This morning, whether you woke up in a warm house in New York, took the train to work in Washington DC, or started your tractor to plant corn in Iowa, you impacted the world by the energy you used.

Currently, fossil fuels (coal, gas, and other petroleum products) supply about 90% of the energy used worldwide, but global warming, diminishing supply, and a dependence on erratic imported sources demonstrate that relying on fossil fuels is not a sustainable choice.

US energy policy now mandates that 40% of US fuel will be "renewable" by 2022. Renewable energy includes biofuels, geothermal, solar, wind, ocean current, and hydroelectric, but right now, they account for about 5% of the US energy supply. Finding sustainable energy systems to warm our houses, help us travel, grow our food, and make breakfast in the morning without causing social or environmental damage is perhaps the most exciting and critical challenge we face today.