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Oct 20, 2009

Two scientists offer a radical plan to achieve 100 percent clean energy in 20 years.

By Mark Z. Jacobson and Mark A. Delucchi

In December, leaders from around the world will meet in Copenhagen to try to agree on cutting back greenhouse gas emissions. The most effective step to implement that goal would be a massive shift away from fossil fuels to clean, renewable energy sources.

If leaders can have confidence that such a transformation is possible, they might commit to an historic agreement. We think they can.

The Plan

There is massively abundant potential wind, water and solar (WWS) supply. The challenge is translating potential into actual energy, and our plan calls for millions of wind turbines, water machines and solar installations. The numbers are large, but the scale is not insurmountable: society has achieved similar massive transformations before.

Is it feasible to transform the world’s energy systems? Could it be accomplished in 20 years? We think so, if politicians make the right decisions.

Our plan, outlined below, demonstrates one way to build a fully renewable energy future.

Clean Technologies Only

Renewable energy comes from enticing sources: wind, which also produces waves; water, which includes hydroelectric, tidal and geothermal energy (water heated by hot underground rock); and solar, which includes photovoltaics and solar power plants that focus sunlight to heat a fluid that drives a turbine to generate electricity. Our WWS plan includes only technologies that work or are close to working today on a large scale, rather than those that may exist 20 or 30 years from now.

To ensure that our system remains clean, we consider only technologies that have near-zero emissions of greenhouse gases and air pollutants over their entire life cycle, including construction, operation and decommissioning.

For example, when burned in vehicles, even the most ecologically acceptable sources of ethanol create air pollution that will cause the same mortality level as when gasoline is burned. Nuclear power results in up to 25 times more carbon emissions than wind energy, when reactor construction and uranium refining and transport are considered.

Carbon capture and sequestration technology can reduce carbon dioxide emissions from coal-fired power plants, but will increase air pollutants as well as other deleterious effects of coal mining, transport and processing.

Similarly, we consider only technologies that do not present significant waste disposal or terrorism risks.

According to our plan, WWS will supply electric power for heating and transportation—industries that will have to revamp if the world has any hope of slowing climate change.

We have assumed that most fossil-fuel heating (as well as ovens and stoves) can be replaced by electric systems and that most fossil-fuel transportation can be replaced by battery and fuel-cell vehicles. Hydrogen, produced by using WWS electricity to split water (electrolysis), would power fuel cells and be burned in airplanes and by industries.

Building a Clean Energy World

Clearly, there is no shortage of potential renewable energy supply. How can the world transition to a new, clean infrastructure to generate the 11.5 terawatts of electricity that will be demanded in 2030?

We have chosen a mix of technologies emphasizing wind (51 percent of demand) and solar (40 percent). The remaining 9 percent of demand would be met by mature water-related methods. Of course, other combinations of wind and solar could be as successful.

Admittedly, the numbers sound big: 3.8 million large wind turbines; 89,000 photovoltaic and concentrated solar power plants, averaging 300 megawatts each; 900 hydroelectric stations. And smart regional, national and international distribution systems to link it all together.

Building such an extensive infrastructure will take time. But so did the current power plant network. On a global basis, over 20 years, the scale of the WWS infrastructure is not a barrier. But a few materials needed to build it could be scarce or subject to price manipulation.

Potential Constraints

Enough concrete and steel exist for the millions of wind turbines, and both those commodities are fully recyclable. The most problematic materials may be rare-earth metals such as the neodymium used in turbine gearboxes. Although the metals are not in short supply, the low-cost sources are concentrated in China. Manufacturers are moving toward gearless turbines, however, so that limitation may become moot.

Photovoltaic cells rely on amorphous or crystalline silicon, cadmium telluride, or copper indium selenide and sulfide. Limited supplies of tellurium and indium could reduce the prospects for some types of thin-film solar cells, though not for all, and the other types might be able to take up the slack. Large-scale production could be restricted by the silver that cells require. Finding ways to reduce the silver content could tackle that hurdle. Recycling parts from old cells could ameliorate material difficulties as well.

Three components could pose challenges for building millions of electric vehicles: rare-earth metals for electric motors, lithium for lithium-ion batteries and platinum for fuel cells. More than half of the world’s lithium reserves lie in Bolivia and Chile, which could pose geopolitical risks. More problematic is the claim by Meridian International Research that not enough economically recoverable lithium exists to build the number of batteries needed in a global electric-vehicle economy.

As Cheap as Coal

The logical next question is whether we can afford clean power.

Today, wind, geothermal and hydroelectric power cost less than 7 cents per kilowatt hour (kWh). By 2020, wave and hydro should be 4 cents/kWh or less. By comparison, in the U.S. in 2007, conventional power cost about 7 cents/kWh and is projected to be 8 cents in 2020.

Solar power is still expensive, but should be competitive by 2020. An analysis by Vasilis Fthenakis of Brookhaven National Laboratory indicates that photovoltaic systems as well as concentrated solar systems with enough storage to generate electricity around the clock should drop to about 10 cents/kWh.

Clean energy transportation needs to be driven by batteries or fuel cells. Estimates by Mark A. Delucchi and Tim Lippman (University of California, Berkeley), show that mass-produced electrical vehicles could have lifetime costs per mile comparable to conventional cars, as long as gasoline is at least $2 per gallon.

The global cost of constructing a WWS system could be on the order of $100 trillion, not including transmission. But this investment, which would be paid back through the sale of energy, would produce a sustainable planet.

Political Will

Our analyses strongly suggest that the costs of WWS will become competitive with traditional sources. In the interim, however, certain forms of WWS power—especially solar—will be significantly more costly than fossil power. Thus, some combination of subsidies and carbon taxes would be needed for a time.

Of course, taxing fossil fuels or their use to reflect their environmental damages makes sense. But at a minimum, existing subsidies for fossil energy, such as tax benefits for exploration and extraction, should be eliminated to level the playing field. Promotion of alternatives that are less desirable than WWS power, such as subsidies for biofuels, should also be ended since they simply delay deployment of cleaner systems.

Finally, each nation needs to be willing to invest in a robust, long-distance transmission system that can carry large quantities of WWS power from where it is produced to centers of consumption, typically cities. Reducing consumer demand during peak usage periods also requires a smart grid that gives generators and consumers much more control over electricity supply and demand.

With sensible policies, the United States and the rest of the world could be generating 25 percent of their new energy supply with WWS sources in 10 to 15 years and almost 100 percent of new supply in 20 to 30 years. With extremely aggressive policies, all existing fossil-fuel capacity could be retired and replaced within 20 years.

A decade ago, it was not clear that a global WWS system would be technically or economically feasible. Now that we know it is, we hope global leaders can figure out how to make WWS power politically feasible as well.

They can start by committing to meaningful climate and renewable energy goals now.


Author Bios

Mark Z. Jacobson is a professor of civil and environmental engineering at Stanford University, where he is the director of the atmosphere/energy program. He develops computer models to study the effects of energy technologies and their emissions on climate and air pollution.

Mark A. Delucchi is a research scientist at the Institute of Transportation Studies at the University of California, Davis. He focuses on energy, environmental and economic analyses of advanced, sustainable transportation fuels, vehicles and systems.


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