Debt of coal-based power plants may nearly treble in three years to Rs 5 lakh crore if the issue of stranded electricity generation units is not addressed urgently, NITI Aayog chief executive officer Amitabh Kant said on Wednesday. Inaugurating the 20th India power forum here, Kant said the industry must find ways to put in use 40 gigawatt (GW) of stranded thermal power units and soon replace 92 GW of pollution-generating sources such as petcoke and diesel.