Energy systems are influenced by the need to reduce greenhouse gas (GHG) emission, natural disasters, innovative new technologies, legal systems, and the national population. The recent changing situation of energy systems in the world is universal in many countries in a certain context, for instance, the need for the GHG emission reduction. Japan, however, is facing much more difficulties at the supply side, which is caused by natural disasters such as earthquakes, especially in the electric power systems.
Energy systems are the most important infrastructure among various kinds of infrastructures that support the whole of Japanese society. We need a common and long-term policy for energy and electric power systems, because it takes a long time to develop technologies to improve various components and systems architecture of energy and electric power systems.
Therefore, Japanese government has published a long-term perspective of energy demand and supply for 2030 [1] on July 16, 2015, following the latest Energy Basic Plan published on April 11, 2014 [2]. In this perspective, renewable energy systems (RESs) are expected to cover 22–24% in terms of kWh. Approximately 40% of these RESs will be solar power (photovoltaic) and wind power, whose intermittent output, however, may cause instability of the electric power grid.
Hereafter, we define 2030 as middle term and 2050 as long term in this paper regardless of the various definitions used by different stakeholders.
At the technology side, the Council for Science, Technology and Innovation (CSTI) of Japan is investigating the energy value chain in 2030 to realize ‘Society 5.0’ [3]. At the same time, CSTI is seeking possible technologies for 80% reduction of GHG (mostly CO2 in the case of Japan) emission in 2050 [4]. In academia and industry, many investigations have been conducted [5-17]. For instance, Ref. [5] describes technology roadmaps for future energy system beyond 2030 covering a variety of societal aspects, such as the use of secondary energy media, energy supply infrastructure, electric power generation, primary and secondary sectors, commercial and residential energy utilization, and transportation.
In this review paper, we describe the fundamental points of view and the present status of energy systems in Japan in Section 2, future energy systems in 2030 and 2050 in Section 3, and smart technologies to realize future system in Section 4. We conclude in Section 5.
2 Fundamental Point of Views of Energy Systems and the Present Status of Japan
2.1 Japan in the world
Estimated total energy flow in the world in 2014 [18] shows that ∼80% of primary energy is derived from fossil resources. Thirty-six percent is used to generate electric power, and most of the remaining primary energy is in the form of oil that is used mainly for transportation and chemicals production. This means that electric power is the most important energy category to be considered. Therefore, we focus on electric power systems rather than energy systems in this paper hereafter.
Electrification ratio at the demand side of Japan was 17% in 1980 and 24.5% in 2010 [19]. World average was 12.2% in 1980 and 19.8% in 2010. Even compared to North America (21.7%) and Western Europe (OECD) (21.0%) in 2010, Japan is well electrified. World's total electricity generation in 2014 was 23 816 TWh [20]. Of this, 24% was generated in China followed by 18% in the United States. Japanese electricity generation ratio is only 4% in the world, occupying the fifth position. The annual electricity consumption per capita shows that Japan is at the fourth position (∼7800 kWh/year/person), whereas Canada is at the first position (15 000 kWh/year/ person) [20].
Figure 1 [21-23] shows System Average Interruption Duration Index (SAIDI) for all unplanned interruptions including exceptional events. Roughly speaking, SAIDI means unplanned blackout time including rare large disasters. This figure shows that Japanese electric power systems is a highly reliable one.
SAIDI (system average interruption duration index) in selected countries. [21-23]
2.2 3E + S as the fundamental point of views
In Japan, the fundamental point of view of energy systems is considered as the balance of 3E + S, which means ‘energy security’, ‘environmental conservation’, ‘economic efficiency’, and ‘safety’. In this paper, the we focus only on the three ‘E's, because the main topic of ‘S’ comprises nuclear safety against large natural disasters.
Energy security means stable supply of energy including the import of primary energy. Environmental conservation in Japan practically means the reduction of CO2 emission. Economic efficiency directly means the reduction of the cost of supplying energy. A ‘tri-lemma’ [24] exists among energy security, environment, and economic efficiency. For example, increased use of coal is beneficial in terms of economic efficiency, while it is apparent that it will negatively affect environmental conservation. Considering the possibility of future international agreement to more strictly restrict CO2 emission, a drastic reduction in coal usage may be required. This will result in higher dependence on the other types of fossil fuels, which may lead to a degraded energy security of the country.
