In this paper the results of the performance tests of an ortho-para analyzer for hydrogen are presented. The measurement is based on the easy and reliable gauging of the adiabatic heat of conversion between the hydrogen allotropes. A hydrogen gas flow is brought to a defined temperature first by the means of a liquid nitrogen bath at 77 K. Subsequently it is led through a catalyst bed inside an adiabatic cell. The ortho-para ratio can be derived from a precise temperature measurement before and after the catalytic induced conversion. Vice versa, with a known para content of the hydrogen feed, the activity of a given catalyst sample can be determined. The discussion of the results of the performance tests includes a chapter for the essential proper preparation of the necessary ortho-para catalyst material and the use of a suitable database for the thermodynamic properties of orthohydrogen and parahydrogen. A slight drawback of this method is the relative large amount of hydrogen gas required compared to other ortho-para concentration measurements.

This paper elaborates a concept for designing efficient large scale hydrogen liquefaction plants, based on dividing the process into 4 independent stages and finding the optimum solution for each stage. The main focus is put on the precooling stage. Not because of its power consumption, but because it is the stage with the most degrees of freedom in design. Several processes have been discussed, mentioning some of the main advantages and disadvantages. One of the main challenges in efficient hydrogen liquefaction is light gas compression. This is unavoidable, since only light gases can provide cooling at the required temperature levels, but should be minimized by using heavier fluids where possible. Due to the higher exergy efficiency of compression compared to refrigeration, the hydrogen feed pressure should be as high as possible, as long as the pressure reduction in the liquefaction stage is performed by expansion machines instead of throttling.

The goal of the IDEALHY project is to identify processes and components, which allow liquefying hydrogen with a power consumption much lower than with plants built so far. This requires comparing different possible processes concerning power efficiency, investment cost and compactness. The power consumption of a process depends on a number of boundary conditions. Without a clear overall definition of these boundary conditions, all statements and comparisons on the overall power consumption are questionable. So in the first step of the project the participants agreed on common boundary conditions.Then it turned out, that the choice of the high pressure of the feed hydrogen influences strongly the rest of the liquefaction process, especially the region below 80 K. For this region there is an option between helium, hydrogen and neon as refrigerants and their mixtures. For the final choice of the working fluid and the process one has to identify the maximum possible circumferential speed of turbo compressors.

In a prospective hydrogen economy it is necessary to verify the para concentration of the employed hydrogen. In case of a short storage time of about a few days only it has been shown that a partial conversion into para-hydrogen gives an optimized overall efficiency. Hence, an easy and reliable method of measuring the para-hydrogen concentration is needed. In this paper, the concept and construction of a small test cryostat are described and first results are presented. The measuring principle is based on a catalytic induced adiabatic ortho-para conversion of a hydrogen gas flow starting from a known temperature. The operation of the system only requires a certain amount of liquid nitrogen as coolant. To determine the concentration of para-hydrogen it is only necessary to measure the temperature of the gas before and after the adiabatic catalyst cell. The measuring cryostat is used for further investigation of the spontaneous para-ortho conversion in the supercritical state. In addition, the design of the cryostat allows the investigation of different catalyst materials regarding the catalytic activity and possible degradation by using a known para concentration for the measurement.