Solar energy: It's not just for rooftop panels and giant power plants anymore. Designers and researchers are coming up with unique ways to harness the sun's energy. Below, some of the more exciting ones unveiled in the last few weeks.

Sick of dealing with all the people that cram into subways and buses during the morning commute? So is Dave Owsen. The designer has come up with Community Transit, a mass transit system that features solar-powered pods traveling on overhead rail lines.

Wired explains:

Owsen is a fan of Personal Rail Transit systems, and was inspired by the people mover in Morgantown, West Virginia. "This idea was mainly devised to replace bus systems and operate within a city center," he said. "I think it is important to utilize high-speed rail for region-to-region travel, light rail for city-to-city and a system such as this for travel within the city." Best of all, on Community Transit, riders can yak on their phones, blast their iPods, and eschew deodorant without disturbing fellow passengers.

There are certainly a number of advantages to the system, but we can't picture it working in a major city center where thousands of people rely on public transportation at any given time. In a small city, though, the solar-powered pods just might work. Regardless of whether Owsen's design ever makes it into production, we're likely to see transportation pods sometime in the near future--GM recently unveiled its EN-V concept, an electric personal mobility pod that drives autonomously on the road.

Is flying more your speed? Enter the Solar Impulse, a Boeing 747-sized plane that features 12,000 solar cells on its wings. The plane recently finished its first test flight--a 1.5-hour trip above Switzerland. Will it revolutionize the world of flying? Probably not, but the Solar Impulse at least proves that we have alternatives to biofuels.

The sun can also, apparently, help clean our water. IBM is teaming up with Saudi researchers to use the sun's energy to desalinate water in the desert. Ultimately, the plan is to build a plant in Al Khafji, Saudi Arabia, that can generate 7.9 million gallons of water a day, or enough for 100,000 people. The plant will use photovoltaic arrays that concentrate the sun 1,500 times on a single solar cell--that's three times the solar concentration of most concentrating PV panels.

The hot sun can even be used to cool us down, as evidenced by Chromasun's solar air conditioner. The air conditioner turns heat into energy for cooling with a solar collector that concentrates light 25 times. Chromasun's solar collector can't cool an entire building by itself, but it can be used as a supplement during times of peak power usage--i.e. when it's 90 degrees outside. Don't expect to see this on local office buildings anytime soon, though. So far, Chromasun just has a pilot installation in Abu Dhabi.