1.2.1 The Orbit and Rotation of the Earth

Earth orbits the sun in a very slightly elliptical orbit, with an eccentricity є (ratio of major to minor axis) of 0.0167. Earth also rotates once every 23 h 56 min, with respect to the distant stars (a sidereal day), and a period of 24.0 h (the definition of the solar day) about an axis titled at an angle of 23.5° to the plane of that orbit. The average distance between the Earth and the sun is the astronomical unit (AU) of 93 million miles (or 149,597,870.7 km).

The tilted axis of rotation produces the seasonal weather changes we experience, as shown in Figure 1.1...

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Fundamentals of Solar Radiation

The Sun remains fixed in the center of the circle of heavenly bodies, without changing its place; and the Earth, turning upon itself, moves round the Sun.

—Galileo Galilei, 1615


Earth orbits a star, the sun, which is the ultimate source of all energy driving the process of animate and inanimate life cycles on the planet. The sun’s nuclear furnace continually fills the volume of surrounding space with energetic elementary par­ticles and photons of electromagnetic radiation. The sun’s electromagnetic spectrum spans an enormous range of wavelengths of frequencies of radiation, from gamma and x-rays, to ultraviolet (UV), visible, infrared (IR), and radio waves...

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About the Author

Daryl R. Myers is a native Coloradoan. He has a BS in applied mathematics from the University of Colorado School of Engineering. During the Cold War, he served 4 years in the U. S. Army as a Russian linguist. He spent a further 4 years as a physicist at the Smithsonian Institution Radiation Biology Laboratory. In 1978, he joined the Solar Energy Research Institute, now the National Renewable Energy Laboratory (NREL). Daryl contributed to development of many national solar radiometry consensus standards, the U. S. National Solar Radiation Data Base, and joint satellite data validation projects in conjunction with the National Aeronautics and Space Administration (NASA) Earth Observing Systems and the King Abdul Aziz City for Science and Technology (KACST) in the Kingdom of Saudi Arabia...

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Most important, my loving and patient family and spouse have long endured my devotion, sometimes to the point of distraction, to my career. It has been my personal and professional interaction with many colleagues over many years that inspired this book. It is impossible to convey the importance of the collegial and truly friendly interaction I have personally enjoyed with the solar resource assessment and optical radiation physics community. These colleagues actively contributed to my interest and education in the field of solar radiation measurements and resource assessment. Many, regrettably, have slipped the mortal coil and now leave only the legacy of their work. Funding for my entire career (1974 to 2011) has been provided by the U. S...

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Solar radiation transfer through the Earth’s atmosphere and interaction of solar radi­ation with the land, air, and oceans are recognized as the drivers for the Earth’s radiation budget. As a result, there is a large, active climate change modeling com­munity devoted to highly detailed, complex, and often esoteric physical processes relating to solar radiation interactions with the atmosphere. The immense energy resource potential presented by the solar radiation reaching the Earth’s surface has been long recognized. The highly visible products of the climate change scientific community are far too detailed and complex for the renewable energy enthusiast, student, engineer, designer, or financier to acquire, implement, or understand.

Given the importance of understanding the “fuel ...

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Series Editor’s Preface

By 2050, the demand for energy could double, or even triple, as the global popu­lation rises and developing countries expand their economies. All life on earth depends on energy and the cycling of carbon. Energy is essential for economic and social development but also poses an environmental challenge. We must explore all aspects of energy production and consumption, including energy efficiency, clean energy, global carbon cycle, carbon sources and sinks, and biomass as well as their relationship to climate and natural resource issues. Knowledge of energy has allowed humans to flourish in numbers unimaginable to our ancestors. The world’s dependence on fossil fuels began approximately 200 years ago...

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Practical Modeling for
Renewable Energy Applications

Dr. Abbas Ghassemi is the director at the Institute for Energy and Environment (IE&E) and professor of chemical engineering at New Mexico State University. He oversees the operations of WERC: A Consortium for Environmental Education and Technology Development, the Southwest Technology Development Institute (SWTDI), and the Carlsbad Environmental Monitoring and Research Center (CERMC). As the director of IE&E, Dr. Ghassemi is also the chief operating offi­cer for programs worth over $10 million annually in education and research and outreach in energy resources, including renewable energy, water quality and quan­tity, and environmental issues...

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