Glossary

Terms, acronyms, and internal jargon that took you a minute to figure out the first time you heard them. Grouped by category below; alphabetical within each group where it makes sense.

Abbreviations

Term	Meaning
AC	Alternating Current
aFRR	Automatic Frequency Restoration Reserve
CAPEX	Capital Expenditure
CM	Capacity Market
COD	Commercial Operation Date
EOL	End Of Life
FCR	Frequency Containment Reserve (Primary Reserve)
GW	Gigawatt
IRR	Internal Rate of Return
kW	Kilowatt
MW	Megawatt
MWh	Megawatt-hour
NPV	Net Present Value
OPEX	Operating Expenditure
PV	Present Value
RES	Renewable Energy System
TWh	Terawatt-hour
…/kW grid	Per kW of grid export capacity
…/kW RES	Per kW of RES asset peak export capacity
…/kW storage	Per kW of battery export capacity (measured at the inverter AC output)

Definitions

Term	Meaning
Cycle target	Target number of cycles that the storage system performs in a day on average, evaluated on a yearly basis.
Round-trip efficiency	Efficiency of the storage system from inverter AC input to inverter AC output.
Availability	Percentage of time during which your storage project can operate at rated conditions, unaffected by outage.
Storage degradation	Aurora models the impact of degradation on the storage asset's energy capacity (MWh) due to cycling.
Duration	Period for which your storage project could discharge at its rated AC capacity.
End of life value	Remaining value of storage asset that can be recovered after the end of the asset's lifecycle.
Discount rate	Rate at which project's total cashflow is discounted to calculate its net present value.

Cost assumptions sheet

Term	Meaning
Battery system	Containerised battery storage systems; main components include: cells, modules, and battery, thermal and energy management systems.
Inverter	Cost of inverter used to switch from AC to DC during charging and DC to AC during discharge.
Balance of system	Cost of system components excluding battery system and inverter; including control, monitoring and protection components, other electrical balance of system and structural elements of site.
Development	Cost of project development including: project origination and acquisition; connection and planning studies and applications; land acquisition and control and developer overhead and profit.
Grid connection	Cost of establishing a grid connection to the distribution or transmission network.
EPC soft costs	Costs of designing and constructing a storage system site, including specialised workforce, construction labour and overhead and profits for construction contractors.
Fixed O&M	Cost of operation and maintenance, includes costs such as scheduled maintenance, performance monitoring, warranty extension, and extended performance guarantees.
Insurance	Cost of insurance, can include liability, environmental, property, and other insurances such as cyber security.
Business rates	Cost of taxes paid on properties used for non-domestic purposes.
Trading & optimisation fees	Charges for electricity trading as well as optimisation fees for use of software or external providers managing optimised battery use.
Grid charges	Cost of network charges, can vary significantly depending on site and in case local upgrades to distribution grids are required. Typically paid either as annual capacity charge or per kWh exchanged with the grid.
Land lease	Agreement allowing use of land in exchange for rent.
Other	Covers cost such as auxiliary load, admin, communication and other small costs.

Note: More details can be found in the report.

Degraded/undegraded batteries sheet

Term	Meaning
Repower count	The repowering phase the asset is in. Repower Count will start at 0 and equal 1 after the 1st repowering.
Achieved daily cycles	Average number of charge-discharge cycles achieved per day, where each cycle represents a full charge and discharge of the asset (though not necessarily consecutive), calculated based on the asset's current capacity.
Percentage of initial duration remaining	Percentage of initial storage duration remaining at the end of the time period due to degradation.
Total storage charge/discharge volume	Volume of energy charged to the storage asset from the grid / discharged from the grid, measured at the grid connection. Represents contractual value, therefore when relevant churn actions are included in this fact.
'Market_name' discharge/charge cashflow	Revenue obtained and costs incurred by the storage system through the export / import of power in 'Market_name'.
Total energy trading cashflow	Total revenues obtained by exporting power minus the cost for importing power in energy trading markets.
Total capacity-based ancillary services cashflow	Total cashflow for storage asset from payments for both availability and utilisation (if remunerated) across all ancillary service markets.
Capacity Market cashflow	Revenue obtained in Capacity Market auctions.
Storage-from-RES / RES-to-storage cashflow	Cost attributed to the battery asset for charging energy from the RES asset. This cashflow financially accounts for the opportunity cost for the battery asset of not charging from the grid but instead receiving it from the RES asset. Storage-from-RES cashflow = − RES-to-storage cashflow
(RES output)	Indicates that an output is measured at the RES DC output for a solar asset and the RES AC output for a wind asset, rather than at the grid connection point.
RES-to-grid volume	Volume of energy discharged to the grid from the RES.
RES clipping losses	Volume of clipped RES generation measured at the RES output. Clipping occurs when the RES inverter and/or grid export capacity is lower than the RES peak capacity and therefore some proportion of energy produced is not exported to grid or storage.
RES grid curtailment volume	Volume of RES generation lost due to grid curtailment. Grid curtailment occurs when the asset's generation is not exported due to restrictions imposed by the TSO.
RES economic curtailment volume	Volume of RES generation curtailed economically when RES exporting to grid would lead to negative revenue.
RES available volume	RES available generation volume measured at the RES DC output for a solar asset and the RES AC output for a wind asset. When the solar DC peak capacity is oversized relative to the solar inverter capacity, this fact represents the virtual/theoretical generation which would happen if the solar was not clipped by the inverter.
Total project cashflow	Total gross margin for the entire site, including adjustment cashflows for storage asset inability to meet planned commitments and RES contribution for co-located sites if applicable.
Storage energy retention after degradation	Fraction of initial storage energy capacity volume remaining at the end of the time period due to degradation. It determines when repowering is triggered. This is not affected by efficiency degradation, see "Storage duration remaining after degradation" for the combination of both degradation types.
Storage duration remaining after degradation	Fraction of initial storage duration remaining at the end of the time period due to degradation. Storage duration at a fixed power level is affected by both energy capacity volume degradation, see "Storage energy retention after degradation", and DC-DC roundtrip efficiency degradation (if enabled). This fact captures the combined impact of these effects on usable storage duration.

Markets, tariffs and services

Term	Meaning
Day-ahead market	Wholesale market where commitments to generate or consume electricity are traded one day prior to delivery.
Intraday market	Wholesale spot market where commitments to generate or consume electricity are traded up to few minutes before delivery, adjusting for real-time demand and supply.
aFRR market	Automatic Frequency Restoration Reserve, secondary reserve market for several countries in Continental Europe. Includes a capacity-based and an energy-based components procured in separate tenders, response time is 5min.
mFRR market	Manual Frequency Restoration Reserve, tertiary reserve market. Includes a capacity-based and an energy-based component procured in separate tenders, response time is 15min.
FCR market	Frequency Containment Reserve, primary reserve market for initial containment of frequency deviations, capacity-based, response time is 30sec.