utility grid
Q.2 Which of the following renewable energy sources is most affected by the daily temperature variation?
Solar photovoltaic
Wind
Geothermal
Biomass
Explanation - PV output depends on solar irradiance, which varies with temperature and cloud cover throughout the day, while wind, geothermal, and biomass are less directly temperature‑dependent.
Correct answer is: Solar photovoltaic
Q.3 In a wind turbine, the "cut‑in speed" refers to:
The maximum wind speed the turbine can safely operate at
The minimum wind speed at which the turbine begins to generate power
The wind speed at which the turbine reaches its rated power
The speed of the generator shaft
Explanation - Cut‑in speed is the lowest wind speed at which the turbine's control system starts the rotor turning to produce electricity.
Correct answer is: The minimum wind speed at which the turbine begins to generate power
Q.4 Which energy storage technology is most commonly paired with solar PV to provide nighttime power in residential systems?
Lithium‑ion batteries
Pumped hydro storage
Compressed air energy storage
Flywheel storage
Explanation - Lithium‑ion batteries have high energy density, relatively low cost, and are suitable for the scale of residential solar installations.
Correct answer is: Lithium‑ion batteries
Q.5 The term "capacity factor" for a renewable power plant is defined as:
The ratio of actual energy produced over a period to the maximum possible energy if it ran at full capacity continuously
The percentage of the plant’s capacity that is reserved for emergency use
The ratio of installed capacity to the total demand of the grid
The amount of power the plant can provide during peak demand
Explanation - Capacity factor = (actual energy output) / (rated capacity × time). It reflects how often a plant operates at its rated output.
Correct answer is: The ratio of actual energy produced over a period to the maximum possible energy if it ran at full capacity continuously
Q.6 Which of the following grid codes is essential for integrating large amounts of renewable energy?
Voltage ride‑through (VRT) requirements
Harmonic distortion limits for residential loads
Maximum permissible transformer size
Standardized cable color codes
Explanation - VRT ensures that generators stay connected during short voltage dips, which is critical when many variable renewable resources are present.
Correct answer is: Voltage ride‑through (VRT) requirements
Q.7 A hybrid renewable system that combines solar PV, wind turbines, and battery storage is primarily aimed at:
Maximizing the use of a single resource
Reducing overall system cost by eliminating storage
Improving reliability and reducing intermittency
Increasing the complexity of control systems
Explanation - Hybrid systems balance the variable outputs of solar and wind, while storage smooths fluctuations, providing a more constant power supply.
Correct answer is: Improving reliability and reducing intermittency
Q.8 What does the term "dispatchable" mean when referring to a power source?
It can be turned on or off according to grid operator commands
It always runs at a constant output
It produces electricity without any emissions
It is connected directly to the consumer’s premises
Explanation - Dispatchable generation can be scheduled or curtailed to match demand, unlike most variable renewables which depend on weather.
Correct answer is: It can be turned on or off according to grid operator commands
Q.9 Which of the following statements about pumped hydro energy storage (PHES) is FALSE?
It can provide both short‑term and long‑term storage
It requires significant topographical elevation differences
It has a higher round‑trip efficiency than most battery technologies
It can be built with minimal environmental impact
Explanation - PHES often involves large reservoirs, land use changes, and ecological disruption, making environmental impact a concern.
Correct answer is: It can be built with minimal environmental impact
Q.10 The "levelized cost of electricity" (LCOE) is a useful metric because it:
Shows the total profit a plant will generate
Compares the cost per megawatt‑hour over the plant’s lifetime, including capital, O&M, and fuel
Indicates the maximum power output the plant can achieve
Measures the environmental impact of electricity generation
Explanation - LCOE normalizes all costs over the expected energy production, allowing fair comparison among technologies.
Correct answer is: Compares the cost per megawatt‑hour over the plant’s lifetime, including capital, O&M, and fuel
Q.11 Which control strategy is most commonly used to manage power output from a solar farm with battery storage during peak demand periods?
Maximum power point tracking (MPPT) only
Load following with state‑of‑charge (SoC) constraints
Constant frequency operation
Voltage droop control
Explanation - The system follows the grid’s load demand while ensuring the battery stays within safe SoC limits to avoid over‑charging or deep discharge.
Correct answer is: Load following with state‑of‑charge (SoC) constraints
Q.12 What is the main advantage of using a DC microgrid for renewable integration?
Eliminates the need for any converters
Reduces conversion losses when interfacing directly with PV and batteries
Allows the use of standard AC appliances without modification
Provides higher fault current levels for protection
Explanation - Many renewables and storage devices generate DC; a DC microgrid avoids multiple DC‑AC‑DC conversions, improving overall efficiency.
Correct answer is: Reduces conversion losses when interfacing directly with PV and batteries
Q.13 In the context of renewable energy integration, what does "curtailment" refer to?
Increasing the output of a plant beyond its rated capacity
Deliberately limiting the output of a renewable plant due to grid constraints
Storing excess energy in underground reservoirs
Switching off backup diesel generators
Explanation - Curtailment occurs when the grid cannot accommodate the full generation from a renewable source, so the plant’s output is reduced.
Correct answer is: Deliberately limiting the output of a renewable plant due to grid constraints
Q.14 Which of the following is NOT a typical benefit of integrating renewable energy into an existing power system?
