Masatsugu Amano

Maximum output control of photovoltaic (PV) array

A photovoltaic (PV) system output depends on environmental parameters such as the solar insolation and the PV module temperature. If it is possible to predict the maximum power point under the outdoor environment and to operate at that point, the PV system can generate the maximum output every time. In this paper, a maximum power point control method that maximizes the output of a PV array is proposed. This method determines the maximum output operation point from the I-V characteristics introducing empirically the effects of the solar insolation and the module temperature. The authors derived two main parameters from this analysis; one is the power gain G, and another is the environmental operation parameter X. At the operation point determined by this method, G becomes larger than that of under the same environmental conditions. G becomes large with the increase of X, and the large X mainly means low solar insolation. The characteristics of PV module which will supply more power especially at large X should satisfy the following points; the fill factor of the module should be lower and the short circuit current of the module should be larger than those of arrays currently available in the market.

Influence of the internal structure and temperature in the reaction layer on the electric output in a solar thermal cell

A solar thermal cell is composed of the chemical reaction of 2-propanol/acetone/hydrogen and a fuel cell. We have examined the influence of the internal structure and the temperature in the solar thermal cell on the output of the cell. As the main results, (1) with increasing the temperature of the positive electrode, the short circuit current of the cell has increased, (2) with decreasing the thickness of the electrode space, the output of the cell has increased and (3) under the condition that the electrodes are kept in good contact with the polymer electrolyte, the performance of the cell increases and the short circuit current reaches 80 mA.

Performance characteristics of barometric-type open-cycle OTEC system

Open Cycle-Ocean Thermal Energy Conversion (OC-OTEC) system has a merit to use a heat exchanger of direct contact type without a heat transfer tube. Therefore, it is expected that the capital cost of OC-OTEC is reduced by use of this simply designed heat exchanger. However, non-condensable gas is released in the system, because in a direct contact evaporator, the steam driving a turbine is generated by surface sea water including air, and existing air causes a reduction of system performance. From the above point of view, we carried out an experimental study on the operating characteristics and the effect of structure of a heat exchanger and the existence of non-condensable gas on the performance of a direct contact heat exchanger in an experimental apparatus of barometric type OC-OTEC. As a result, the performance of the direct contact evaporator can be satisfied. However, we cannot get satisfactory results in a direct contact condenser. Therefore, we conducted further experiments through the improvement of the structure of the condenser and the control of the non-condensable gas. Finally, we concluded that the major factor affecting the system performance is the non-condensable gas, but its effect can be ignored when its concentration is below 8%.

Measurement of Solid Oxide Fuel Cell System Flow Rate by Tracer Gas Method

A high-precision method to measure efficiency of fuel cells with a 0.1% margin of error is proposed. This method is principally divided into two procedures: determining the composition of fuel gas to be fed into a fuel cell system and measuring the flow rate of the fuel gas. The composition of the fuel gas is determined by an FTIR (Fourier transform infrared spectrometer) and/or a QMS (quadrapole mass spectrometer) with a built-in sonic nozzle sampling system. The flow rate was measured by the tracer gas method; that is, a given amount of tracer gas, such as one of the noble gases, was introduced into the line of the fuel gas, then, the mixed gas was sampled at the point where the tracer gas had been well mixed, and the concentration of the tracer gas was determined by the QMS. In this paper, a gravimetric calibration method using a highly sensitive balance is also proposed for flow control of the tracer gas. Also proposed are calibration of the FTIR and the QMS to establish the required low uncertainty or high accuracy of the measurement of the efficiency.

Solar Tri-Generation: New Concept of Solar Energy System

It is general that each of the heat and electricity is individually supplied even if their resources are the same. However, from the viewpoint of the effective use of energy resources, development of co-generation producing both of them is promoted. To enhance more the utilization of energy resources, it is considered to supply three different types of energy from one energy resource. This is a basic concept of tri-generation and we named it first in the world. Tri-generation we proposed supplies heat, electricity and fuel. By this definition, we can easily understand that tri-generation is realized by utilizing solar energy. Therefore, we call it solar tri-generation. In this paper, the methods of system structure and the feature of solar tri-generation are described and we conducted a simplified analysis to make clear the effectiveness of solar tri-generation in the comparison of effective use of solar energy with a solar co-generation consisting of photovoltaic cell modules and photovoltaic/thermal modules. Furthermore, from the viewpoint of CO2 emission reduction, we conducted a simplified analysis to make clear the characteristics of energy consumption in the three systems of a fossil fuel fired co-generation and, a solar co-generation and a tri-generation with fossil fuel fired co-generation.Copyright