SCEJ 85th Annual Meeting (2020) / IChES 2020

X202

Contribution of hydrogen-related technologies forrealizing decarbonized power systems
Matsuhashi R.*

1．Introduction
Due to the serious concern on the global warming,
decarbonization of energy systems are becoming themost significant requirement all over the world. While
many countries focus on the decarbonization in 2050,
Japanese government also submitted a target to United
Nations, in which our country attempts to realize thedecarbonized society in the latter half of this century.
In this document, feasibility of the decarbonizedpower systems is explored. In particular, contribution ofhydrogen-related technologies is discussed in order torealize the systems.

3．A case study to implement hydrogen-relatedtechnologies for a decarbonized society
In this section, the author explains results of a case study toimplement hydrogen-related technologies in the powersystem of Kyushu region. For detailed information on
developing the mathematical model, the readers areappreciated to refer to the article.3)
Evaluation results are shown in Figures 1, 2, 3, 4, 5 and 6.
Figure 1 shows the relationship between constraints on CO2emissions rate and variable costs of power generation. TheCO2 emission rate at 0% means that decarbonized powersystem is realized.
The variable costs change gradually when the constraints
are higher than 10%. When the constraints are lower than10%, the costs change steeply.
（ yen／ kWh）
Cost of power generation

2. Aspects to implement hydrogen-related
technologies for a decarbonized society
In a decarbonized society, hydrogen is expected to play asignificant role.1) However, we must take various aspects into
consideration to implement hydrogen-related technologies.
One of the important aspects is a large scale integration ofvariable renewable power sources. In Japan, solar power
generation has shown explosive growth mainly because of
the feed-in-tariff institution. Although this contributes todecarbonize power systems, operators of power systems
have to prepare large quantity of reserve capability, due toforecast errors in solar power generation. They are forced tooperate many partial load fossil-fired power stations, so thatthe efficiency and the cost of power systems become worse.
Thus the management of forecast errors in renewable powersources is significant to avoid the inefficient power system
operations. In this respect, hydrogen production managing
the forecast error deserves attention2).
Furthermore, increase of solar power generations
influences a transient stability of power systems, since they
do not have inertia, which synchronous generators have. Dueto a page limitation, the author would appreciate that readers
could refer to the details of the transient stability.3) In short, itis necessary to maintain a certain share of synchronousgenerators. In this context, hydrogen produced fromrenewable power sources through electrolysis could be used
for power generation by synchronous generators, which
contributes to maintain the transient stability. As such, wecould realize decarbonized power systems even fromvariable renewable power sources3). This system is described
more in details in section 3.
On the other hand, co-benefits of hydrogen production
should also be taken into consideration to improve
acceptability of the system. For instance, a co-benefit could

be realized in the energy consumption for aquaculture asfollows.
Most of energy demand for aquaculture such as shrimp
farms is consumed by aeration system which uses electricmotors to drive aerators for improving dissolved oxygen inponds.4) Therefore, we proposed an optimal design foradvanced aeration system in which electricity by renewable
power sources produce onsite pure oxygen throughelectrolysis to control dissolved oxygen level in shrimp
ponds. 4) The optimal results showed that life cycle cost andCO2 emission of the proposed system were lower than theconventional mechanical aeration system. 4)25232119171513119750.0%

20.0%

40.0%

60.0%

80.0%

CO2 emissions rate

Figure 1. Relationships between CO2 emissions rate andcosts of power generation

Optimal capacities of hydrogen storage also change
steeply, when the constraints are higher than 10% asshown in figures 2 and 3. In particular, the optimal
capacity becomes a huge value of 1.8 billion Nm3 in thecase of the decarbonized power system.

sum of the change in absolute values amounts to 8.2 times ofthe storage capacity. Therefore the burden of the capital
investment of hydrogen storage could be decreased by 4.1
times even in the decarbonized system.

