2 Solar Spectra
27
Fig. 2.8 The spectra of different artificial indoor light sources and sunlight through window glass.
The spectral intensity of the different indoor lamps are individually adjusted (normalized), so that
their maxima are approximately at the same height. Thus, this figure allows for a spectral comparison
of the different lamps, but gives no information on their intensity. Information on the intensity of
indoor lighting sources is given in the preceding Fig. 2.7. Reproduced from [9, 10]
is just about 100 lx (see Sect. 2.4, for the definition of “lux”). Other applications,
where solar cells have to provide electric energy from indoor lighting are:
1. Remote controls (for TV sets, audio amplifiers, electrically driven window blinds
etc.), in order to eliminate the need for batteries
2. Temperature sensors
3. Smoke sensors for fire alarms
4. Internet of things (IOT): smart sensors and controls.
2.4 “Lux” as a Unit of Light Measurement
The lux (symbol: lx) is the unit of illuminance derived from the SI system,
6 measuring luminous flux per unit area. It is equal to one lumen per square metre. It is
used as measure of the light intensity as perceived by the human eye. It is important
6 The International System of Units (SI, abbreviated from the French Système international
(d’unités)) is the modern form of the metric system and is the most widely used system of
measurement.
27
Fig. 2.8 The spectra of different artificial indoor light sources and sunlight through window glass.
The spectral intensity of the different indoor lamps are individually adjusted (normalized), so that
their maxima are approximately at the same height. Thus, this figure allows for a spectral comparison
of the different lamps, but gives no information on their intensity. Information on the intensity of
indoor lighting sources is given in the preceding Fig. 2.7. Reproduced from [9, 10]
is just about 100 lx (see Sect. 2.4, for the definition of “lux”). Other applications,
where solar cells have to provide electric energy from indoor lighting are:
1. Remote controls (for TV sets, audio amplifiers, electrically driven window blinds
etc.), in order to eliminate the need for batteries
2. Temperature sensors
3. Smoke sensors for fire alarms
4. Internet of things (IOT): smart sensors and controls.
2.4 “Lux” as a Unit of Light Measurement
The lux (symbol: lx) is the unit of illuminance derived from the SI system,
6 measuring luminous flux per unit area. It is equal to one lumen per square metre. It is
used as measure of the light intensity as perceived by the human eye. It is important
6 The International System of Units (SI, abbreviated from the French Système international
(d’unités)) is the modern form of the metric system and is the most widely used system of
measurement.