But more than anything we valued elegant solutions to persistent problems.

Consider: today, solar energy accounts for less than 1 percent of energy used in the United States. The main reason is cost. To convert sunlight to electricity, we can use efficient but expensive photovoltaic cells made from crystals of the same silicon used in computer chips, or we can use solar cells made from films of semiconducting materials that are cheaper but less efficient; but we don’t know how to make cells that are efficient and cheap. Now, by harnessing plasmons–a type of wave that moves through the electrons at the surface of a metal when they are excited by light–we might do both (see “Light-Trapping Photovoltaics”). Researchers at the University of New South Wales and other universities discovered that by depositing nanomaterials on the surfaces of thin-film photovoltaic cells, they could exploit plasmons so that photons “bounced back and forth within the cell, allowing longer wavelengths to be absorbed.” That’s a cool idea: it neatly transcends the limitations of current technologies.

Finally, this year’s 10 technologies, beyond displaying the editors’ tastes for novelty, difficulty, and elegance of conception, are a testament to our optimism. They expand human possibility by supplanting established ways of doing things. For decades, almost everyone who wanted to replace fuels made from hydrocarbons worried about which biomass to use, even though it wasn’t clear how we would grow the biomass or efficiently turn its sugars into fuel. They simply asked: corn, switchgrass, or algae? In “Solar Fuel”, we describe an effort to engineer photosynthetic microörganisms that use sunlight to convert carbon dioxide directly into ethanol or diesel. That is the kind of thing we like: it has the blithe confidence of magic.

But write and tell me what you think at jason.pontin@technologyreview.com.