CEA Energy Storage & Grid Integration 2 — Questions and Answers
Question 1: What is the primary purpose of frequency regulation in grid-connected battery energy storage systems (BESS)?
- Reduce peak demand charges
- Maintain grid frequency within acceptable bounds (e.g., 59.95–60.05 Hz) (Correct answer)
- Store excess renewable energy for later use
- Provide black-start capability to the grid
Correct answer: Maintain grid frequency within acceptable bounds (e.g., 59.95–60.05 Hz)
Frequency regulation services require fast-responding storage to inject or absorb power to keep grid frequency within tight operational limits.
Question 2: Which metric best describes a battery's ability to deliver stored energy relative to its rated capacity over its lifetime?
- Round-trip efficiency
- State of health (SOH) (Correct answer)
- Depth of discharge (DOD)
- C-rate
Correct answer: State of health (SOH)
State of health (SOH) quantifies capacity fade and power degradation compared to the battery's original specifications.
Question 3: A utility-scale vanadium redox flow battery (VRFB) is best characterized by which operational advantage over lithium-ion?
- Higher energy density per unit volume
- Independent scaling of power and energy capacity (Correct answer)
- Lower upfront capital cost per kWh
- Faster charge/discharge response time
Correct answer: Independent scaling of power and energy capacity
In flow batteries, power (stack size) and energy (electrolyte volume) are decoupled, allowing independent optimization of each parameter.
Question 4: In grid integration planning, what does 'interconnection queue' refer to?
- The order in which storage projects receive FERC approval for rate tariffs
- The backlog of generation and storage projects awaiting grid connection studies (Correct answer)
- Priority sequencing for dispatch during grid emergencies
- The list of substations eligible for smart inverter upgrades
Correct answer: The backlog of generation and storage projects awaiting grid connection studies
The interconnection queue is the backlog of projects awaiting transmission studies and approvals before connecting to the grid.
Question 5: Which IEEE standard governs the interconnection and interoperability requirements for distributed energy resources including storage?
- IEEE 1547 (Correct answer)
- IEEE 519
- IEEE 1675
- IEEE 2030
Correct answer: IEEE 1547
IEEE 1547 sets technical requirements for interconnection of distributed energy resources, including ride-through, voltage, and frequency response.
Question 6: What is the 'duck curve' phenomenon, and how does energy storage address it?
- Excess overnight demand flattened by thermal storage charging during the day
- A mid-day dip in net load caused by solar generation, addressed by storage absorbing excess and discharging at evening ramp (Correct answer)
- High morning demand peaks met by pumped hydro releasing stored water
- Seasonal energy surplus stored in hydrogen for winter use
Correct answer: A mid-day dip in net load caused by solar generation, addressed by storage absorbing excess and discharging at evening ramp
The duck curve shows low net load midday (solar overgeneration) and steep evening ramps; storage charges during the dip and discharges during the ramp.
Question 7: Which FERC order opened wholesale electricity markets to energy storage participation by requiring ISOs/RTOs to remove barriers?
- FERC Order 745
- FERC Order 841 (Correct answer)
- FERC Order 2222
- FERC Order 888
Correct answer: FERC Order 841
FERC Order 841 (2018) required ISOs/RTOs to establish rules enabling electric storage resources to participate in all wholesale market segments.
CEA Energy Storage & Grid Integration 2
What is the primary purpose of frequency regulation in grid-connected battery energy storage systems (BESS)?