It doesn't depend that much on the orange which is just the electrolyte. It actually depends on the electrodes. Look up a good source of electrochemistry and you can build a orange (or any citric fruit) powered cell with two coins or two different metallic electrodes. But one cell has very little power, so yes, you need a truckload to hold enough energy.What's the energy density of an orange? Pretty low, I'm guessing. Probably take a semi-truck load or more to equal a Volt battery.