H2Tech - Q3 2021 - 34

HYDROGEN STORAGE
ral gases. All materials used must be effectively impermeable
to H2
make gas tight connections in piping and joints, and possible
microbial activity requires mitigation. Consequently, the limitations
of H2
to deployment of H2 as a utility-scale fuel.4
A variety of methods are available for storing H2;5
storage technologies have been an impediment
however,
the primary storage technologies in commercial use are liquefaction,
compressed gas in aboveground tanks, and salt cavern
storage. For vehicle refueling and light industrial applications,
multiple tube tanks (3-15 tanks of 0.5 m or 3.3 ft in diameter
× 6 m-12 m or 19.7 ft-39 ft in length), or spherical tanks are
manifolded together to provide storage. Typical maximum
pressure is 200 bar (2,900 psi). Some commercially available
tube tanks are encased in steel-wire-wound, composite sleeves
to increase the operating pressure to 275 bar-690 bar (3,988
psi-10,000 psi). At an operating pressure of 275 bar (3,988
psi), an 8.8-m (26-ft) tank can store (+/-) 34 kg of H2
. However,
for HES to support the ramping requirements of wind
and solar power generation, load shifting at a utility scale requires
tens to hundreds of MWs.6 TABLE 1 shows the storage
requirement for various-sized gas turbines, which is substantially
greater than the capacity of aboveground, compressed
gas tank capacities.
Liquefaction storage is a technically viable solution and
a comparatively mature technology that still has opportunities
for cost reduction.5
For a liquefaction H2
storage system,
40%-50% of the CAPEX is the liquefaction plant and 50%-
60% is the cost of the tank(s). The OPEX includes the energy
costs of liquefying the H2
and managing the H2
that warms
and boils off (0.1 vol% or less per day), which then needs to
be reliquefied or used in operations. Worldwide, installed H2
20
40
60
80
100
1
3
5
7
9
11
13
Hour of day
FIG. 2. Average location marginal price (LMP) by hour of day.
1.7
10
20
30
40
50
60
70
80
90
100
Hour ending
FIG. 3. Weekly locational marginal power price by hour.
34 Q3 2021 | H2-Tech.com
138.4
185.4
232.4
0.2
1.8
20.8
32
44.4
91.4
1
8
8
8
8
8
8
8
8
8
375
375
375
375
375
375
375
375
375
375
695
695
5,040
68,640
105,600
146,487
301,587
456,687
611,787
766,887
15
17
19
21
23
at operating conditions, materials must be resistant to
H2 embrittlement and corrosion, greater care must be taken to
liquefaction capacity is (+/-) 355,000 kg, but approximately
10% of that capacity is a single, 34-metric-tpd liquefaction facility
operated by NASA. The NASA facility also contains the
world's two largest cryogenic H2
tanks with a capacity of 3,218
m3
each (+/- 225,260 kg).7
As shown in TABLE 1, the combined volume of both tanks is
sufficient to support a 44 MW-138 MW peaking turbine. Arguably,
the cost of liquefied storage can come down, and facilities
can be scaled up, as it has happened with liquefied natural gas
(LNG), but the cost and complexity of liquefaction and storage
is likely to remain substantially greater than geologic storage.
Other near-surface underground compressed gas storage
solutions may be viable for H2
abandoned mines and buried pipe,8
, such as mined rock caverns,
but they have significant
size limitations, substantial technical risks and high construction
costs.
Although H2
fundamentals of how to store utility-scale volumes of H2
differs in many respects from natural gas, the
parallel
natural gas. The costs of underground storage of gas in a salt
cavern, excluding compression facility costs, are approximately
1/25th the cost of cryogenic (liquid) tanks and about 1/10th
the cost of compressed gas for storage of 400,000 sft3
m3) and larger. Consequently, geologic storage of H2
(11,326
is presently,
and is likely to be in the future, the most economic method
for storing H2
at a utility scale.
and supporting dispatchable generation capacity
The need for dispatchable energy. The intermittency
of wind generation and the daylight limitation of photovoltaic
(PV) solar generation require energy storage to mitigate
weather-driven fluctuations in wind and solar resources, time
shift excess power generation output to resource-constrained
low- to no-sunlight hours, and mitigate extreme weather
events (cold and warm) resulting from stagnant air masses,
where demand peaks and renewable generation are curtailed.
Daily time-shifting. An hourly bar graph of the annual av6-8
hr
erage locational marginal price (LMP) for electric power ($/
MWhr) at a California independent system operator (CAISO)
price node outside of San Francisco, California is shown
TABLE 1. Storage requirement and technology by generator size
Storage with
Net output,
MW
0.08
Duration,
hr
1
Fuel rate,
kg/MWhr
375
Type
10% reserve, H2
34
kg
of storage
Single
tube tank
15-pack
12-m
tubetank
Subsurface
containment
storage
Salt
cavern
$/MWhr
1
5
9
13
17
21
25
29
33
37
41
45
49
53
57
61
65
69
73
77
81
85
89
93
97
101
105
109
113
117
125
121
129
133
137
141
145
149
153
157
161
165
$/MWhr
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