The all-new Blue Freedom kit offers yet another alternative to solar panels, fuel cells, muscle-powered dynamos, wind turbines, AC-charged back-up batteries and other portable power solutions. "The world's smallest hydropower plant" transforms the power of running water into phone chatting, internet browsing, music listening, GPS navigating and other mobile device activities, and it does so from a package built to fit in a backpack.

We've covered other portable hydroelectric generator systems in the past, and some like the HydroBee were rather compact. Blue Freedom claims its kit is the smallest. It's close to 2 oz (57 g) lighter than the HydroBee and looks considerably more compact. The relatively lightweight, slim Blue Freedom package can be carried in a backpack.

Developed in Germany, the Blue Freedom charging kit consists of a 4.7-in (12-cm-) -diameter micro turbine, a 5W generator and a 5,000 mAh lithium-polymer internal battery. The turbine takes a plunge into a running water body and the unit's base stays ashore, letting you charge devices directly by way of the USB 2A and 1A ports. You can also store energy in the integrated battery for later use. A built-in LED light helps you see at night.

Blue Freedom tells us that the micro turbine doesn't need to be situated in a specific way in relation to the direction of current, and is instead designed to flow with the water and deliver efficient charging. The kit is designed to operate in temperatures between 41 and 104 F (5 and 40 C) and altitudes up to 16,400 feet (5,000 m).

The idea of a small, packable hydropower system is certainly interesting, and the Blue Freedom appears to be a slickly designed package, but it left us asking: Why? It seems like solar panels are more versatile and easier to set up, allowing you to charge your device on the move as well as in place. Sunlight also tends to be a more readily-available commodity than running water when traveling off the grid.

According to the governments of US and Canada, two world leaders in hydropower production, hydropower is the most efficient means of generating electricity, transforming up to 90 percent of available water energy into usable electricity. Compare that to around 15 percent for solar panels, and you can start to see why a portable hydropower charger could prove quite superior.

Now we have no expectations that a micro turbine bobbing around in a ripple is going to be anywhere near as efficient as a full-sized hydropower plant, but Blue Freedom's estimates do look promising. The company tells us that the hydropower kit should charge its internal 5,000 mAh battery in three to four hours, assuming a water flow rate of 1.2 m/sec (2.7 mph). An iPhone 6 would take about one to two hours at that same water rate.

The Blue Freedom's times are much better than portable solar kits we've covered. For example, the Powertraveller Solarmonkey Adventurer takes 8 to 10 hours to charge its 2,500-mAh lithium-polymer battery. The Solar Joos Orange has received high marks for device-charging speeds from publications like Wired, but its internal 5,400 mAh battery takes 12 hours to charge via solar. So the simple answer to our question of "why" is "because you can power up the internal battery in a few hours, rather than over the course of half a day."

Blue Freedom's charging times are only a manufacturer estimates based on a prototype, so they're not worth getting too excited over yet. Still, assuming the Blue Freedom is well designed, it should be able to offer quicker, more efficient off-grid charging than other portable options.

Depending upon the nature of the trip, the Blue Freedom may or may not be more convenient than other types of chargers. It'd be a good solution for camping (near a suitable stretch of creek or river), in which you're staying in one place for an extended period and would be able to charge at night, when there's no sunshine to harvest. On the other hand, it wouldn't be very useful for trips through the city, desert or any stretch of land not adjacent to a flowing water body, which breaks down to a lot of stretches of land. The base station does include a microUSB port for charging the internal battery, so you could use other forms of energy, including solar panels, in the event that you can't find running water. That will of course add to its 0.9-lb (400-g) pack weight and 7.9 x 2.2-in (20 x 5.5-cm) size.

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Blue Freedom: A mini hydropower plant for charging mobile devices