A reduction of greenhouse gas emissions has become one of the most important issues that power companies have to solve. The objective of this study is to assess performance of two kinds of environmental policies that are carbon tax and cap-and- trading of CO₂ emission permits on an electricity market. For that purpose, we develop a multi-agent model based on reinforcement learning that simulates a CO₂ emission trading market as well as an electricity market. By conducting model simulations, we obtain the following results. We confirm the major outputs of the model such as market shares and market prices of electricity in various carbon taxes. We also confirm duality principle between carbon tax and CO₂ emission cap-and- trading when the carbon price is at 2000 JPY/t-CO₂. However, in a case of different allocation of CO₂ emissions, we observe duality principle could collapse and the carbon price in the collapse case could become much higher than the carbon price with the duality principle. This is because the CO₂ allocation affects the income and expenditure of each agent and changes the strategy of each agent in the CO₂ market as well as the electricity market. Thus, the institutional design of CO₂ emission cap-and-trading requires careful consideration for income and expenditure of agents in the market.

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Humid air gas turbine systems that are regenerative cycle using humidified air can achieve higher thermal efficiency than that of the combined cycle (GTCC) though these systems don’t need steam turbine, high combustion temperature and high pressure ratio. Especially, the advanced humid air turbine (AHAT) is seemed to be near practical used because the composition is simpler than other systems. And the thermal efficiency difference of AHAT and GTCC grows by the small and medium-size gas turbine. To verify the system concept and cycle performance of AHAT, 3.6MW pilot plant was constructed. The plant consists of a gas turbine with a two-stage radial compressor, a two-stage axial turbine, a reverse-flow type of single-can combustor, a recuperator, a humidification tower, a water recovery tower, and other components. As a result of the running test, it has been confirmed the plan output 3.6MW and the validity of AHAT as a power generating system. In this study, the thermodynamic characteristic of the AHAT system is analyzed, and various characteristics are verified by the running test results of this AHAT pilot plant through the year.

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Bioenergy is one of effective measures to decrease GHG emission, because of its carbon neutrality. However, high costs for transportation, feedstock, and energy conversion are a barrier to promote the utilization of bioenergy. There is an economical trade-off relation between a scale effect of plant capacity and transporting distance of fuel supply, because most biomass resources are widely distributed throughout a region. Both transportation and process conversion costs can be reduced by developing an efficient bioenergy production system. Biomass is a local energy which has various types of resources. Its installed potential should be evaluated in a specific area. This study aims at developing an optimal method to analyze minimum cost of transportation and process conversion system utilized in Ibaraki prefecture. An optimal plant size and a location of bioenergy conversion plant are determined by minimizing transportation cost (p-median problem) with exogenous value of the number of plants. Cost, benefit and CO₂ emission reduction are estimated by the optimization model and the geographic information system. From the model analysis we can obtain an optimal transportation process and the number of profitable conversion plants for each biomass resource in Ibaraki prefecture.

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