We are all familiar with batteries powering our everyday devices from phones to computers to electric vehicles. While this technology works well it has the disadvantage of being reliant on chemicals that can be caustic and can take a long time to recharge. The competing technology of supercapacitors and ultracapacitors however do not need dangerous chemicals and can recharge very quickly, but at a price. Capacitors also discharge very quickly and are not as able to maintain a constant output as a battery. Researchers at the University of West Florida, as reported by the American Institute of Physics' Journal of Renewable and Sustainable Energy (paper), however have designed a new kind of ultracapacitor that can produce a constant output voltage.
All capacitors store energy in the electric fields of two charged plates that are separated by an insulator. Ultracapacitors improve upon this by coating the plates with activate carbon, a porous material, which increases the surface area and amount of charge the plates can store. They also use an electrolyte as the insulator because the ions within the electrolyte will collect at the plates, effectively creating a second layer of charge storage.
What the researchers have done is add a system to remove the capacitor plates from the electrolytic fluid as it discharges. This affects the charge on the plates and resistance between them, which together control the output voltage. With precise control of the motion, the output voltage can be regulated like this. Next the researchers want to improve this design for other ultracapacitors and make it possible to operate at any angle.