Renewables: what we meant to say.

Thanks for your response to my previous letter [on renewables, Sept/Oct 2006]. Unfortunately I was hoping for a more substantive, less touchy-feely response to such an important issue. Are we to place all our eggs in the renewables basket simply on the basis of your declaratory statement that IEA "vastly underestimates the potential growth of renewable energy"?

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Clearly, there are examples of experts underestimating the growth of whatever new technology. But my concern is that this proves nothing. I could just as easily make the opposite argument. I could, for example, quote Paul Maycock who, as a Department of Energy expert in 1980, projected the cost of solar cells falling to under US$1 per peak watt in six years (Forbes, October 13, 1980). As you no doubt know, a quarter-century later, their cost is still about three times that price. Anyone making an investment decision at that time on the basis of that expert would have lost his or her shirt.

I was hoping that World Watch might provide researchers, funders, politicians, and planners with substantive arguments for why certain technological options are promising and should be supported. If it cannot, this might simply indicate that no technologies hold out the potential for economically, safely, and adequately meeting our future energy needs. But in this case, mankind (and World Watch) ought to be discussing the implications for the future state of the world of being in this predicament.

ALLEN INVERSIN

Riverdale, Maryland, U.S.A.

Chris Flavin and Janet Sawin respond (Editor's Note: see www.worldwatch.org/ww/renewables/ for accompanying documentation): Our apologies to Mr. Inversin for the brevity of our earlier reply to his letter, which came at a busy time. Our conclusion that renewable energy, combined with high levels of energy efficiency, is a robust alternative to fossil fuels is based on scientific and engineering studies that document the vast scale of the renewable energy resource base--including solar, wind, geothermal, and biological resources--as well as the rapid advance in energy conversion technologies now under way.

Wind power is a good example. A 1991 study by the Pacific Northwest National Laboratory found that land-based wind resources in just three states could theoretically meet all U.S. electricity needs, even with significant environmental, urban, and other exclusions. Since then, wind power technology has advanced significantly, and wind turbines can now be used to capture the stronger, more consistent winds offshore. The U.S. Department of Energy estimates the offshore U.S. wind potential (within 5-50 nautical miles) at 900 gigawatts (GW), equal to 92 percent of current U.S. generating capacity. Researchers at Stanford University recently concluded that previous studies have considerably underestimated wind's potential because they did not take into account the higher-altitude winds that can be reached with modern wind turbines. The Stanford researchers estimated global wind energy potential at 72,000 GW. This means that, with current technology, wind could supply more than 10 times as much electricity as the world now uses. No one expects the world to rely on a single source of electricity, but the evidence is clear that wind power can provide a larger share of electricity than either nuclear or hydropower do today.

Solar energy is even more abundant. The solar energy striking the surface of the Earth each day is sufficient to meet the world's electricity needs for an entire year. Researchers at the National Renewable Energy Laboratory and Platts Research and Consulting estimate that just seven states in the U.S. southwest could provide more than 7,000 GW of solar generating capacity--nearly seven times the nation's existing electric capacity from all sources. A little more than 10,000 square kilometers--equivalent to 3.4 percent of the land in New Mexico--could produce 30 percent of current U.S. electricity, enough to replace half the coal now used for power generation. In addition, it is estimated that the United States has 16,240 square kilometers of roof area and 6,086 square kilometers of building facades that are suitable for installing solar photovoltaics (PVs); mounting solar panels on just half of this area could supply a further 25 percent of U.S. electricity. Additional solar energy can be used to provide water and space heating in buildings, displacing large quantities of natural gas.

The potential of bioenergy is limited by the availability of fertile land and water, but recent studies indicate that it is larger than most people realize. Today's bioenergy production is based on a combination of food crops (mainly sugarcane and corn) and waste materials from agriculture, forestry, and cities. But the technology is advancing rapidly, dramatically increasing the energy yields per hectare. In the near future, more advanced technologies will allow the conversion of any cellulosic material (such as straw or wood) into liquid bio-fuels. A joint study by the U.S. Departments of Energy and Agriculture concludes that the nation has enough biomass resources to sustainably meet well over one-third of current U.S. petroleum needs by relying on cellulosic resources and technologies. The legendary Silicon Valley venture capitalist Vinod Khosla, who is investing tens of millions of dollars in bioenergy companies, published an extensive article in the October 2006 issue of Wired magazine arguing that new technology will allow advanced biofuels to one day provide all the country's liquid fuel.