Reduced greenhouse‑gas emissions
Improved system inertia
Diversification of energy sources
Decreased dependence on imported fuels
Explanation - Renewables like solar PV and wind provide little rotational inertia compared with synchronous generators, often requiring synthetic inertia solutions.
Correct answer is: Improved system inertia
Q.15 The term "feed‑in tariff" (FIT) is used to:
Regulate the voltage levels at distribution substations
Set a guaranteed price for renewable electricity fed into the grid
Measure the harmonic distortion of renewable generators
Define the maximum allowed size of a solar installation
Explanation - FIT policies incentivize renewable deployment by offering a fixed, often above‑market price for each kilowatt‑hour exported.
Correct answer is: Set a guaranteed price for renewable electricity fed into the grid
Q.16 Which parameter most directly influences the amount of wind power that can be extracted from a turbine?
Blade length (rotor radius)
Generator cooling method
Foundation depth
Number of gear teeth
Explanation - Power extracted is proportional to the swept area (πr²); larger blades capture more wind energy.
Correct answer is: Blade length (rotor radius)
Q.17 When integrating a large solar PV plant into a weak grid, which ancillary service becomes particularly important?
Reactive power support
Frequency regulation
Black‑start capability
Voltage ride‑through
Explanation - Weak grids are prone to voltage fluctuations; VRT ensures the PV plant stays connected during short dips, maintaining stability.
Correct answer is: Voltage ride‑through
Q.18 Which of the following best describes a "smart inverter" in modern renewable systems?
An inverter that can only convert DC to AC
An inverter equipped with communication and grid support functions such as volt‑var control
An inverter that uses mechanical switches for power conversion
An inverter that operates only during daylight hours
Explanation - Smart inverters can actively manage voltage, frequency, and provide ancillary services, helping with grid integration.
Correct answer is: An inverter equipped with communication and grid support functions such as volt‑var control
Q.19 What is the primary environmental concern associated with large‑scale solar farms built on desert land?
High water consumption for cooling
Disruption of local wildlife habitats and soil erosion
Excessive noise generation
Release of harmful gases during operation
Explanation - Desert solar farms can alter habitats, affect flora/fauna, and increase soil compaction and erosion if not managed properly.
Correct answer is: Disruption of local wildlife habitats and soil erosion
Q.20 Which of the following control techniques is used to mitigate the "flicker" effect caused by wind turbines?
Pitch control of turbine blades
Dynamic braking
Active power factor correction
Frequency shifting
Explanation - Adjusting blade pitch changes the turbine’s aerodynamic torque quickly, smoothing output power and reducing flicker.
Correct answer is: Pitch control of turbine blades
Q.21 In a renewable energy context, the term "firm capacity" refers to:
The maximum possible output under ideal conditions
The portion of a renewable plant’s capacity that can be reliably counted on for dispatch
The total installed capacity of all renewable assets in a region
The capacity of a plant after accounting for maintenance downtime
Explanation - Firm capacity is a statistical measure of the guaranteed power output, considering variability and probability of availability.
Correct answer is: The portion of a renewable plant’s capacity that can be reliably counted on for dispatch
Q.22 Which technology converts solar thermal energy into electricity by using a working fluid to turn a turbine?
Photovoltaic (PV) panels
Concentrated solar power (CSP)
Solar water heating
Solar air heaters
Explanation - CSP concentrates sunlight onto a receiver, heating a fluid that drives a turbine for electricity generation.
Correct answer is: Concentrated solar power (CSP)
Q.23 What is the effect of adding a battery energy storage system (BESS) to a wind farm regarding grid frequency?
It makes the frequency fluctuate more
It provides fast frequency response, helping to stabilize the grid
It eliminates the need for any turbine control
It reduces the turbine’s cut‑in speed
Explanation - BESS can inject or absorb power within milliseconds, counteracting frequency deviations caused by wind variability.
Correct answer is: It provides fast frequency response, helping to stabilize the grid
Q.24 Which of the following is a key challenge when integrating high levels of solar PV into an existing distribution network?
Increased short‑circuit currents
Reverse power flow causing voltage rise
Higher harmonic distortion from inverters
Excessive transformer heating due to DC currents
Explanation - When generation exceeds local load, power flows back toward the substation, raising voltage beyond acceptable limits.
Correct answer is: Reverse power flow causing voltage rise
Q.25 What does the acronym "O&M" stand for in the context of renewable power plants?
Operation and Maintenance
Output and Measurement
Optimization and Monitoring
Oversight and Management
Explanation - O&M covers all activities required to keep a plant running efficiently over its lifespan.
Correct answer is: Operation and Maintenance
Q.26 Which of the following is a primary reason for using power electronic converters in wind turbines?
To increase the mechanical strength of the blades
To enable variable speed operation and match grid frequency
To cool the generator during operation
To store wind energy directly as electricity
Explanation - Converters decouple turbine speed from grid frequency, allowing optimal aerodynamic performance and grid compliance.
