modelISO9806QuasiDynamicHeatLoss

Calculate the heat loss of a PVT/solar collector using ISO9806:2013
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Extends from IDEAS.Fluid.SolarCollectors.BaseClasses.EN12975HeatLoss (Calculate the heat loss of a solar collector per EN12975).

Information

This component computes the quasi-dynamic heat loss from a solar thermal or PVT collector to the environment, following the methodology described in the international standard ISO 9806:2013. It extends the original IDEAS.Fluid.SolarCollectors.BaseClasses.EN12975HeatLoss model for code reuse, but implements the more comprehensive quasi-dynamic formulation.

The heat loss is calculated for each segment i ∈ {1, ..., nseg} as:

Qlos,i = Ac / nseg · [ΔTi · (c1 - c2 · ΔTi + c3 · u) + c4 · (EL - σ · Tenv4) - c6 · u · G]

where:

  • ΔTi = Tenv - Tflu,i: temperature difference between environment and fluid in segment i
  • c1: linear heat loss coefficient (alias for a1)
  • c2: quadratic heat loss coefficient (alias for a2)
  • c3: wind speed dependence of heat loss
  • c4: sky long-wave irradiance dependence
  • c6: wind speed dependence of thermal zero-loss efficiency
  • u: wind speed normal to the collector plane
  • EL: long-wave irradiance from the sky
  • G: global solar irradiance on the tilted collector plane
  • σ: Stefan–Boltzmann constant (5.67×10⁻⁸ W/m²·K⁴)

This model provides a more accurate representation of collector heat loss under dynamic environmental conditions, as required by ISO 9806:2013. It is suitable for use in simulations where wind speed, sky radiation, and irradiance vary over time.

Implementation Notes

The model inherits from IDEAS.Fluid.SolarCollectors.BaseClasses.EN12975HeatLoss for structural consistency and reuse of base functionality, but the naming and equations have been overwritten to reflect the ISO 9806 standard. Parameters a1 and a2 are overwritten to c1 and c2 for clarity.

References

  • ISO 9806:2013. Solar thermal collectors — Test methods. ISO.

    • Parameters

    TypeNameDefaultDescription
    Modelica.Units.SI.AreaA_c (from PartialParameters)Area of the collector
    IntegernSeg (from PartialParameters)3Number of segments
    Modelica.Units.SI.CoefficientOfHeatTransfera1 (from EN12975HeatLoss)a1 from ratings data
    Reala2 (from EN12975HeatLoss)a2 from ratings data
    Modelica.Units.SI.CoefficientOfHeatTransferc1Linear heat loss coefficient (a1)
    Realc2Quadratic heat loss coefficient (a2)
    Modelica.Units.SI.SpecificHeatCapacityc3Wind speed dependence of heat loss
    Modelica.Units.SI.DimensionlessRatioc4Sky long-wave irradiance dependence
    Realc6Wind speed dependence of thermal zero-loss efficiency

    Connectors

    TypeNameDefaultDescription
    Modelica.Blocks.Interfaces.RealInputTEnv (from PartialHeatLoss)Temperature of surrounding environment
    Modelica.Blocks.Interfaces.RealInput[nSeg]TFlu (from PartialHeatLoss)Temperature of the heat transfer fluid
    Modelica.Blocks.Interfaces.RealOutput[nSeg]QLos_flow (from PartialHeatLoss){QLos_internal[i]*smooth(1, if TFlu[i] > TMedMin2 then 1 else IDEAS.Utilities.Math.Functions.smoothHeaviside(TFlu[i] - TMedMin, dTMin)) for i in 1:nSeg}Limited heat loss rate at current conditions
    Modelica.Blocks.Interfaces.RealInputwinSpePlaWind speed normal to collector plane
    Modelica.Blocks.Interfaces.RealInputHGloTilGlobal irradiance on the tilted plane
    Modelica.Blocks.Interfaces.RealInputHHorIRLong-wave (sky) irradiance [W/m2]

    Revisions

    • July 7, 2025, by Lone Meertens:
      First implementation PVT model. This is for #1436. .