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Energy Storage Systems Flashcards

7 cards from real ESCO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Energy Storage Systems flashcards as text

  1. What is the primary purpose of a battery energy storage system (BESS) in a commercial ESCO project?

    Answer: To store excess energy and dispatch it when needed to reduce costs or improve reliability

    A BESS stores surplus or off-peak energy and dispatches it during peak periods to reduce demand charges and improve energy reliability.

  2. Which energy storage technology dominates new commercial and utility-scale installations as of the mid-2020s?

    Answer: Lithium-ion batteries

    Lithium-ion batteries dominate new commercial installations due to their high energy density, falling costs, and long cycle life.

  3. What does 'round-trip efficiency' measure in an energy storage system?

    Answer: The ratio of energy output to energy input over a complete charge-discharge cycle

    Round-trip efficiency is the ratio of energy recovered during discharge to energy consumed during charging, expressed as a percentage.

  4. In a chilled water thermal energy storage (TES) system, energy is stored as:

    Answer: Cooling capacity, typically in the form of chilled water or ice

    Chilled water TES stores cooling energy by chilling water or making ice during off-peak hours for use during peak cooling periods.

  5. What depth of discharge (DOD) is generally recommended for lithium-ion batteries to balance usable capacity and cycle longevity?

    Answer: 80-90% to balance usable capacity and longevity

    Operating lithium-ion batteries at 80-90% DOD balances maximizing usable capacity while maintaining reasonable cycle life.

  6. What is the 'usable capacity' of a battery energy storage system?

    Answer: The portion of total capacity that can be used without damaging the battery

    Usable capacity is the portion of total rated capacity accessible within safe operating limits set by the battery management system.

  7. In ESCO projects, demand charge management through energy storage involves:

    Answer: Discharging stored energy during peak demand intervals to reduce the building's peak load

    Energy storage discharges during peak demand windows to shave the highest demand spikes, reducing the monthly demand charges on the utility bill.