Correct answer is: To enable variable speed operation and match grid frequency
Q.27 The "duck curve" is a visual representation of:
Solar panel temperature variation throughout the day
Net load on the grid after accounting for solar generation, showing a dip during midday and a steep rise in the evening
Wind speed fluctuations over a year
Battery state‑of‑charge patterns in a microgrid
Explanation - The duck curve illustrates how solar reduces daytime load, creating a steep ramp demand as the sun sets.
Correct answer is: Net load on the grid after accounting for solar generation, showing a dip during midday and a steep rise in the evening
Q.28 Which renewable energy technology can provide baseload power with minimal weather dependence?
Solar PV
On‑shore wind
Geothermal
Wave energy
Explanation - Geothermal plants draw heat from the earth’s interior, delivering steady output irrespective of surface weather conditions.
Correct answer is: Geothermal
Q.29 A "net‑metering" arrangement typically allows a consumer to:
Sell excess electricity at market price
Receive credit for excess generation at the same rate as consumption
Store unlimited amounts of electricity on the grid
Avoid paying any electricity bills
Explanation - Net‑metering credits the consumer for each kilowatt‑hour exported, offsetting future consumption charges.
Correct answer is: Receive credit for excess generation at the same rate as consumption
Q.30 What is the typical efficiency range of modern commercial solar PV panels?
5‑10%
15‑22%
30‑35%
45‑50%
Explanation - Commercial crystalline silicon modules usually achieve 15‑22% conversion efficiency under standard test conditions.
Correct answer is: 15‑22%
Q.31 Which of the following factors most directly influences the levelized cost of energy (LCOE) for a wind farm?
Average wind speed at the site
Height of the transmission towers
Color of turbine blades
Number of maintenance crew members
Explanation - Higher wind speeds increase energy production, reducing LCOE by spreading fixed costs over more kilowatt‑hours.
Correct answer is: Average wind speed at the site
Q.32 In a renewable microgrid, the term "islanding" refers to:
Connecting the microgrid to multiple utility grids simultaneously
Operating the microgrid independently of the main grid during outages
Placing solar panels on island-shaped rooftops
Using only wind turbines on isolated islands
Explanation - Islanding enables a microgrid to continue supplying local loads when the upstream grid is unavailable.
Correct answer is: Operating the microgrid independently of the main grid during outages
Q.33 Which of the following is a common method to increase the capacity factor of a solar PV plant?
Installing tracking systems that follow the sun’s path
Using thinner glass on the panels
Reducing the inverter size
Operating panels at higher temperatures
Explanation - Sun‑tracking mounts keep panels perpendicular to solar rays longer, raising daily energy yield and capacity factor.
Correct answer is: Installing tracking systems that follow the sun’s path
Q.34 Which of the following grid‑integration challenges is specifically addressed by using synthetic inertia from power electronic converters?
Voltage sags caused by lightning
Frequency stability during sudden load changes
Harmonic distortion from nonlinear loads
Over‑voltage due to line resonance
Explanation - Synthetic inertia mimics the inertial response of rotating machines, helping the grid resist rapid frequency deviations.
Correct answer is: Frequency stability during sudden load changes
Q.35 In a wind turbine, the "tip‑speed ratio" (λ) is defined as:
The ratio of blade length to wind speed
The ratio of rotor tip speed to wind speed
The ratio of generator rpm to blade pitch angle
The ratio of tower height to rotor diameter
Explanation - λ = (rotor tip speed) / (wind speed); optimal λ maximizes aerodynamic efficiency.
Correct answer is: The ratio of rotor tip speed to wind speed
Q.36 Which renewable energy technology uses the principle of the Seebeck effect?
Solar PV
Thermoelectric generators
Wind turbines
Hydroelectric turbines
Explanation - The Seebeck effect converts temperature differences directly into electric voltage.
Correct answer is: Thermoelectric generators
Q.37 When a solar PV system is connected to a grid with a high penetration of renewables, which type of inverter control mode is most beneficial for voltage regulation?
Constant Power Factor (CPF)
Volt‑Var Control (VVC)
Maximum Power Point Tracking (MPPT)
Frequency Droop Control
Explanation - VVC allows the inverter to inject or absorb reactive power based on local voltage, supporting grid voltage stability.
Correct answer is: Volt‑Var Control (VVC)
Q.38 Which of the following is NOT a typical characteristic of a renewable‑based distributed generation (DG) system?
Small scale, close to load
High predictability of output
Potential for reducing transmission losses
Capability to provide ancillary services
Explanation - Renewable DG (solar, wind) is inherently variable, making output prediction more challenging than conventional DG.
Correct answer is: High predictability of output
Q.39 The main advantage of using a "behind‑the‑meter" (BTM) solar system is:
It feeds power directly into the utility grid
It reduces the customer’s electricity bill by offsetting on‑site consumption first
It eliminates the need for inverters
It provides power only during night time
Explanation - BTM systems prioritize self‑consumption, lowering net purchases from the utility.
Correct answer is: It reduces the customer’s electricity bill by offsetting on‑site consumption first
Q.40 Which of the following technologies is most suitable for providing long‑duration (days to weeks) energy storage for renewable integration?
Lithium‑ion batteries
Pumped hydro storage
Supercapacitors
Flywheel energy storage
Explanation - PHES can store large amounts of energy for extended periods, whereas batteries and supercapacitors are better for short‑term storage.
