How much sustainable electricity can we produce?

The recent Energy agreement is too much focused on the reduction of CO2 (very important indeed). It pays too little attention to the possible sources of energy, available in the future. In this post (in Dutch), I make a couple of calculations that indicate the toughness of the job producing sufficient electricity in 2050 to attain the 1,5%-target by deploying sun and wind energy only. I would be very happy if somebody would verify these calculations.