Their website https://rotaheat.co.uk/ explains:

As water drives the hydropower system, it turns a magnetic coupling within the Rotaheater, generating heat through a process similar to the way an induction hob works.  The Rotaheater then transfers this heat to water, or another fluid, which circulates through your heating system, providing a steady, clean source of warmth without relying on traditional fossil fuel or electricity supplies.

His email to me last week says :

Rotaheat created a web page targeted at micro-hydro site owners which I thought you might find of interest:  https://rotaheat.co.uk/small-hydro-big-heat-lower-costs/

Rotaheat has started a project with the objective of simplifying the installation of hydro-thermal solutions for micro-hydro sites.  We are currently working to validate our hypothesis for what the market would value.  I would appreciate if you would consider asking your members to spend a few minutes and respond to a short ‘product needs’ questionnaire?  The survey is accessible at:  https://forms.office.com/e/c6Er9Cb7Yr

Robert Thompson  ( 07768 002058

Although Hampshire Mills Group does not promote or endorse particular products I thought it would be of interest to members either for their own use or for passing to others who might be interested.  I leave it to you to explore further.