Correct answer is: Pumped hydro storage
Q.41 In power system studies, a "N‑1 contingency" analysis checks:
The effect of losing any single component on system reliability
The maximum number of generators that can be connected
The daily energy production of a solar farm
The optimal location of wind turbines
Explanation - N‑1 ensures the grid can withstand the failure of any one element without violating operational limits.
Correct answer is: The effect of losing any single component on system reliability
Q.42 Which of the following statements best explains why offshore wind farms often have higher capacity factors than on‑shore farms?
They use larger turbines that are more efficient
Wind speeds over the sea are generally higher and more consistent
Offshore farms have better cooling for generators
They operate at lower blade pitch angles
Explanation - The marine environment offers smoother, stronger winds, leading to higher energy production per turbine.
Correct answer is: Wind speeds over the sea are generally higher and more consistent
Q.43 A "virtual power plant" (VPP) is:
A single large solar farm
An aggregation of distributed energy resources that are coordinated to act as a single plant
A nuclear reactor with renewable backup
A power plant that operates only in virtual reality simulations
Explanation - VPPs combine many small assets (PV, storage, demand response) to provide grid services similar to a conventional plant.
Correct answer is: An aggregation of distributed energy resources that are coordinated to act as a single plant
Q.44 Which factor most directly impacts the degradation rate of lithium‑ion batteries used for renewable storage?
Depth of discharge (DoD)
Color of the battery casing
Ambient humidity
Frequency of voltage spikes
Explanation - Higher DoD accelerates capacity loss; operating within moderate DoD ranges extends battery life.
Correct answer is: Depth of discharge (DoD)
Q.45 The "power‑electronic interface" in a renewable energy system primarily serves to:
Convert mechanical energy to heat
Synchronize renewable output with grid voltage, frequency, and waveform standards
Store solar energy as chemical fuel
Increase the wind turbine blade length
Explanation - Power electronics (inverters, converters) ensure that variable renewable generation meets grid code requirements.
Correct answer is: Synchronize renewable output with grid voltage, frequency, and waveform standards
Q.46 Which renewable energy source can directly provide electricity without the need for a power conversion stage?
Solar photovoltaic
Hydroelectric (turbine‑generator)
Wind turbine
Concentrated solar power
Explanation - Hydro turbines directly drive generators that produce AC electricity, whereas solar PV, wind, and CSP require converters.
Correct answer is: Hydroelectric (turbine‑generator)
Q.47 In the context of renewable integration, "load shifting" usually involves:
Moving electricity consumption from peak to off‑peak periods using storage or demand response
Changing the location of a wind farm
Physically moving solar panels to follow the sun
Altering the grid frequency
Explanation - Load shifting balances demand with renewable supply, reducing the need for peaking generators.
Correct answer is: Moving electricity consumption from peak to off‑peak periods using storage or demand response
Q.48 Which of the following is a direct benefit of using high‑efficiency (≥ 95%) power converters in renewable systems?
Reduced need for cooling systems
Higher harmonic distortion
Increased system cost without performance gains
Decreased overall system efficiency
Explanation - Higher efficiency means less heat is generated, lowering cooling requirements and improving reliability.
Correct answer is: Reduced need for cooling systems
Q.49 The "capacity credit" of a renewable generator is:
The total installed capacity of the generator
The portion of its capacity that can be counted towards meeting reliability standards
The price paid for each megawatt of capacity
The number of turbines in a wind farm
Explanation - Capacity credit reflects the contribution of a variable resource to system adequacy, accounting for its availability.
Correct answer is: The portion of its capacity that can be counted towards meeting reliability standards
Q.50 A major challenge when integrating large offshore wind farms is:
Lack of sufficient wind resources
High transmission losses over long submarine cables
Excessive shading of the turbines by nearby buildings
Inability to install pitch‑controlled blades
Explanation - Long distances require high‑voltage DC (HVDC) transmission to minimize losses, adding complexity and cost.
Correct answer is: High transmission losses over long submarine cables
Q.51 Which of the following policies encourages the development of community‑owned renewable projects?
Carbon tax
Feed‑in tariff with community quotas
Renewable Portfolio Standard (RPS) with ownership caps
Mandatory coal phase‑out
Explanation - FITs with specific provisions for community projects incentivize local ownership and participation.
Correct answer is: Feed‑in tariff with community quotas
Q.52 In a hybrid solar‑wind‑storage system, the optimal control algorithm typically aims to:
Maximize renewable curtailment
Minimize the use of storage while satisfying demand and grid constraints
Operate the wind turbines at constant speed
Keep the battery at 100 % state of charge at all times
Explanation - Efficient operation uses generation directly when possible and reserves storage for periods of deficit.
Correct answer is: Minimize the use of storage while satisfying demand and grid constraints
Q.53 Which renewable technology can be installed on existing agricultural land without significantly reducing crop production?
Floating offshore wind
Agro‑photovoltaics (dual‑use solar)
Concentrated solar power
Geothermal binary plants
Explanation - PV panels are mounted at heights allowing crops to grow beneath, providing both energy and agricultural output.
Correct answer is: Agro‑photovoltaics (dual‑use solar)
Q.54 When a renewable generator provides "frequency regulation" services, it is:
Changing its output power in response to grid frequency deviations
Increasing its voltage output
Operating only during daylight hours
Storing energy in a separate battery system
Explanation - Frequency regulation involves adjusting active power to help keep grid frequency within prescribed limits.