In the context of energy security, it is noted that the self-sufficiency ratio in Japan has been decreasing in recent years because the import of liquefied natural gas (LNG) has increased after the Great East Japan Earthquake to cover the nuclear power supply that faces difficulty in restarting its operation due to the stricter safety standards and public resistance. The major import partner countries to Japan are as follows: Half of the coal imported is from Australia, half of the petroleum from Saudi Arabia and UAE, and half of the LNG from Australia, Qatar, and Malaysia [25].
To ensure high reliability of the energy supply chain within Japan, the diversity of import partners and the importing sea lane are essential for better energy security. It should be noted that Japan depends heavily on the Middle Eastern countries (over 80%) for petroleum. This results in critical bottlenecks in the petroleum sea lane from the Middle Eastern countries to Japan, as schematically shown in Fig. 2. To counter this situation, two options are being considered. One is the import of shale gas and oils from North America. Now that the improvement of the Panama Canal has been completed (June 2016), importing the shale gas from the Gulf of Mexico has started. The other is the use of the Arctic Sea route to access North Sea oil.
Schematic of present and prospective (in the near future) sea lane of petroleum import to Japan
Figure 3 [26, 27] shows the CO2 emission unit and the levelized cost of electricity estimated for each type of generation plants. Although solar and wind power systems are associated with negligible CO2emission, those are considered less economically viable than most of the conventional options except for oil-fired thermal power plants, which are used only to cover the peak demand. The data is based on the 2014 model plant by the Generation Cost Working Group of METI of Japan [27]. The cost of onshore wind power is ¥21.6/kWh. The cost of residential solar power is ¥29.4/kWh, while that of nonresidential solar power is ¥24.2 /kWh. Table I [28, 29] shows GHG reduction target by COP21, Paris Agreement. Japan's target is challenging; i.e. 26% reduction by 2030 compared to 2013. The reduction target of each country must be carefully reviewed, because the prerequisites such as base line, base year, and the definition of reduction ratio are different in different countries. The majority of the breakdown of 26% of Japan is energy-origin domains (21.9%), followed by CO2 absorption by forests (but not by the ocean) (2.6%). [30, 31]
The generation efficiency of thermal power plant is being continuously improved to reduce both the fuel cost and CO2 emission. METI of Japan has developed the roadmap for next-generation thermal power plant up to 2030, where ∼10% conversion efficiency improvement of both LNG- and coal-based thermal plants is expected [32].
Electricity price for domestic and industrial consumers is shown in Fig. 4(a) and (b), respectively [33]. Electricity price for residential use in Japan is in the middle position among the shown countries, while the price for industry is the second highest. After the Great East Japan Earthquake, both prices are increasing gradually as the import of LNG is increasing.
Electricity price for residential and industrial customers [33]
The Japanese government is liberalizing the policy in energy domains including electric power, gas, and heat [34]. For electric power, liberalization is proceeding in three steps. In 2015, the Organization for Cross-regional Coordination of Transmission Operators (OCCTO) was established as the first step. Since April 2016, any consumer can purchase electricity from any electric retail company with the benefit of full liberalization for retailers. In 2020, legal unbundling for electric utilities is scheduled. Liberalization for gas and heat is in a similar situation.
2.3 Situation of RES implementation
Table II [35, 36] shows the installed capacity and registration status of each RES under Feed-in Tariff (FIT) scheme. After July 2012, when the FIT was implemented by the Japanese government, the installation of RESs, especially solar power, has dramatically increased. On the contrary, the installment of wind power, which has large potential in Japan, is in a different situation [37]. The sluggish growth in the installation of wind power generators compared to solar power systems is partly due to the longer lead time necessary for the environmental assessment process as well as the location of regions of strong winds where the land or onshore area has been often developed for other purposes such as fishery.
