by EDA in the Azores on the islands of Graciosa and Flores. This system uses an 18 megawatt-second flywheel to improve power quality and thus allow increased renewable energy usage. As the description suggests, these systems are again designed to smooth out transient fluctuations in supply, and could never be used to cope with an outage exceeding a couple of days. Powercorp in Australia have been developing applications using wind turbines, flywheels and low load diesel (LLD) technology to maximize the wind input to small grids. A system installed in Coral Bay, Western Australia, uses wind turbines coupled with a flywheel based control system and LLDs. The flywheel technology enables the wind turbines to supply up to 95 percent of Coral Bay's energy supply at times, with a total annual wind penetration of 45 percent. Hydrogen Hydrogen is being developed as an electrical energy storage medium. Hydrogen is produced, then compressed or liquefied, cryogenically stored at −252.882 °C, and then converted back to electrical energy or heat. Hydrogen can be used as a fuel for portable (vehicles) or stationary energy generation. Compared to pumped water storage and batteries, hydrogen has the advantage that it is a high energy density fuel. 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. Hydrogen can be produced either by reforming natural gas with steam or by the electrolysis of water into hydrogen and oxygen (see hydrogen production). Reforming natural gas produces carbon dioxide as a by-product. High temperature electrolysis and high pressure electrolysis are two techniques by which the efficiency of hydrogen production may be able to be increased. Hydrogen is then converted back to electricity in an internal combustion engine, or a fuel cell. The AC-to-AC efficiency of hydrogen storage has been shown to be on the order of 20 to 45%, which imposes economic constraints. The price ratio between purchase and sale of electricity must be at least proportional to the efficiency in order for the system to be economic. Hydrogen fuel cells can respond quickly enough to correct rapid fluctuations in electricity demand or supply and regulate frequency. Whether hydrogen can use natural gas infrastructure depends on the network construction materials, standards in joints, and storage pressure. The equipment necessary for hydrogen energy storage includes an electrolysis plant, hydrogen compressors or liquifiers, and storage