(EnergyAsia, February 11 2010, Thursday) — US-based Asia Energy Management Systems Inc has offered to buy a 21.4% stake in Sri Lankan hydro power company Vallibel Power Erathna PLC for 800 million rupees. (US$1=170 rupees). Accuity Partners, the offer manager, said in a disclosure to the Colombo Stock Exchange that Asia Energy has an undertaking…