Operation planning of an independent microgrid for cold regions by the distribution of fuel cells and water electrolyzers using a genetic algorithm

An energy system using a microgrid was examined in this work. The motivations for this study are to promote green energy usage, discuss concerns regarding energy supply during disasters, and improve the efficacy of waste heat usage. To create a society based on clean hydrogen energy, this paper studied the use of a microgrid to supply energy to six houses in a cold region. The proposed microgrid consisted of photovoltaics, a water electrolyzer, a fuel cell, and a heat pump; furthermore, this microgrid was not accompanied by any external energy supply. In this paper, the optimized calculation results obtained from the genetic algorithm (GA) were compared between a system operated using one set of large capacity equipment (a concentrated system) and a system operated using two or more pieces of distributed small-capacity equipment (a distributed system). From this comparison, the operation efficiency of each set of equipment was characterized using the difference in the load factor of the fuel cell and that of the water electrolyzer of each system. Moreover, the optimal capacities of the solar cell, fuel cells, water electrolyzers, and heat pumps while operating an energy-independent microgrid with the concentrated system and the distributed system were presented.     

Power generation efficiency of an SOFC–PEFC combined system with time shift utilization of SOFC exhaust heat

A microgrid, with little environmental impact, is developed by introducing a combined SOFC (solid oxide fuel cell) and PEFC (proton exchange membrane fuel cell) system. Although the SOFC requires a higher operation temperature compared to the PEFC, the power generation efficiency of the SOFC is higher. However, if high temperature exhaust heat may be used effectively, a system with higher total power generation efficiency can be built. Therefore, this paper investigates the operation of a SOFC–PEFC combined system, with time shift operation of reformed gas, into a microgrid with 30 houses in Sapporo, Japan. The SOFC is designed to correspond to base load operation, and the exhaust heat of the SOFC is used for production of reformed gas. This reformed gas is used for the production of electricity for the PEFC, corresponding to fluctuation load of the next day. Accordingly, the reformed gas is used with a time shift operation. In this paper, the relation between operation method, power generation efficiency, and amount of heat storage of the SOFC–PEFC combined system to the difference in power load pattern was investigated. The average power generation efficiency of the system can be maintained at nearly 48% on a representative day in February (winter season) and August (summer season).     

Induced radioactive nuclides of 10-MeV radiotherapy accelerators detected by using a portable HP-Ge survey meter

The radioactivation of linear accelerator components for radiation therapy is interest for radiation protection in general, and particularly, when decommissioning these structures. The energy spectra of gamma rays emitted from the heads of two accelerator models, EXL-15SP and Clinac iX, after 10-MeV X-ray irradiation, were measured using a high-purity germanium semiconductor survey meter. After spectrum analyses, activities of (24)Na, (28)Al, (54)Mn, (56)Mn, (57)Ni, (58)Co, (60)Co, (64)Cu, (65)Zn, (122)Sb, (124)Sb, (181)W, (187)W, (196)Au, and (198)Au were detected. One centimetre deep dose-equivalent rate of the heads of the linear accelerator was measured using the survey meter. The dose rate decreased to ～10 % of its initial rate after 1 week. Long-term activations were few, the radioactivity level was low, and a cooling time of several days was effective for reducing dose rate to an acceptable level for decommissioning.     

Performance characteristics of external cavities to generate deep-ultraviolet coherent lights resonant to 3pP1−4sP0 cyclic transition of Si

We developed a robust 252 nm single-mode coherent continuous-wave light source through two-stage highly efficient frequency conversion systems using external cavities. In the first stage, we obtained the second harmonics (SH) power of 630 mW from the LBO-installed external cavity by frequency doubling of a 746 nm Ti: sapphire laser with an efficiency of almost 50% [Y. Asakawa, H. Kumagai, K. Midorikawa, M. Obara, Opt. Commun. 217 (2003) 311.]. In the second stage, 252 nm light power was obtained by doubly resonant sum-frequency mixing of 373 nm light from the first-stage conversion system and 780 nm light from another Ti:sapphire laser. In the sum-frequency external cavity, the maximum 252 nm light power of over 150 mW is obtained, which is about three times larger than that obtained in our previous experiment.     

