Solar irradiance spectrum above the Earth's atmosphere and at the surface. Where, h is Planck's constant in eV, c is the speed of light in m s −1 and λ is the wavelength of the light in nm. This is equivalent to about 2.3 eV, which can be calculated using eqn (1.1). The temperature of the Sun (5800 K at the surface) means the solar spectrum peaks at around 550 nm, in the green portion of the visible region. 2 Of this, 30% is reflected back by the atmosphere or the Earth's surface. Approximately, 46% of solar radiation falls within visible light wavelengths, as shown in Figure 1.2. Visible light, the region of the spectrum our eyes can detect, is composed of relatively short wavelengths in the range 400 to 700 nm. 1 Wavelengths below 200 nm (X-rays, γ-rays and UV radiation) are absorbed by nitrogen and oxygen in the atmosphere, the region between 200 and 300 nm (UV radiation) is absorbed by O 3 in the stratosphere, wavelengths above 700 nm (IR radiation) are partially absorbed by CO 2, O 3 and water. The Sun emits photons across a broad range of wavelengths, getting smaller (higher in energy) from radio waves to gamma rays, as shown in Figure 1.1. This radiation is spread in the form of electromagnetic waves and a particle of the electromagnetic radiation is known as a photon. This energy eventually makes its way from the centre of the Sun to the outer regions and is emitted in the form of electromagnetic radiation. From the law of conservation of energy, energy is released because the helium nucleus has a slightly lower mass than the sum of the original hydrogen nuclei. Four hydrogen nuclei are fused to form a helium nucleus and a neutron is released. Heat and light from the Sun, solar energy, is one of the cleanest and most abundant sources of renewable energy.ĭuring most of the Sun's life, energy comes from the fusion of hydrogen nuclei. Although the Sun is about 90 million miles away from us, it takes only about 8.5 minutes for light to travel from the Sun to Earth. The Sun is the major source of energy on Earth and has been producing energy for billions of years. Finally, to set the scene for subsequent chapters, three types of thin-film PV technologies are introduced: cadmium telluride (CdTe), copper–indium–gallium–selenide (CIGS) and amorphous silicon (a-Si), and their advantages and disadvantages over crystalline Si modules are discussed. Chapter 1 also discusses the installed capacity, targets and current policy for power generation from PVs across different countries. ![]() A few other developing countries also constitute the emerging market for PVs. At present China, India, USA, Japan and Germany are the biggest solar markets in the world, accounting for most of the growth in solar power. The global status of solar PV modules in terms of their contribution to energy generation is also discussed. The various steps involved in the development of silicon solar cells, from the reduction of sand to fabrication of solar cells, are described in detail. 1-55Įnergy Materials Laboratory, School of Natural and Environmental Science, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.Į-mail: Institute of Solar Energy (NISE), Gurgaon, Haryana 122003, India.Ĭhapter 1 is an introductory chapter on photovoltaics (PVs) and gives a technological overview on silicon solar cells. Bora, CHAPTER 1:Silicon Solar Cells, in Solar Energy Capture Materials, 2019, pp.
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