Shipping liquid air or LN2 via large tanker has the terrific advantage that pollution would not be a risk. However, shipping LN2 is just not economically feasible due to the low energy density of 570 kJ/kg. LNG has an energy density of 5.15x10^4 Btu/kg, or 5.43x10^4 kJ/kg, about 95 times that of LN2. LNG shipping by large tanker is only marginally economic even with that high energy density.
Shipping LNG or hydrogen in some form also has very little risk of pollution, though carries some risk of explosive accident. It remains to be seen how much risk carrying hydrogen by tanker has because the storage technology is not yet been developed. Carrying hydrogen energy by ship might be facilitated by converting it to methanol by combining it with atmospheric carbon dioxide. Methanol should not carry much long term pollution risk either, compared to oil. It appears that energy produced by windmill for consumption in a global market should be produced directly in the form of hydrogen. For this reason research on means to convert shaft horsepower directly into hydrogen production is a key research field. Regards, Horace Heffner
