Two recent studies lay out compelling scenarios under which virtually all of the world’s energy needs could be met with renewable energy sources by 2050. But despite their similar end goals, the energy futures foreseen in these two reports—published by the World Wildlife Fund (WWF) and a team of university scientists, respectively—are vastly different.

Wind turbine in South Africa

A wind turbine in South Africa. Will there be more of them in 2050?

WWF’s The Energy Report, published last week in collaboration with Ecofys, a Dutch think tank specializing in renewable energy, concludes that it is technologically and economically feasible for 95 percent of all energy to come from renewable sources by 2050. The authors argue that such a transformation would even be cheaper than relying on conventional, carbon-intense energy sources.

Meanwhile, Mark Z. Jacobson from Stanford University and Mark A. Delucchi from the University of California at Davis have written an ambitious two-part paper titled “Providing all global energy with wind, water, and solar power,” soon be published in Energy Policy. The study concludes that the electrification of all energy sectors can lead to a fully renewable energy supply by as early as 2030, or—if political and social obstacles are taken into account—by 2050.

These are only the latest in a long list of studies claiming that our future energy demand can be satisfied almost exclusively using renewable energy sources, such as wind, solar, or hydropower. Other examples include papers by the European Climate Foundation (ECF) and the European Renewable Energy Council (EREC) that present pathways toward a 100-percent renewable energy supply for Europe by 2050. And in January 2011, the Berlin-based German Advisory Council on the Environment (SRU) presented the German Federal Environment Minister with a detailed report on how to achieve a fully renewable electricity supply in Europe’s largest economy within four decades. A similar report was published by the German Federal Environment Agency (UBA) in July 2010.

The two latest studies agree that a sustainable renewable energy supply is not only economically feasible but also brings economic advantages in the long term. The WWF report, for instance, estimates that despite the huge investment needed to promote renewable energy, renewables will provide a positive cash flow after 2035, leading to 2 percent higher annual GDP growth in 2050. And Jacobson and Delucchi note that already, the private cost of onshore wind power can be lower than that of conventional fossil-fuel generation, and will continue to fall in the future. Moreover, the social cost of renewable energy is likely to be less than that of an energy supply that is based on fossil fuel.

But while both studies conclude that an (almost) fully renewable energy supply will be technologically and economically possible by 2050, their approaches, methodologies, and findings differ in significant ways. The proposed measures to achieve the 100-percent goal are not identical, nor do the studies share the same definition of (sustainable) renewable energy.

Jacobson and Delucchi do not consider biomass or biofuels to be sustainable energy sources because these renewable sources cannot reduce greenhouse gases and air-pollutant emissions to near zero. Therefore, their scenario is based on the electrification of the world’s energy supply by 2030/2050. This means that every vehicle, machine, and device would need to be electrified or running on electrolytic hydrogen. The electricity would be generated solely from wind, water, and sunlight (WWS), with 50 percent from wind turbines, 20 percent from solar photovoltaic (PV) roof systems and power plants, 20 percent from concentrated solar plants (CSP), 4 percent from hydroelectric plants, 4 percent from geothermal energy, and 2 percent from wave and tidal plants.

In WWF’s Energy Report, on the other hand, biomass and biofuels would become the most important piece of our future energy mix. The authors argue that most future energy demand will still have to be met by fuels, particularly in transportation and industry. In this scenario, the 2050 energy mix looks dramatically different: 40 percent biomass, 14 percent PV, 12 percent wind, 12 percent CSP, 6 percent geothermal, 6 percent hydro, 5 percent solar thermal (heating), and a marginal amount of wave and tidal. The report also concludes that we will not be able to replace all fossil fuels in the industry sector by 2050 and that 5 percent of the future energy supply would remain non-renewable.

This dramatic divergence in scenarios is the result of differing approaches to determining the potentials of renewable energy sources. WWF looked primarily at the availability of supportive policies, recent growth rates, and the technical efficiency potentials for renewables. Jacobson and Delucchi, meanwhile, focused on resource endowments and the availability of developable locations, and then calculated technical potentials of deployment. The two authors also incorporated an analysis of potential supply chain risks and assessed the generation costs of different renewables technologies. Wind power enjoys such a dominant position in their scenario because they project costs of $0.04 per kilowatt-hour or less by 2020.

The WWF report identifies investments and improvements in energy efficiency as a key solution to decrease future energy demand and to realize the 95-percent renewable energy supply goal. The study performs a systematic analysis of future energy demand and assumes that technological improvements will lead to roughly 50-percent efficiency gains in transportation and major industrial sectors. Moreover, the calculations build on large enhancements in demand-side energy efficiency.

Surprisingly, Jacobson and Delucchi do not focus on demand-side energy conservation and do not include extensive guidelines on how low-energy technologies could help achieve the 100-percent renewables goal. Rather, since the scenario aims for a full electrification of the energy supply, energy savings would be achieved automatically through the better efficiencies that electric heating/lightning/engines provide.

Both studies share the conviction that ambitious policy efforts are needed to achieve the identified targets. They each stress that immediate action as well as good long-term planning is necessary. However, while the WWF report does not specifically analyze the political obstacles that such a transformation may face, Jacobson and Delucchi conclude that “barriers to the plan are primarily social and political, not technological or economic.” Unfortunately for our planet and for our own future, these barriers are quite large. But reports like these—which lay out a vision of what could be—can only help.

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