modelElectricalPVT
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block), IDEAS.Fluid.SolarCollectors.BaseClasses.PartialParameters (Partial model for parameters).
Information
This component computes the electrical power output of a photovoltaic-thermal (PVT) collector using the PVWatts v5 methodology (Dobos, 2014), adapted for PVT systems. It is part of a validated, open-source Modelica implementation that relies solely on manufacturer datasheet parameters, as described in Meertens et al. (2025).
The model calculates the electrical output for each segment i ∈ {1, ..., nseg} as:
Pel,i = (Ac / nseg) · (Pnom / A) · (Gtilt / Gnom) · (1 + γ · ΔTi) · (1 - eleLosFac)
where:
- ΔTi = Tcell,i - Tref: temperature difference between PV cell and reference temperature
- Pnom: nominal PV power under STC [W]
- A: gross collector area [m²]
- Ac: effective collector area (equal to A if not otherwise specified)
- Gtilt: global irradiance on the tilted collector plane [W/m²]
- Gnom: nominal irradiance (typically 1000 W/m²)
- γ: temperature coefficient of power [%/K]
- eleLosFac: lumped system loss factor
The PV cell temperature is estimated from the fluid temperature and thermal power density using:
Tcell,i = Tm,i + qth,i / UAbsFluid
The internal heat transfer coefficient UAbsFluid is approximately calculated from datasheet parameters. For the mathematical description and visualisation, see IDEAS.Fluid.PVTCollectors.UsersGuide.
Electrical performance and losses
The electrical submodel includes an overall system loss factor eleLosFac.
PVWatts reports a total electrical power loss of 14%, resulting from the following mechanisms:
| Electrical power loss mechanism | Default value |
|---|---|
| Soiling | 2 % |
| Shading | 3 % |
| Mismatch | 2 % |
| Wiring | 2 % |
| Connections | 0.5 % |
| Light‑induced degradation | 1.5 % |
| Nameplate rating | 1 % |
| Availability | 3 % |
| Total | 14 % |
For well-maintained, unshaded modules, experimental validation (Meertens et al., 2025)
found that using eleLosFac = 9% gives excellent agreement with
measured electrical output. For PVT collectors with a high positive tolerance on the
electrical output, this system loss factor can even be lower.
Users may adjust eleLosFac to account for site-specific soiling or shading effects.
Implementation Notes
This model is designed for (unglazed) PVT collectors and supports discretization into multiple segments to capture temperature gradients along the flow path. It is compatible with the thermal model based on ISO 9806:2013 and is suitable for dynamic simulations where irradiance and fluid temperatures vary over time.
References
- Dobos, A. P. (2014). PVWatts Version 5 Manual. NREL/TP-6A20-62641
- Meertens, L., Jansen, J., Helsen, L. (2025). Development and Experimental Validation of an Unglazed Photovoltaic-Thermal Collector Modelica Model that only needs Datasheet Parameters, submitted to the 16th International Modelica & FMI Conference, Lucerne, Switzerland, Sep 8–10, 2025.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.Area | A_c (from PartialParameters) | Area of the collector | |
| Integer | nSeg (from PartialParameters) | 3 | Number of segments |
| Modelica.Units.SI.Irradiance | HGloHorNom | 1000 | global horizontal irradiances |
| Modelica.Units.SI.Efficiency | eleLosFac | 0.09 | PV loss factor |
| Modelica.Units.SI.Temperature | TpvtRef | 298.15 | Reference cell temperature |
| Real | gamma | Temperature coefficient [1/K] | |
| Modelica.Units.SI.Power | P_nominal | Nominal PV power | |
| Modelica.Units.SI.Area | A | PV area | |
| Modelica.Units.SI.Efficiency | eta0 | Zero-loss efficiency | |
| Modelica.Units.SI.DimensionlessRatio | tauAlpEff | Effective transmittance–absorptance product | |
| Modelica.Units.SI.CoefficientOfHeatTransfer | c1 | First-order heat loss coefficient | |
| Modelica.Units.SI.Efficiency | etaEl | Electrical efficiency | |
| Modelica.Units.SI.CoefficientOfHeatTransfer | UAbsFluid | ((tauAlpEff - etaEl)*(c1 + abs(gamma)*HGloHorNom))/((tauAlpEff - etaEl) - eta0) | Heat transfer coefficient between the fluid and the PV cells, calculated from datasheet parameters |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Blocks.Interfaces.RealInput[nSeg] | Tflu | Fluid temperatures per segment [K] | |
| Modelica.Blocks.Interfaces.RealInput[nSeg] | Qth | Thermal power density per segment [W/m2] | |
| Modelica.Blocks.Interfaces.RealInput | HGloTil | Global tilted irradiance [W/m2] | |
| Modelica.Blocks.Interfaces.RealOutput | Pel | Total electrical power output [W] | |
| Modelica.Blocks.Interfaces.RealOutput | TavgCel | Average PV module temperature [K] | |
| Modelica.Blocks.Interfaces.RealOutput | TavgFlu | Average fluid temperature [K] |
Revisions
-
July 7, 2025, by Lone Meertens:
First implementation PVT model. This is for #1436.