Table II. Renewable options under FIT in Japan [33, 36]
Unit: MW
Before FIT
Installed capacity
Registration for FIT
−2012.6
2012.7–2013.3
2013.4–2014.3
2015.4–2016.3
Solar (residential)
4700
969
1307
1670
4640
Solar (non-residential)
900
704
5735
16 870
75 290
Wind
2600
63
47
370
2840
Small hydro
9600
2
4
150
780
Biomass
2300
30
92
430
3700
Geothermal
500
1
0
10
80
Total
20 600
1769
7185
19 480
87 330
8954
Figure 5 [38] shows the registered capacity, capacity applied for connection, and capacity connected to the electric grid in each electric power company in Japan, focusing on the solar power only. Thick black dashed lines show the upper limit of RES connection to each electric power company within the present scheme of output control.
Cumulative capacity of FIT registration and installed solar power in Japan [38]
In California, as a result of a large number of solar power installations, the duck curve shown in Fig. 6 [39] is already recognized as a serious and urgent issue. In 2013, the California Public Utilities Commission (CPUC) defined the energy storage mandate as state low AB2514. This mandate requires the installation of 1325 MW energy storage (battery) by 2020 to three electric power companies (PG&E, SCE, and SDG&E) in California. This is divided into 700 MW at the transmission system, 425 MW at the distribution system, and 200 MW at the customer side [40].
One important mission of OCCTO, Japan, described in Section 2.2 is to resolve the capacity limits of each area covered by each electric power company, by considering whole of Japanese electric power network capacity. OCCTO has the authority to coordinate electric power companies with high margin and those with low margin across the region. Although the system size is still small, other technical solutions such as the applications of storage measures are already conducted as demonstration experiments.
2.4 Energy saving status
The GDP and per capita energy consumption for selected countries are shown in Fig. 7 [5], from which one can see that Japan is one of the most efficient countries. Although the United States and Oceania are rich in terms of GDP, there appears to be much scope for energy saving compared to the world average. In Japan, the energy saving measures have been highly promoted after the oil crises in 1973 and 1979 when oil price jumped up by ∼5 times [41]. Approximately 40% of improvement in per capita energy consumption has been achieved by 1990. Further, 10% of improvement was achieved during next 20 years from 1990 to 2010. As a result, the total domestic energy consumption increased by only 1.2 times from 1973 to 2014 while the GDP increased 2.4 times during the same period. The breakdown is as follows: 1.7 times in transportation sector, 2.0 times in residential sector, 2.4 times in commercial sector, and 1.6 times in the industrial sector. [17] This breakdown indicates that energy saving in residential and commercial sectors is very important.
The total figure is useful in grasping the whole energy system architecture, to subsequently look deeper into each technology and then to consider the interaction of each subsystem. It will help in avoiding a certain ‘Galapagosization’ or dead end.
Future energy system in Japan beyond 2030 based on feasible technologies has been dealt with in the document Energy Technology Roadmaps of Japan [5]. Although most of the energy infrastructure is centralized at present in Japan, a harmonization of centralized and decentralized systems is desirable and expected. The energy conversion among electric power, gas, heat, and hydrogen will be expected to improve the system value such as 3E + S described before. In order to achieve this expectation, the combination of each system is important. That is, a system-of-systems (SoS) architecture will be essential. It is necessary to perform information sideways in the cyber layer to realize the SoS architecture utilizing big data, artificial intelligence, and the internet of thing (IoT) technologies.
3.2 Middle-term direction toward 2030
Japanese government has published the Energy Basic Plan in April 2014 [2] and the long-term perspective of energy demand and supply in July 2015 [1]. They also published government policy for energy up to 2030 in May 2016 [17]. The Japanese government has shown three items for the policy in the publication of 2016: The first one is the increase of RESs, representing negligible CO2 emission option; the second one is the increase of energy saving by decreasing the energy consumption; and the third one is the new energy systems such as the application of information technologies (IT) and hydrogen.
Regarding electric power, Japanese government plans to achieve 16% energy saving in 2030 to maintain the energy volume at the same level as in 2013. RESs are expected to increase from 11% in 2013 to 22–24% in 2030. Most of the present 11% was generated by hydro, and only a small percent was generated by solar and wind power in 2013. The expectation to improve to 22–24% in 2030 will be based on solar power, biomass, and geothermal generations. Hydro system is not expected to increase much because most of suitable locations have already been developed. Only small and medium size hydro power projects are left for new development. Offshore wind power system is expected to increase substantially after 2030. Biomass, geothermal, and hydro are controllable RESs, while solar and wind power are variable RESs with intermittent outputs that depend on the weather. Those need additional measures such as battery to maintain the stability of the electric power network.
