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Glossary: Energy Storage

Definitions of key terms in our Energy Storage Research

Akansha Singh avatar
Written by Akansha Singh
Updated over a month ago

  1. AC load panel – electrical junction box that distributes low voltage AC power to auxiliary systems within the battery enclosure

  2. Battery electric vehicle (BEV) – An electric vehicle that runs solely from battery power.

  3. Battery energy storage system (BESS) – the entire energy storage facility, including all site civil and electrical balance of plant

  4. Battery management system (BMS) – hardware and software solution for monitoring critical battery cell parameters such as temperature, voltage and current and responsible for maintaining the safe operation of battery cells

  5. Balance of plant (BOP) – supporting or auxiliary systems, or both, required to allow the energy storage system to operate

  6. Commercial operation date (COD) – the calendar date on which the energy storage system becomes operational and connected to the grid

  7. DC combiner – electrical junction box that distributes DC power to and from the battery modules within the enclosure

  8. Energy management system (EMS) – generally a site-level controller responsible for optimising the dispatch of energy storage (and generation if applicable) assets at the project site in conjunction with inputs from plant operators and market or utility inputs

  9. Engineering, procurement, and construction (EPC) – the full designbuild process of a complex facility, usually overseen by a single EPC contractor

  10. Heating, ventilation, and air conditioning (HVAC) – Umbrella term for heating, cooling, and air handling.

  11. Medium voltage (MV) – voltages can range from 1 to 69 kV and are generally attributed to the site collection system feeding the site substation

  12. Original equipment manufacturer (OEM) – In energy storage, the OEM typically refers to the battery manufacturer or the manufacturer of the primary storage technology if not a battery.

  13. Plug-in hybrid electric vehicle (PHEV) – An electric vehicle with a gas engine for backup and the capability to charge the battery directly.

  14. Power conversion system (PCS) – bi-directional inverter and medium voltage transformer responsible for converting AC power from site collection system to DC power for charging site batteries and vice versa

  15. Supervisory control and data acquisition (SCADA) - systems used to monitor and control a plant or equipment

  16. Uninterruptible power supply (UPS) – battery backup generally used to power critical safety systems in the event of system fault

  17. AMPC – Advanced Manufacturing Production Credit, also known as Section 45X. Tax credit available to manufacturers of specific energy equipment. Typically equal to $45/kWh for battery modules + cells, and 0.25¢ – 2¢/W for string inverters.

  18. DC – domestic content bonus credit, also known as the domestic content bonus adder or simply domestic content. 10% credit on top of the base 30% investment tax credit for proving that a substantial portion of project equipment was produced domestically.

  19. 45X – see AMPC

  20. 7x16: Shaped output profile for 16 hours a day, 7 days a week. Typically, hours 7 – 23. CCA: Community choice aggregator, seen in California.

  21. CfD: Contract-for-difference. Form of financial hedge. Pays the difference in an agreed-upon settlement price between the buyer and seller. Also known as a virtual PPA.

  22. Corporate: Data center owner, industrial manufacturer, or some other large corporate entity in the context of energy procurement.

  23. DA: Day-ahead (e.g., DA energy prices).

  24. DRRS: Dispatch reliability reserve service. Proposed nonspin ancillary product with a 4-hour minimum duration requirement.

  25. ECRS: ERCOT contingency reserve service, an ancillary product introduced on June 10th, 2023 with a 2-hour minimum duration requirement. Calls help increase grid frequency during periods of high net load.

  26. ELCC: Effective load carrying capability, typically expressed as a percentage of nameplate power capacity. Measures how much a resource can contribute to the reliability of an electric grid during times of peak load.

  27. IOU: Investor-owned utility.

  28. IRR: Internal rate of return.

  29. LSE: Load-serving entity (public utilities, investor-owned utilities, municipalities, community choice aggregators, energy service providers).

  30. Month-hour: 288-point (24 x 12) time series based on a single, representative 24-hour day for each month of the year.

  31. RRS: Regulation reserve service. ERCOT’s ancillary product for spinning reserves.

  32. RT: Real-time (e.g., RT energy prices).

  33. Shaped output: Generation (typically variable, like wind or solar) that is shaped (typically using storage) to match a desired profile, like 7x16.

  34. TBx: Top-bottom x (e.g., TB4 = top & bottom 4) power prices. Represents the cumulative difference between the x highest and x lowest power prices in each day. Used as a proxy for energy arbitrage revenue and a metric for power price volatility.

  35. VRE: Variable renewable energy (e.g., wind and solar).

  36. VRE penetration: Percentage of generation from VRE.

  37. NPV: Net present value.

  38. Offtake: See PPA.

  39. PCM: Performance credit mechanism: Proposed annual incentive paid to generators at the end of each year based on actual availability during periods of high grid stress. Planning reserve margin: Adder to peak net load forecasts for the purposes of future capacity planning.

  40. PPA: Power purchase agreement. Contracted agreement for power at a defined quantity and price.

  41. PY: Planning year, in the context of ISO capacity planning.

  42. RA: Resource adequacy. Requirement for load-serving entities to procure enough contracted capacity to meet planning reserve margins. Seen in CAISO and SPP. REC: Renewable energy credit.

  43. RRS: Regulation reserve service. ERCOT’s ancillary product for spinning reserves.

  44. RT: Real-time (e.g., RT energy prices).

  45. Shaped output: Generation (typically variable, like wind or solar) that is shaped (typically using storage) to match a desired profile, like 7x16.

  46. TBx: Top-bottom x (e.g., TB4 = top & bottom 4) power prices. Represents the cumulative difference between the x highest and x lowest power prices in each day. Used as a proxy for energy arbitrage revenue and a metric for power price volatility. VRE: Variable renewable energy (e.g., wind and solar).

  47. VRE penetration: Percentage of generation from VRE.

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