Glossary

Wind energy and platform terminology used throughout Ridgeline.

AEP (Annual Energy Production)

The total energy output of a wind project over one year, typically measured in GWh. Used to calculate capacity factor and revenue projections.

AFCR (Annualized Fatigue Consumption Rate)

The rate at which a turbine’s structural fatigue life is consumed per year. Higher AFCR means faster fatigue accumulation, often due to site conditions exceeding design class assumptions.

BOP (Balance of Plant)

All infrastructure at a wind site other than the turbines themselves: substations, collection system cabling, access roads, meteorological towers, and communications.

Capex Reserve

Budget set aside for expected major component replacements. Calculated from component RUL estimates and replacement costs, weighted by probability of failure within a planning horizon.

Capacity Factor

Ratio of actual energy production to theoretical maximum (if turbines ran at rated power 100% of the time). A 35% capacity factor means the project produces 35% of its nameplate potential. Typical US wind sites range 25–45%.

CMS (Condition Monitoring System)

Sensor network on turbine drivetrain components (vibration accelerometers, oil particle counters, temperature sensors) that provides early warning of developing faults.

CMMS (Computerized Maintenance Management System)

Software system that tracks work orders, maintenance schedules, spare parts inventory, and technician dispatching.

COD (Commercial Operation Date)

The date a wind project began selling electricity to the grid. Used to determine turbine age and warranty timelines.

DD (Due Diligence)

The structured investigation and evaluation process before acquiring a wind asset. Covers technical condition, financial performance, contractual obligations, and risk profile.

ELCR (Equivalent Load Cycle Ratio)

A measure comparing actual fatigue loading against the turbine’s design load envelope. Values above 1.0 indicate the turbine is being loaded beyond design assumptions.

FSA (Full Service Agreement)

A comprehensive service contract (typically with the OEM) that covers all turbine maintenance including major component repairs/replacements. Contrasted with parts-only or self-perform arrangements.

IEC Class

International Electrotechnical Commission wind turbine classification based on site wind conditions. Class I (high wind), Class II (medium wind), Class III (low wind). Each class has subclasses for turbulence intensity (A = high, B = medium, C = low). A turbine’s IEC class must match or exceed site conditions.

IE Report (Independent Engineer Report)

Third-party technical assessment of a wind project, typically commissioned during financing or acquisition. Covers energy yield, turbine condition, and project risks.

ISO/RTO

Independent System Operator / Regional Transmission Organization. The grid operator for the region where the wind site is located. US examples: ERCOT (Texas), SPP (Great Plains), MISO (Midwest), PJM (Mid-Atlantic), CAISO (California).

ISP (Independent Service Provider)

Third-party maintenance company (not the turbine OEM) that services wind turbines.

MTBF (Mean Time Between Failures)

Average time between component failures across a fleet. Used as a reliability metric and for estimating unscheduled maintenance budgets.

NPV (Net Present Value)

The sum of all future cash flows discounted to present value. In Ridgeline, used to express the total lifetime O&M cost in today’s dollars.

NTF (Nacelle Transfer Function)

Correction factor between wind speed measured at the nacelle-mounted anemometer and free-stream wind speed. Used in energy yield calculations.

P50 AEP

The Annual Energy Production estimate with a 50% probability of exceedance. There is a 50/50 chance actual production will be higher or lower than this figure. P50 is the median estimate used for most financial modeling.

RUL (Remaining Useful Life)

Estimated years of service remaining for a component before it needs replacement. Based on age, condition score, operating history, and fleet-average failure rates.

SCADA (Supervisory Control and Data Acquisition)

The control and monitoring system for wind turbines. Collects operational data (power output, wind speed, temperatures, alarms) at typically 10-minute or 1-second intervals.