The New Energy and Industrial Technology Development Organization (NEDO) of Japan has formulated PV2030+, the roadmap of solar power, which was updated in September 2014 based on the previous PV2030 [42]. In PV2030+, it is expected that the levelized cost of electricity will reduce to ¥7/kWh in 2030, which is comparable to thermally generated electricity cost. NEDO considers this cost leveling as ‘grid parity’. Various types of offshore wind power stations exist, such as bottom-mounted and floating systems. [43, 44]. Europe and the United States are rich in sea with shoals, whereas the sea becomes deep suddenly in most of Japan's coastal regions. For this reason, floating wind system rather than bottom-mounted system is preferred in Japan to best utilize the huge potential of wind power. The technology for floating systems is under development all over the world; nevertheless, the technology for bottom-mounted wind power is under development in Europe.
A specific energy saving policy is planned in the four sectors of transportation, commerce, residential use, and industry, as shown in Fig. 8 [45]. In each policy in these four sectors, the characteristic points are as follows. Next-generation vehicles such as the electric vehicle (EV)/plug-in hybrid vehicle/fuel cell vehicle (FCV) in the transportation sector; net zero-emission building (ZEB)/net zero emission house (ZEH) including smart building and smart house in the commercial and residential sectors; and the top runner system in industry.
Specific energy saving policies for four sectors in Japan [45]
For next-generation vehicles, automatic driving has been extensively studied recently. The purpose of automatic driving is to improve fuel consumption, reduction of traffic congestion, reduction of accidents due to human errors, and the improvement in comfort by reducing the driving operation load. Although automatic driving and the energy saving are not directly linked, it appears that there is commonality in those technologies to achieve the final goal.
Images of ZEH and ZEB are shown in Fig. 9 [46]. The definition of ZEH and ZEB is almost the same [46, 47]. In other words, both reduce energy consumption and simultaneously realize self-production of electric energy as well as thermal energy. Generally speaking, home energy management system (HEMS) and building energy management system (BEMS) are implemented in order to control the entire house and building.
One of the IT applications for new energy system is the distributed energy resource aggregation system shown in Fig. 10 [48, 49]. The idea of this system is simple and actually available in the market in the United States, while only demonstration experiments are conducted in Japan. The resource aggregator aggregates small power generations from independent commercial buildings and residential houses to act as a large positive generator in total; conversely, they aggregate small energy savings to act as a large negative generator in total. The aggregated positive and negative generators are controlled by communicating with the energy management system (EMS) of the electric power companies in the final stage.
The key for the market penetration of FCV is hydrogen. The Japanese government has constructed the roadmap consisting of three phases [50]. In phase 1, FCV together with hydrogen refueling stations and residential fuel cell system with the common gernric name of ENE-FARM will be increased with subsidy policies. Figure 11 [51] shows a number of installed units of ENE-FARM. Figure 12 shows an example of a H2 refueling station at Kyushu University, which has been in operation since 2009. H2 is produced by water electrolysis using electricity from either the grid or RESs at Kyushu University. Seventy-eight H2 refueling stations are in operation, and 14 stations are under consideration as of November 1, 2016 [52] in Japan.
In phase 2, hydrogen produced from lignite, which is not well-utilized presently, or large-scale overseas RESs such as wind power, will be introduced. Liquefaction and as organic hydride or ammonia are considered as measures to ship hydrogen to Japan. The price of hydrogen is expected to be ¥30/Nm3(plant delivery price) by late 2020s. This price is competitive with that of gasoline. In addition, by 2030, it is expected that hydrogen will be used to reduce the CO2 emission from thermal power plants by co-firing or even by substituting for LNG fuel.
In phase 3, ‘CO2-free’ hydrogen produced by the following two methods is expected. The first is the combination of lignite and carbon capture and storage (CCS), and the other is the significant expansion of RESs such as wind power generation overseas. Note that CCS is associated with CO2 emission because separating all CO2 from the streamline is not economically viable, thus a certain portion remains and is emitted to the atmosphere.
