Abstract: In this experiment, we investigated the performance of
two types of heat sink, swaged- and extruded-type, used in the inverter
of industrial electricity generator. The swaged-type heat sink has 62
fins, and the extruded-type has 38 fins having the same dimension as
that of the swaged-type. But the extruded-type heat sink maintains the
same heat transfer area by the laterally waved surface which has 1 mm
in radius. As a result, the swaged- and extruded-type heat sinks
released 71% and 64% of the heat incoming to the heat sink,
respectively. The other incoming heat were naturally convected and
radiated to the ambient. In spite of 40% decrease in number of fins, the
heat release performance of the extruded-type heat sink was lowered
only 7% than that of the swaged-type. We believe that, this shows the
increment of effective heat transfer area by the laterally waved surface
of fins and the better heat transfer property of the extruded-type heat
sink.
Abstract: In recent times there has been a growing interest in the
development of quasi-two-dimensional niobium pentoxide (Nb2O5)
as a semiconductor for the potential electronic applications such as
capacitors, filtration, dye-sensitised solar cells and gas sensing
platforms. Therefore once the purpose is established, Nb2O5 can be
prepared in a number of nano- and sub-micron-structural
morphologies that include rods, wires, belts and tubes. In this study
films of Nb2O5 were prepared on gold plated silicon substrate using
spin-coating technique and subsequently by mechanical exfoliation.
The reason this method was employed was to achieve layers of less
than 15nm in thickness. The sintering temperature of the specimen
was 800oC. The morphology and structural characteristics of the
films were analyzed by Atomic Force Microscopy (AFM), Raman
Spectroscopy, X-ray Photoelectron Spectroscopy (XPS).
Abstract: In this paper, an attempt has been made to obtain nonsensitive
solutions in the multi-objective optimization of a
photovoltaic/thermal (PV/T) air collector. The selected objective
functions are overall energy efficiency and exergy efficiency.
Improved thermal, electrical and exergy models are used to calculate
the thermal and electrical parameters, overall energy efficiency,
exergy components and exergy efficiency of a typical PV/T air
collector. A computer simulation program is also developed. The
results of numerical simulation are in good agreement with the
experimental measurements noted in the previous literature. Finally,
multi-objective optimization has been carried out under given
climatic, operating and design parameters. The optimized ranges of
inlet air velocity, duct depth and the objective functions in optimal
Pareto front have been obtained. Furthermore, non-sensitive solutions
from energy or exergy point of view in the results of multi-objective
optimization have been shown.
Abstract: Space exploration is a highly visible endeavour of
humankind to seek profound answers to questions about the origins
of our solar system, whether life exists beyond Earth, and how we
could live on other worlds. Different platforms have been utilized in
planetary exploration missions, such as orbiters, landers, rovers, and
penetrators.
Having low mass, good mechanical contact with the surface,
ability to acquire high quality scientific subsurface data, and ability to
be deployed in areas that may not be conducive to landers or rovers,
Penetrators provide an alternative and complimentary solution that
makes possible scientific exploration of hardly accessible sites (icy
areas, gully sites, highlands etc.).
The Canadian Space Agency (CSA) has put space exploration as
one of the pillars of its space program, and established ExCo program
to prepare Canada for future international planetary exploration.
ExCo sets surface mobility as its focus and priority, and invests
mainly in the development of rovers because of Canada's niche space
robotics technology. Meanwhile, CSA is also investigating how
micro-penetrators can help Canada to fulfill its scientific objectives
for planetary exploration.
This paper presents a review of the micro-penetrator technologies,
past missions, and lessons learned. It gives a detailed analysis of the
technical challenges of micro-penetrators, such as high impact
survivability, high precision guidance navigation and control, thermal
protection, communications, and etc. Then, a Canadian perspective of
a possible micro-penetrator mission is given, including Canadian
scientific objectives and priorities, potential instruments, and flight
opportunities.
Abstract: The excessive consumption of fossil energies (electrical energy) during summer caused by the technological development involves more and more climate warming.
In order to reduce the worst impact of gas emissions produced from classical air conditioning, heat driven solar absorption chiller is pretty promising; it consists on using solar as motive energy which is clean and environmentally friendly to provide cold.
