Solar Energy: An Introduction, Michael E. Mackay, Oxford U. Press, 2015. $98.50 (336 pp.). ISBN 978-0-19-965210-5 Buy at Amazon
In the preface to Solar Energy: An Introduction, author Michael Mackay reminds the reader that the Sun is the “ultimate energy source for humankind.” If we can efficiently harvest its radiation directly through photovoltaic (PV) or solar thermal devices, we have the potential to mitigate climate change, broaden economic prosperity, and improve air quality. Mackay’s Solar Energy introduces students to a wide range of applied physics and engineering topics, including thermodynamics, solid-state physics, light absorption and emission, PV devices, solar chimneys, solar towers, and solar thermal flat-plate collectors.
The text is designed for upper-level undergraduates or graduate students interested in solar energy. A Distinguished Professor of Materials Science and Engineering at the University of Delaware, Mackay initially engages the reader through the use of Fermi problems to estimate the world’s yearly carbon dioxide generation rate and the power expended by a human being. He then proceeds with detailed discussions of the generation of solar radiation, the basic principles of doing work, and the PV and solar-thermal devices that form the bridge between radiation collection and work output.
Like many authors before him, Mackay takes on the challenge of trying to briefly explain (in a 10-page section of chapter 6) the solid-state physics that leads to a bandgap in semiconductor materials. Attempting to elucidate that fundamental feature of PV devices requires tackling quantum mechanics, from Schrödinger’s equation to band theory. For students with prior background, that review should be sufficient. For those completely new to the field, it will be a challenging introduction. That said, a strength of Mackay’s text is that its nine chapters are fairly self-contained; readers and instructors can pick and choose from them without sacrificing continuity or insight.
The latter part of the text focuses on solar thermal devices and nicely complements standard PV treatments. In the US, the installed capacity of solar thermal generation is roughly 1.5 GW, a fraction of the 27 GW from PV generation. However, solar thermal devices offer energy-storage options that continue to make them an interesting part of the discussion. Mackay’s treatment covers the basics of heat transfer and explains the power of computational tools to generate insights that have long been outside the scope of more traditional approaches.
It is challenging to stay current with a topic like solar energy and its range of related issues, such as fluctuating fossil-fuel prices and renewable-energy tax incentives. For example, Mackay claims that the best silicon-based laboratory PV devices operate “at around 20% efficiency,” but Panasonic declared in April 2014 that it had achieved 25.6% efficiency. The author highlights the value of access to internet information and expects students to go online to solve some of the more open-ended problems given in the book; they will have to do the same to get the latest information on the rapidly evolving state of commercial PV and solar thermal devices. Also, a problem that asks the student to calculate the “momentum of an electron traveling at the speed of light” (by neglecting special-relativity effects) risks leading an unprepared reader down a rabbit hole. It’s a reminder that instructors, and students, too, need to be critically engaged.
Solar Energy is an engaging collection of important information and insights that fills a valuable space between the growing collection of energy-themed textbooks and the more specialized treatises on renewable energy, solar engineering, and PV devices. It has its limitations, as described above, but any text that attempts such broad coverage will have comparable flaws.
Solar Energy should help readers understand and use the basic science and tools Mackay presents to affect the future—as scientists, engineers, and citizens. It is a timely contribution in a world where carbon emissions and PV installations continue to increase and where the renewable-energy community continues to face the challenge of coupling energy production and storage to fully utilize the power of solar energy.
Nancy Haegel is center director for materials science at the National Renewable Energy Laboratory in Golden, Colorado. Prior to that, she taught materials science and physics courses at the university level for more than 25 years.