Windhan is a scam. One of its key members Mr Matiss Paegle is a participant of proven scam AsicVault / Asicfuel: https://bitcointalksearch.org/topic/asicvault-scam-participants-5186716
Also, their website https://windhanenergy.io is dead since summer.
Windhan Ltd-d was created at the same time AsicVault scheme finally collapsed - autumn 2018, and at the same place and by the same persons https://www.teatmik.ee/en/personlegal/14611233-Windhan-O%C3%9C
And there are many other similarities btw Windhan scam and Asicvault scam in general and even in details. As we are collecting data on the person who is behind AsicVault scam (Hando Eilsen) so expect more on Windham also coming up soon.