Modeling and Design of Net ZEBs as Integrated Energy Systems - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 59

configuration cannot be obtained. It is also essential when additional
information other than the cell temperature is required, such as the thermal
output of a BIPV/T system or energy flow through an STPV system to the
adjacent space. This method requires that the properties of each layer are
known (or estimated); the method is applicable to any BIPV configuration.
An energy balance is applied for each layer, taking into account radiative,
convective, and conductive heat exchanges between layers and the
environment. The models can be steady-state or dynamic and can be one,
two or three dimensional. For BIPV systems without any heat recovery, a
one-dimensional model in the direction normal to the collector surface is
generally sufficient.
InBIPV/Tsystems,asignificanttemperaturegradientexistsinthedirection
of the heat removal fluid flow. For most purposes a one-dimensional model
is still sufficient, but the collector is usually divided into a number of control
volumes in the direction of the flow in order to obtain a better
approximation of the temperature of the fluid and PV cells. The choice of a
steady-state or dynamic model is based on the level of resolution required.
For daily or annual yield, a steady-state model is comparable to a dynamic
model for a sheet-and-tube PV/T (Zondag et al. , 2002).
Figure 2.15 represents a simple one-dimensional finite difference model for
a BIPV/T system (air system) with a possible STPV layer. In this system,
it is assumed that (i) the various layers of the PV module are thin enough
so their heat capacity can be neglected, and (ii) the PV module has uniform
properties. Theenergy andmassbalance (perunitarea), forthe n -thcontrol
volume, are given by