Correct answer is: Changing its output power in response to grid frequency deviations
Q.55 Which of the following best describes the role of a "reactive power compensator" in a renewable‑rich grid?
It stores excess active power
It supplies or absorbs reactive power to maintain voltage levels
It converts DC to AC
It monitors wind speed
Explanation - Reactive power devices (capacitors, STATCOMs, smart inverters) help control voltage, which can be challenging with high renewable penetration.
Correct answer is: It supplies or absorbs reactive power to maintain voltage levels
Q.56 In a solar PV system, "temperature coefficient" indicates:
The increase in efficiency with higher temperature
The rate at which power output decreases as temperature rises
The change in panel color with temperature
The speed of the inverter’s cooling fan
Explanation - PV modules typically lose about 0.4–0.5 % of their power for each degree Celsius increase above 25 °C.
Correct answer is: The rate at which power output decreases as temperature rises
Q.57 What is the main advantage of using a "direct drive" wind turbine over a geared design?
Lower rotational speed
Reduced mechanical losses and maintenance due to the absence of a gearbox
Higher cut‑in wind speed
Simpler blade pitch control
Explanation - Direct drive eliminates the gearbox, decreasing wear, noise, and maintenance costs.
Correct answer is: Reduced mechanical losses and maintenance due to the absence of a gearbox
Q.58 Which of the following is a typical characteristic of a "behind‑the‑meter" (BTM) battery system?
It feeds power directly into the utility grid at all times
It stores excess generation for later on‑site consumption
It requires a feed‑in tariff to operate
It cannot be used with solar PV
Explanation - BTM batteries are installed on the consumer side of the meter to increase self‑consumption of locally generated renewable energy.
Correct answer is: It stores excess generation for later on‑site consumption
Q.59 In renewable energy planning, "resource mapping" primarily involves:
Identifying the geographic locations with the best solar irradiance, wind speeds, or hydro potential
Drawing electrical schematics for power plants
Measuring the temperature of inverter components
Calculating the cost of land acquisition
Explanation - Resource mapping uses meteorological and topographic data to locate sites with high renewable energy potential.
Correct answer is: Identifying the geographic locations with the best solar irradiance, wind speeds, or hydro potential
Q.60 A "grid‑forming inverter" differs from a conventional "grid‑following inverter" because it:
Can create a stable voltage and frequency reference on its own, allowing islanded operation
Only works with wind turbines
Requires a large battery bank to function
Operates only during nighttime
Explanation - Grid‑forming inverters can act as a voltage source, enabling microgrid or islanded operation without external grid support.
Correct answer is: Can create a stable voltage and frequency reference on its own, allowing islanded operation
Q.61 Which of the following is a direct consequence of high penetration of solar PV on distribution feeders?
Reduced line loading during midday
Increased need for transformer cooling
Higher short‑circuit currents during night
More frequent transformer oil leaks
Explanation - When PV supplies local loads, current flow on the feeder decreases, reducing thermal loading on conductors and transformers.
Correct answer is: Reduced line loading during midday
Q.62 The term "energy return on investment" (EROI) for a renewable technology measures:
The ratio of total energy produced over the system’s lifetime to the energy required for its construction, operation, and decommissioning
The financial profit earned per megawatt installed
The amount of CO₂ saved per kilowatt‑hour generated
The speed at which a turbine can start rotating
Explanation - EROI quantifies the net energy benefit of a technology, indicating its sustainability.
Correct answer is: The ratio of total energy produced over the system’s lifetime to the energy required for its construction, operation, and decommissioning
Q.63 Which renewable energy technology typically employs a "binary cycle" to generate electricity?
Geothermal
Solar photovoltaic
On‑shore wind
Biomass combustion
Explanation - Binary geothermal plants use a secondary fluid with a low boiling point to drive a turbine, allowing electricity generation from lower‑temperature resources.
Correct answer is: Geothermal
Q.64 What is the purpose of "anti‑islanding protection" in grid‑connected renewable inverters?
To keep the inverter operating when the grid is down
To shut down the inverter automatically when it detects loss of the utility grid
To increase the inverter’s efficiency
To synchronize the inverter with a backup diesel generator
Explanation - Anti‑islanding ensures safety for utility workers by preventing an inverter from feeding power into a de‑energized grid.
Correct answer is: To shut down the inverter automatically when it detects loss of the utility grid
Q.65 Which of the following statements best describes the concept of "flexibility" in a power system with high renewable penetration?
The ability to quickly adjust generation or consumption to match supply and demand
The mechanical flexibility of wind turbine blades
The use of flexible solar panels that can bend
The capacity of transformers to handle overloads
Explanation - System flexibility includes fast‑responding generators, storage, and demand‑side management to accommodate variability.
Correct answer is: The ability to quickly adjust generation or consumption to match supply and demand
Q.66 In a renewable energy context, a "Power Purchase Agreement" (PPA) is:
A contract where a buyer agrees to purchase electricity at a predetermined price for a set period
A government subsidy for solar panels
A technical specification for inverter efficiency
A type of battery technology
Explanation - PPAs provide revenue certainty for project developers and price stability for purchasers.
