Takashi Horigome

New proposal for photovoltaic-thermal solar energy utilization method

Abstract One of the most effective methods of utilizing solar energy is to use the sunlight and solar thermal energy such as a photovoltaic-thermal panel (PV/T panel) simultaneously. From such a viewpoint, systems using various kinds of PV panels were constructed in the world. In these panels, solar cells are set up at an absorber collecting solar thermal energy. Therefore, temperature of solar cell increases up to the prescribed temperature of thermal energy use, although it is lower than the cell temperature when using only solar cell panel. For maintaining cell conversion efficiency at the standard conditions, it is necessary to keep the cell at lower temperature. In this paper, electric and thermal energy obtained from a PV/T panel is evaluated in terms of energy. Based on this evaluation, the method of not to decrease cell conversion efficiency with collecting solar thermal energy was proposed.

Investigation of nitrate salts for solar latent heat storage

Abstract Solar thermal applications require some means of thermal energy storage. Amongst several storage concepts, latent heat storage is quite suitable because of its high storage density and almost constant temperature during charging and discharging. The temperature range between 200 and 300°C is considered to be important for solar total energy systems. In this temperature range, sodium nitrate and its mixed salts with other nitrates including eutectic and off-eutectic salts are candidates. The present paper deals with heat transfer in a latent heat storage unit utilizing these salts. A method of rough estimation of the thermal conductivity of the storage materials is described, and the temperature history of the storage material experimentally obtained is compared with numerical solutions and found to be in reasonably good agreement. It is seen that the temperature of the heat transfer surface quickly drops soon after the appearance of a solid phase due to low thermal conductivity of these salts. Ways to avoid this temperature drop are discussed.

Solar thermal energy storage using heat of dilution: Analysis of heat generation in multistage mixing column

Abstract Storage of solar energy is important for the future success of solar energy utilization systems such as solar thermal power plants. Various papers have described the storage methods for storing solar energy. Because of the results of assessing the storage methods proposed in these papers, the method based on heat of dilution was selected by reasons of the ease of heat transfer, the controllability of reaction and the recovery of heat stored. The effectiveness of heat recovered from heat of dilution in the case of storing solar energy in the form of heat of dilution was considered in this paper. Sulfuric acid and water solution used as the typical example of heat of dilution, since its thermodynamic properties were well known. Two liquids were mixed in two different systems of multistage mixing column, and an application of heat of dilution to multipurpose energy utilization was analyzed. The utility of heat of dilution was explained from the results of thermal characteristics of each system.

A terrestrial solar thermal electric power system—Development of basic model system☆

Abstract A model system of a distributed collector power system was constructed at the Electrotechnical Laboratory, Tanashi, Tokyo, Japan in the summer of 1975. This model system consisted of a cylindrical parabolic concentrator, heat transfer loop and storage-type heat exchanger and has been used for evaluating the system performance and the dynamic characteristics of each subsystem and the whole system. This paper presents the performance of each subsystem used in the model system and summarizes results obtained from tests made on the whole system.

A terrestrial solar energy power system

Development of an effective solar energy utilization technique is of prime importance in solving the energy crisis mankind is confronted with today. In recent years advancements have been made in high temperature measurements, high efficiency selective radiation materials, high temperature heat pipes, heat storage medium, semiconductor manufacturing techniques, space technology, etc. In this article the authors outline a solar energy utilization system (a terrestrial solar energy power system) and discuss the feasibility of a solar energy power system.

Measuring System for Dynamic Characteristics of Semiconductor Switching Elements and Switching Loss of Thyristors

Thyristors today are used in various electrical apparatus where high operational reliability is of prime importance. For better operational reliability, it is essential that thyristors be used most effectively. It especially is important to predict quantitatively the thyristors internal impedance (dynamic impedance) which varies by time and by switching loss as transiential stress is applied to the thyristor when it is turned-on and -off, and to design a thyristor circuit basing on the predicted dynamic impedance. This article introduces an outline of a measuring system which can be used for quantitative determination of dynamic characteristics of thyristors and discusses switching loss determined with the measuring system. The measuring system consists primarily of two A/D converters. Dynamic characteristics of a thyristor, either of a normal type or high-speed type, can be quantitatively measured in one turn-on or turn-off operation. This article also discusses the effect of variation of the element area of the thyristor on the switching loss.