In this paper we argue that supercapacitors are the best choice for energy storage in an intelligent wireless sensor system. Furthermore we present recent research on carbon allotropes used as electrode. To compare these materials we introduce a theoretical model to estimate the maximum surface area and maximum capacitance obtainable for carbon electrodes. The purpose of the model is to elucidate what material features are crucial for obtaining a higher energy density in electrochemical double layer capacitors which will particularly benefit energy storage in wireless intelligent sensor systems since a supercapacitor will deliver a higher energy density over time and will have a longer lifespan than a battery. The result of the comparison is that composite materials especially nitrogen-doped graphene nanosheets show great promise with their high capacitance compared to other carbon allotropes.