One key component of the Plan B climate stabilization strategy is solar energy. Solar is even more ubiquitous than wind energy and can be harnessed with both solar photovoltaics (PV) and solar thermal collectors.

Solar PV — both silicon-based and thin film — converts sunlight directly into electricity. The growth in solar cell production climbed from an annual expansion of 38 percent in 2006 to an off-the-chart 89 percent in 2008, before settling back to 51 percent in 2009. At the end of 2009, there were 23,000 megawatts of PV installations worldwide, which when operating at peak power could match the output of 23 nuclear power plants. Germany, with an installed PV power generating capacity of almost 10,000 megawatts, is far and away the world leader in installations.

On the manufacturing front, the early leaders — the United States, Japan, and Germany — have been overtaken by China, which produces more than twice as many solar cells annually as Japan. World PV production has roughly doubled every two years since 2001 and exceeded 20,000 megawatts in 2010.

Historically, photovoltaic installations were small-scale — mostly residential rooftop installations. Now that is changing, as utility-scale PV projects are being launched in several countries. The United States, for example, has under construction and development some 77 utility-scale projects, adding up to 13,200 megawatts of generating capacity. Morocco is now planning five large solar-generating projects, either photovoltaic or solar thermal or both, each ranging from 100 to 500 megawatts.

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More and more countries, states, and provinces are setting solar installation goals. Italy’s solar industry group is projecting 15,000 megawatts of installed capacity by 2020. Japan is planning 28,000 megawatts by 2020. The state of California has set a goal of 3,000 megawatts by 2017. Solar-rich Saudi Arabia recently announced that it plans to shift from oil to solar energy to power new desalination plants that supply the country’s residential water. It currently uses 1.5 million barrels of oil per day to operate some 30 desalting plants.

With installations of solar PV climbing, with costs continuing to fall, and with concerns about climate change escalating, cumulative PV installations could reach 1.5 million megawatts (1,500 gigawatts) in 2020. Although this estimate may seem overly ambitious, it could in fact be conservative, because if most of the 1.5 billion people who lack electricity today get it by 2020, it will likely be because they have installed home solar systems. In many cases, it is cheaper to install solar cells for individual homes than it is to build a grid and a central power plant.

The second, very promising way to harness solar energy on a massive scale is a large-scale solar thermal technology, often referred to as concentrating solar power (CSP), that uses reflectors to concentrate sunlight on a liquid, producing steam to drive a turbine and generate electricity. One of the attractions of utility-scale CSP plants is that heat during the day can be stored in molten salt at temperatures above 1,000 degrees Fahrenheit. The heat can then be used to keep the turbines running for eight or more hours after sunset.

CSP first came on the scene with the construction of a 350-megawatt solar thermal power plant complex in California. Completed in 1991, it was the world’s only utility-scale solar thermal generating facility until the completion of a 64-megawatt power plant in Nevada in 2007.

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Although solar thermal power has been slow to get under way, utility-scale plants are being built rapidly now, led by the United States and Spain. The United States has more than 40 solar thermal power plants operating, under construction, and under development that range from 10 to 1,200 megawatts each. Spain has 60 power plants in these same stages of development, most of which are 50 megawatts each. The American Solar Energy Society notes that solar thermal resources in the U.S. Southwest can satisfy current U.S. electricity needs nearly four times over.

In July 2009, a group of 11 leading European firms and one Algerian firm, led by Munich Re and including Deutsche Bank, Siemens, and ABB, announced that they were going to craft a strategy and funding proposal to develop solar thermal generating capacity in North Africa and the Middle East. Their proposal would meet the needs of the producer countries and supply part of Europe’s electricity via undersea cable.

This initiative, known as the Desertec Industrial Initiative, could develop 300,000 megawatts of solar thermal generating capacity — huge by any standard. Caio Koch-Weser, vice chair of Deutsche Bank, noted that “the Initiative shows in what dimensions and on what scale we must think if we are to master the challenges from climate change.”

Even before this proposal, Algeria — for decades an oil exporter — was planning to build 6,000 megawatts of solar thermal generating capacity for export to Europe via undersea cable. The Algerians note that they have enough harnessable solar energy in their vast desert to power the entire world economy. This is not a mathematical error. The German government was quick to respond to the Algerian initiative. The plan is to build a 1,900-mile high-voltage transmission line from Adrar deep in the Algerian desert to Aachen, a town on Germany’s border with the Netherlands.

At the global level, Greenpeace, the European Solar Thermal Electricity Association, and the International Energy Agency’s SolarPACES program have outlined a plan to develop 1.5 million megawatts of solar thermal power plant capacity by 2050. For Earth Policy Institute’s Plan B to save civilization, we suggest a more immediate world goal of 200,000 megawatts by 2020, a goal that may well be exceeded as the economic potential becomes clearer.

The pace of solar energy development is accelerating as the installation of rooftop solar water heaters — solar thermal collectors on a smaller scale — takes off. This technology is sweeping China like wildfire, with an estimated 1.9 billion square feet of rooftop solar thermal collectors installed, enough to supply 120 million Chinese households with hot water. Other developing countries such as India and Brazil may also soon see millions of households turning to this inexpensive water heating technology. Once the initial installment cost of rooftop solar water heaters is paid back, the hot water is essentially free.

In Europe, where energy costs are relatively high, rooftop solar water heaters are also spreading fast. Systems typically pay for themselves in electricity savings within 10 years. In Austria, 15 percent of all households now rely on them for hot water. As in China, in some Austrian villages, nearly all homes have rooftop collectors. And some 2 million Germans are now living in homes where water and space are both heated by rooftop solar systems.

The U.S. rooftop solar water heating industry has historically concentrated on a niche market — selling and marketing 100 million square feet of solar water heaters for swimming pools between 1995 and 2005. The industry was poised to mass-market residential solar water and space heating systems when federal tax credits were introduced in 2006. Led by Hawaii, California, and Florida, annual U.S. installation of these systems has more than tripled since 2005. The state of Hawaii requires that all new single-family homes have rooftop solar water heaters. California aims to install 200,000 solar water heaters by 2017, and New York State aims to have 170,000 residential solar water systems in operation by 2020.

With the cost of rooftop heating systems declining, many other countries will likely join Israel, Spain, and Portugal in mandating that all new buildings incorporate rooftop solar water heaters. Worldwide, Plan B calls for a total of 1,100 thermal gigawatts of rooftop solar water and space heating capacity by 2020.

Moving fast to harness the world’s enormous solar potential would bring a clear win for local economies and for the climate.

Adapted from World on the Edge by Lester R. Brown. Full book available online at

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