This paper presents a cost-benefit analysis of climate change with a focus on two tipping elements: melting of Greenland ice sheet (GIS) and collapse of Atlantic meridional overturning circulation (AMOC). We employ an integrated assessment model based on the DICE-2016R2 framework. Effects of melting GIS on AMOC are newly modeled. Simulation results show that the effects of GIS on AMOC largely increase the social cost of carbon and lower the optimal CO₂ emissions compared to the original DICE-2016R2. In a case with the GIS effects, the optimal global CO₂ emissions reaches zero by around the year 2090, much earlier than the original model, implying the role of low-carbon and negative emissions technologies to manage the impacts and risks of tipping elements. Estimated global average temperature rise in 2100 from the pre-industrial level is also lowered from 3.5 degrees Celsius in the original DICE-2016R2 to 3.2 degrees Celsius with the GIS effects. Our results support that tipping elements and these interactions would be important factors for designing long-term climate strategies.

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Energy and electricity are very important for continuous growth and development, especially for fast-growing regions of the world. However, with the expansion of energy and electricity sector, the concern of environmental protection also arises. The cheaper electricity generation technologies from traditional fossil fuels involve huge emission of carbon which could easily jeopardize the global plan for climate action. In this study, we utilize the Dynamic Multi-Sector Energy Economic Model (DMSEE) to obtain long-term electricity sector expansion using traditional fuels and modern carbon-free nuclear and renewable energy options. The uniqueness of this model is the incorporation of economic interrelationships among top-down economic sectors and technological constraints of the bottom-up electricity sub-sectors simultaneously. To investigate the techno-economic shifts over time, we applied the model to one of the developing regions of the world, Bangladesh. The country is experiencing double digit growth in the electricity sector due to large-scale activities in the industry and service sectors. Carbon-emission limits of 25% and 50% with respect to projected growth have been considered to obtain potential scope of nuclear and renewable energy options considering technical and economic limitations simultaneously. The results of the analysis provide significant policy implications on the electricity generation mix under different circumstances.

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Residential solid oxide fuel cell (SOFC) generates electricity all day with high efficiency, so it can be used as a base load power source to replace thermal power plant (Plant). This paper provided the evaluation on energy and CO₂ saving effectiveness and the generation cost of residential SOFC based on household energy demand by Total Residential End-use Energy Simulation model developed by authors. In addition, the generation cost of SOFC was compared to generation cost of Plant based on the future scenario. The generation cost of SOFC will be lower than the cost of Plant in the future scenario that consider the increase of CO₂ tax and initial cost reduction of SOFC. If a SOFC is installed into a household in which generation cost of SOFC is lower than the generation cost of Plant, the generation capacity of SOFC in Kansai-region in maximum is approximately case A: 4.3 million kW (renewable energy surcharge is included in the cost of Plant) case B: 0.06 million kW (renewable energy surcharge is not included in the cost of Plant). In the case A, the capacity is enough to replace a Plant.

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This paper proposes a novel planning model for electricity-hydrogen energy system in consideration of imported hydrogen, hydrogen demand and renewable energy that is largely penetrated. The model is designed to reveal the optimal ratio of domestic and imported hydrogen production and uses non-linear variables such as start-up costs and partial load efficiency of thermal power generation plants with linear programming in an approximation manner. By using this model, the optimal power supply mix and hourly operation of the energy system in Kyushu, Japan in 2030 are explored. As the introduction of domestic renewable energy increases, domestically produced hydrogen will become more competitive than imported hydrogen, though the use of imported hydrogen is important for thorough decarbonization. The results show that the optimal solution is to use domestic or imported hydrogen up to the amount of surplus renewable energy and the hydrogen price.

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This paper presents thermodynamic analysis and exergy analysis in oxy-hydrogen cycle compared to gas turbine combined cycle (GTCC) with H2/Air combustion and GTCC with LNG/Air combustion, using thermal efficiency analysis software (EnergyWin®). First, the thermal efficiency for oxy-hydrogen cycle was clarified as functions of gas turbine inlet temperature and pressure. The overall thermal efficiency (LHV basis) of oxy-hydrogen cycle resulted in 2–11% points higher than that of GTCC with H₂ or LNG. Exergy loss for combustor, which decreases by 2–4% points, is the most improved. One of the reasons is that setting up higher pressure ratio of compressor for oxy-hydrogen cycle enables to adapt to higher combustor inlet temperature. It indicates oxy-hydrogen cycle can achieve high thermal efficiency. On the other hand, the application limit of state quantity such as compressor outlet temperature for oxy-hydrogen cycle, because of the strict condition with current thermal power plant technology, was also clarified. The effect of high pressure turbine (called steam turbine 1 in this paper) inlet pressure is analyzed for oxy-hydrogen cycle. Furthermore, net thermal efficiency of oxy-hydrogen cycle considering oxygen production is also estimated to clarify its performance.

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The introduction of variable and distributed renewable energy into the energy system is an important approach for decarbonization and the transition to sustainable regions. The purpose of this study is to clarify the geographic distribution of renewable energy resources and energy demand in Japan, as well as the effectiveness of regional cooperation for the introduction of renewable energy. First, energy consumption, renewable energy potential, and generation costs were estimated for 1,741 municipalities. As a result, a maldistribution was revealed: the northeast of Japan has inexpensive and exportable resources, while the west of Japan has expensive and less than demanded resources. We also analyzed the energy self-sufficiency and fiscal capacity of each region, and found that about 95% of the municipalities are limited in their ability to implement their local energy policies individually. Then, we designed a cross-border region, taking into account the cooperation among municipalities with different characteristics. As a result, in the base case, 49 cross-border regions were formed by 284 municipalities, and 108 municipalities shifted to a sustainable state with sufficient renewable energy resources and financial capacity. Furthermore, it was found that 10.4% of the regional energy shortage could be eliminated through energy sharing.

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Recently, many renewable energy sources are connected to power systems. Renewable energy sources such as PV and wind connected to power systems via inverters are called inverter sources. When the percentage of inverter sources increases, the percentage of synchronous generators such as hydro, thermal and nuclear decreases. When many inverter sources are connected to power systems with small capacity which are not synchronously connected to other power systems, the percentage of synchronous generators significantly decreases. Therefore, influences of power system characteristics such as synchronizing power decrease, power system inertia decrease and short circuit capacity decrease are concerned. And influences of power system stability such as transient stability decrease, frequency and voltage fluctuation increase and distortion level increase are also concerned. Previously, power system inertia estimation and power system stability monitoring were done by off-line. Therefore, on-line power system inertia estimation and power system stability monitoring system is newly developed for the purpose of precise understandings of Japanese Eastern (50Hz) and Western (60Hz) power systems.

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In this paper, we will describe demonstration experiment of P2P electric power trading using block chain conducted in Kanazawa Institute of Technology Hakusan-roku Campus. The P2P trading was experimented by combination of block chain platform developed by The Kansai Electric Power Company and the open platform experimental filed of Kanazawa Institute of Technology. The generation systems are the solar, wind, electric bicycle, stirling engine and thermo-electric with biomass system connected to DC distribution system. In addition, we are also utilizing power from electric vehicle. Two stationary storage batteries are connected to DC systems. The consumers are 8 cottages where many cottages are really inhabited by faculty and staff. The P2P trading was conducted in the fourth quarter in FY2019 and FY2020 using these real data. In the first year, basic verification of P2P trading was conducted such as consistency of trading between sellers and buyers, handling of storage batteries related to renewable energy, and impact of bidding order. In the second year, verification of the use of electric vehicle for P2P transactions was mainly conducted such as reduction of imbalance due to additional bidding and actual power value execution. We will show the details of the P2P trading demonstration experiment and evaluation results.

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