Blue Freedom, a tiny 7.9 x 2.2-in portable hydropower kit that is lightweight, can fit in a small backpack. The kit contains a 4.7 inch diameter micro turbine, a 5W generator and 5,000 mAh lithium-polymer internal battery. The turbine is dipped into a running water source while the base unit stays on the shore. You can charge devices directly from the base unit via USB ports or let the internal battery store the energy for later use. The company estimates that an iPhone would get 10 hours’ worth of charge with the turbine spending just one hour in the water. A smartphone would fully charge in 2 to 3 hours while the internal battery can fully charge in just 3 to 4 hours at a water flow rate of 1.2 m/sec (2.7 mph). The kit could be a nice addition to a solar backpack if you’re worried about overcast weather or know you’ll have access to a water source at some point during your trip. It would be reassuring to have more than one option if you’re taking a long off-grid trip.