such as backup grid power. Supercapacitor Supercapacitors, also called electric double-layer capacitors (EDLC) or ultracapacitors, are a family of electrochemical capacitors that do not have conventional solid dielectrics. Capacitance is determined by two storage principles, double-layer capacitance and pseudocapacitance. Supercapacitors bridge the gap between conventional capacitors and rechargeable batteries. They store the most energy per unit volume or mass (energy density) among capacitors. They support up to 10,000 farads/1.2 Volt, up to 10,000 times that of electrolytic capacitors, but deliver or accept less than half as much power per unit time (power density). While supercapacitors have specific energy and energy densities that are approximately 10% of batteries, their power density is generally 10 to 100 times greater. This results in much shorter charge/discharge cycles. Also, they tolerate many more charge-discharge cycles than batteries. Supercapacitors have many applications, including: Low supply current for memory backup in static random-access memory (SRAM) Power for cars, buses, trains, cranes and elevators, including energy recovery from braking, short-term energy storage and burst-mode power delivery Chemical Power to gas Power to gas is the conversion of electricity to a gaseous fuel such as hydrogen or methane. The three commercial methods use electricity to reduce water into hydrogen and oxygen by means of electrolysis. In the first method, hydrogen is injected into the natural gas grid or is used for transportation. The second method is to combine the hydrogen with carbon dioxide to produce methane using a methanation reaction such as the Sabatier reaction, or biological methanation, resulting in an extra energy conversion loss of 8%. The methane may then be fed into the natural gas grid. The third method uses the output gas of a wood gas generator or a biogas plant, after the biogas upgrader is mixed with the hydrogen from the electrolyzer, to upgrade the quality of the biogas. Hydrogen The element hydrogen can be a form of stored energy. Hydrogen can produce electricity via a hydrogen fuel cell. Green hydrogen, from electrolysis of water, is a more economical means of long-term renewable energy storage in terms of capital expenditures than pumped-storage hydroelectricity or batteries. At penetrations below 20% of the grid demand, renewables do not severely change the economics; but beyond about 20% of the total demand, external storage becomes important. If these sources are used to make ionic hydrogen, they can be freely expanded. A 5-year community-based pilot program using wind turbines