Energy Yield Calculation
Energy Yield is calculated in AutoPV and displayed in the Energy Yield Report. This report includes the site and system parameters, irradiation data, the static calculation models, equipment details, losses and the energy yield outputs.
Typical Meteorological Year (TMY) Data
A TMY is a single year of data that best represents the long-term data set for a specified historical time period. TMY data includes the irradiance, temperature, wind velocity and air pressure of a specified location. The TMY data is constructed from at least ten years of weather data. The TMY used by AutoPV for the energy yield analysis is obtained from the PVGIS-SARAH3 2005-2023 database.
Models
AutoPV uses the calculation models indicated in the tables below for the energy yield simulation. The transposition model is dependent on whether the PV modules are monofacial or bifacial.
Monofacial Modules
| Model Names | Models Implemented |
|---|---|
| Transposition | Perez |
| IAM | Ashrae |
| Temperature | PVSyst |
| DC | PVWatts |
| AC | PVWatts |
| Losses | PVWatts |
Bifacial Modules
| Model Names | Models Implemented |
|---|---|
| Transposition | Hay-Davies |
| IAM | Ashrae |
| Temperature | PVSyst |
| DC | PVWatts |
| AC | PVWatts |
| Losses | PVWatts |
PV Array Orientation and Environment
The following PV array orientation and environment parameters can be specified in the energy yield inputs:
| Parameter | Default Value |
|---|---|
| Albedo | 0.2 |
| Axis Azimuth | 0° |
| Max Tracking Angle | 55° |
| Backtracking | Enabled |
Losses
Both Collection losses and System losses are user inputs. The IAM, Temperature and Inverter losses are all calculated by AutoPV.
The Temperature losses are currently calculated with the following constants: Uc = 29, Uv = 0. The IAM losses are currently calculated using the Ashrae Model.
The losses below are the default losses used by AutoPV if no inputs are given.
| Collection Losses | Default Value [%] |
|---|---|
| Soiling | -2.00 |
| Shading | -3.00 |
| Snow | 0.00 |
| Degradation | 0.00 |
| Module Mismatch | -2.00 |
| DC Wiring | -1.00 |
| LID | -1.50 |
| Module Quality | +1.00 |
| Connections | 0.00 |
| Availability | 0.00 |
| System Losses | Default Value [%] |
|---|---|
| AC Wiring | -1.00 |
| MV Line | -0.40 |
| Transformer (Constant) | -0.10 |
| Transformer (Resistive) | -1.00 |
Results
The Energy Yield results include the Annual Energy Production, Specific Production and the Performance Ratio.
Monthly results are given for the following data:
- Ambient Temperature -
TEMP - Global Horizontal Irradiation -
GHI - Direct Normal Irradiation -
DNI - Diffuse Horizontal Irradiation -
DHI - Global Plane of Array Irradiation -
G_POA - Global Effective Irradiation -
G_EFF - Effective Output Energy of Array -
E_ARR - Effective Input Energy to the Grid -
E_GRID - Performance Ratio -
PR
Monthly Averages Example
The results include two bar graphs of the monthly energy production and the monthly performance ratio.
Finally, the results include a losses diagram between the Nominal Array Energy and the Annual Energy Into Grid.
Losses Diagram Example
