PEM electrolysis

The new frontiers of hydrogen energy systems described in this paper will be PEM-electrolysis combined with renewable energy sources, biolysis with use of biological methods based on the genetics, and mechanolysis combined with any moving phenomenon and object, in hydrogen production area. 

Barbir F (2005) PEM electrolysis for production of hydrogen from renewable energy sources. Sol Energy 78 661-669... 

Hydrogen filling station Developed three H2 filling stations (PEM electrolysis, natural gas reforming and by-product hydrogen system). 

Figure 3.5. Process diagram of alkaline electrolysis for the production of H2 Polymer Electrolyte Membrane (PEM) Electrolysis...

Grigoriev SA, Porembsky VI, Fateev VN, (2006). Pure hydrogen production by PEM electrolysis for hydrogen energy. International Journal of Hydrogen Energy 31(2) 171— 175... 

The committee believes that PEM electrolysis is subject to the same basic cost reduction drivers as those for fuel cells. Cost breakthroughs in (1) catalyst formulation and loading, (2) bipolar plate/flow field, (3) membrane expense and durability, (4) volume manufacturing of subsystems and modules by third parties, (5) overall design simplifications, and (6) scale economies (within limits) all promise to lower... 

A second commercially available electrolyzer technology is the solid polymer electrolyte membrane (PEM). PEM electrolysis (PEME) is also referred to as solid polymer electrolyte (SPE) or polymer electrolyte membrane (also, PEM), but all represent a system that incorporates a solid proton-conducting membrane which is not electrically conductive. The membrane serves a dual purpose, as the gas separation device and ion (proton) conductor. High-purity deionized (DI) water is required in PEM-based electrolysis, and PEM electrolyzer manufacturer regularly recommend a minimum of 1 MQ-cm resistive water to extend stack life. 

In renewable-based energy systems PEM electrolysis seems to have an advantage over alkaline in that the thin membrane and ion transport mechanism can react to nearly instantaneously with the rapidly changing energy output of renewable sources, especially wind. Stacks involving the circulation of a liquid electrolyte have inherently more inertia in the transport of ions in solution than the PEM systems. 

Rasten, E., Hagen, G., and Tunold, R., Anode catalyst materials for PEM-electrolysis, in New Materials for Electrochemical Systems IV. Extended Abstracts of the Fourth International Symposium on New Materials for Electrochemical Systems, Montreal, Quebec, Canada, July 9-13, 2001, pp. 278-280. 

A feasibility study on hydrogen production by PEM electrolysis with off-peak electricity was conducted in Central Research Institute of Electric Power Industries (CRIEPI) to evaluate the effect of availability and electric power transmission. [10]... 

PEM electrolysis process has been proposed especially for wind turbines or solar photovoltaic (PV) panel utilizations. In this case, the electrolysis represents... 

Recently, PEM electrolysis moved to the fore again with the creation of a new company, Proton Energy Systems of Rocky Hill, Connecticut, to... 

Reduce the cost of proton exchange membrane (PEM) electrolysis to levels of 1250/kW for 10,000 standard cubic feet per day (scfd) at production levels of 10,000 units per year. 

Evolve the use of PEM electrolysis as an energy storage device to enable renewable energy technology as a sustainable source of electricity. 

The polymer electrolyte membrane (PEM) electrolysis operates at temperatures of 30-100 °C. The electrodes have platinum as a catalyst. A few industrial companies undertake strong efforts to develop this kind of electrolysis. To date, the efficiency of alkaline electrolysis has not been reached. It is expected that PEM electrolysis is suitable to build plants for small power units as well. 

For several decades, commercial alkaline electrolyzers have been available in a variety of series with outputs of up to approximately 750 Nm h hydrogen. Product development for PEM electrolysis only began around 25 years ago, and thus there are fewer commercial systems (<30 Nm h ) available compared to alkaline electrolysis. However, aU major manufacturers of PEM electrolyzers are currently developing and constructing 1 MW systems (see Table 11.4). High-temperature electrolysis is currently being pursued only sporadically by industry, which means that some demonstration systems exist, but no commercial products are yet available. 

As can be seen in Fig. 11.2 from the various partial reactions, in alkaline electrolysis the water is fed into the cathode side and COTiverted there, while in PEM electrolysis the process usually takes place on the anode side. In high-temperature electrolysis, the required water is fed into the cathode, but in the form of water vapor, as the operating temperature is approximately 700-1000 °C. 

Figure 11.4 shows a typical voltage curve for PEM electrolysis and its distribution into the different voltage losses for overpotential and ohmic losses. 

Fig. 11.4 Schematic of a current density/voltage curve for PEM electrolysis and distribution of the various voltage losses during operation...

One important technical evaluation criterion for electrolytic processes is the efficiency, i.e. the cost-benefit ratio for an industrial electrolysis system. When determining the efficiency, it is expedient to utilize the heating value (3.54 kWh Nm ) or the thermoneutral voltage Vth = 1.48 V because in commercial electrolysis systems for alkaline and PEM electrolysis, water is added in its liquid state. As such, the efficiency referring to the heating value of hydrogen specifies how efficiently the electrolyzer or the entire electrolysis system with all auxiliary components can be operated. 

In contrast to PEM electrolysis, which has only been utilized for around 25 years, alkaline electrolysis systems of various dimensions and types with outputs of up to 750 Nm h hydrogen have been available for some decades. For alkaline electrolysis, usually a potassium hydroxide solution with a concentration of 20-40 wt% is used. This is determined by the operating temperature, which is usually at 80 °C, since the ohmic losses can be minimized by a suitable concentration of the alkaline solution and thus optimal electrical conductivity [8]. The current density ranges from 0.2 to 0.4 A cm. The state of the art of large alkaline electrolyzers has not changed much over the last 40 years [9]. This becomes apparent in the fact that since the introduction of water electrolysis more than 100 years ago, only a few thousand systems have been produced and put into operation. Some of the systems listed in Table 11.3 are no longer produced, or their manufacturers have vanished from the market. 

To use water electrolysis to produce hydrogen through surplus renewable electricity, the partial load toleration for a highly variable power output is particularly important for safe operation. PEM electrolysis has an advantage here over alkaline electrolysis due to the use of polymer membranes and the associated higher gas purity According to the manufacturer, the partial load can be adjusted down to 0 % on cell and stack level (see Table 11.4), while in industrial facilities the lower limit is estimated to be at approximately 5 % of the nominal power due to the power consumption of the peripheral components. For alkaline electrolyzers, the lower partial load range is currently specified as 20-40 % [9]. 

Fig. 11.7 Typical ranges for current density/voltage curves for alkaline and PEM electrolysis...

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