Solar absorption machine is composed by four components using Lithium Bromide /water as a refrigerating couple. LiBr- water is the most promising in chiller applications due to high safety, high volatility ratio, high affinity, high stability and its high latent heat. The lithium bromide solution is constitute by the salt lithium bromide which absorbs water under certain conditions of pressure and temperature however if the concentration of the solution is high in the absorption chillers; which exceed 70%, the solution will crystallize.
The main aim of this article is to study the phenomena of the crystallization and to evaluate how the dependence between the electric conductivity and the concentration which should be controlled.
Abstract: This paper compares planning results of the electricity and water generation inventory up to year 2030 in the State of
Kuwait. Currently, the generation inventory consists of oil and gas fired technologies only. The planning study considers two main cases. The first case, Reference case, examines a generation inventory based on oil and gas fired generation technologies only.
The second case examines the inclusion of renewables as part of the generation inventory under two scenarios. In the first scenario, Ref-RE, renewable build-out is based on optimum economic performance
of overall generation system. Result shows that the optimum installed
renewable capacity with electric energy generation of 11% . In the second scenario, Ref-RE20, the renewable capacity build-out is
forced to provide 20% of electric energy by 2030. The respective energy systems costs of Reference, Ref-RE and Ref-RE20 case
scenarios reach US dollar 24, 10 and 14 billion annually in 2030.
Abstract: In this paper, we proposed the effects of Mo thickness
on the properties of AZO/Mo/AZO multilayer thin films for
opto-electronics applications. The structural, optical and electrical
properties of AZO/Mo/AZO thin films were investigated.
Optimization of the thin films coatings resulted with low resistivity of
9.98 × 10-5 )-cm, mobility of 12.75 cm2/V-s, carrier concentration of
1.05 × 1022 cm-3, maximum transmittance of 79.13% over visible
spectrum of 380 – 780 nm and Haacke figure of merit (FOM) are 5.95
× 10-2 )-1 under Mo layer thickness of 15 nm. These results indicate an
alternative candidate for use as a transparent electrode in solar cells
and various displays applications.
Abstract: ZnO+Ga2O3 functionally graded thin films (FGTFs)
were examined for their potential use as Solar cell and organic light
emitting diodes (OLEDs). FGTF transparent conducting oxides (TCO)
were fabricated by combinatorial RF magnetron sputtering. The
composition gradient was controlled up to 10% by changing the
plasma power of the two sputter guns. A Ga2O3+ZnO graded region
was placed on the top layer of ZnO. The FGTFs showed up to 80%
transmittance. Their surface resistances were reduced to < 10% by
increasing the Ga2O3: pure ZnO ratio in the TCO. The FGTFs- work
functions could be controlled within a range of 0.18 eV. The
controlled work function is a very promising technology because it
reduces the contact resistance between the anode and Hall transport
layers of OLED and solar cell devices.
Abstract: Recently, nanomaterials are developed in the form of nano-films, nano-crystals and nano-pores. Lanthanide phosphates as a material find extensive application as laser, ceramic, sensor, phosphor, and also in optoelectronics, medical and biological labels, solar cells and light sources. Among the different kinds of rare-earth orthophosphates, yttrium orthophosphate has been shown to be an efficient host lattice for rare earth activator ions, which have become a research focus because of their important role in the field of light display systems, lasers, and optoelectronic devices. It is in this context that the 4fn- « 4fn-1 5d transitions of rare earth in insulating materials, lying in the UV and VUV, are the aim of large number of studies .Though there has been a few reports on Eu3+, Nd3+, Pr3+,Er3+, Ce3+, Tm3+ doped YPO4. The 4fn- « 4fn-1 5d transitions of the rare earth dependent to the host-matrix, several matrices ions were used to study these transitions, in this work we are suggesting to study on a very specific class of inorganic material that are orthophosphate doped with rare earth ions. This study focused on the effect of Ce3+ concentration on the structural and optical properties of Ce3+ doped YPO4 yttrium orthophosphate with powder form prepared by the Sol Gel method.
