Saildrone is a company that provides Unmanned Surface Vessels, powered primarily by wind and solar. The Coast Guard has already been experimenting with some of the these to provide Maritime Domain Awareness.
Naval News reports on their presence at Sea Air Space 2021, including a new, much larger, 72 foot long class of saildrones.
Meanwhile the US Naval Institute News Service reports these “Uncrewed” surface vessels might be used for ASW, towing passive sensors.
Chuck Hill's CG Blog 
Saildrone survives Category 4 Hurricane. https://gcaptain.com/drone-sails-into-hurricane-sam-and-lives-to-tell-the-tale-heres-video-to-prove-it/
Pingback: “Autonomous vessels can help the Coast Guard safeguard our waters” –Work Boat | Chuck Hill's CG Blog
Apparently, the Navy is testing these as well. https://www.defensenews.com/news/your-navy/2021/12/13/the-navy-is-testing-this-adorable-sailboat-drone/