o Electrochemical and Photoelectrochemical coupled with biosystems (see
Chap. 11)
• High-temperature processes driven by Solar Power Concentrators.
Each of these three technologies will be discussed and examples of application
are presented.
10.3 The Solar Spectrum
Figure 10.1 shows the solar spectrum. From left to the right, Ultraviolet (UV),
Visible (Vis), and Infrared (IR) regions are shown with their characteristic wavelengths and abundance. Clearly, the abundance depends on whether we measure the
spectrum at sea level or outside the atmosphere. UV represents only ca. 8% of the
total emitted radiations, while Vis (42.3%) and IR (49.4%) represent the largest part
of it. UV radiations are used in chemistry: for example, TiO 2 (Titanium dioxide) is
largely used as photocatalyst for the oxidation of organic toxic compounds under
UV-irradiation. As shown in Fig. 10.1, UV represents only a tiny part of the solar
radiation; therefore, for pushing the efficiency of the process, catalysts should be
used as concentrators of the radiations. Most simply, UV lamps are used instead of
using direct solar light in industrial applications, leaving to solar light the duty
when very large surface applications are targeted, such as in the autocleaning of
façades of buildings [3]. Visible radiations are used in photosynthetic pathways in
Nature and are wished to drive Solar Driven Processes (SDP). Developing photocatalysts which operate under Vis-light is a key target for developing useful SDPs
in the chemical industry. IR radiations are used for driving thermal reactions more
than photochemical processes.
Due to the low density of solar energy, in order to increase the number of
photons that hit the target, devices which focus the solar radiations in a spot are
often used. Alternatively, Xe-lamps are used as solar simulators, eventually coupled
to filters for a better selection of wavelengths. Such lamps are fed with electricity (if
PV is used, the source of energy will be the Sun) and emit radiations of wavelength
similar to those of the solar spectrum [4]. In this case, the light intensity can be
higher than that of the Sun. Using filters, it is possible to cut UV or IR radiations or
even narrow the Vis-light to some of its components. Visible light is also known as
“white light”, as it has no color due to the combination of the radiations from blue
to red (the colors of the “rainbow” that can be clearly seen in Fig. 10.1 in the Vis
portion of the spectrum).
10.2 Utilization of Solar Energy for Driving Chemical Reactions
179
Chap. 11)
• High-temperature processes driven by Solar Power Concentrators.
Each of these three technologies will be discussed and examples of application
are presented.
10.3 The Solar Spectrum
Figure 10.1 shows the solar spectrum. From left to the right, Ultraviolet (UV),
Visible (Vis), and Infrared (IR) regions are shown with their characteristic wavelengths and abundance. Clearly, the abundance depends on whether we measure the
spectrum at sea level or outside the atmosphere. UV represents only ca. 8% of the
total emitted radiations, while Vis (42.3%) and IR (49.4%) represent the largest part
of it. UV radiations are used in chemistry: for example, TiO 2 (Titanium dioxide) is
largely used as photocatalyst for the oxidation of organic toxic compounds under
UV-irradiation. As shown in Fig. 10.1, UV represents only a tiny part of the solar
radiation; therefore, for pushing the efficiency of the process, catalysts should be
used as concentrators of the radiations. Most simply, UV lamps are used instead of
using direct solar light in industrial applications, leaving to solar light the duty
when very large surface applications are targeted, such as in the autocleaning of
façades of buildings [3]. Visible radiations are used in photosynthetic pathways in
Nature and are wished to drive Solar Driven Processes (SDP). Developing photocatalysts which operate under Vis-light is a key target for developing useful SDPs
in the chemical industry. IR radiations are used for driving thermal reactions more
than photochemical processes.
Due to the low density of solar energy, in order to increase the number of
photons that hit the target, devices which focus the solar radiations in a spot are
often used. Alternatively, Xe-lamps are used as solar simulators, eventually coupled
to filters for a better selection of wavelengths. Such lamps are fed with electricity (if
PV is used, the source of energy will be the Sun) and emit radiations of wavelength
similar to those of the solar spectrum [4]. In this case, the light intensity can be
higher than that of the Sun. Using filters, it is possible to cut UV or IR radiations or
even narrow the Vis-light to some of its components. Visible light is also known as
“white light”, as it has no color due to the combination of the radiations from blue
to red (the colors of the “rainbow” that can be clearly seen in Fig. 10.1 in the Vis
portion of the spectrum).
10.2 Utilization of Solar Energy for Driving Chemical Reactions
179