Historical introduction to capacitor technology

At present, the important capacitor technologies are impregnated foil-polymer film (for high voltage, high current), metalized film, ceramic, electrolytic, and electric double layer, although metalized paper is still used occasionally in "soggy foil" designs, i.e., self-clearing, fluid-impregnated, high-voltage capacitors. Each of these major technologies faces challenges as they compete with each other for market share.