As a key advisor to the president, the next U.S. secretary of energy will play a key role in shaping policies that could encourage more renewable-energy production and research.

But who should have the job?

Even before the election ended, speculation had begun about who had made the list of candidates that Barack Obama will consider when selecting the next head of the Department of Energy, which has an annual budget of roughly $23 billion and 100,000 employees and contractors.

The energy secretary will be busy providing his or her thoughts on weighty issues that the new president has promised to tackle, including fixing the country's aging electric grid, creating a program to trade carbon-emissions credits and advancing research in a wide range of renewable and conventional sources of energy.

Here's our list of just a few of the possible choices for the next U.S. energy czar:

Dan Reicher

As the director of climate change and energy initiatives at Google.org, Reicher has set the investment agenda for the popular search giant. He campaigned for Obama and has the advantage of experience in the behemoth energy department: He was the assistant secretary for energy efficiency and renewable energy from 1997 to 2001. He also has served as president of New Energy Capital, a renewable-energy investment firm in Hanover, N.H, and previously held positions as an attorney for the Natural Resources Defense Council and as the assistant attorney general of Massachusetts.

Nancy Floyd

As the founder and managing director of Nth Power, a venture capital firm long focused on greentech, Floyd has a deep background in the technology sector, and particularly in energy. At the Democratic National Convention in August, she delivered a speech backing Obama and promoting U.S. renewable-energy investments. She's on the board of the American Council on Renewable Energy and serves as an advisor to the National Renewable Energy Lab, run by the energy department. She founded NFC Energy Corp., a wind-energy development business, in 1982 and sold it in a deal that generated a 25-times return on the investment.

Arnold Schwarzenegger

California's leader may be Republican, but he has positioned himself as a Green Governator by supporting regulations that promote renewable energy and other greentech sectors. He signed the Global Warming Act of 2006, otherwise known as AB32, which puts the state on a path to establishing new or stricter rules and programs to reduce greenhouse-gas emissions. Sure, his vision of a "hydrogen highway" hasn't materialized, but his hope to have "solar everywhere" in California could. In fact, Schwarzenegger seems to be everywhere these days when it comes to announcing or dedicating solar-energy projects (see here, here and here). Hiring him to head the energy department would help Obama to fulfill his pledge to create a bi-partisan environment in his government.

Al Gore

OK, so it's a long shot that Gore would want to return to government. He has won a Nobel Prize and the freedom to champion his own clean-energy agenda, not anyone else's. But he remains a good candidate for the job, not the least because he is a renewable-energy advocate with an ample governing experience. He has played a key role in injecting climate change into the national consciousness. Obama could use Gore's advice and fame to chart new policies and carry them out.

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Tags: cleantech, floyd, gore, nthpower, obama, reicher, schwarzenegger