Imagine you’re hiking near a wilderness creek or you’re out on a canoe trip, and you’re desperate to charge your cell phone. You could have brought along a $20 solar panel, or this, a $159 water turbine that weighs more, …
Imagine you’re hiking near a wilderness creek or you’re out on a canoe trip, and you’re desperate to charge your cell phone. You could have brought along a $20 solar panel, or this, a $159 water turbine that weighs more, …