LH2 CRYOGENIC STORAGE
MULTI PURPOSE - The same service station that provides freshly charged hydrogen batteries, doubles up as an energy store for the national grid of the country concerned, without silos. Why put in load levelling stations that only have one function? We hoped this would be a topic of discussion at UN COP 26 in Glasgow, Scotland in November 2021. But it never got that far, where coal was the main negotiating point, and Australia, China, India and Russia refused to agree phasing out.
Producing hydrogen as a gas is one thing. Storing it for mobile applications is another.
Cryogenics is one way of increasing the energy density of hydrogen, with the drawback that the minus freezing temperatures makes handling the fluid more complicated, than dealing with compressed gas at ambient temperatures.
THE HYDROGEN COLOUR SPECTRUM
Hydrogen is an invisible colourless gas. But we use a spectrum of colours to describe how hydrogen is produced, or naturally formed. In essence, the spectrum is used to express how dirty or clean a method of producing the gas is. The chart is only a guide, because each method is subject to variations that can render a process cleaner or dirtier, depending on the efficiency of the application. It is literally, 50 shades of grey for the dirtier conversions.
In addition to producing the gas, the level of compression for storage, or liquefaction, uses more energy, as will converting the gas to ammonia, etc. All these factors have to be taken into consideration depending on the end use. For example, cars will more than likely use highly compressed gas in type IV cylinders, where trucks might benefit from LH2. Each method increases the potential carbon footprint. Ships are likely to use liquid hydrogen, but low pressure gas cylinders (that do not yet exist) would be a more efficient use for transport, where marine cryogenic cylinders are heavy and expensive, and there are as yet no IMO rules, the recommendations for gas vessels being far more onerous than for train and truck tankers.
Houses and factories could use piped gas. Then again, properly designed homes can generate their own solar electricity and heat, or be retro-fitted. That is not the case with industry in most applications. Storage is the main problem for industrial use, heralding a return to gas silos, or large cryogenic cylinders that are expensive and boil off at the rate of 1% a day. Hence, are not economically viable.
Food for thought!
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