You’ve probably heard the term “thin film solar”—and registered that there’s a lot of excitement about this promising green technology. But you might also have wondered, "What exactly is thin film solar, and how’s it different from traditional the traditional solar panels I'm used to seeing on rooftops?" Wonder no more. Here’s your cheat sheet.

Thin film solar works basically the same way traditional panels do. Thin sheets of solar material absorb the sun’s rays and turn it into energy. Those solar-powered calculators you’ve been using for years? The panel you see on the front of it is made out of thin film.

The promise

The main difference between the rooftop panels you've seen forever and thin film is versatility. Traditional panels are big, heavy, and rigid. Thin film is thin, light, and flexible. That means it can be used in innumerable ways that traditional solar never could.

Thin film solar placed on the sides of buildings could multiply the amount of power a building could generate. Even on roofs, panels made out of thin film are significantly lighter than traditional panels, meaning homeowners and developers usually don’t have to shell out the extra bucks to reinforce the roof.

But thin film can be used in so many other ways as well. Thin film is what the panels are made out of on those solar-powered backpacks or portable chargers you've seen cropping up in the last few years. An Iowa-based company has also started building tents with thin film solar panels on them. The military is a primary customer. They can easily see how not having to lug generators and fuel could help their troops move faster and more efficiently. But the shelters can also be a boon to any group headed out on an expedition far from the grid.

An added benefit of thin film, say the eco-minded, is that at least one particular method of manufacturing thin film solar—which borrows techniques from printing to produce long rolls of solar material—is less chemical intensive than traditional panel manufacturing processes.

Thin film solar was just 8 percent of the solar market in 2006, but some are predicting that could grow to 20 percent in 2010. The head of the Prometheus Institute, a public policy organization researching sustainable technologies, predicted last year that thin film solar would be generating more than nine gigawatts of power in 2012, up from one gigawatt last year.

Solar as a whole is still not as cheap as fossil fuels. Sheets of thin film solar can’t necessarily be produced any less expensively than the panels of old. And manufacturers are still trying to figure out how to efficiently produce thin solar in mass quantities.

Theory is one thing. But money—specifically investments—are often the best guide to whether a technology is likely to take off. Two weeks ago, California-based Nanosolar, which has received over $500 million in funding, announced that had received over $4 billion in orders for its solar panels, including from companies that are building solar energy plants in the United States and abroad.

^{Photo credits: Top: Nanosolar; Laptop charger: Brunton; Field shelter: PowerFilm; Backpack: Volatic; Solar array: NREL}