A roundup of green headlines that caught our eye this week:

• Environmentally-friendly shopping garnered attention at the Web 2.0 Summit in San Francisco this week, with start-ups pitching their companies to the venture capital crowd. The New York Times' Bits blog reports that an Internet start-up named GoodGuide rates more than 60,000 products on environmental, health and social impacts. The company's founder created the site when he learned his daughter's sunscreen contained carcinogenic chemicals. Bits also reports on a solar panel installation company and a video broadcast start-up.
• Green Wombat visited California start-up Cool Earth Solar for a Fortune Magazine story on a novel solar power technology to generate electricity from balloons. A single balloon of thin-film reflective plastic with a photovoltaic cell will generate one kilowatt of power. Put together 10,000 balloons and you can light up a town. Cool Earth is building a prototype plant and says a 1.5-megawatt plant will be built next year near Tracy, Calif.
• The U.S. military is marching ahead on the green energy front. My NEXT100 colleague Jonathan Marshall recently posted on the U.S. Army's energy efficiency and sustainable energy projects. Now Earth2Tech notes that the U.S. Navy has awarded a $3 million contract to Ocean Power Technologies to test the company's PowerBuoy system to generate electricity from ocean waves to power oceanic data and communication systems.

The long struggle to extend federal tax credits for the renewable energy industry resembled a season of The Perils of Pauline: By one count it took nine votes in Congress before the long-awaited investment and production credits finally passed last week as part of the $700 billion financial rescue package.

The solar industry won an eight-year extension of a 30 percent credit for residential and commercial solar power installations. One industry-sponsored study predicts that this credit will create more than 400,000 new jobs in the solar power industry.

The bill also extends production tax credits to the biomass, geothermal and marine (wave and tidal) energy industries for two years, and to the wind power industry for one year.

By spurring the development of renewable energy, the credits promise a win for the environment, a win for the increasingly depressed U. S. economy, a win for emerging industries, and a win for PG&E and other utilities that have contracted with renewable power companies to provide cleaner energy for their customers.

Since the start of 2007, PG&E has contracted for more than 2,600 megawatts of new renewable power. Many of those projects are still under development and count on tax credits as a condition of financing and development. Failure to renew the credits could have put them, and hundreds like them around the country, in jeopardy.

PG&E worked hard to help Congress understand the need to act, in partnership with organizations such as Alliance to Save Energy, Business Council for Sustainable Energy, Clean Energy Now, Edison Electric Institute, and Solar Energy Industry Association. PG&E chief executive Peter Darbee stressed the critical need for tax incentives in an address to the 2008 United Nations Investor Summit on Climate Risk and in a lead opinion column in the San Francisco Chronicle, among other places.

Extension of the tax credits removes the single biggest hurdle to the development of renewable power, but not the only one. As the California Public Utilities Commission (and many other parties) have noted, continuing challenges include the cost and delay in building transmission to serve new renewable power plants, developer inexperience, financing uncertainty, and site control and permitting.

A roundup of green headlines that caught our eye this week.

• A $10,000 premium for the GM plug-in Chevy Volt's lithium-ion batteries probably means a long wait for affordable electric cars.
• Wanted: Wildlife Biologists. Solar energy developers are snapping up biologists to survey power plant sites in California (including a PG&E project) and the desert Southwest for protected species and to prepare habitat-protection plans.
• A rival for Cow-Power? Food giant Kraft has found a way to turn whey, a cheese byproduct, into biomethane gas to power dairy plants. Will this frighten Little Miss Muffet?
• While Google eyes wave-powered floating data centers on the high seas, San Francisco-based International Data Center plans to dock retrofitted data center ships at piers and take electricity from nearby utilities, reducing operating costs.

I recently read on Peak Energy that Google is rumored to be exploring computing at sea, using wave power. I always thought water and electricity were a bad mix, but Google sees a match made in data center heaven.

According to Big Gav, Google engineers calculate that an array of pontoons, with pumps to convert wave motion into electricity, spread over a square kilometer could produce 30 megawatts of electricity, enough to operate a single floating data center. To give you a sense, 1 megawatt of electricity powers roughly 750 homes for a year -- that is a lot of energy. I wonder what effects this could have on the temperature of the ocean if we shipped all our data centers out to sea?

Also envisioned is equipment to use the direct current electricity to run DC-capable computers, which some people consider more energy-efficient than using alternating current. Now that could be something land lubbers could get behind as well.

I thought you might want to see ZDNet's Green Enterprise show on some of our renewable  energy innovations. ZDNet correspondent Sumi Das talks with Hal La Flash, PG&E's director of clean-energy technology, and discusses the utility's green programs and goals.

ZDNet highlights a wall-mounted solar power system at the San Francisco service center, a new hybrid-electric bucket truck, and emerging renewable energy from biogas to wave power.

Check out the video below.

Washington state utility Tacoma Power has put its Tacoma Narrows pilot tidal power project on hold after a study found that tidal generation won't pencil out economically for at least 8 to 10 years. The utility on Feb. 28 said it will consider other resources such as wind, geothermal and biomass power to meet renewable energy targets.

Tacoma Power said a follow-up study to an earlier tidal study of the Narrows waterway by the Electric Power Research Institute found that the amount of energy that could be generated was less than EPRI estimated and that tapping the tides requires advancements in turbine technology.

"Tidal power technology is where wind technology was decades ago," said Tacoma Power Superintendent Gary Armfield. "Right now, it wouldn't be a sound nvestment at this site for Tacoma Power and its customers," Armfield said.

"We're not closing the door on this technology," said Tacoma Public Utilities Director Bill Gaines. "But we do recognize that its potential is longer-term. Right now we need to focus on short-term solutions to meet renewable energy requirements," he said in a press release.

Utilities, including PG&E, are eyeing tidal and wave energy to generate electricity and some have pilot programs in early stages.PG&E has entered into a long-term, two megawatt  commercial wave energy power purchasing agreement with Canada's Finavera Renewables Inc. Located off the Northern California coast, the Humboldt County Offshore Wave Energy Power Plant will be developed by Finavera Renewables. The project is expected to begin delivering renewable, clean electricity in 2012.