Technical and economic assessment of methods for the storage of large quantities of hydrogen

Abstract The storage of large quantities of hydrogen is analysed on the basis of five conceptual scenarios. These scenarios are representative of possible practical situations. They involve storage above ground as a cryogenic liquid as well as high-pressure storage both above and below ground. The latter includes natural and specially created cavities. No comparison is made between these various methods since in practice one would rarely be free to make a choice among various alternatives. Each scenario is defined and then costed in detail. The incremental cost of storage is calculated and the sensitivity determined for variations of throughput, capital cost and electricity cost. Also included in the data are the costs of electrolytic hydrogen and of hydrogen liquefaction. The cost of storage can add between 30 and 300% to the cost of hydrogen so that large offsetting benefits have to exist in order to give economic viability. There is a considerable interplay between the magnitude of the capital charges and the system throughput or utilization. In the case of the electrolyser alone, non-continuous operation results in a considerable increase in the unit hydrogen costs. For storage systems where the unit capital charges are high then the operating costs are very sensitive to changes in both throughput and capital costs. A hidden capital charge occurs in some cases of underground storage where a large inventory of cushion gas is inaccessible to the user, but is necessary to define the minimum size of the reservoir. The results clearly show the need to consider many factors in order to optimize a storage system. In practice, this has to be done for each specific situation and general consideration can be very misleading.