High pressure electrolysis

If only operated during low off-peak rate times would have low ann load factor need more expensive H2 storage Assume high pressure electrolysis cell with drastically lower capital cost of mass production cost higher efficiency Assumed oxygen recovery for by-product sales with large central plant case, but only minor economic impact... 

Enthalpy is an intrinsic property of a substance and a function of temperature and pressure.19 In practice the Gibbs free energy is the net internal energy available to do work, less work done by changes in pressure and temperature.20 Exergy, on the other hand, is defined as the total amount of work that can be harnessed and becomes more relevant in high-temperature and high-pressure electrolysis. 

As previously mentioned, high pressure electrolysis is effective in activation of CO2 reduction at Pt electrode. Hara et al. reported that CO2 can be reduced in aqueous 0.1-M KHCO3 under 30 atm mainly to HCOO and CO with the faradaic efficiency of 50.4% and 6.1% respectively at the current density 163 mA cm . ... 

In an advanced plant concept for the low-power range, PHOEBUS 2, high-pressure electrolysis is employed to avoid the compression step. Other new components are an air-driven PEM fuel cell and optionally metal hydride as an alternative storage concept. The goal is a simplification of the whole system. 

If hydrogen should be produced at higher pressures, we have two options (i) high-pressure electrolysis and pumping of water or (ii) atmospheric electrolysis and H2 is compressed to the desired pressure by a compressor [see Onda et al. (2004) and Laoun (2007)]. 

Table 6.19.8 indicates that the energy required for high-pressure electrolysis including water pumping is lower than the energy required for atmospheric electrolysis and H2 compression, since the compression energy for water is much less... 

What fraction of compression work would be saved by using high-pressure electrolysis at 20 MPa followed by regular compression to fill a compressed hydrogen tank to 70 MPa, compared to only compression from 0.1 MPa ... 

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