Within this catalogue, fuels are divided into three groups (see Table 2).
Group 1 (LHC) is liquid at ambient condition. Group 2 and 3 fuels are converted into the more energy dense transport form either via pressurization, cooling or reaction with a carrier3 (latter only relevant for H2). The advantages and disadvantages for each of these packing methods are listed in Table 3 below.
2 Might be a combination of cooling and pressurization
3 See definition/description in 1.4.3 and Table 1-4
Group Description Include Transport form Transport options
Pipeline Truck/ 3 H2NG Require extreme cooling to liquify
(see H2 and NG) • H2
• Methane/NG Pressurized gas NG: P=60-80 bar, T=Amb
Table 18: Transport groups, which fuel belong to each group, possible transport form/phase and possible transport options
Liquid fuels (LHC)
All fuels and LOHC that are liquids at P=1.025 bar and T=50°C will be treated as one group called liquid fuels (LHC). This group includes:
1. All hydrocarbons with carbon number (CNO) larger and equal to 5 (gasoline, diesel, HFO, MGO, Jet fuels, etc.)
2. All alcohols (Methanol, Ethanol, Propanol, etc.)
3. All liquid organic hydrogen carriers (LOHC) (see examples in Table 1)
All these fuels are stored and transported in the same manner as conventional liquid-hydrocarbons.
Liquid at ≥ 20 bar (L20) - NH3, DME and LPG
This fuel group (L20) include fuels that are liquid at (P=20 bar, T=50°C) and vapor at (P=1.025 bar, T=50°C). All fuels within this group will all be transported and stored as liquids.
This group include NH3, DME an LPG. Pure ethane is also part of this group but will require a little higher pressure to liquify than the others.
The liquefaction will always be via pressure when transported in pipeline while either pressurization, cooling or both can be applied when transported via truck, rail and ships.
Pressurized Cooled Carrier3 (only H2)
Advantages
1. Low compression loss
2. Low transportation loss 1. High volumetric energy density compared
with compressed gas 1. Higher volumetric energy density compared with both CH2 and 2. LH2 Stored at ambient condition 3. Existing infrastructure can be
used
4. Neglectable transport and standby loss
5. Long term storage without loss 6. Safety – less flammable fluid
Disadvantages
1. Low volumetric energy density requiring many tours if transported with trucks/ships.
2. Cost intensive as high amount of steel is required due to the high pressure (thick tank walls)
1. Capital cost of installing refrigeration/cryogenic unit 2. High conversion loss
3. Normally high loss when transferring fluid from one vessel to another (all surfaces must be kept cold)
4. Boil off (or cooling or highly isolated) under transportation/standby
1. Capital cost of installing conversion unit 2. High conversion loss
3. Extra transport fuel as weight of carrier must be transported too (both forth and back)
Table 19: Advantages and disadvantages for different methods of converting group 2+3 into more energy dense transport form.
H2 and NG
Fuels that are gaseous at 20 bar can either be transported as compressed gas (will always be the case for pipe-transport), cryogenic liquid or via a carrier (the latter is only for H2). Hydrogen and natural gas require cryogenic cooling for liquefaction.
Pipe transport: As cooling is impractical, H2 and NG will always be transferred as compressed gas in transmission pipes.
Mobile transport: NG will normally be transported as a liquid. Hydrogen is today mostly transported as compressed gas but liquid transportation exist too. As hydrogen require extreme cooling, its optimal transportation (and storage) form is still under development. Figure 3 gives an overview of different ways hydrogen can be transported/storage.
Figure 4: Different H2 storage and transport technologies
For compressed underground and tank storage see ref. 7.
Transport of hydrogen via existing NG-grid: Today no H2
is allowed in the Danish NG-grid. Investigation have been made [ref. 16] and it is expected that 10%
hydrogen can be added with minor modifications and more (but still moderate) investment is required to allow up to 20% H2.
The disadvantages of admitting H2 to the existing net is that any users that need pure H2 (or pure CH44) need to separate H2 from CH4 which is expensive. Normally a PSA will be applied for such separation and here the natural gas will come out at low pressure and need to be re-pressurized.
Liquid hydrogen require liquefaction. The energy
loss under liquefication process is very high (see Cryogenic Liquefaction of H2) meaning that LH2 only is optimal for very long-distance transport.
Hydrogen carriers are substances that are able to bind several hydrogen atoms. As hydrogen is more expensive to store/transport than other fuels, extensive research has lately been carried out to investigate whether hydrogen carriers are optimal for storage and transportation of hydrogen.
Different types of hydrogen carriers are listed in Table 4 together with their advantages/disadvantages.
Table 20: Different type of hydrogen carriers
4 Most of todays gas-turbines cannot take larger amount of hydrogen.
Description Component
(examples) TRL Advantages Disadvantages
Adsorbent Solid that adsorb hydrogen on the surface or in the pores of complex materials via intermolecular
1 Materials can be reused many times
Stable materials
Immature technology
Ion
hydrides Compounds consisting of hydride ions (H+) and electropositive metals, typically an alkali or alkaline earth metal
LiH, NaH, KH, MgH 2 Flexible source of hydrogen Can be stored infinite under dry conditions
Must not be exposed to any moist before the dehydration, pyrophoric
Dehydrogenation is strongly exothermic =>
waste heat
Highly alkaline waste after hydrogen release Covalent
metal hydrides
The hydride is part of complex ions, where hydride is covalent bound to a metal atom
LiBH4, NaBH4, LiAlH4,
NH4BH4 2 More stable than ion hydrides Metallic
hydrides Hydride is nonstoichiometric bound/adsorbed/absorbed to precious metals and its alloys.
Hydrogen is released by heating
Precious metals (Pd,
Pt) 2 Knowledge available from the Ni-Hydrogen battery technology
High cost as currently made in small quantities and as require >95% purity
Liquid that relatively easy can be hydrogenated/dehydrogenated.
See Table 1 and ref. 7. 7 Transported and handled as
liquid fuel are handled today Many different technologies for releasing hydrogen
H2 righ
chemical Non carbon-based compounds that relatively easy can be hydrogenated/dehydrogenated.
Very high cracking temperature required NH3 is poison to PEM fuel cell, i.e. no NH3
traces after cracking
Figure 5: Separating H2 from NG using PSA ref. 19
Liquid organic hydrocarbons (LOHC) and hydrogen rich chemicals are all transported as liquids (thus covered by LHC in this catalogue). Adsorbent, ion hydrides and covalent metal hydrides are solids and need special transportation which is not included in this catalogue.