Why: Lithium-ion batteries make electric cars possible at mass-market prices.
Key innovation: Nanostructured electrodes result in lithium batteries more durable and safer than those in cell phones and laptops.
Why: Advanced biofuels could help reduce the use of gasoline and diesel.
Key innovation: Its genetically engineered yeast turns sugars into a building block of diesel fuel, which is usable in the existing transportation infrastructure.
Why: It efficiently produces solar thermal power, which focuses sunlight to heat water into steam.
Key innovation: A boiler is heated directly with sunlight that bounces off mirrors.
Why: Reducing the cost of constructing solar thermal plants will make them more competitive with fossil-fuel plants.
Key innovation: Software controls the mirrors that focus rays from the sun, eliminating the need to position them by hand.
Why: New types of photovoltaics are reducing the cost of solar power.
Key innovation: "Thin-film" solar panels based on cadmium telluride, which are cheaper than conventional silicon panels, have made the company one of the world's largest photovoltaic manufacturers.
Why: Increasing the time that turbines are operational will lower the cost of wind power.
Key innovation: Co-developed a direct-drive wind turbine that eliminates the need for a gear-box. Having fewer moving parts reduces the chance of costly mechanical failure.
Why: Biofuels could be far cheaper if they weren't made from corn, sugarcane, and other forms of biomass.
Key innovation: Designed microbes that convert carbon dioxide and water directly into fuels.
Why: Improving the electric grid is crucial to making alternative energy sources less expensive.
Key innovation: Developed wind turbines and other technologies for different aspects of the electric grid, from generation to transmission to distribution.
Why: Computer intelligence in the electric grid will make energy distribution more efficient.
Key innovation: Developed hardware and software that standardize the way disparate parts of the grid communicate.
Why: Extremely large-scale production of solar panels is reducing the technology's cost.
Key innovation: Developed its own solar cells and equipment for manufacturing them cheaply.
Why: Genetically engineered microbes are a promising way to make biofuels.
Key innovation: Created synthetic bacterial cells, possibly paving the way for organisms specifically tailored to make fuels.
Why: Conventional solar power is still too expensive to compete with fossil fuels, in part because of the cost of manufacturing silicon-based solar cells.
Key innovation: Developed a cheaper method for making silicon wafers, the most expensive component of a solar module.