Geothermal and ocean energy round out the world's renewable energy portfolio. Although their near-term role is limited by the availability of economical conversion technologies, scores of companies are now developing devices to harness geothermal heat and the energy in the world's waves, tides, and ocean currents. These technologies are just beginning to become competitive, but globally, wave and ocean thermal energy are each estimated to be of the same order of magnitude as present world energy use. The Electric Power Research Institute estimates that U.S. near-shore wave resources could generate 2.3 trillion kWh of electricity per year, equivalent to 60 percent of current U.S. electricity consumption.

Resource availability does not place a practical limit on the potential role of renewable energy, as it does with oil. Rather, economics and policy are the two factors that have limited its deployment to date. Although some renewable energy sources, including ethanol and wind power, are already competitive at current energy prices, other renewable technologies are still more expensive than fossil fuels (at least when external economic, social, environmental, and security costs are not accounted for). But this is changing rapidly as technology advances, spurred in part by the kind of double-digit growth rates that dramatically reduced the cost of technologies such as personal computers and mobile phones. A classic study by the Boston Consulting Group found that each time cumulative production of a manufactured device doubles, production costs fall by between 20 and 30 percent. The all-time cumulative production of wind turbines has doubled in the past three-and-a-half years, while cumulative production of solar PVs has doubled in just two-and-a-half years.

Other technical challenges must also be surmounted for large-scale reliance on renewable energy to be feasible. Many renewable resources are intermittent, and while it has been demonstrated that they can provide at least 20 percent of grid electricity without making any major adjustments in the power grid, as their contribution grows backup or storage capability will have to be added. Fortunately, batteries and other storage technologies are also advancing rapidly, driven (along with renewables) by a surge of venture capital investment. In the long run, hydrogen derived from water through electrolysis will provide a means of storing and transporting energy captured from the full range of renewable resources. Scores of companies are working on fuel cells that efficiently turn hydrogen into electricity to power homes, industries, and motor vehicles.

Of course, the more quickly energy efficiency advances--and the need for energy supply falls--the greater contribution renewable energy can make. Despite significant improvements in energy efficiency over the past 30-some years, the potential for future savings in the United States and elsewhere remains enormous. Take buildings, which account for more than 40 percent of global energy use. Experts believe that the integration of intelligent design with several efficiency measures could reduce energy use in buildings by 50-80 percent while providing significant economic savings.

It will naturally take time for renewable energy to displace fossil fuels--just as it took decades for oil to replace coal and wood. But this transition is well under way. Global investment in renewable energy has doubled since 2001, and is estimated at $38 billion in 2005. This compares with total investment in the conventional power sector in 2004 of about $150 billion. Riding a surge of new government policies in dozens of countries, capital is flowing into the new technologies--from major corporations such as General Electric, Siemens, and BP, from large banks such as Goldman Sachs, and from dozens of venture capital firms. Global biofuels production increased 20 percent in 2005, and the production of wind turbines and solar PVs both increased 44 percent. In the last two years, U.S. additions to its wind energy generating capacity exceeded additions to either its coal-fired or nuclear capacity.

The tipping point will come when the world adds enough renewable resources to the energy supply each year that demand for fossil fuels levels off--halting the growth in carbon dioxide emissions. Reaching this point is primarily a matter of political will. We believe that if policy and technology continue to advance at the pace they have in the past five years, that point will be reached 10-15 years from now.

There are no physical or practical limits that would prevent renewable resources from one day providing all of the world's energy. The urgency of the world's energy security and climate problems, and the policies that governments enact to address them, will help determine the pace at which this transition occurs.

For more information on renewable energy technologies, global trends, policies, and potential, we refer you to Renewables Global Status Report Update 2006 (available at www.ren21.net), American Energy: The Renewable Path to Energy Security (www.AmericanEnergyNow.org), and Biofuels for Transportation Summary Report (www.worldwatch.org/taxonomy/term/62).