Do you know that some animals can produce electricity? There are many varieties of catfish and eels that can give out low voltage electric currents from their bodies. Contrary to what some people believe, the currents that they produce are too weak to kill a person, but they help the fish to survive in the sea.
Electricity-producing fishes usually have poorly developed eyesight. They cannot see well and so need this extraordinary ability as a form of protection and as a means of getting food for themselves. Whenever the fish's electric field is distorted by the presence of a foreign object, the fish is immediately alerted. It then produces electricity as a reaction. If the foreign object happens to be a potential predator, it gives the fish sufficient time to make its escape while the enemy is temporarily immobilized by the shock. If it is a smaller fish, its next meal is assured.
Perhaps one day, we can learn to tap the energy of such fishes and rear a tankful of them to light our homes!