Correct answer is: A contract where a buyer agrees to purchase electricity at a predetermined price for a set period
Q.67 Which of the following is a common method for reducing the variability of wind power output on a short‑term basis?
Installing larger turbines
Using short‑term energy storage such as batteries or flywheels
Increasing the tower height
Applying anti‑icing coatings
Explanation - Fast‑response storage can smooth out rapid fluctuations in wind generation.
Correct answer is: Using short‑term energy storage such as batteries or flywheels
Q.68 Which of the following metrics is most appropriate for comparing the land‑use efficiency of different renewable technologies?
Capacity factor
Energy density (MWh per hectare per year)
Levelized cost of electricity
Cut‑in wind speed
Explanation - Energy density directly relates the amount of electricity produced to the land area occupied.
Correct answer is: Energy density (MWh per hectare per year)
Q.69 A "smart grid" enhances renewable integration primarily by:
Increasing the physical size of power lines
Implementing advanced communication, monitoring, and automated control to manage variable generation and demand
Replacing all AC equipment with DC
Removing all protective relays
Explanation - Smart grid technologies provide real‑time visibility and flexibility, crucial for high levels of renewables.
Correct answer is: Implementing advanced communication, monitoring, and automated control to manage variable generation and demand
Q.70 Which renewable technology typically utilizes a "heat‑pipe" for efficient heat collection?
Solar photovoltaic
Solar thermal (concentrated)
Wind turbine
Hydrogen fuel cell
Explanation - Heat pipes transport thermal energy from the receiver to the power block with minimal losses.
Correct answer is: Solar thermal (concentrated)
Q.71 When integrating solar PV with a battery, the "state‑of‑charge" (SoC) limit is set to:
Prevent the battery from exceeding 100 % and dropping below a safe minimum (e.g., 20 %)
Maintain the battery at exactly 50 % at all times
Allow the battery to discharge completely before recharging
Ensure the battery never charges above 10 %
Explanation - SoC limits protect battery life by avoiding over‑charge and deep‑discharge conditions.
Correct answer is: Prevent the battery from exceeding 100 % and dropping below a safe minimum (e.g., 20 %)
Q.72 Which of the following is a key advantage of using high‑voltage direct current (HVDC) transmission for offshore wind farms?
Lower line losses over long distances compared to AC
Ability to transmit power without any converters
Reduced need for offshore foundations
Higher frequency operation
Explanation - HVDC minimizes reactive power and capacitive losses, making it ideal for transmitting power from remote offshore sites.
Correct answer is: Lower line losses over long distances compared to AC
Q.73 Which of the following best defines "grid inertia"?
The resistance of transmission lines to current flow
The kinetic energy stored in rotating masses (e.g., turbine generators) that helps stabilize frequency
The ability of a solar panel to resist mechanical stress
The amount of reactive power a battery can supply
Explanation - Inertia slows frequency changes after disturbances, providing time for control actions.
Correct answer is: The kinetic energy stored in rotating masses (e.g., turbine generators) that helps stabilize frequency
Q.74 Which of the following renewable sources is most suitable for providing fast‑response ancillary services such as primary frequency control?
Large hydro (with turbine control)
Solar PV with battery storage
On‑shore wind without storage
Biomass power plant
Explanation - Battery‑backed PV can change output within milliseconds, meeting the speed requirements of primary frequency control.
Correct answer is: Solar PV with battery storage
Q.75 In the context of renewable integration, "demand response" primarily refers to:
Increasing the size of renewable generators
Changing consumer electricity usage patterns in response to price signals or grid conditions
Installing larger inverters
Building more transmission lines
Explanation - Demand response shifts or reduces load to better match renewable generation, enhancing grid stability.
Correct answer is: Changing consumer electricity usage patterns in response to price signals or grid conditions
Q.76 Which renewable technology can be directly coupled with a desalination plant to provide both electricity and heat?
Solar photovoltaic
Concentrated solar power (CSP)
Wind turbine
Geothermal
Explanation - CSP produces high‑temperature thermal energy that can drive both turbines for electricity and processes for desalination.
Correct answer is: Concentrated solar power (CSP)
Q.77 The main reason for installing "reactor‑level" voltage regulators in a renewable‑rich grid is to:
Increase the power factor of generators
Maintain voltage levels within acceptable limits despite fluctuating generation
Reduce harmonic distortion from inverters
Accelerate the aging of transformers
Explanation - Voltage regulators adjust tap settings to keep voltage stable as renewable output varies.
Correct answer is: Maintain voltage levels within acceptable limits despite fluctuating generation
Q.78 Which of the following best explains why "distributed generation" (DG) can reduce transmission losses?
DG produces power far from load centers
DG is typically located close to the point of consumption, shortening the distance electricity must travel
DG uses higher voltage levels than transmission lines
DG always operates at full capacity
Explanation - Proximity reduces resistive losses that occur over long transmission distances.
Correct answer is: DG is typically located close to the point of consumption, shortening the distance electricity must travel
Q.79 Which of the following is a direct advantage of integrating renewable energy sources with a "microgrid" architecture?
