10 Module Deployment and Energy Rating
261
Nevertheless, spectral mismatch correction can be relevant close to sunrise and
sunset: furthermore, the temperature of the module is typically higher than in fixed
installations, as G(t) is higher at any time than in the case of fixed orientation.
10.3.2 Concentrating Photovoltaics (CPV) and Energy
Rating
A second remarkable exception to the protocol for energy rating listed in Sect. 10.2.5
is concentrating photovoltaics (CPV), where high-efficiency PV cells are placed
on the focus of an optical concentrating system, made either of Fresnel lenses or
mirrors, in order to increase light intensity from 10 times the direct irradiance (low
concentrations) up to 1000 times (high concentrations). The advantage is in principle
twofold:
• it achieves PV material cost reduction—the relatively inexpensive optical concentrating system collects light on a 10–1000 times larger area than the area of
the PV cells, which allows to use at a reasonable price the most expensive and
highest efficiency PV cell technologies, such as the multi-junction alloys of III–V
group cells (e.g. the triple-junction GaInP/GaAs/Ge, GaInP/GaInAs/Ge, or other
alloys and higher number of junctions);
• it reaches higher efficiencies: thanks to more than 44%-efficiency cells, CPV
modules can achieve efficiencies around 40% or above, thus, double those of
commercial non-concentrating modules.
CPV was once referred to as the “third generation” of PV, aiming to reach high
efficiency at low-cost. But the disruptive cost reduction of c-Si since the 2010s has
put severe concerns on the real benefits of CPV, so that at the time of writing most
market forecasts and stakeholders predict little or no future for it at all. Nevertheless,
it is worthy here of mentioning where energy rating for CPV modules would differ
from that of conventional flat-panel modules on fixed installations.
First of all, CPV modules need to be placed on a 2-axis tracker, to allow the direct
irradiance to be collimated to the receiver: as a consequence, the diffuse component
D(t) is irrelevant for CPV, as it does not reach the cell, and energy rating should be
calculated only based on the direct component B(t).
Furthermore, since the module is on a 2-axis tracker, there is no effect due to the
angle of incidence, which in principle should simplify the calculation. Another important simplification is temperature correction: since CPV cells are hit by extremely
high irradiance, they would reach critically high temperatures, unless the cells were
actively cooled during operation. In fact, the operating temperature of CPV cells is
kept under control by active cooling and therefore the temperature correction for
energy rating should be more straightforward.
But on the other hand, as CPV cells are almost certainly multi-junction cells,
the spectral mismatch between the standard reference spectrum (either the standard
261
Nevertheless, spectral mismatch correction can be relevant close to sunrise and
sunset: furthermore, the temperature of the module is typically higher than in fixed
installations, as G(t) is higher at any time than in the case of fixed orientation.
10.3.2 Concentrating Photovoltaics (CPV) and Energy
Rating
A second remarkable exception to the protocol for energy rating listed in Sect. 10.2.5
is concentrating photovoltaics (CPV), where high-efficiency PV cells are placed
on the focus of an optical concentrating system, made either of Fresnel lenses or
mirrors, in order to increase light intensity from 10 times the direct irradiance (low
concentrations) up to 1000 times (high concentrations). The advantage is in principle
twofold:
• it achieves PV material cost reduction—the relatively inexpensive optical concentrating system collects light on a 10–1000 times larger area than the area of
the PV cells, which allows to use at a reasonable price the most expensive and
highest efficiency PV cell technologies, such as the multi-junction alloys of III–V
group cells (e.g. the triple-junction GaInP/GaAs/Ge, GaInP/GaInAs/Ge, or other
alloys and higher number of junctions);
• it reaches higher efficiencies: thanks to more than 44%-efficiency cells, CPV
modules can achieve efficiencies around 40% or above, thus, double those of
commercial non-concentrating modules.
CPV was once referred to as the “third generation” of PV, aiming to reach high
efficiency at low-cost. But the disruptive cost reduction of c-Si since the 2010s has
put severe concerns on the real benefits of CPV, so that at the time of writing most
market forecasts and stakeholders predict little or no future for it at all. Nevertheless,
it is worthy here of mentioning where energy rating for CPV modules would differ
from that of conventional flat-panel modules on fixed installations.
First of all, CPV modules need to be placed on a 2-axis tracker, to allow the direct
irradiance to be collimated to the receiver: as a consequence, the diffuse component
D(t) is irrelevant for CPV, as it does not reach the cell, and energy rating should be
calculated only based on the direct component B(t).
Furthermore, since the module is on a 2-axis tracker, there is no effect due to the
angle of incidence, which in principle should simplify the calculation. Another important simplification is temperature correction: since CPV cells are hit by extremely
high irradiance, they would reach critically high temperatures, unless the cells were
actively cooled during operation. In fact, the operating temperature of CPV cells is
kept under control by active cooling and therefore the temperature correction for
energy rating should be more straightforward.
But on the other hand, as CPV cells are almost certainly multi-junction cells,
the spectral mismatch between the standard reference spectrum (either the standard