3.3 Long-term direction toward 2050
Although there exists no basic plan by the Japanese government, it is very certain that RESs will increase [53]. We study here the following three cases of RES introduction volumes: case 1, standstill status 2030 (22–24% RES); case 2, 50% RESs; case 3: 100% RESs. We have estimated the installed generation capacity, shown in Fig. 13, for each case based on several assumptions. The daily demand profile on the maximum peak demand day in 2001 [54] is shown for comparison. This figure shows that the electric power systems will be unable to operate stably without drastic measures to adjust the outputs from the unstable RESs, especially in cases 2 and 3. Even at present, the impact of RESs on the grid stability is recognized to be significant in some regions such as small island regions, thus large-scale battery storage systems are being installed to mitigate the influence.
Capacity estimation of RES installations in 2030. Daily demand profile on the maximum peak demand day in 2001 [54] is also shown. Demand shown is the total of ten major electric power companies in Japan
There exist various kinds of storage systems with a different applicable domains in terms of the storage duration and capacity. Note that hydrogen, which practically means the use of an electrolyzer, is also considered as one of the potential candidates in future (Fig. 14 [51]). Battery is applicable for small but fast fluctuation absorption, while hydrogen is considered as a countermeasure for large and long-term fluctuation or temporal and spatial supply–demand mismatch. The combination of hydrogen, battery, and output control of RES generation is expected to be feasible in terms of system cost and effective use of energy, as shown in Fig. 15.
Combination with suppression, battery, and hydrogen for surplus RES power Illustrated by authors referring the discussion in the text (modified from Ref. [55]).
3.4 Status of study in European Union and the United States
The EU is considering the electric power system in 2050 under the name of ‘e-Highway 2050’ shown in Fig. 16 [56, 57]. Because it takes a long time to construct electric power systems, it is necessary to carefully consider it, so EU is conducting investigations assuming five different scenarios. For each scenario of power supply, such as 100% renewables, power demand and power demand patterns are assumed and simulated to power flow from generation to consumption to obtain optimal electric power network. The optimal electric power network varies depending on the scenario, and it is difficult to predict which scenario will be realized in 2050. For this reason, the parts common to each scenario, that is, the electric power system to be augmented commonly in all scenarios, are the candidates to be reinforced in the near future.
In the United States, the Grid Modernization Initiative (GMI) project shown in Fig. 17 [58, 59] is taken up as the successor of the Smart Grid project. The objectives of GMI is to overcome terrorism, natural disasters, increased RESs, and new services such as EV.
Grid modernization initiative project in the United States [58, 59]
The idea of GMI are twofold. One is the combination of centralized and distributed electric power systems. The other is intelligent demand control. Many research items are being proposed to realize GMI. The following are the examples: Microgrid systems that can supply electric power in the relevant area in the case of the electric power systems failure due to a natural disaster, EMS, and distribution management system for intelligent control of both demand and supply sides, power electronics device for power flow control, and measurement sensor and data platform for electric power system visualization.
Because various information technologies are essential for the realization of GMI, many IT companies are entering this market.
4 Smart Technology for 2030 and 2050
4.1 Energy system as system of systems for 2030
As described in the introduction, the Council for Energy Strategy (CES), which belongs to CSTI of Japan, is making an effort to create a new value chain by combining the energy technology and related systems such as solar power, battery, and transportation systems.
That is, CES is trying to realize Society 5.0 in the energy field by applying the concept of SoS. Figure 18 shows the components of SoS organized by CES [60]. Each system in the cyber layer is connected in an interactive manner through the energy and IoT's service platforms. Although energy flows in physical layer is more or less unidirectional from the production side to the consumption side, information flow in cyber layer is multidirectional, which would create new values in the overall energy value chain.