Elimination of all renewable generation variability
Improved resilience and ability to operate independently during grid outages
Guarantee of zero emissions for the entire region
Reduction of the need for any storage devices
Explanation - Microgrids can island themselves, maintaining power supply for critical loads during main‑grid failures.
Correct answer is: Improved resilience and ability to operate independently during grid outages
Q.80 In wind turbine design, the "rated wind speed" is:
The wind speed at which the turbine starts rotating
The wind speed at which the turbine produces its maximum (rated) power
The wind speed at which the turbine shuts down to avoid damage
The average wind speed over a year at the site
Explanation - Beyond the rated speed, the turbine uses pitch control or other methods to keep output constant.
Correct answer is: The wind speed at which the turbine produces its maximum (rated) power
Q.81 Which renewable energy source can be integrated with existing natural gas turbines in a "combined cycle" configuration to improve overall efficiency?
Solar photovoltaic
Wind
Biomass
Geothermal
Explanation - Biomass can provide a steady heat source for the steam cycle, complementing the gas turbine in a combined‑cycle plant.
Correct answer is: Biomass
Q.82 The term "dispatchability" of a renewable source is most closely related to its:
Physical size
Ability to be controlled to meet a scheduled output
Color
Manufacturer
Explanation - Dispatchable resources can be turned on/off or adjusted to follow grid operator commands.
Correct answer is: Ability to be controlled to meet a scheduled output
Q.83 When planning a solar farm, "tilt angle" of the panels is chosen primarily to:
Match the local wind speed
Maximize solar irradiance capture over the year
Reduce the weight of the mounting structure
Increase the panel’s temperature coefficient
Explanation - Proper tilt aligns the panel surface perpendicular to the sun’s rays for optimal energy harvest.
Correct answer is: Maximize solar irradiance capture over the year
Q.84 Which of the following technologies can provide "black‑start" capability to restart a grid after a total blackout?
Solar PV with battery storage
Wind turbine without storage
Hydroelectric plant with reservoir
Both A and C
Explanation - Both battery‑backed PV and hydro with reservoir can supply the initial power needed to energize other generators.
Correct answer is: Both A and C
Q.85 In renewable energy economics, the "payback period" refers to:
The time required for the cumulative cash flow to equal the initial investment
The time a wind turbine takes to reach its rated speed
The lifespan of a solar panel
The duration of a power purchase agreement
Explanation - Payback period indicates how long it takes for an investment to be recovered through savings or revenue.
Correct answer is: The time required for the cumulative cash flow to equal the initial investment
Q.86 Which of the following is a commonly used metric to evaluate the reliability of a renewable generation forecast?
Mean absolute error (MAE)
Capacity credit
Levelized cost of electricity
Cut‑in wind speed
Explanation - MAE quantifies the average magnitude of forecast errors, indicating forecast accuracy.
Correct answer is: Mean absolute error (MAE)
Q.87 The "heat rate" of a power plant is a measure of:
The amount of heat rejected to the environment per megawatt‑hour generated
The efficiency of converting fuel energy into electrical energy (lower is better)
The temperature at which the plant operates
The speed at which the turbine spins
Explanation - Heat rate (Btu/kWh) indicates fuel consumption; a lower heat rate means higher efficiency.
Correct answer is: The efficiency of converting fuel energy into electrical energy (lower is better)
Q.88 Which renewable technology typically uses a "Stirling engine" for conversion of heat to electricity?
Solar photovoltaic
Concentrated solar power (CSP)
Wind turbine
Biomass gasifier
Explanation - Stirling CSP systems focus sunlight onto a receiver that heats the working gas in a Stirling engine to generate power.
Correct answer is: Concentrated solar power (CSP)
Q.89 In power system protection, a "distance relay" is used to:
Measure the power output of a solar farm
Detect faults on transmission lines based on impedance
Control the blade pitch of wind turbines
Monitor battery state‑of‑charge
Explanation - Distance relays calculate line impedance to determine fault location and initiate tripping.
Correct answer is: Detect faults on transmission lines based on impedance
Q.90 Which of the following statements about "net zero" energy buildings is correct?
They generate exactly as much electricity as they consume over a year, typically using on‑site renewables
They never use any electricity from the grid
They rely exclusively on wind power
They require a nuclear backup system
Explanation - Net‑zero buildings balance annual energy use with on‑site generation, often employing PV, solar thermal, and efficient design.
Correct answer is: They generate exactly as much electricity as they consume over a year, typically using on‑site renewables
Q.91 Which of the following is a key driver for the increasing adoption of renewable energy in emerging economies?
Abundant coal reserves
High cost of renewable technologies
Desire for energy independence and decreasing costs of solar and wind
Strict regulations against renewable deployment
Explanation - Falling equipment prices, climate commitments, and the need for reliable power in remote areas promote renewables.
Correct answer is: Desire for energy independence and decreasing costs of solar and wind
Q.92 When a solar PV system is connected to a battery via a DC‑DC converter, the converter’s main function is to:
Increase the voltage to match the grid
Regulate the voltage/current to safely charge/discharge the battery
Convert AC to DC
Provide frequency support to the grid
Explanation - DC‑DC converters control the charging profile and protect the battery from over‑voltage or over‑current.
