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Definitions

This page summarizes key terms used across the Novasense Portal and documentation.

Solar modelling​

  • Climate: The long-term average of atmospheric conditions, including temperature, precipitation, and wind patterns, over decades for a particular region.
  • Meteorology: The scientific study of the atmosphere and its processes that produce weather, focusing on short-term atmospheric phenomena.
  • Irradiance on the inclined plane (GPOA): Plane-of-array irradiance derived from satellite and ground-based meteorological data and transposed to the plant tilt and orientation.
  • Module temperature: Estimated from ambient temperature and mounting conditions, using coefficients aligned with PVSyst thermal calculation method.
  • Typical meteorological year (TMY): Synthetic dataset that combines hourly weather data from many years (climatic period) into a single "representative" year, preserving the statistical distribution of key variables (such as solar irradiance, temperature, wind, and humidity). It is used to model and predict the performance of solar energy systems under average climatic conditions over a long period of time.

Electrical modelling​

  • Measured power: Produced electrical power from a solar plant, measured at inverter output (inverter internal measurements) or at grid injection point (power meter).
  • Potential power: Modelled electrical power at inverter output considering weather conditions, module efficiency, and temperature, but without considering any system losses. Idealized modelled power used for the performance ratio calculation.
  • Theoretical power: Modelled electrical power at inverter output considering weather conditions, module efficiency, temperature, all expected system losses, and significant permanent near-shading sources, but without temporary near-shading effects caused by snow coverage or unusual soiling. Realistic modelled power used for the energy performance index calculation as well as for losses calculations. Novasense calculates the theoretical power at inverter level using either a standard physical model (comparable to a simulation with default loss parameters) or a machine learning model depending on the plant context.
  • Expected system losses: All expected losses occurring between solar module surface and AC measurement point (e.g., soft expected soiling, module glass reflection, module degradation, cable losses, module mismatch losses, inverter conversion efficiency).
  • Unexpected system losses: Losses caused by component failures, unusual soiling, any non-permanent source of module shading, incl. snow coverage, any internal or external source of solar inverter active power limitation. Most of the unexpected losses are categorized as anomalies in the Novasense Portal as soon as they reach a plant-specific anomaly detection threshold.
  • Measured/potential/theoretical energy: Integral of the measured, potential, respectively theoretical power over a given period. Electrical yield, Energy or simply Production can be considered synonymous within the Novasense Portal.
  • Machine learning model: Regression model predicting electrical values based on input features (essentially solar irradiance components, sun position, temperature), learning the relationship between those features and the predicted electrical values from a historical dataset during a reference period usually covering multiple seasons.

KPI and performance​

  • Specific yield: The total energy generated, normalized by installed power (kWh/kWp), over a defined period.
  • Expected energy: Sum of the measured energy and the Novasense categorized anomalies, calculated only during periods with irradiance above MIT.
  • Performance Ratio (PR): A performance indicator that compares the measured energy with the potential energy, capturing system losses from irradiation to AC output. Novasense reports a temperature-corrected PR following usual normative requirements.
  • Energy Performance Index (EPI): The ratio between measured energy and theoretical energy.

Availability and losses​

  • Minimum Irradiance Threshold (MIT): The irradiance level used to define useful time for availability calculations and consideration period for categorized energy losses. Novasense uses 60 W/m2 by default, configurable per plant.
  • Time-based availability: The ratio of useful time minus downtime to useful time, where useful time is defined by irradiance above MIT.
  • Energy-based availability: The ratio of produced energy to expected energy, considering losses only during periods with irradiance above MIT.
  • Contractual availability: Availability adjusted for contractually agreed exclusion factors. This is not yet implemented in the Novasense portal but can be provided as additional services.
  • Uptime: The period when a plant operates normally and irradiance is above MIT.
  • Downtime: The period when the plant is not generating power due to faults, maintenance, or other issues.
  • Underperformance: An inverter is underperforming when its measured electrical values at inverter or MPPT level are above zero but deviate significantly from expected values according to the Novasense model.

Monitoring and control​

  • Anomaly detection: Automated detection of deviations or faults in plant operation using time-series performance data across inverter, MPPT, and string levels.
  • Operational status: The current operating state of a plant, inverter, or MPPT (for example normal operation, outage, missing data, or night period).
  • Alarm category: A standardized label used to classify detected anomalies and losses by root cause.
  • Alarm category: No data: Missing or partially missing device measurements.
  • Alarm category: MPPT/Inverter outage: Loss of production due to inverter or MPPT total outage.
  • Alarm category: Grid problem: Loss of production due to grid unavailability.
  • Alarm category: String anomaly: Underperformance linked to a failed, disconnected string or strongly unexpected system losses.
  • Alarm category: Snow coverage: Losses attributed to module coverage by snow.
  • Alarm category: Power limitation: Losses attributed to active power limitation due to internal temperature derating, components sizing mismatches or inverter settings.
  • Alarm category: Power control: Power limitation specifically attributed to proven remote control commands.

Hardware and sizing​

  • Booster: The DC-DC stage in an inverter that raises input DC voltage to the level required by the inverter stage.
  • Boosterless inverter: An inverter without a DC-DC booster. It typically offers higher efficiency but requires tighter DC voltage sizing.
  • MPPT Operating Voltage Range: The absolute minimum and maximum DC voltage range in which the inverter can operate.
  • Full-load MPPT Voltage Range: The DC voltage range where the inverter can deliver maximum power without limitation.

Commercial and reporting​

  • Actual revenue: Revenue calculated from measured production and the plant contract terms (feed-in tariffs or dynamic market pricing).
  • Theoretical revenue: Revenue calculated from theoretical production using the same contract structure to estimate revenue potential.
  • Budget: Monthly production and revenue estimate, usually based on a simulation during the planning phase, based on a typical meteorological year (TMY). Compared to the theoretical energy, a budget is derived from climatic data and is usually calculated for the whole lifetime of a power plant. In opposition, the theoretical energy is derived from meteorological data and represents an estimate of what a plant should have produced under effectively observed weather conditions over a specific period of time.
  • Layout check: A configuration review that highlights inconsistencies between design documentation and the built system.
  • Automatic reporting: Automated, structured performance reporting used to track system health and production trends.