July 2004

E-Mail This Article Printer-Friendly Version GHW’s new advanced 500 kW, 30 bar PME electrolyzer, shown here mounted in a standard container.

BEIJING/MUNICH - GHW, a Norwegian-German maker of advanced electrolyzers, has developed a new, more compact variant of advanced pressure alkaline electrolyzers that the company says is suitable for on-site hydrogen production at filling stations.

The company released details of the new device in a presentation by GHW’s general manager Rolf A. Brand at HYFORUM 2004 in May in Beijing (H&FCL June 04). In 1999, GHW had installed an earlier, more complex 450 kW version at Munich airport. Two other smaller, older electrolysers have been successfully operating in hydrogen fueling stations in Hamburg and Reykjavik for the last one and two years, respectively.

These previous versions were “just as complex, expensive and susceptible to failure” as those built by the competition, Brand told H&FCL by e-mail. GHW realized early on that the traditional technologies used in these early versions “would not have permitted us to get into the hydrogen energy market, which was our goal from the start,” he added.

“As far as we can see, our new PME (for Pressure Module Electrolyzer) will revolutionize the electrolyzer market because of its outstanding characteristics, performance and its lower price,” said Brand. Development of the PME is supported by the European Union with Euro 3.1 million - to Brand, clear proof of the project’s significance.

Load Following, Load Levelling

GHW stands for the German equivalent of High-Performance Electrolyzer Co. The company, based in Ottobrunn near Munich, is a joint venture of MTU, a DaimlerChrysler company; Norsk Hydro Electrolysers; and the German HEW utility.

Technically, the prototype 500 kW 3 MPa device is a pressurized alkaline bipolar filter press electrolyzer. GHW first developed a smaller 100 kW prototype nine years ago. One of the device’s attractions is its ability to adjust hydrogen output automatically in sync over the wide range of electrical loads typical for European grid systems - in effect, functioning also as a load leveler (H&FCL May 95).

Brand said the system’s basic concept allows the electrolyzer to work with rapid electric load variations within 10-120% of nominal load. Low cost is achieved by integrating all pressure-bearing functional components into one single 3 MPa (436 psi) pressure vessel, and pressure plus relatively small cell areas - 0.8 m2 for units of up 1 MW per single cell, and 2.3-2.5 m2 for units bigger than 1 MW - permit high current densities and result in a relatively small foot print: Brand says the footprint is only about 1/3rd or 1/4th of that of a conventional atmospheric electrolyzer.

This new PME concept minimizes or does away with a number of functional and control components, such as the gas separators for hydrogen and oxygen separation from the lye, the lye pump and the lye circulation system, valves and sensors, according to Brand’s paper.

The device has no lye pump at all. Lye circulation is achieved by the gas lifting effect of the product gases generated in the cell. At low loads, little gas is produced and lye circulation is low; at high loads, more gas is generated and lye circulation is high. Lye streams are separated into anolyte moving through the anodic cell half into the oxygen separator and the O2 lye reservoir, and the catholyte moves through the cathodic cell half into the hydrogen separator and the H2 lye reservoir, according to Brand’s description. The production power range per electrolyser unit is up to 700 Nm3 of hydrogen (3MW). The energy consumption for the system is low, according to the paper, about 4 kW/Nm3 of hydrogen. Current density is 8-10 kA/ m2.

According to Brand, this first 500 kW test unit will be scaled up to 2.5 MW in the next version. The target price is about Euro 400/kW. Contact: GHW, Rolf Brand, phone 0049/89/607 314 02; e-mail rolf.brand@mtu-online.com.