Abstract: Majority of pepper farmers in Malaysia are using the
open-sun method for drying the pepper berries. This method is time
consuming and exposed the berries to rain and contamination. A
maintenance-friendly and properly enclosed dryer is therefore
desired. A dryer design with a solar collector and a chimney was
studied and adapted to suit the needs of small-scale pepper farmers in
Malaysia. The dryer will provide an environment with an optimum
operating temperature meant for drying pepper berries. The dryer
model was evaluated by using commercially available computational
fluid dynamic (CFD) software in order to understand the heat and
mass transfer inside the dryer. Natural convection was the only mode
of heat transportation considered in this study as in accordance to the
idea of having a simple and maintenance-friendly design. To
accommodate the effect of low buoyancy found in natural convection
driers, a biomass burner was integrated into the solar dryer design.
Abstract: Bangladesh is a developing country with large
population. Demand of electrical energy is increasing day by day
because of increasing population and industrialization. But due to
limited resources, people here are suffering from power crisis
problem which is considered as a major obstacle to the economic
development. In most of the cases, it is extremely difficult to extend
high tension transmission lines to some of the places that are
separated from the mainland. Renewable energy is considered to be
the right choice for providing clean energy to these remote
settlements. This paper proposes a cost effective design of off-grid
wind-diesel hybrid power system using combined heat and power
(CHP) technology in a grid isolated island, Sandwip, Bangladesh.
Design and simulation of the wind-diesel hybrid power system is
performed considering different factors for the island Sandwip.
Detailed economic analysis and comparison with solar PV system
clearly reveals that wind-diesel hybrid power system can be a cost
effective solution for the isolated island like Sandwip.
Abstract: The purpose of this paper is to investigate the adjust-
ment of solar shading devices in office buildings in two different
seasons by occupants, and its influence on the lighting control and
indoor illuminance levels. The results show that occupants take
inappropriate measures both in reducing solar radiation in summer
and in admitting solar gains in winter, resulting in an increase in
lighting energy and a reduction in indoor illuminance. Therefore,
movable shading devices, controlled automatically, are suitable for
building applications to reduce energy consumption.
Abstract: To investigate the energy performance of solar shading devices, this paper carried out a survey on the current status of solar shading utilization in buildings in Ningbo and performed building simulations to evaluate the energy savings potential by adopting different solar shading devices. Results show that solar shading utilization in this area is not popular and effective, and should be considered firstly in the design stage since the potential for energy savings is up to 6.8% for residential buildings and 9.4% for commercial buildings.
Abstract: In this paper a stochastic scenario-based model predictive control applied to molten salt storage systems in concentrated solar tower power plant is presented. The main goal of this study is to build up a tool to analyze current and expected future resources for evaluating the weekly power to be advertised on electricity secondary market. This tool will allow plant operator to maximize profits while hedging the impact on the system of stochastic variables such as resources or sunlight shortage.
Solving the problem first requires a mixed logic dynamic modeling of the plant. The two stochastic variables, respectively the sunlight incoming energy and electricity demands from secondary market, are modeled by least square regression. Robustness is achieved by drawing a certain number of random variables realizations and applying the most restrictive one to the system. This scenario approach control technique provides the plant operator a confidence interval containing a given percentage of possible stochastic variable realizations in such a way that robust control is always achieved within its bounds. The results obtained from many trajectory simulations show the existence of a ‘’reliable’’ interval, which experimentally confirms the algorithm robustness.
Abstract: The precision of heat flux simulation influences the
temperature field and test aberration for TB test and also reflects the
test level for spacecraft development. This paper describes TB tests for
a small satellite using solar simulator, electric heaters, calrod heaters
to evaluate the difference of the three methods. Under the same
boundary condition, calrod heaters cases were about 6oC higher than
solar simulator cases and electric heaters cases for
non-external-heat-flux cases (extreme low temperature cases). While
calrod heaters cases and electric heaters cases were 5~7oC and 2~3oC
lower than solar simulator cases respectively for high temperature
cases. The results show that the solar simulator is better than calrod
heaters for its better collimation, non-homogeneity and stability.
Abstract: Heat powered solid sorption is a feasible alternative to
electrical vapor compression refrigeration systems. In this paper,
activated carbon (powder type Maxsorb and fiber type ACF-A10)-
CO2 based adsorption cooling cycles are studied using the pressuretemperature-
concentration (P-T-W) diagram. The specific cooling
effect (SCE) and the coefficient of performance (COP) of these two
cooling systems are simulated for the driving heat source
temperatures ranging from 30 ºC to 90 ºC in terms of different
cooling load temperatures with a cooling source temperature of 25
ºC. It is found from the present analysis that Maxsorb-CO2 couple
shows higher cooling capacity and COP. The maximum COPs of
Maxsorb-CO2 and ACF(A10)-CO2 based cooling systems are found
to be 0.15 and 0.083, respectively. The main innovative feature of
this cooling cycle is the ability to utilize low temperature waste heat
or solar energy using CO2 as the refrigerant, which is one of the best
alternative for applications where flammability and toxicity are not
allowed.
