Perhaps others have developed the concept of using a sail on land to generate electrical power, I don’t know. Yet because the thought occurred to me I write a note about it here in order to let others research or develop that concept.
Fundamentally one can catch a lot more wind with a large square sail than with the much smaller surfaces of propeller-like blades. People have let wind provide the mechanical moving energy directly for centuries instead of using an indirect means to directly convert a large area of a sail to mechanical and eventually via an alternator- electric power.
The larger the the more force would be exerted upon it in a wind. There would be two masts on a turntable connected at the corners to a tensioned line and various reduction gears that would turn an alternator via the extreme force on the tensioned connector cables.
The tensioned cables could be spring-loaded, or they might compress in-line elements connected to reduction gears, or they could be fashioned in numerous configurations such as around pulleys and with compressible springs etc.
A strong point about land sails for generating electric power would be the low cost of sails as well as low maintenance and installation costs. probably someone thought of tying sails into mechanical systems before, yet I don’t want to fail to note the concept anyway.