Modeling and Design of Net ZEBs as Integrated Energy Systems - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 68

Fig. 2.19 Performance comparison between a flat plate collector and a
vacuum tube collector ( T i is inlet temperature, T a is ambient temperature
and G incident solar radiation)
Concentrating Collectors
Concentrating collectors are used to supply heat to processes requiring high
temperatures. They focus solar radiation by using reflecting mirrors that
concentrate the flux on the tube containing the circulating working fluid.
These mirrors are often made out of aluminum for its high reflectivity and
reasonable price. Two types are available: the first is stationary while the
second follows the path of the sun to maximize the energy captured.
For stationary systems, a parabolic shaped bowl is used to circumvent the
apparent movement of the sun. This allows the concentration of solar
radiation in a wide band of incident angles. Two methods are used for
collectors with a displacement system following the path of the sun: the
first follows the path exactly according to the height and azimuth of the sun
(dual-axis tracking), while the second will follow the path along a single
direction (single-axis tracking).
2.2.2.2 Modeling of Solar Thermal Collectors
The interest in solar collector modeling began with the industrialization of
the first collectors in the late 1940s. Models were developed to predict the
potential of solar energy in building applications. There are several models
in the literature that can be divided into three categories: stationary models,
quasi-dynamic models, and dynamic models.