Abstract: Contour filter strips planted with perennial vegetation
can be used to improve surface and ground water quality by reducing
pollutant, such as NO3-N, and sediment outflow from cropland to a
river or lake. Meanwhile, the filter strips of perennial grass with biofuel
potentials also have economic benefits of producing ethanol. In
this study, The Soil and Water Assessment Tool (SWAT) model was
applied to the Walnut Creek Watershed to examine the effectiveness
of contour strips in reducing NO3-N outflows from crop fields to the
river or lake. Required input data include watershed topography,
slope, soil type, land-use, management practices in the watershed and
climate parameters (precipitation, maximum/minimum air
temperature, solar radiation, wind speed and relative humidity).
Numerical experiments were conducted to identify potential
subbasins in the watershed that have high water quality impact, and
to examine the effects of strip size and location on NO3-N reduction
in the subbasins under various meteorological conditions (dry,
average and wet). Variable sizes of contour strips (10%, 20%, 30%
and 50%, respectively, of a subbasin area) planted with perennial
switchgrass were selected for simulating the effects of strip size and
location on stream water quality. Simulation results showed that a
filter strip having 10%-50% of the subbasin area could lead to 55%-
90% NO3-N reduction in the subbasin during an average rainfall
year. Strips occupying 10-20% of the subbasin area were found to be
more efficient in reducing NO3-N when placed along the contour
than that when placed along the river. The results of this study can
assist in cost-benefit analysis and decision-making in best water
resources management practices for environmental protection.
Abstract: A novel typical day prediction model have been built and validated by the measured data of a grid-connected solar photovoltaic (PV) system in Macau. Unlike conventional statistical method used by previous study on PV systems which get results by averaging nearby continuous points, the present typical day statistical method obtain the value at every minute in a typical day by averaging discontinuous points at the same minute in different days. This typical day statistical method based on discontinuous point averaging makes it possible for us to obtain the Gaussian shape dynamical distributions for solar irradiance and output power in a yearly or monthly typical day. Based on the yearly typical day statistical analysis results, the maximum possible accumulated output energy in a year with on site climate conditions and the corresponding optimal PV system running time are obtained. Periodic Gaussian shape prediction models for solar irradiance, output energy and system energy efficiency have been built and their coefficients have been determined based on the yearly, maximum and minimum monthly typical day Gaussian distribution parameters, which are obtained from iterations for minimum Root Mean Squared Deviation (RMSD). With the present model, the dynamical effects due to time difference in a day are kept and the day to day uncertainty due to weather changing are smoothed but still included. The periodic Gaussian shape correlations for solar irradiance, output power and system energy efficiency have been compared favorably with data of the PV system in Macau and proved to be an improvement than previous models.
Abstract: A new technique based on Pattern search optimization is proposed for estimating different solar cell parameters in this paper. The estimated parameters are the generated photocurrent, saturation current, series resistance, shunt resistance, and ideality factor. The proposed approach is tested and validated using double diode model to show its potential. Performance of the developed approach is quite interesting which signifies its potential as a promising estimation tool.
Abstract: The world demand for potable water is
increasing every day with growing population. Desalination
using solar energy is suitable for potable water production
from brackish and seawater. In this paper, we present a
theoretical study of solar distillation in a single basin under
the open environmental conditions of Chabahar-Iran. The still
has a base area of 2000mm×500mm with a glass cover
inclined at 25° in order to obtain extra solar energy. We model
the still and conduct its energy balance equations under minor
assumptions. We computed the temperatures of glass cover,
seawater interface, moist air and bottom using numerical
method. The investigation addressed the following: The still
productivity, distilled water salinity and still performance in
terms of the still efficiency. Calculated still productivity in
July was higher than December. So in this paper, we show
that still productivity is directly functioning of solar radiation.