Energy Storage Systems – MCQs – EE

1. What is the main purpose of an energy storage system?
(A) To increase transmission losses
(B) To store energy for later use
(C) To reduce energy conversion efficiency
(D) To decrease system voltage

2. Which of the following is not an energy storage method?
(A) Battery storage
(B) Flywheel storage
(C) Transformer coupling
(D) Supercapacitor storage

3. The most commonly used energy storage system in renewable energy applications is:
(A) Thermal energy storage
(B) Chemical battery storage
(C) Magnetic energy storage
(D) Flywheel system

4. Pumped hydro storage stores energy in the form of:
(A) Thermal energy
(B) Potential energy of water
(C) Magnetic energy
(D) Chemical energy

5. In compressed air energy storage (CAES), energy is stored as:
(A) Electrical energy
(B) Chemical energy
(C) Mechanical energy in compressed air
(D) Magnetic energy

6. The main disadvantage of pumped hydro storage is:
(A) Requires suitable geographical location
(B) Low efficiency
(C) Uses toxic materials
(D) High maintenance cost

7. Supercapacitors store energy through:
(A) Electrostatic charge separation
(B) Chemical reactions
(C) Magnetic induction
(D) Thermal gradients

8. The energy density of supercapacitors is:
(A) Lower than batteries
(B) Higher than batteries
(C) Same as fuel cells
(D) Infinite

9. Which type of battery is commonly used in electric vehicles (EVs)?
(A) Lead-acid battery
(B) Nickel-cadmium battery
(C) Lithium-ion battery
(D) Zinc-carbon battery

10. The main advantage of lithium-ion batteries is:
(A) High energy density and long cycle life
(B) Low voltage output
(C) High weight
(D) High memory effect

11. The round-trip efficiency of a storage system is defined as:
(A) Ratio of energy output to energy input
(B) Input minus output energy
(C) Power loss per hour
(D) Total energy stored

12. Typical round-trip efficiency of lithium-ion batteries is around:
(A) 50–60%
(B) 70–80%
(C) 85–95%
(D) 30–40%

13. Thermal energy storage typically uses:
(A) Molten salts, water, or phase change materials
(B) Compressed air
(C) Lithium compounds
(D) Flywheels

14. The main advantage of thermal energy storage is:
(A) Large capacity and low cost
(B) Compact size
(C) Fast discharge rate
(D) High voltage output

15. Flywheel energy storage stores energy in the form of:
(A) Rotational kinetic energy
(B) Thermal energy
(C) Chemical potential energy
(D) Gravitational energy

16. The main advantage of flywheel systems is:
(A) Long cycle life and quick response time
(B) Compact size and low cost
(C) High energy density
(D) Long discharge duration

17. The self-discharge rate is highest in which energy storage system?
(A) Flywheel
(B) Lithium-ion battery
(C) Pumped hydro
(D) Lead-acid battery

18. Superconducting Magnetic Energy Storage (SMES) stores energy in:
(A) Magnetic field created by DC current in a superconducting coil
(B) Compressed gas
(C) Electrochemical cells
(D) Capacitors

19. The efficiency of SMES systems is typically:
(A) 50–60%
(B) 65–75%
(C) 90–95%
(D) 30–40%

20. Energy density of a storage system refers to:
(A) Amount of energy stored per unit mass or volume
(B) Power output per second
(C) Efficiency of conversion
(D) Heat dissipation rate

21. Power density refers to:
(A) Energy delivered per unit time
(B) Energy per unit volume
(C) Voltage per unit resistance
(D) Power factor correction

22. The main drawback of lead-acid batteries is:
(A) Heavy weight and limited cycle life
(B) High cost
(C) Low voltage
(D) High internal resistance

23. Hybrid energy storage systems (HESS) combine:
(A) Different types of storage to balance energy and power needs
(B) Only batteries and resistors
(C) Mechanical and electrical sensors
(D) Two identical storage units

24. Energy management systems in storage are used to:
(A) Optimize charging and discharging cycles
(B) Increase system losses
(C) Reduce battery voltage
(D) Prevent solar charging

25. Cycle life of a battery is defined as:
(A) Number of charge/discharge cycles before capacity drops below a set limit
(B) Time taken for full charge
(C) Number of cells in a battery
(D) Power output per cycle

26. State of Charge (SOC) indicates:
(A) Current energy level of the storage system as a percentage of total capacity
(B) The battery temperature
(C) Power density
(D) Voltage drop

27. Depth of Discharge (DoD) represents:
(A) Percentage of energy removed from total capacity during discharge
(B) Efficiency of the inverter
(C) Maximum current drawn
(D) Energy retained at full charge

28. The efficiency of a pumped hydro system is typically:
(A) 30–50%
(B) 50–60%
(C) 70–85%
(D) 90–100%

29. Battery Energy Storage Systems (BESS) are widely used for:
(A) Grid stabilization and peak shaving
(B) Power generation
(C) Frequency increase
(D) Transmission loss reduction

30. The main advantage of energy storage in renewable systems is:
(A) Balancing supply and demand during intermittent generation
(B) Increasing pollution
(C) Reducing power quality
(D) Decreasing energy efficiency