Seasonal hydrogen system

In 1980 the idea of a seasonal hydrogen system in the form of methyl cydohexane was presented by Taube andTaube [232,233], In 1984, a 16-ton demonstration truck was powered by hydrogen produced on board the truck and directly coupled to the combustion engine [234], During 1985/86, an improved version with an on-board hydrogen production of approx. 3 (gH2) s which corresponds to a thermal power of 360 kW, was constructed and experimentally tested [235]. 

With respect to the electrolyser, preliminary analysis showed that the most suitable sizes were 12, 15 and 16 kW, which have a hydrogen production capacity of 2.4, 3 and 3.2 N m3/h respectively. It was also expected that the optimal sizes of the hydrogen storage tank were relatively small, namely 40, 50 and 60 kg of stored hydrogen, due to lack of seasonal hydrogen storage for the specific power system. Finally, the sizes of PEM fuel cell to be considered in the optimisation process were 2, 2.5 and 3 kW. 

Our studies showed that the biogeochemical system of the redox layer is subjected to temporal variability on a seasonal scale (connected with the seasonality of OM production) and interannual changes. Surface ventilation of dissolved oxygen down to the depth of the CIL (ag = 14.5 kg nr3) occurs in the winter from a combination of the NW shelf and the centers of the gyres. The intensity of ventilation is determined by climate forcing which may be determined by large-scale climate patterns like the NAO. This ventilation sets the upper boundary conditions for the downward transport of O2. Therefore, the position of the hydrogen sulfide boundary in the density field is connected with the climate variability, related to the NAO index. 

As derived from the analysis presented in this table, the most significant total annualised cost factor comes from the fuel cell, which accounts for 48% of the total cost of Fair Isle s wind-hydrogen autonomous power, followed by wind turbines, which contribute approximately 36% of total annualised costs. Due to lack of seasonal storage for hydrogen in this system, the electrolyser and hydrogen storage tank are relatively small and therefore are considered as minor cost factors for this system. 

As mentioned before, this system provides power to the mountain cabin only during April, May, July, August and September. Therefore, we can conclude that this is an autonomous power system with a good potential for seasonal storage of hydrogen (if this is necessary to cover power demand of the cabin) when a renewable energy source, namely a wind turbine, is incorporated. 

The only regulator used in this system is a line regulator rated for hydrogen. It is brass and thus has to be watched for corrosion. A better regulator would be nickel plated brass or stainless steel. Because this was an experimental unit destined only for seasonal work, this was not a particular issue with us. 

If hydrogen is ever to replace natural gas as a utility fuel, very large quantities obviously will have to be stored somewhere. Storage, to maintain a buffer for seasonal, daily, and hourly swings in demand, is essential with any system for the transmission of a gas. Storage facilities even out the ups and downs of demand, including temporary interruptions and breakdowns, and still permit steady, maximum-efficiency production. 

Gillham DJ and Dodge AD (1987) Chloroplast superoxide and hydrogen peroxide scavenging systems from pea leaves Seasonal variations. Plant Sci 50 105-109... 

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