A task of terawatts

The ultimate answer to humanity's energy problems rises every morning and sets every evening. The Sun shines down on the Earth with a power of 174,000 TW, providing the amount of energy every hour that humankind uses every year. It lifts water from the surface of the sea to fall back down on the high mountains of the land, drives ocean currents from the tropics to the poles, spins winds from pole to pole and powers the green engine of life.

Unfortunately, humanity is now, like Hamlet, too much in the Sun. After having been reduced to waste heat, solar energy no longer leaves the planet as easily as it once did. Instead it tarries in the atmosphere, thanks to the ever stronger greenhouse effect. The best way to deal with this change is a threefold strategy: drive up the efficiency with which energy is used through better technology, wider appreciation of the issues and targeted regulation; drive up the price of emitting carbon disproportionately through trading schemes, taxes and further regulations; and drive down the costs of generating energy in ways that involve no use of fossil fuels, most notably from the unending flows of light, wind, water and plant growth that the Sun so generously provides.

The tendency among governments and traditional utilities to see renewable energy sources as oddities or add-ons is thus deeply misplaced. These sources are, alongside nuclear power, the fossil fuel-free future that is so urgently needed. None is without its problems, and the renewables tend to suffer from the drawback that flows driven by the Sun are generally diffuse, not concentrated, and sporadic. Yet there is a great opportunity for technological progress in many of these fields, most notably in solar power and in energy storage.

The great challenge is how to scale these new technologies up for a global market. A significant part of the answer is investment in focused research and development. However, there is also a role for regulation and subsidy. The types of subsidy that have worked to date are expensive even at the megawatt scale. At the scale of tens and then hundreds of gigawatts they are likely to be unsustainable. Perhaps worse is the risk that poorly designed subsidies will damage markets and thwart the development they seek to encourage. However, this is reason to encourage technologies in a smart and flexible way, not to leave the markets alone. The challenge is not how to save the world most efficiently, just how to save the world.

We are pleased to acknowledge the financial support of TOTAL S.A. in producing this reprint collection. As always Nature Publishing Group carries sole responsibility for all editorial content and peer review.

Oliver Morton, Chief News & Features Editor, Nature