15.8.3
One can distinguish between high concentration PV (HCPV) with typical concentration
ratios between 300 and 1,000, and low concentration PV with concentration ratios below
100 [115] (LCPV). HCPV is applied for high end III-V solar cells and requires two-axis
tracking of the Sun, while for LCPV, which is applied to c-Si and other solar cells, singleaxis tracking is sufficient [115].
Different optical elements can be used to concentrate the sunlight [117]. First, there
are reflective optical elements such as parabolic concentrators, compound parabolic
concentrators (CPCs) comprising two parabolic surfaces, and V-through concentrators.
Refractive lenses can also be used. As normal lenses would become very thick, most of the
time Fresnel lenses are used, where the lens is collapsed back to zero thickness at a
number of points [117]. A disadvantage of Fresnel lenses is that they show more optical
losses than conventional lenses. To reach high concentration ratios exceeding 200,
secondary optics is required, which also may increase the acceptance angle of the incident
sunlight [117]. Most modern HCPV systems use Fresnel lenses as primary optics [115].
Currently, microconcentrators with diameters ranging from μm to a few mm are also being
investigated [118]. More information on the different concepts and building blocks for
concentrator systems can be found in [117].
Other aspects of concentrator PV
As we will discuss in Chapter 18, sunlight arrives at a PV module as direct and diffuse
radiation. As for concentrated solar power (which we discuss in Chapter 22), only direct
radiation can be concentrated and hence converted into electricity in a CPV system.
Hence, CPV systems must be mounted at arid places with a lot of direct sunlight and a low
percentage of diffuse radiation.
As mentioned above, CPV requires single- or even dual- tracking of the sunlight in
order to concentrate it onto the solar cell independently of the position of the Sun. The
tracking systems guarantee optimal light concentration on the small PV device during the
entire day. Mounting the modules on a tracking system adds costs to the system which
must be recovered by the increased efficiency of the CPV system.
Especially for HCPV, the irradiance received by the module is very high. Without
cooling, this would lead to very high temperatures of several hundreds of ºC and hence
would destroy the cell. Either passive cooling or active cooling can be applied. Passive
cooling for example is done with heat sinks that are thermally connected to the solar cells
and transport the heat to the surrounding air via convection. If the system is actively
cooled via a cooling liquid that transports the heat away from the solar cell, this waste heat
One can distinguish between high concentration PV (HCPV) with typical concentration
ratios between 300 and 1,000, and low concentration PV with concentration ratios below
100 [115] (LCPV). HCPV is applied for high end III-V solar cells and requires two-axis
tracking of the Sun, while for LCPV, which is applied to c-Si and other solar cells, singleaxis tracking is sufficient [115].
Different optical elements can be used to concentrate the sunlight [117]. First, there
are reflective optical elements such as parabolic concentrators, compound parabolic
concentrators (CPCs) comprising two parabolic surfaces, and V-through concentrators.
Refractive lenses can also be used. As normal lenses would become very thick, most of the
time Fresnel lenses are used, where the lens is collapsed back to zero thickness at a
number of points [117]. A disadvantage of Fresnel lenses is that they show more optical
losses than conventional lenses. To reach high concentration ratios exceeding 200,
secondary optics is required, which also may increase the acceptance angle of the incident
sunlight [117]. Most modern HCPV systems use Fresnel lenses as primary optics [115].
Currently, microconcentrators with diameters ranging from μm to a few mm are also being
investigated [118]. More information on the different concepts and building blocks for
concentrator systems can be found in [117].
Other aspects of concentrator PV
As we will discuss in Chapter 18, sunlight arrives at a PV module as direct and diffuse
radiation. As for concentrated solar power (which we discuss in Chapter 22), only direct
radiation can be concentrated and hence converted into electricity in a CPV system.
Hence, CPV systems must be mounted at arid places with a lot of direct sunlight and a low
percentage of diffuse radiation.
As mentioned above, CPV requires single- or even dual- tracking of the sunlight in
order to concentrate it onto the solar cell independently of the position of the Sun. The
tracking systems guarantee optimal light concentration on the small PV device during the
entire day. Mounting the modules on a tracking system adds costs to the system which
must be recovered by the increased efficiency of the CPV system.
Especially for HCPV, the irradiance received by the module is very high. Without
cooling, this would lead to very high temperatures of several hundreds of ºC and hence
would destroy the cell. Either passive cooling or active cooling can be applied. Passive
cooling for example is done with heat sinks that are thermally connected to the solar cells
and transport the heat to the surrounding air via convection. If the system is actively
cooled via a cooling liquid that transports the heat away from the solar cell, this waste heat