The main goal of the IDEAS Buildings library is to set up models that allow simulating building envelope models. These models may be coupled to models from the Fluid or Electric packages. In this user guide we outline the main principles of the library.
The main physical principles that are modelled in IDEAS are
Furthermore models for specifying additional boundary conditions are
A qualitative description of these models can be found below. If you need to know the implementation then look at the Modelica equation sections.
Interior convection
Interior convection is modelled between surfaces and the zone air
volume. Correlations are used to compute the heat flow rate from
the temperature difference. By default these correlations are
non-linear but they may be linearised as well.
Air cavities within walls are simulated using a correlation that
takes into account both radiative and convective heat transfer. It
is assumed that the cavity is not ventilated.
Exterior convection
Exterior convection is modelled using a wind speed dependent
correlation.
Interior longwave radiation
Interior longwave radiation between surfaces may be modelled using
two appraoches; either using an
equivalent radiative star point or using
view factors . Longwave radiation equations are linearised by
default to avoid large non-linear algebraic loops. Computations
using a fourth order equation may be enabled by setting
linIntRad=false in the zone model. Surface
emissivities are taken into account in these computations. The view
factor implementation assumes the zone to have a rectangular
geometry.
Exterior longwave radiation
Exterior longwave radiation is simulated by computing heat exchange
with a weighted temperature of the outside air and the sky
temperature. The weighting factor depends on the surface
orientation. These equations are linear by default, but may be
computed using a fourth order equation using
linExtRad=false.
Interior shortwave radiation
Interior shortwave radiation occurs whenever sun light enters the
zone through a window. When passing through the window, part of the
sun light is
absorbed. In
IDEAS.Buildings.Components.BaseClasses.RadiativeHeatTransfer.ZoneLwGainDistribution
we assume that the light always hits the floor. A fraction of the
light, equal to the emissivity of the material, will be absorbed.
The remaining fraction is reflected within the zone and is absorbed
by the remaining surfaces.
Exterior shortwave radiation
Exterior shortwave radiation injects heat on the outer surface of
surfaces. The magnitude of this heat injection depends on the
surface emissivity and orientation and the weather conditions
(direct and diffuse solar radiation). Surface shading by objects is
currently not supported.
Thermal conduction
Thermal conduction through solids is modelled using a series
discretisation of the wall.
Window shading
A few models allow to compute the shading of windows. These models
limit the amount of direct or diffuse solar irradation hitting the
window. Long wave radiation computations are not affected.
Air
infiltration
Air infiltration is computed for each zone independently, assuming
a user provided constant n50 value. Air exchange between zones is
not modelled by default, but may be added manually.
The main models in the Buildings package are:
We refer to the examples for some demonstrations of how to use
the Building models. Note that you must make sure that each model
contains an instance of IDEAS.BoundaryConditions.SimInfoManager
since this defines the boundary conditions of the model. This
instance must have the keyword inner. The
SimInfoManager may be used to define some general model properties
(see the parameters list), as well as the location of the modelled
building, which affects the solar calculations.
The user should make sure that the propsBus ports
of each surface are connected to one zone model.
The IDEAS Templates may be used to provide some structure to your model but they need not be used.
IDEAS.Buildings.Examples contains examples that demonstrate several functionalities of the library. IDEAS.Buildings.Components.Examples contains examples that focus more on the component level and that are primarily used for unit test purposes. IDEAS.Buildings.Validation.Tests contains examples that verify the implementation of some models. These models often contain a 'Command' that runs the model and shows some results.
IDEAS is validated using BESTEST. The validation models may be found in package IDEAS.Buildings.Validation.
In addition to this conservation of energy may be checked. An example of how to do this may be found in IDEAS.Buildings.Validation.Tests.EnergyConservationValidation.
Many of the example models are unit tested. Developers use this to check model consistency when model equations are changed.