Pharmacokinetic study of an oral cephalosporin, cefdinir, in hemodialysis patients

The pharmacokinetics of cefdinir were investigated in six hemodialysis patients. For the present study, two tests were carried out, one with 4 h of hemodialysis and the other without hemodialysis. Cefdinir was given orally to each patient in a dose of 100 mg, and blood was collected serially for 48 h after dosing in the test without dialysis and for 72 h in the test with dialysis. In the test without dialysis, the maximum plasma concentration (Cmax) was 2.36 +/- 0.53 micrograms/ml (mean +/- standard deviation) and the time to Cmax was 9.00 +/- 2.45 h. The terminal elimination half-life (t1/2) and area under the concentration-time curve (AUC) were 16.95 +/- 1.20 h and 69.05 +/- 14.84 micrograms.h/ml, respectively. In the test with dialysis, t1/2 during hemodialysis decreased approximately to one-sixth of that obtained in the test without dialysis, although t1/2 in the latter elimination phase did not differ from that in the nondialysis test. AUC was reduced to 43% of that in the test without dialysis. The fractional removal of cefdinir by hemodialysis was 61%. These findings indicate that clearance of cefdinir is prolonged in patients with renal failure, and cefdinir is well removed by introduction of hemodialysis, although t1/2 (during hemodialysis) and AUC were two and eight times higher than the data previously reported for healthy volunteers, respectively. The pharmacokinetic data suggest that 100 mg of oral cefdinir once a day would result in a sufficient concentration in plasma in hemodialysis patients, but this remains to be confirmed by multiple-dose studies.     

Noninvasive online measurement of particle size and concentration in liquid–particle mixture by estimating equivalent circuit of electrical double layer

ABSTRACT

Three electrical elements (i.e., resistance, capacitance, and relaxation frequency) of electrical double layer (EDL) formed around particles have been extracted by a measuring–fitting combination for a novel noninvasive online measurement technique of particle size and concentration in a liquid–particle mixture. The measuring–fitting combination means measuring the impedances with electrical-impedance spectroscopy (EIS) method, and fitting the equivalent circuit with Levenberg–Marquardt method. The liquid–particle mixture in the impedance measurement is made of sodium chloride solution and stainless particles; the equivalent circuit is established corresponding to the contents in the liquid–particle mixture. As a result, the influence of the particle size and concentration on the electrical elements in the EDL which are the resistance, capacitance, and relaxation frequency in the EDL are clarified and discussed. This method is useful for determination of the particle size and concentration in liquid–particle mixture.     

Fourth Sound Measurement of Superfluid 3He in Aerogel

The fourth sound resonance experiment has been done on liquid ³He in 98.5% porosity aerogel. Aerogel was grown inside the pores among the sintered silver powder to avoid the vibration of the aerogel strands by the sound experiment. The measurement was performed at zero magnetic field and 27 bar. We observed the phase transition between the A-like and B-like phases and also their coexistent state. The A-like to B-like phase transition occurs not at a temperature but within a temperature band. In this band, the A-like phase gradually converts to the B-like phase. Possible picture of the coexistent state is discussed.     

Negative Ion Mobility in Superfluid 3He Under High Magnetic Field

The negative ion mobility has been measured in superfluid ³He at pressures above 20 bar under high magnetic field up to 14 Tesla. It does not depend on the temperature in the normal phase, followed by a rapid increase below the superfluid transition in both A ₁ and A ₂ phase. The isothermal mobility is found to be independent of the magnetic field in the normal and A ₂ phase, while it decreases with increasing magnetic field in the A ₁ phase. This field dependence is explained by taking account of the field dependence of the transition temperature (T _{A 1}) between the normal and the A ₁ phase. Therefore the scattering cross section between, the negative ion and the ³He quasiparticles has no magnetic field dependence both in the superfluid and the normal phase.     

Observation of Laminar and Turbulent Flow in Superfluid 4He using a Vibrating Wire

No Heading We have investigated the laminar and the turbulent flow in superfluid ⁴He using a vibrating wire made of thin NbTi ( 2.5 m). The wire velocity as a function of applied force has shown a large hysteresis at the first cooling from normal fluid to the superfluid state. But after a couple of increasing and decreasing wire velocity we have found that the hysteresis vanished and the laminar and the turbulent flow are clearly separated at a critical velocity. The wire moving just after the first cooling must be influenced by remnant vortices nucleated through the superfluid transition. The appearance of the laminar flow below the critical velocity suggests that vortex strings on the wire seem to be selected as suitable sizes by a vibrating flow at higher velocities. We also measured the velocity dependence after immersing the wire directly into the superfluid and found that the laminar region expands up to a velocity much higher than the critical velocity observed above. This result indicates that remnant vortices are considerably reduced by the immersing method.PACS numbers: 67.40.Vs, 47.27.Cn