Takuya Oda

Novel carbon-free integrated system of hydrogen production and storage from low rank coal is proposed and evaluated. To measure the optimum energy efficiency, two different systems employing different chemical looping technologies are modeled. The first integrated system consists of coal drying, gasification, syngas chemical looping, and hydrogenation. On the other hand, the second system combines coal drying, coal direct chemical looping, and hydrogenation. In addition, in order to cover the consumed electricity and recover the energy, combined cycle is adopted as addition module for power generation. The objective of the study is to find the best system having the highest performance in terms of total energy efficiency, including hydrogen production efficiency and power generation efficiency. To achieve a thorough energy/heat circulation throughout each module and the whole integrated system, enhanced process integration technology is employed. It basically incorporates two core basic technologies: exergy recovery and process integration. Several operating parameters including target moisture content in drying module, operating pressure in chemical looping module, are observed in terms of their influence to energy efficiency. From process modeling and calculation, two integrated systems can realize high total energy efficiency, higher than 60%. However, the system employing coal direct chemical looping represents higher energy efficiency, including hydrogen production and power generation, which is about 83%. In addition, optimum target moisture content in drying and operating pressure in chemical looping also have been defined.

The fast-increasing introduction of renewable energy sources (RESes) leads to some problems in electrical power network due to fluctuating generated power. A power system must be operated with provision of various reserve powers like governor free capacity, load frequency control and spinning reserve. Therefore, the generator’s schedule (unit commitment schedule) should include the consideration of the various power reserves. In addition, it is necessary to calculate the annual operational costs of electric power systems by solving the unit commitment per week of thermal power generators and pumped storages in order to compare and examine the variance of the operational costs and the operating ratio of the generators throughout the year. This study proposes a novel annual analysis for the thermal power generator and pumped storages under a massive introduction of RESes. A weekly unit commitment schedule (start/stop planning) for thermal power generator and pumped storages has been modeled and calculated for one year evaluation. To solve the generator start/stop planning problem, Tabu search and interior point methods are adopted to solve the operation planning for thermal power generators and the output decision for pumped storages, respectively. It is demonstrated that the proposed method can analyze a one-year evaluation within practical time. In addition, by assuming load frequency control (LFC) constraints to cope with photovoltaic (PV) output fluctuations, the impact of the intensity of LFC constraints on the operational cost of the thermal power generator has been elucidated. The increment of the operational cost of the power supply with increasing PV introduction amount has been shown in concrete terms.

The increase of electric vehicles (EVs) has led to some challenging problems and opportunities, especially related to electricity issues. The uncontrolled charging and discharging of EVs can reduce the quality of electricity grid due to frequency and voltage instabilities. However, the optimized utilization of EVs also offers high potential for ancillary service including frequency control and storage. The adoption of EVs and used EV batteries is expected to be able to improve the total economic performance of EVs as well as reduce the environmental impact. In this chapter, the utilization of EVs, together with their used batteries, to support the electricity (load leveling) in a smallscale energy management system (EMS) is analyzed and demonstrated. The demonstration bed consists of five EVs, five used EV batteries, and photovoltaic (PV) panels. The EMS forecasts the load of the office building and the possibly generated power from PV panels. In addition, it also calculates the potential of EVs which are available for joining the load leveling program. EMS will control all the charging and discharging behaviors of connected EVs and used EV batteries, therefore the grid load can be maintained to be lower than the calculated peak-cut threshold. It is found that the utilization of EVs to support small-scale EMS through direct contract is feasible, and hence applicable. At the end of the chapter, some suggestions earned from demonstration test are also listed for further consideration.

The increasing global demand for palm oil and its products has led to a significant growth in palm plantations and palm oil production. Unfortunately, these bring serious environmental problems, largely because of the large amounts of waste material produced, including palm kernel shell (PKS). In this study, we used computational fluid dynamics (CFD) to investigate the PKS co-firing of a 300 MWe pulverized coal-fired power plant in terms of thermal behavior of the plant and the CO₂, CO, O₂, NO_x, and SO_x produced. Five different PKS mass fractions were evaluated: 0%, 10%, 15%, 25%, and 50%. The results suggest that PKS co-firing is favorable in terms of both thermal behavior and exhaust gas emissions. A PKS mass fraction of 25% showed the best combustion characteristics in terms of temperature and the production of CO₂, CO, and SO_x. However, relatively large amounts of thermal NO_x were produced by high temperature oxidation. Considering all these factors, PKS mass fractions of 10%–15% emerged as the most appropriate co-firing condition. The PKS supply capacity of the palm mills surrounding the power plants is a further parameter to be considered when setting the fuel mix.

The utilization of electric vehicles (EV) and their used batteries in supporting small-scale energy management systems were studied. Both theoretical study and practical demonstration were performed to measure the feasibility of the developed system. Each five EVs and used EV batteries were used along with 20 kW photovoltaic (PV) panels as a renewable energy source. The main objective of the developed system is performing a peak-load shifting by utilizing EVs, used EV batteries and PV panels. The planning of load leveling was performed 24 h ahead for each 30 min period. The studies showed that the application of EVs and used EV batteries in supporting certain small-scale energy management systems is feasible. In addition, some findings during the demonstration test were listed and analyzed for the purpose of further system development and deployment.

State-of-the-art integrated macroalgae utilization processes, consisting of drying, gasification, and combined cycle, are proposed and their performance with respect to energy efficiency are evaluated. To achieve high exergy efficiency, the integration is performed through two main principles: exergy recovery and process integration. Initially, the energy involved in one process is recirculated intensively through exergy elevation and effective heat coupling. Furthermore, the unrecoverable energy from one process will be utilized in the other processes through process integration. As the result, the total exergy destruction from the whole integrated processes can be minimized significantly leading to significant improvement in energy efficiency. The first analysis relates to the performance of integrated drying process, especially the influence of target moisture content to energy consumption. Furthermore, the influences of gasification fluidization velocity to the total generated power and power generation efficiency are also calculated. As the results of study, the proposed integrated-processes proved a very high energy efficiency. A positive energy harvesting with the total power generation efficiency of about 40% could be achieved.

The study investigated the effect of the improved partial load COP of adsorption chillers on the cogeneration system in an office building. The partial load COP of the adsorption chiller was maximized by optimizing the cycle time. The COP of the adsorption chiller was increased with smaller partial load ratios by the extended cycle time. The performance of the cogeneration system with an adsorption chiller was analyzed by simulation, and the energy saving ratio of the system was presented. The energy saving ratio was compared with that by the cogeneration system with an absorption chiller. The results showed that the adsorption chiller was advantageous given that the adsorption chiller had the same rated COP value as the absorption chiller.