Chapter 2
Solar Spectra
Adinath Funde and Arvind Shah
Abstract Every living being on Earth is using either a direct form of energy from the
sun i.e. sunlight, as in the case of plants, or a derived form as in the case of animals.
Solar energy is, thus, the basis of all forms of life on Earth. In the present era for
human beings, there is an ever increasing demand of energy for use in every walk
of life e.g. industry, transport, technology driven gadgets, healthcare etc. The future
livelihood of human beings demands an extensive use of solar energy by photovoltaics technology for sustainable development. The adoption of solar photovoltaic
technology is ultimately dependent on the nature of sunlight that reaches the Earth.
The sunlight reaching a location on the surface of the Earth is affected by (a) sunearth geometry and (b) atmospheric effects. This chapter addresses the effects of
Earth’s atmosphere on sunlight before it reaches the Earth at a given location. It
gives the various spectra of sunlight, as received, for different times of the day and
for different atmospheric and environmental conditions. It also discusses the reflection of sunlight by the ground surface, i.e. the so-called “albedo”. Finally, it gives
some representative examples for the spectra of indoor lighting and other low-light
sources.
1 The words “spectrum” and “spectral irradiance” are synonyms and will be interchangeably used
throughout the book.
A. Funde (B)
School of Energy Studies, Savitribai Phule Pune University, Ganeshkhind, Pune, India
e-mail: adinathf@gmail.com
A. Shah
EPFL (PV-Lab), Neuchâtel, Switzerland
e-mail: arvind.shah@epfl.ch
© Springer Nature Switzerland AG 2020
A. Shah (ed.), Solar Cells and Modules, Springer Series in Materials Science 301,
https://doi.org/10.1007/978-3-030-46487-5_2
17
Solar Spectra
Adinath Funde and Arvind Shah
Abstract Every living being on Earth is using either a direct form of energy from the
sun i.e. sunlight, as in the case of plants, or a derived form as in the case of animals.
Solar energy is, thus, the basis of all forms of life on Earth. In the present era for
human beings, there is an ever increasing demand of energy for use in every walk
of life e.g. industry, transport, technology driven gadgets, healthcare etc. The future
livelihood of human beings demands an extensive use of solar energy by photovoltaics technology for sustainable development. The adoption of solar photovoltaic
technology is ultimately dependent on the nature of sunlight that reaches the Earth.
The sunlight reaching a location on the surface of the Earth is affected by (a) sunearth geometry and (b) atmospheric effects. This chapter addresses the effects of
Earth’s atmosphere on sunlight before it reaches the Earth at a given location. It
gives the various spectra of sunlight, as received, for different times of the day and
for different atmospheric and environmental conditions. It also discusses the reflection of sunlight by the ground surface, i.e. the so-called “albedo”. Finally, it gives
some representative examples for the spectra of indoor lighting and other low-light
sources.
1 The words “spectrum” and “spectral irradiance” are synonyms and will be interchangeably used
throughout the book.
A. Funde (B)
School of Energy Studies, Savitribai Phule Pune University, Ganeshkhind, Pune, India
e-mail: adinathf@gmail.com
A. Shah
EPFL (PV-Lab), Neuchâtel, Switzerland
e-mail: arvind.shah@epfl.ch
© Springer Nature Switzerland AG 2020
A. Shah (ed.), Solar Cells and Modules, Springer Series in Materials Science 301,
https://doi.org/10.1007/978-3-030-46487-5_2
17