Architecture of the energy system by CES of CSTI in Japan [60]
We will introduce the strategic research initiated by the Japanese Government, while we are aware that many individual initiatives are being taken including those by us [61-67]. CSTI has been operating a cross-ministerial Strategic Innovation Promotion Program (SIP) since 2014, scheduled for 5 years. Currently, eleven SIPs are going on. One of them is on power electronics [68]. Many items from fundamental device technology to power electronics application systems are being studied. SiC and GaN devices are the main target devices to reduce power loss to only 10% compared to conventional Si device in near future. Another example of SIPs for Society 5.0 is on energy carrier where technologies related to the carrier of energy, especially focusing on hydrogen, is investigated [69]. Their major research area are categorized into five, i.e. hydrogen production utilizing solar heat, ammonia, organic hydride, liquefied hydrogen, and the safety of energy carrier.
SoS integrated with power system and next-generation vehicle system
An example of SoS for Society 5.0 is the combination of power and next-generation vehicle systems as illustrated in Fig. 19. EV can be regarded as a distributed battery system that can spatially move by itself. FCV can be also regarded as a fuel cell system that can move by itself. In future, EVs and FCVs will be constantly connected to the vehicle and power information network. Because they are connected to the network and the state of charge of battery of the EV, and the remaining hydrogen in the vessel loaded on FCVs is monitored, the charging and discharging from them can be controlled by the power aggregator so as to meet the requirement from the power information network. At the same time, if a catastrophic disaster causes troubles, such as a wide-area power outage in the electric power systems, EVs and FCVs can play the role of emergency generators.
4.2 Innovative technologies to 2050
Article 2 of the Paris Agreement (COP21) states that ‘Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase 1.5°C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change’ [70]. CES is investigating specific technologies shown in Fig. 20 [71] to reach this ultimate goal. The target technologies are categorized into three domains: energy saving, energy storage, and power generation.
Specified technologies for COP21 in 2050 by CE [71]
Energy saving focuses on, for example, an innovative energy-efficient production system utilizing membrane and catalyst as well as superlight materials for automobile and materials durable for heat over 1800 °C. In the energy storage area, next-generation battery system beyond the present lithium-ion battery is targeted. ‘CO2’-free hydrogen and power generation by hydrogen are also specified as important technologies. In the aea of power generation, solar power with doubled efficiency and cost comparable to that of base-load power are specified as well as nonconventional geothermal energy.
CCS and carbon capture and utilization (CCU) are also listed as important technologies. Japan has only a few candidate sites in land and sea for carbon storage; therefore, seeking the technology for CCU will be important as a long-term perspective. An example of CCU is the combination of exhaust heat utilization, waste water treatment, and algae culture [72]. CO2 from coal thermal generators and nutrients from waste water treatment plants activate the algae to produce green oil. Although CCU is in the stage of research and development, feasibility assessment is required both with respect to cost and the system size. System size is important considering the huge amount of CO2 emitted from coal-based thermal power plants, corresponding to ∼20% of Japanese CO2 emission [73]. While we admit that the role of coal- or fossil-fuel-based thermal power plants may decrease, a high throughput will be eventually required for CCU technology.
We show the future energy perspective toward 2050 in Fig. 21. At the supply side, the electrification ratio will further increase, and electric power is expected to be supplied mainly RESs. Thermal generators can exist to compensate for the output fluctuation of the variable RESs, but the combination with the CCS&U is necessary to realize the ultralow carbon emission within Japan. Furthermore, batteries and hydrogen would be largely implemented so as to mitigate the fluctuation of RES outputs. While we admit that this story is challenging, it does not go beyond the extrapolations of the present trend.
On the other hand, it is expected that major changes will occur at the consumer side. There are several reasons for this. One is that the grid parity of solar power will be achieved, or even the cost of solar power will become cheaper than that of the gird power. For this reason, the amount of electric power generated by the consumer will increase to the self-sufficiency level. In addition, it is highly probable that the electric power generated by RESs will be more than the consumption. ENE-FARM and next-generation vehicles such as EV and FCV will be introduced to a significant degree. Including other options, the introduction of distributed power sources will drastically increase. Because IoT, where everything is connected to the information network, is becoming commonplace, it becomes possible to control these distributed power sources through the information network. Thus, the EMS will be introduced at various levels of consumers. If community EMS is introduced at the consumer side, it may function autonomously in the energy market. One example is the electric power supply and demand adjustment at the consumer side. Each consumer supplies surplus electric power to a supply-deficient consumer via the electric distribution network. It is noteworthy that the supply-deficient consumer at a certain time can become a supply-surplus consumer at a different time by supplying the power to external entities. This is a type of decentralized power trading that is realized by optimizing the physical constraint of electric power transportation and the consistency of electric power transaction including the cost and the price.
