Electrolysis efficiency

The electrolysis efficiency must be 100 per cent, i.e. the charge passed must be consumed only in the studied electrode reaction. There are four possible sources of error ... 

For the operating voltage at the optimum power point Vp and the Faradaic current for water splitting of /p, the overall solar to hydrogen generation PV electrolysis efficiency is given by... 

In the case of the hydrogen path, it is assumed that surplus wind electricity is used to produce hydrogen via electrolysis (efficiency 70%). Hydrogen is then stored in pressure tanks at 50 bar and is re-electrified at peak load in gas turbines (GT, efficiency 40%) or gas-steam turbines (GST, efficiency 60%), with a hydrogen-to-natural-gas ratio of 8 2. 

A proper estimation of the electrolysis efficiency provides guidance to the improvement of the processes and the electrolyser design. In this study, the current efficiency, r c, of the electrolysis system was determined from the experimentally produced amount of hydrogen, H2(exp), divided by the theoretical value, H2(theor) calculated from the Faraday s law ... 

Experimental data on photo or solar electrolysis efficiencies are contained in Table 4. Other compilations are available.313 76 In most of the instances, the attained laboratory efficiencies are well below the ideal limit (c.f., Table 3) although some of the numbers claimed (see entries 1, 9, 14, 15, for example, in Table 4) are indeed impressive. However, some of the values claimed have been questioned by others.214 Further independent verification is undoubtedly warranted, and the losses associated with process scale up are, as yet, unknown. 

The efficiency of electrolysis takes a strong dip when the Ir02 content drops and the catalyst approaches pure Pt, in accordance with earlier experience. However, already at 10% Ir content, the electrolysis efficiency is near 95%, rising only a little with further addition of Ir. At 10% Ir, the drop in the fuel cell efficiency for electricity production has been reduced only from 55 to 53%, so the technology for acceptable operation in both modes seems finally to be established. This will prove important for some of the hydrogen introduction scenarios described in Chapter 5. 

Finally, for the hydrogen fuel cell car, the solar radiation to wind conversion-efficiency is taken as 100% (following arguments of Sorensen, 1996c), the wind turbine efficiency as 35%, the electrolysis efficiency as 80%, the fuel cell conversion efficiency as 55% and the rest as for methanol. The overall accumulated efficiencies are 1.4 x 10 for the methanol route and 0.054 for the wind-hydrogen route. 

In hydrogen production, HYSOLAR achieved an overall electrolysis efficiency of about 69 percent, according to a paper presented at the 1996 World Hydrogen Energy Conference. 

Surface processing and annealing of the Pd-Ag membrane before use could allow for increased permeability in our operative environment. In order to check the electrolysis efficiency, flow rates of non-permeated and permeated hydrogen streams were investigated during a long electrolysis... 

Electrolysis efficiency is always lower than 100% and for this reason the true yield is higher than the theoretical yield. However, because the pattern is linear, the real value can be extrapolated correctly by multiplying Equation [16.23] for a constant value of 1.07. 

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