It shouldn't come as a surprise that Silicon Valley and the rest of the Bay area is the nation's No. 1 spot for clean- energy jobs. But did you know that Houston, where oil runs deep, and the Rust Belt region of the Midwest are making huge strides in green energy and alternative fuels?

A new report by Clean Edge Inc., a research firm devoted to clean energy, notes that green jobs are represented in dynamic industry sectors, such as electric vehicles, energy storage, advanced lighting, building materials and the energy grid.

Silicon Valley continues to lead in the U.S. as Cisco, Google, Intel and others get on the bandwagon. Los Angeles is second, with Boston, New York and Denver rounding out the top five.

Houston, which ranked 15th last year, is now eighth, courtesy of biofuels and wind energy. Plus, Houston's city government is the nation's top municipal buyer of green power. San Diego also has made strides from 11th to seventh, thanks to biofuels.

Worldwide, clean-energy jobs exceed 3 million, according to sources cited in the study, and that number is likely to grow as other countries ramp up their green presence. China, South Korea, Japan and other nations are the heavy hitters in clean jobs.

Those countries "are hiring thousands of factory workers to crank out solar panels, lithium-ion batteries, and a wide-range of wind turbine components. At the same time, traditional European clean-tech leaders like Germany and Denmark continue to expand...," the report said.

The United States, thanks to a significant infusion from President Obama's stimulus package, is advancing as well.

In Colorado, Abound Solar is retrofitting a closed automotive transmission factory near Kokomo, Ind., into a photovoltaic plant thanks to a state, county and federal incentives. Nine advanced electric-vehicle battery plants have opened in the United States, with much of the $2.4 billion boost in that sector headed to Michigan.

But political and economic considerations could slow U.S. progress. The report says that feed-in tariffs, which offer stable payment to power generators through long-term purchase agreements, could significantly boost clean energy initiatives in this country.

Those programs are popular in Germany, Canada and Britain, but haven't caught on big in the U.S. (Sacramento Metropolitan Utility District recently created one). The report also warns of clean-tech jobs potentially moving south of the border to Mexico, and suggests that more efforts in this nation should be directed to the low-hanging fruit of energy efficiency.

"Eager supporters of clean energy, however, sometimes overlook the easy efficiency fixes and instead channel enthusiasm - and dollars - toward the generation of renewable energy.

The report ends with five initiatives that its authors should be put into place: