• Energy Research

The purpose of this paper is to analyze energy consumption and supply on a prefectural scale, and to visualize and compare the regional energy demand-supply distribution considering potential of renewable energy. The final energy consumption and the final energy consumption per capita are related to the industrial sector. Total final energy consumption is reported to be 13,297 PJ, of which 6,136 PJ is used for the industrial sector. In the residential and commercial sector, population is the most effective on the final energy consumption. On the other hand, final energy consumption per capita in residential sector is tied to the climate: cold areas like Hokkaido, Tohoku, and Hokuriku have larger consumption than other areas. Energy expenditure per capita in residential sector is also large in cold areas; for instance, 98,581 JPY/capita is spent for energy in Hokkaido. The energy supply system in Japan depends on thermal power generation that is large scale-centralized; Chiba has the largest thermal power generation estimated at 390 PJ. By contrast, thermal power generation in Yamanashi is the smallest in Japan estimated at 0.5 PJ. Renewable resources are widely distributed in Japan, but renewable energy supply which is calculated at 374 PJ is very small. Onshore wind power and solar power have enough potential, evaluated at 2,985 PJ, to substitute thermal power plants. This study indicates that development of local energy systems, especially local heat supply system, is important to introduce local renewable energy, and introduction of renewable energy leads to more balanced regional energy demand-supply distribution.

From the view point of future coal utilization technology for the thermal power generation systems, the coal gasification combined cycle system has drawn special interest recently. In the coal gasification combined cycle power generation system, it is necessary to develop a high temperature gas turbine combustor using a low–BTU gas (LBG) which has high thermal efficiency and low emissions. In Japan a development program on the coal gasification combined cycle power generation system has started in 1985 by the national government and Japanese electric companies. In this program, is planned to develop the 1300 °C class gas turbines. However, in the case of using a hot type fuel gas cleaning system, the coal gas fuel to be supplied to gas turbines will contain ammonia. Ammonia will be converted to nitric oxides in the combustion process in gas turbines. Therefore, low fuel–NOx combustion technology is one of the most important research subjects. This paper describes low fuel–NOx combustion technology for 1300 °C class gas turbine combustor using low BTU coal gas fuel. Authors have showed that the rich–lean combustion method is effective to decrease fuel–NOx (1). In general in rich–lean combustion method, the fuel–NOx decreases, as the primary zone becomes richer. But flameholding becomes very difficult in even rich primary zone. For this reason this combustor was designed to have a flameholder with pilot flame. Combustion tests were conducted by using a full scale combustor used in 150 MW gas turbine at the atmospheric pressure condition.

The present work intends to address the lack of energy access and low waste collection services through the integration of waste-to-energy (WTE) technologies into the electrical system, aiming for a low-carbon growth. A minimization of cost approach was applied using linear programming. Venezuela was used as the case study for five cases under two scenarios. In Scenario A, the current waste collection service rate was considered (88%), whereas in Scenario B, it was assumed to improve to 94%. Cases 1 to 5 were as follows: Current fuel subsidy, No fuel subsidy, Subsidies on WTE, Carbon tax policy and Carbon-reduction policy. Total carbon emissions were analysed. In all cases except for the first one, WTE technologies were present in the energy matrix, reducing carbon emissions by approximately 3–5.4 × 106 tonne of carbon. Furthermore, a difference of 1–2 × 106 tonne of carbon between scenarios was observed. The last two cases achieved higher emission reductions with an abatement cost of $169 tC−1 and $89 tC−1, respectively. Despite the lower abatement cost of the carbon reduction policy, this research proposes the implementation of a carbon tax because it could finance the improvement of waste management practices.

Concern about global warming calls for an advanced approach for designing an energy system to reduce carbon emissions as well as to secure energy security for each country. Conventional energy systems tend to introduce different technologies with high conversion efficiency, leading to a higher average efficiency. Advanced energy systems can be achieved not by an aggregate form of conversion technologies but by an innovative system design itself. The concept of LCS (low carbon society) is a unique approach having multi-dimensional considerations such as social, economic and environmental dimensions. The LCS aims at an extensive restructuring of worldwide energy supply/demand network system by not only replacing the conventional parts with the new ones, but also integrating all the necessary components and designing absolutely different energy networks. As a core tool for the LCS design, energy-economic models are applied to show feasible solutions in future with alternatives such as renewable resources, combined heat and power, and smart grid operations. Models can introduce changes in energy markets, technology learning in capacity, and penetration of innovative technologies, leading to an optimum system configuration under priority settings. The paper describes recent trials of energy models application related to waste-to-energy, clean coal, transportation and rural development. Although the modelling approach is still under investigation, the output clearly shows possible options having variety of technologies and linkages between supply and demand sides. Design of the LCS means an energy systems design with the modelling approach, which gives solution for complex systems, choices among technologies, technology feasibility, R&D targets, and what we need to start.

For achieving a carbon–neutral energy system, economical flexibility mechanisms are crucial to accommodate intermittent and decentralized renewable energy sources. Power-to-X (P2X) is a promising technology for this purpose. This study aims to elucidate the systematic effects and competition of dynamically operated power-to-X (P2X) technologies as a flexibility option in comprehensive renewable energy systems. We developed a linear programming model to optimize energy systems incorporating P2X technologies, including water electrolysis, methanation, Fischer–Tropsch synthesis, and Haber–Bosch synthesis, and investigated the impact of P2X flexibility on the system structure and energy costs, focusing on Japan as a case study. The results demonstrate that each P2X technology effectively shifts electricity loads and reduces curtailment by more than 80%. The contribution of each P2X technology varies, with water electrolysis playing a dominant role due to its relatively low fixed costs and large scale. Furthermore, the mechanism significantly reduces system costs by 35% and supply costs of electricity and hydrogen by 41% and 30%, respectively, by reducing the required capacities of electricity generators, stationary batteries, and transmission grids. Therefore, P2X has a cost advantage over these flexibility options. The results also highlight that the maximum effect is achieved when the capacity factor of P2X is 30%. However, synthetic hydrocarbons would require a carbon price of over 356 EUR/tCO2 to compete with fossil fuels. Domestic electrofuels would face tough competition with global fuel costs. Nevertheless, the reduction in electricity costs through P2X, along with its contribution to energy security, may incentivize its adoption.

As for research on sector-coupled energy systems, few studies comprehensively deal with energy carriers and energy demand sectors. Moreover, few studies have analyzed energy conversion functions such as Power-to-Gas, Power-to-Heat, and Vehicle-to-Grid on the energy system performance. This study clarifies the required renewable resources and costs in the sector-coupled energy system and cost-optimal installed capacity and operation. We formulated an optimization model considering sector coupling and conducted a case study applying the model in the Tohoku region. As a result, due to sector coupling, the total primary energy supply (TPES) is expected to decrease, and system costs are expected to increase from 1.8 to 2.4 times the current level. System costs were minimized when maximizing the use of V2G by electric vehicles and district heating systems (DHS). From the hourly analysis, it becomes clear that the peak cut effect by Power-to-Heat and the peak shift effect by Vehicle-to-Grid result in leveling the output of electrolyzer and fuel synthesizer, which improves the capacity factor reducing capacity addition. Since a large amount of renewable energy is required to realize the designed energy system, it is necessary to reduce the energy demand mainly in the industrial sector. Besides, in order to reduce costs, it is required to utilize electric vehicles by V2G and provide policy support for district heating systems in Japan.

This study uses optimization modeling to study efficient ways to integrate renewable energy systems to provide electricity and heat in rural Japan. The model provides minimum cost system configuration and operation taking into account hour-by-hour energy availability and demand. Grid electricity is available to rural areas of Japan, but it is relatively expensive. Local renewable energy generation can be economic while using grid electricity to compensate for the intermittency of the renewable generation. In the model, renewable electricity can be provided by a combination of wind, photovoltaic, and biomass. Heat can be provided by petroleum, LPG, and geothermal heat pumps (GHPs). We find that due to the relatively high cost of grid electricity, there is significant penetration of wind generation. In turn, the penetration of wind creates economic conditions that encourage GHP penetration. The integrated renewable system reduces the annual cost of the entire system by 31%, and reduces the carbon emissions by 50%.

The paper examines the effects of research and development (R&D) on the capital cost reductions and the introduction of renewable energy technologies, namely solar photovoltaics (PV) and wind technologies. The proposed model in the study deals with the dynamics of technological learning. Functional form is a new kind of three-factor learning curve as a function of the cumulative capacity and the knowledge stock accumulated by public and private R&D expenditures. An econometric analysis is used to identify the influence of the knowledge stock on the capital costs of renewable energy technologies. Moreover, the study clarifies the relationship between the cost reductions and the market penetration. If the expenditures for public and private R&D in 2010 are fixed until 2050, then the model predicts that the capital costs of solar PV systems in 2050 become $1,750 /kW. Sensitivities of the annual R&D growth rate for the technologies are tested. The model also provides important results that the increase by four times of R&D budgets is necessary in order to reach the cost reduction targets by the Japanese government. The proposed methodology herein is helpful for decision makers to forecast how the costs of renewable energy technologies will change, and thereby providing the basis for R&D planning.