Pioneer Valley Renewables and Leviathan Energy have a patented flow technology for in-water turbines that double the efficiency and halve the starting speed of what is on the market. For a sailboat owner, that means less drag for the electricity produced, and the ability to recharge batteries more easily while at anchor.
The shroud/blade technology was developed by Pioneer Valley Renewables and Leviathan Energy and validated by the US Navy. Mostly intended for utility size underwater turbines, the US Navy also gave the company a grant to develop a smaller, portable solution, which is the inspiration for its availability for the boating industry.
The turbines are available in 10 and 30 centimeter diameter versions.