Meanwhile, central-type control as in a large-scale power system is indispensable at the supply side. Otherwise, the electric power company cannot control large-scale power supply including thermal power generators. For this reason, centralized EMS and decentralized community EMS need to closely cooperate, especially in electric power systems. In this context, the concept of a virtual power plant (VPP) is important. In 2050, it is expected that the aggregation shown in Fig. 10 will be greatly enhanced as next-generation VPP in a form that is further expanded in quantity, function, and time resolution. We must point out, again, that the concept of SoS is extremely important in systematizing these technology developments.
4.3 Reference architecture model for smart systems
A model of a complicated system including business, software, and hardware systems is frequently described as an architecture model. The first one is the smart grid architecture model (SGAM) shown in Fig. 22 [74], which is organized by the CEN-CENELEC-ETS Smart Grid coordination group. This kind of architecture model should be referred here, because numerous stakeholders are involved to accomplish standardization and study of all items, which have complicated interaction each other. It is difficult to overview whole of the system and interactions between items, especially for extremely large systems. That is, they need the concise description of domains (generation to consumption), zones (process to market), and interoperability layers (component to business).
The idea of SGAM can be applied not only to electric power systems but also to the whole energy system including electric power, gas, and heat systems. An example of the extension of SGAM to heat and gas energy is shown in Fig. 23 [75]. Physically, this figure shows the following: Electricity is supplied from electric power generation systems such as a solar power plant. Hydrogen is produced and stored by electrolysis, for example, using electricity from solar power. Electric power is again generated by fuel cells using the stored hydrogen and flows back into electric power network. Heat from the fuel cell as a combined heat and power (CHP) system is supplied to the buildings. At the information side, this figure shows the two communications. One communication path exists between the EMS of distributed energy resources (DERs) and hydrogen storage. The other communication path exists between BEMS and fuel cell system as CHP. This figure gives an overview of the physical energy flow interactions, as well as the information flow interactions for monitoring and controlling between the three models of electric power, gas, and heat systems.
The energy systems in Japan are facing an urgent need for dramatic changes because of the expected decrease in population, a strong need for global warming mitigation, and the safety, robustness, and resilience against natural disasters. Smart technologies utilizing IoT and SoS technologies are expected to contribute to resolving these difficulties and creating new values in the energy value chain toward 2030 and 2050.
In this paper, we have described the current status, policies of Japanese government, and technological trends of energy systems in Japan from the view point of 3E + S.
In order to achieve simultaneously a drastic reduction in CO2 emission, reasonable energy cost, high energy security, as well as nuclear safety in future, directions toward 2030 and 2050 were discussed considering various technology options. The innovation at consumer side will become much more important, best utilizing distributed RESs, storage measures, EVs, and distributed EMS utilizing advanced VPP functionality and SoS integration.
Biographies
Yoshio Izui (Fellow) received the B.E., M.E., and Dr. Eng. degrees in electrical engineering from the University of Tokyo, Tokyo, Japan, in 1981, 1983, and 1986, respectively. He joined Mitsubishi Electric Corporation, Amagasaki, Hyogo, Japan, in 1986. He is currently affiliated with the Advanced Technology Research and Development Center, where he is engaged in the research and management of energy and electric power systems, especially on the smart grid and smart community-related technologies. Dr. Izui is a member of the IEEE, IEICE, IPSJ, SICE, ISCIE, JNNS, and ANNS. He is also a member of the Energy Strategic Council for Science, Technology and Innovation, Japan.
Michihisa Koyama (Non-member) received the B.E., M.E., and Ph.D. (Eng.) degrees in chemical system engineering from the University of Tokyo, Tokyo, Japan, in 1997, 1999, 2002 respectively. He joined as Professor at the INAMORI Frontier Research Center, Kyushu University (KU), in 2008. Earlier, he was a postdoctoral fellow at the University of Tokyo and an Assistant Professor at Tohoku University. Since 2016, he is also serving as Unit Director, Technology Integration Unit, GREEN, National Institute for Materials Science, KU.
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