A £10bn Severn barrage is among options for future energy provision recommended by the Welsh Assembly Government.
The barrage would stretch 10 miles across the Bristol Channel
The UK Government is conducting an energy review looking at how the UK can meet its future energy needs.
As well as the barrage, the assembly government submission calls for a range of solutions including clean energy and renewable technologies.
The assembly government said a barrage tapping the River Severn's tidal energy was an "exceptional opportunity".
The 10 mile-long barrage would run from Lavernock Point, near Cardiff, to Brean Down, near Weston-super-Mare.
According to the assembly government, the scheme could provide as much energy as two nuclear power stations for 150 years.
Mr Davies said: "The barrage would be equivalent to around two nuclear power stations operating continuously, lasting not 40 to 50 years with a problematic legacy but operating for 150 years plus.
"Throughout its life the barrage would produce zero-carbon electricity on a totally predictable, low-cost and reliable basis."
The assembly government submission added that the Severn Barrage should be accompanied by development of new technologies to extract energy from underground coal reserves and the use of other low-emission energy sources.
Tidal barrages have operated in France for decades
He said: "There is no doubt that clean coal and gas fired fuel power stations will play a major role in Welsh electricity production for the next 20 years and more.
"Wales (is) about to play an important UK gas supply role through the £2bn liquid natural gas developments under way at Milford Haven.
"Also attractive are other new technologies for extracting energy from underground coal reserves, which, combined with carbon capture and storage, could create a major Wales and UK low carbon energy source."