Correct answer is: Regulate the voltage/current to safely charge/discharge the battery
Q.93 In renewable integration studies, "Monte Carlo simulation" is typically used to:
Predict the exact output of a wind turbine for the next hour
Assess the impact of uncertain variables (e.g., wind speed) on system performance through random sampling
Design the mechanical structure of solar panels
Calculate the thermal efficiency of a geothermal plant
Explanation - Monte Carlo methods run many scenarios with random inputs to evaluate probabilistic outcomes such as reliability or cost.
Correct answer is: Assess the impact of uncertain variables (e.g., wind speed) on system performance through random sampling
Q.94 Which renewable technology is most suitable for providing baseload power in regions with limited water resources?
Large‑scale solar PV with storage
On‑shore wind
Hydropower with large reservoirs
Tidal power
Explanation - When paired with sufficient battery capacity, solar PV can deliver steady output without water consumption.
Correct answer is: Large‑scale solar PV with storage
Q.95 The main purpose of a "reactor" (inductor) in a power‑electronics based renewable converter is to:
Store magnetic energy to smooth current ripple
Increase the voltage of the output
Convert DC to AC directly
Measure wind speed
Explanation - Inductors filter high‑frequency switching currents, reducing ripple and protecting downstream components.
Correct answer is: Store magnetic energy to smooth current ripple
Q.96 Which of the following renewable energy sources can be effectively used for "co‑generation" (simultaneous heat and power production)?
Solar photovoltaic
Wind turbines
Biomass combustion
Offshore wind
Explanation - Biomass can drive a turbine for electricity while the waste heat is captured for heating or industrial processes.
Correct answer is: Biomass combustion
Q.97 In a renewable energy‑rich grid, "synthetic inertia" is typically provided by:
Large synchronous generators only
Power electronic converters (e.g., inverters) that emulate inertia through control algorithms
Mechanical flywheels without any power electronics
Passive resistors
Explanation - Advanced inverter controls can inject a short‑term power surge proportional to frequency changes, mimicking physical inertia.
Correct answer is: Power electronic converters (e.g., inverters) that emulate inertia through control algorithms
Q.98 Which renewable technology often requires "anti‑icing" systems to maintain performance in cold climates?
Solar photovoltaic
On‑shore wind turbines
Geothermal
Hydropower
Explanation - Ice accumulation on blades reduces lift and can cause imbalance; heating or aerodynamic de‑icing systems mitigate this.
Correct answer is: On‑shore wind turbines
Q.99 The "levelized cost of storage" (LCOS) is analogous to LCOE but focuses on:
The cost per kilowatt‑hour that a storage system can deliver over its lifetime
The cost of installing new transmission lines
The price of raw materials for batteries
The market price of electricity
Explanation - LCOS spreads all capital, O&M, and efficiency losses over the total usable energy output of the storage system.
Correct answer is: The cost per kilowatt‑hour that a storage system can deliver over its lifetime
Q.100 Which of the following best describes a "soft" start‑up of a renewable generator?
Rapidly applying full power to the grid
Gradually ramping up output to avoid voltage spikes and mechanical stress
Starting the generator only when the sun sets
Shutting down the generator during high wind speeds
Explanation - Soft start reduces inrush currents and mechanical loads, protecting equipment and maintaining grid stability.
Correct answer is: Gradually ramping up output to avoid voltage spikes and mechanical stress
Q.101 In renewable integration, "grid defection" refers to:
A consumer disconnecting from the grid and relying solely on local generation and storage
A fault that causes a section of the grid to trip
Increasing the size of the national grid
Using diesel generators as backup
Explanation - Defection means the user becomes self‑sufficient, often using PV + battery systems, reducing grid load.
Correct answer is: A consumer disconnecting from the grid and relying solely on local generation and storage
Q.102 Which of the following renewable energy sources can directly provide "heat" without the need for a separate conversion step?
Solar thermal
Wind turbine
Solar photovoltaic
Biomass gasification
Explanation - Solar thermal collectors absorb sunlight as heat, which can be used directly for water heating or industrial processes.
Correct answer is: Solar thermal
Q.103 The primary purpose of a "synchronizing controller" in a grid‑connected inverter is to:
Adjust the inverter’s output frequency and phase to match the grid before connection
Increase the inverter’s efficiency to 100 %
Cool the inverter during hot weather
Convert AC back to DC
Explanation - Synchronization ensures seamless connection without causing transients or instability.
Correct answer is: Adjust the inverter’s output frequency and phase to match the grid before connection
Q.104 Which of the following statements about "energy arbitrage" in renewable‑plus‑storage systems is correct?
Storing cheap renewable energy when abundant and selling it during peak price periods
Buying electricity from the grid to charge the battery during high‑price periods
Operating the storage system only during nighttime
Using the storage to increase the capacity factor of a coal plant
Explanation - Arbitrage exploits price differentials, improving revenue and aiding grid balancing.
Correct answer is: Storing cheap renewable energy when abundant and selling it during peak price periods
Q.105 Which renewable energy source can be directly coupled with a "heat pump" to increase overall system efficiency?
Solar thermal
Wind turbine
Hydropower
Geothermal (low‑temperature)
Explanation - Solar thermal heat can be upgraded by a heat pump, delivering higher‑temperature heat for space heating or hot water.
Correct answer is: Solar thermal