H2Tech - Q3 2021 - 36

HYDROGEN STORAGE
the annual mean peak price. Evening peaks can last longer
than 7 hr, and the daily price " trough " shortens from 6 hr-8
hr to 2 hr-4 hr. HES would allow " charging " in anticipation of
a weather event (0-115 hr), which would provide the ability
to shave more efficiently the 2 hr-3 hr needle peaks over the
following 250 hr on an hourly dispatch basis, vs. the battery
duty-cycle of 4 hr-6 hr.
In the same winter event, the absence of longer-duration,
dispatchable generation exacerbated price volatility (FIG. 7).
The extended evening peak, greater than 4 hr, results in a
greater dispatch of reserve battery storage resources. Due to
the battery duty cycle, demand falls suddenly and prices collapse
around midnight (hours 24, 48, 72, 120 and 144) until
1,000
1,200
200
400
600
800
730 1,460 2,190 2,920 3,650 4,380 5,110 5,840 6,570 7,300 8,030 8,760
Hour of year
FIG. 5. Seasonality of major price spikes (> $100/MWhr) and duration
in 2019.
50
100
150
200
250
300
Month hour
FIG. 6. Locational marginal power prices for February 2019 winter
events.
200
250
300
50
100
150
24
48
72
FIG. 7. February 2019 first winter event.
36 Q3 2021 | H2-Tech.com
96
Hour starting
Hour of month
FIG. 8. Eight-day summer event, 2020.
120
144
168
Multi-day event
< 8 hr
the reserve battery sources fully discharge. The exhaustion
of battery resources coincident with the lack of PV solar generation
in the early morning results in a morning peak price
that can exceed the evening peak. This is the only time of year
when the morning peak price is of similar magnitude to the
evening peak price.
Summer events. Price behavior during an 8-d summer heat
event in 2020 is shown in FIG. 8. Note the log scale on the price
axis. Large price peaks (> $750/MWhr) are the result of shorter
daily troughs and fewer cheap hours for charging storage,
due to air conditioning adding to load starting in late morning
and overnight price peaks (> $100 MWhr) with 6 hr-9 hr of
duration. Prices of > $500 MWhr generally occur later in the
evening and last for 1 hr-3 hr. As in the winter scenario, HES
can build H2
fuel inventory in anticipation of the weather event
and then selectively discharge to shave the needle peaks.
Seasonal charging, dispatch and capacity. As in the natural
gas markets, the electrical power markets benefit from having
a mix of storage alternatives, particularly those that are
dispatchable and can retain energy efficiently over long time
periods. The natural gas markets benefit from a combination
of fast response, low-volume line pack, large seasonally cycled
aquifer storage, multi-cycle depleted reservoir, high-cyclability
salt cavern storage and liquefaction peakshaving. The authors
view batteries as being analogous to line pack. Pumped
hydraulic storage is analogous to aquifer storage in that it is
expensive, has a long lead time to construct and has unique siting
challenges, but also has a low variable cost once in service.
HES can fill the role of multi-cycle storage that, unlike
Annual mean peak
other commercially available energy storage technologies, can
time-shift energy weekend-to-weekday, month-to-month and
seasonally. TABLE 2 describes a two-cycle, seasonal operation
plan for varying size of generators. It assumes that outside
summer and winter peak months, the facility is charging constantly.
During the peak seasons, it discharges at a rate of 4
hr/d-4.5 hr/d. The base project " charges " with a 20.8-MWe
electrolysis facility that can produce 415 kg/hr of H2
with a
ramp time of less than 5 min, with water consumption of 90.8
l/min (24 gal/min). On discharge, a gas-fired, simple-cycle
turbine fueled with 100% H2
speed, the unit can fire on 85% H2
1,000
is assumed. To improve ramping
and 15% methane during
100
Summer mean peak price
10
1
Real-time LMP, $/MWhr
Real-time LMP, $/MWhr
1
20
39
58
77
96
115
134
153
172
191
210
229
248
267
286
305
324
343
362
381
400
419
438
476
457
495
514
533
552
571
590
609
628
647
666
$/MWhr
$/MWhr
1
23
45
67
89
111
133
155
177
199
221
243
265
287
309
331
353
375
397
419
441
463
485
507
551
529
573
595
617
639
661
683
705
727
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