Alkaline technology

In conclusion, it is now over 120 years since the alkaline electrolyzer emerged, and over 50 years since PEM and SO electrolyzers were developed. While exact data are hard to come by, almost all (99%) of the crurerrt market for electrolyzers is dominated by alkaline technology. However, in recent years, PEM electrolyzers have noticeably gained ground. As was slated in section 2.1, water electrolysis accormts for a very marginal proportion (less than 1%) of worldwide hydrogen production. 

Alkaline electrolysis is a mature technological solution, although technological developments continue, as we shall see. It is the technology used on the market today. In PEM electrolysis, there have been many developments which have been extrapolated from PEM fuel ceUs, and the technology has reached a level of maturity where it is cottunercially viable. Finally, HTE is still under development, as we shall show. 

In this section, we aim to give readers the essential technological knowledge about each different form of technology. However, this discussion is by no means 

0 ) Two 200Nra H alkaline electrolyzers each functioning at atmospheric pressing, from Norsk Hydro (photo taken fimm [KRU 02]) 

Nickel, as a substrate of the electrodes, is itself a catalyst, but it is very advantageous to coat it with electro-catalysts (metal aUq structured materials noble metals), winch greatly enhances the electrodes electrochemical activity. 

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The high performance of the alkaline cell relative to phosphoric acid and other cells leads to the plausibility of developing the technology for terrestrial application. The leading developer of alkaline technology for space application, UTC Fuel Cells, investigated adaptating the... 

The unusual economics for remote power applications (i.e., space, undersea, and military applications) result in the cell itself not being strongly constrained by cost. The consumer and industrial markets, however, require the development of low-cost components if the AFC is to successfully compete with alternative technologies. Much of the recent interest in AFCs for mobile and stationary terrestrial applications has addressed the development of low-cost cell components. In this regard, carbon-based porous electrodes play a prominent role (6). It remains to be demonstrated whether alkaline cells will prove commercially viable for the transportation sector. Reference (7) provides an in-depth view of the development history and the potential of alkaline technology for terrestrial application. 

H2/O2 alkaline technology using immobilized electrolytes is considered to be fully developed. Confidence in the present cell technology is best represented by the fact that there is no back-up electric power on the Space Shuttle Orbiter. Further improvement of the present H2/O2 design is not considered to be cost effective with one exception maintenance cost can be decreased directly by increasing the cell stack life of the Orbiter power plant. 

Three main water electrolyzer technologies can be distinguished alkaline technology, proton exchange membrane (PEM) technology and solid oxide (SO) technology. Note that these three technologies present numerous similarities respectively with the fuel cells (AFC, PEMFC and SOFC) discussed in... 

The effort in terms of development seems to be greater than that for alkaline technology. Besides seeking to drive down costs and achieve a longer lifetime, two other objectives in terms of performances are envisaged ... 

Table 2.4 hsts the characteristics of a number of commercial products with a more or less well estabhshed identity. At present, the commercial availability of PEM technology is nowhere near as advanced as that of alkaline technology, particularly in terms of very high capacities. 

The third case is a variant of the first. It remains fairly futuristic for PEM and alkaline technologies. It is possible for SO technology with high current densities. 

The common point between these applications is a need for very pure hydrogen, which PEM technology can serve more easily than can alkaline technology, although the ground truth is not quite as simple as this affirmation, particularly at an industrial level. The problem of the energy cost of electrolysis is of little importance in these applications it is essentially the cost of the initial investment, and also that of maintenance, possibly, which is important. 

The first electrolyzers to be deployed were alkaline. They were commercialized from the late 19 Century onwards. Today, alkaline technology is the ultra-dominant form of technology, accounting for 99% of the electrolyzer... 

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