（106Nm3）25
20
15
105(106Nm3)
1490

00.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

1480
1470

CO2 emissions rate

1460

（106Nm3）
2,000
1,800
1,600
1,400
1,200
1,000
800
600
400
200
0
0.0%

1450
1440
1430
1420

165

161

157

153

149

145

141

137

129
133

125

121

117

113

109

97

105

93

89

101

85

81

77

69
73

65

61

57

53

49

45

41

37

33

29

25

21

951

1410

13
17

Figure 2. Relationship between CO2 emissions rate andcapacities of hydrogen storage in the case that CO2 emission
rate is higher than 10%.

Figure 6. Change in storage of hydrogen in a week in
September in the case that CO2 emission rate is 0%.

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

Nevertheless, the cost of power generation becomes highaccording to Figure 2. Thus we need further breakthroughson storage technologies of hydrogen to realize economically
acceptable decarbonized systems.

CO2 emissions rate

Figure 3. Relationship between CO2 emissions rates andcapacities of hydrogen storage.
Figures 4 and 5 show annual changes in hydrogen storage
on the CO2 emissions rates at 10% and at 0%, respectively.
The figure 4 shows weekly changes of stored hydrogen,whereas the figure 5 shows seasonal changes of storedhydrogen. Namely, operation modes shift from weekly toseasonal changes to realize the decarbonized power system.

Figure 4. Annual change in storage of hydrogen in the casethat CO2 emission rate is 10%.

4．Conclusions
In this document, the author first explains the relationships
between the trends toward decarbonized societies andnecessity of hydrogen-related technologies. Then the casestudy was described to introduce hydrogen in a decarbonized
power system. Although hydrogen is expected to play asignificant role in the decarbonized systems, it is difficult toproject when and how to introduce hydrogen-relatedtechnologies. It is influenced by the speed to transition into
decarbonized systems, techno-economic progresses ofhydrogen-related technologies, and institutions on power andenergy systems. Therefore we must promote developmentsof the technologies and the systems taking all the above
factors into consideration.
References1) World Energy Congress，Gathering and inspiring tofacilitate a globally successful energy transition,
https://www.worldenergy.org/experiences-events/world-(106Nm3)

2000
1800
1600

energy-congress, 2019.10.28 accessRyuji Matsuhashi and Tsuyoshi Yoshioka, Optimal designof a coproduction system of electricity and hydrogen to
manage imbalances resulting from forecast errors inphotovoltaic outputs, E3S Web Conf. Volume 64, 2018,2018 3rd International Conference on Power andRenewable Energy, 27 November 2018
3) Ryuji Matsuhashi, Development of Model for Optimal
Operation of Power Systems with Large-Scale Integrationof Solar Power Generation in Kyushu Region, Journal ofClean Energy Technologies, Vol. 5, No. 6, November
2017, pp464-468
4) Nhut Tien Nguyen and Ryuji Matsuhashi, An Optimal
Design on Sustainable Energy Systems for Shrimp Farms,IEEE Access, vol. 7, pp. 165543-165558, 2019.
-------------------------------------------------------------------------------------------

2)

1400
1200
1000
800
600
400
200

1
173
345
517
689
861
1033
1205
1377
1549
1721
1893
2065
2237
2409
2581
2753
2925
3097
32693441
3613
3785
3957
4129
4301
4473
4645
4817
4989
5161
5333
5505
5677
5849
6021
6193
6365
6537
6709
6881
7053
7225
7397
7569
7741
7913
8085
8257
8429
8601

0

Figure 5. Annual change in storage of hydrogen in the casethat CO2 emission rate is 0%.
There is an argument that the capital investment ofhydrogen storage is prohibitively high in the decarbonizedsystem. This is because hydrogen storage must absorb
seasonal change in solar radiation, so that we could usehydrogen for the entire capacity only once in a year.
However, this argument is missing the significant aspect asfollows. The change in stored hydrogen in a week shows
ripples as shown in figure 6, meaning that the storage
quantity increase and decrease even in short periods. The*matu@enesys.t.u-tokyo.ac.jp