For an alternative energy source to stand a chance at replacing fossil fuels, it has to be reliable, so that the consumer doesn’t experience interruptions in power. This is an issue with many proposed sources of alternative energy: wind and waves are not constant, and solar power only provides energy during the day. What is needed is a way to store the energy provided at high-flux times so that it can be released more evenly over time. One solution to this problem is the use of a supercapacitor to temporarily store and release energy.
A capacitor works by storing electrical energy, much like a battery. But whereas a battery stores energy through chemical reactions, a capacitor uses static electricity. Inside a capacitor are two metal plates separated by a non-conducting material, called a dielectric. When the capacitor is charged, positive charges build up on one metal plate and negative charges build up on the other, but the dielectric prevents them from coming into contact. This separation is what stores the charge. In nature, a thundercloud and the ground act as capacitors; a charge separation builds up (negative in the clouds, positive on the ground) until a flash of lightning discharges the stored electricity.
Capacitors can be charged and discharged many times without wearing out. This provides an advantage over regular batteries, which, after their chemical reaction has been used up, are tossed into the garbage. Capacitors are also light and don’t contain any harmful metals or chemicals. The problem is that they don’t hold as much charge as batteries, so to manage large amounts of electricity, we have to use supercapacitors.
The extra capacitance (the ability to hold electric charge) of a supercapacitor is due to an increase in the size of the plates and a decreased distance between them. The plates are again made of metal, but they are coated in a porous substance such as activated charcoal to give them a larger surface area. Additionally, there is no dielectric as in a capacitor; rather, there is a thin insulator separating the two plates, which allows opposite charges to build up on either side of the separator. Because of this double layer of charge, supercapacitors are also sometimes called electric double-layer capacitors.
Supercapacitors are capable of holding thousands or millions of times more charge than regular capacitors. Though this is still much less charge than a battery can hold, the advantage is that supercapacitors can store and release energy nearly instantaneously, and the cycle of charging and discharging can be repeated up to a million times. So while batteries store more energy compared to mass, supercapacitors can release stored energy more quickly.
The ability to temporarily store and quickly release large amounts of energy means that supercapacitors are useful in alternative energy applications. They are already being used with wind turbines, to smooth out intermittent wind power production. Unreliability is one of the biggest hurdles facing some readily available potential energy sources, but the use of supercapacitators could provide a solution, ensuring reliable alternative power to consumers.