The crux of the global warming crisis is how to reduce energy-related carbon dioxide emissions while keeping the lights on. A new In-Depth Report by takes a look at future technologies that might help.

One option is to build wind farms off shore, where stronger breezes can generate more energy than sites on or near shore and turbines won't block residents' ocean views. Leasing the outer continental shelf to offshore wind farms could generate nearly 1,000 gigawatts — slightly more than the country's current electrical capacity, according to a piece by Emily Waltz.

Another possibility is geothermal power, electricity generated by the Earth's own heat. Iceland, where nearly 90 percent of homes are heated with geothermal power and residents would pay an estimated five times more if they used traditional fossil fuels, is at the leading edge of the technology, exporting its expertise to Nevada, Germany and China.

"Wave power" generated by turbines in the tide and energy converters out at sea both produce kinetic energy that creates electricity. It's expensive and still proving itself, Larry Greenemeier writes, but it's working, generating nearly 50,000 kilowatt-hours of energy over a six-month period in New York's East River.

Hydrogen is touted as the green fuel of the future, but what's it like to take drive a hydro-powered car? Steven Ashley takes a spin in one of these vehicles, which exist but aren't yet widely available.

Raising the capital for these techologies could become a significant issue in the midst of the U.S. credit freeze and falling fuel prices, today's New York Times notes. The decline in fuel prices may be a disincentive for people to invest in alt-energy companies; shares of some have already declined, according to the Times.

One fun, counterintuitive concept is the solar-powered fridge, which uses reflective panels or heat sources other than a compressor to turn refrigerant from vapor to liquid. (Read more about how solar power works here.) Whaddya know: The hotter the sun, the better the solar fridge works. The snag? "Most neighborhood associations won't allow these things on your roof," complains the CEO of one startup testing solar-powered iceboxes. We can't imagine why not.

(Image of Pelamis wave energy converter courtesy of Pelamis Wave Power Ltd.)