H2One integrates a photovoltaic power generation system with batteries for storing output power; a hydrogen-producing water electrolysis unit; solid state hydrogen storage—a MmNi₅ (Mischmetal-nickel) alloy); and a hydrogen fuel cell unit. (Mischmetal is an alloy of rare earth elements.)

MmNi₅ alloys belong to a class known as AB₅-type alloys. AB₅ alloys combine a hydride forming metal A, usually a rare earth metal (La, Ce, Nd, Pr, Y or Mischmetal), with a non-hydride forming element—nickel. The nickel can be doped with other metals such as Co, Sn or Al to improve materials stability or to adjust equilibrium hydrogen pressure and temperature required for its charging discharging with hydrogen.

One commercially available MmNi₅ alloy from Sigma-Aldrich offers hydrogen storage capacity of 1.5-1.6 wt.% @25 °C—not at all sufficient for on-board vehicle storage, but not a problem for a stationary system.

In the Resort Model version of H2One installed at Henn na Hotel, this configuration delivers a CO₂-free, environmentally friendly solution for hotels and other resort facilities.

Photovoltaic capacity: 62 kW; Fuel cell output: 54kW; Electricity storage capacity: 1.8 MWh; Hot water supply capacity: 24 liters maximum per minute. Click to enlarge.

Toshiba’s hydrogen EMS (Energy Management System) aligns a number of energy paths to ensure that intermittent power generation satisfies energy demand. The long hours of summer sunshine of Kyushu, the third largest and southernmost of Japan’s main islands, allow H2One’s photovoltaic energy system to generate enough renewable energy to meet all the requirements of the 12 rooms in the Henn na Hotel’s Phase 2, and additional power to electrolyze water and produce hydrogen.

The hydrogen is stored in the system’s integrated tank, ready for use on demand, and in winter powers fuel cells that generate electricity and warm water. The H2One’s capacity is sufficient enough to supply Henn na Hotel’s Phase 2 with electricity all year round.

The H2One installed at Henna Hotel deploys a hydrogen storage tank made with a new hydrogen storage alloy that achieves much improved high-density storage. The tank is less than one-tenth the size of the conventional model it replaces, and suitable for use even in small spaces.

(A hat-tip to David!)