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By Philip Warburg, Boston, Beacon Press, 2015, 250 pages, $27.95, ISBN 978-0-8070-3376-0
Not too long ago solar power was still in the experimental stage. Except, perhaps, for heating water and some minor residential installations it was a technology that might be useful in the future but was not yet ready for application. Warburg shows that in recent years solar power has greatly advanced. Besides many residential installations, there are installations in commercial buildings. And electrical utilities are served by large installations on brownfields and public lands. All of this solar power development has been made possible by reduction in price and increase in efficiency of photovoltaic panels as well as by federal and state subsidies.
By the end of 2014 residential solar installations had reached nearly 600,000 homes, about 1 in every 200. Warburg himself has installed solar panels on the roofs of his house and garage. These supply about 75% of his electric power including the daily charging of an electric car. Residential installations can be paid for directly by the householder who then owns the installation. The householder can also lease the installation or finance it through a “power purchase agreement” in which the householder pays nothing up front but must buy all of the power generated by the installation, typically at a rate that is lower than that of electricity from the grid.
Commercial installations include apartment and university buildings, factories, sports arenas, and shopping centers. Many of these installations are placed on canopies over parking areas and walkways as well as on the flat roofs of large buildings. Two universities that have gone heavily into solar power are Arizona State University and Rutgers University. The installations at ASU include a solar canopy on the Farrington Softball Stadium that not only provides power but also shades the spectators. Other sports arenas that have installed solar panels are the New England Patriots Gillette Stadium and the Washington Redskins’ FedEx Field. Many large corporations have installed or plan to install solar panels on their buildings. These include Apple, Google, Costco, Kohl’s, Macy’s, Staples, Toys R Us, Walgreens, and Walmart. Walmart is a leader in solar power with installations on more than 250 of it stores and plans to reach 1000 stores by 2020.
Supplying solar power to electric utilities requires solar installations covering large areas of land. Brownfields, highly contaminated industrial sites and closed landfills, are unsuitable for most purposes but are ideal locations for large solar installations. Solar installations are going up on closed landfills in New Jersey and on an abandoned industrial site in Chicago. Some companies have installed solar panels on brownfields that they still occupy. Aerojet Rocketdyne in California is using solar arrays to provide part of the power needed to clean up polluted groundwater from previous operations. Overall the EPA has identified brownfield solar projects on landfills in twelve states, hazardous waste sites in ten states, and abandoned factories and mines in several others. These installations have turned liabilities into assets.
Rooftops, parking lots, and brownfields do not have the potential to satisfy the solar power needs of the country. There is, therefore, interest in developing utility-scale solar projects on public lands. Many of these projects are in the southwest where large desert areas and sunny days present excellent conditions for solar power. However, other parts of the country, even New England, have the potential to provide significant solar power. Currently solar arrays have been set up on large areas of public lands in several states including Arizona and California. In addition several Native American tribes are considering investing in solar power on their reservations.
These large utility-scale solar projects have led to concern about environmental impacts and other problems. These projects cover vast areas of land that is largely taken away from other uses. Environmentalists are concerned with the loss of natural habitat with the consequent impact on biodiversity particularly on endangered species. People living in the vicinity of solar installations are concerned with the loss of recreational use of the land and of scenic views. To deal with these problems solar companies are planning to limit their impact on the environment. Solar panels are spaced far enough apart so that they don’t shade each other and leave sufficient space for grass to grow and for animals to move under them. Endangered animals have been relocated either permanently or sometimes temporarily during construction. Areas of land much larger than the areas devoted to solar panels have been set aside as natural areas.
The solar power installations described above are based on photovoltaic panels. In addition Warburg discusses some large installations that use mirrors to focus light and heat a suitable substance, typically molten salt. This heat is then used to produce steam to run standard steam turbines. In addition to the problems posed by photovoltaic panels a concern of these installations is that the intense heat produced by the focused sunlight might kill birds that fly through.
Although mostly devoted to applications of solar power the book also discusses the manufacture of photovoltaic panels and plans for the disposal of panels that have outlived their usefulness. It also considers the financial aspects of solar energy and its impact on the economy. Warburg gives an excellent discussion of the present status of solar energy, its problems, and its prospects for the future. This book is a must read for anyone interested in solar energy.
I noticed one small error: On p. 145, Warburg writes "...assuring a consistent flow of photons ..." and a few lines later "...which will channel the flow of photons ...." He means to say electrons rather than photons.
Kenneth S. Mendelson, Professor Emeritus of Physics