承包商管理制度E-mail address:-f.co.jp(T.Matsushima).
骑车能减肥吗0927-0248/03/$-e front matter r2002Elvier Science B.V.All rights rerved.
PII:S0927-0248(02)00156-3
have developed a new type of concentrating module without lens or sun-tracking mechanisms.
2.Concept and structure
The propod concentrating module was designed and constructed taking into consideration two restrictions:that it should not require special lens or a sun-tracking mechanism.Conventional concentrating modules sometimes u lens of high concentration ratio (B 100Â)[1]that are ud to focus solar light onto the solar cells regardless of the azimuth or altitude of the sun.The processing cost for concentrating lens in this PV system is not negligible,becau they may require special configuration.In the high-concentration modules,special solar cells designed specifically for the application are necessary.Resultant issues such as too inten heat radiation from the cells may ari becau the cell temperatures may sometimes reach such high values that they cannot be neglected.As for sun tracking,it requires special control devices and complicated mechanical apparatus for driving,and the may be costly.
Taking into account the expensiveness and complexity of the previous concentrating modules,we have developed a different type of concentrating module that applies horizontal reflectors.In this mod
ule,any kind of conventional solar panel can be ud,becau they are installed in the usual way with a slightly higher tilt angle.To be specific,in this concept,a single module is constructed by installing a solar panel at a vertical angle witha reflector in front of it on a downward incline to the solar panel.This reflector enables the solar panel to collect more solar light than a conventional one,becau it receives both direct and reflected sunlight.Though a module unit has only one reflector in front of the panel,as can be en in Fig.1,this concentrating module PV system may effectively receive bothdirect and reflected sunlight regardless of the sun’s azimuth or altitude.This is becau the system must be constructed by installing many adjoining units in clo contact and reflector size must be designed by taking the effective light reflection into consideration.
泡面怎么做好吃
Horizon
Inclination angle
Fig.1.Schematic view of concentrating solar module (side view).
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Moreover,additional reflectors may be installed on bothsides of th e module strings so as to project the reflected sunlight onto the whole panels.Conquently,the construction concept of this PV system eliminates the need for sun tracking.
3.Characteristics
Characteristic tests on this concentrating module were carried out under artificial sunlight in laboratories and in actual outdoor sunlight to ascertain the effects on the improvement of the generation characteristics.Small test modules were constructed using two 125-mm-square cells and witha reflector mounted at a righ t angle,as shown in Fig.1.The reflective efficiency of this reflector is over 95%.The width of the reflector is twice that of 125-mm cell and the length is 2.7times the 125-mm cell.3.1.Improvement in output current
Fig.2shows the test results obtained by projecting artificial sunlight from the front onto the module at
veral incident angles.Short-circuit currents were ud as the evaluation index of the module’s characteristics.Two 125-mm square cells with the same specifications as tho of the module were ud as a reference panel.The intensity of the artificial sunlight was 1000W/m 2.The test module delivered less current when the module had no reflectors becau the tilt angle of the panel was higher than that of conventional panels.However,the current clearly incread when the reflector was attached to the front of the panel.The increa was higher when the sun’s altitude was lower and a current increa of approximately two times that of
S h o r t -c i r c u i t c u r r e n t (I s c )[A ]
module (Tilt angle: 20° )Propod module (Inclination angle: 0)
1
Fig.2.Generation characteristics of propod module as function of sun altitude (sunlight:artificial
standard sunlight,solar panel:two 125-mm-square cells).
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conventional panels was achieved at an incident angle of 301.The current increas coincided well with that of sunlight calculated.Obviously,the current increas described above were brought about by the sunlight projected by the reflector,and the amount of the light was greater at lower sun altitudes.Thus,incident angles lower than 501have a large positive effect on increasing output current and are desirable.
The incident angle of the sun with respect to the module changes as the inclination angle of the module varies.This suggests that the generation characteristics of the module can be varied by changing its inclination angle.Taking the above assumption into consideration,the effects of the module’s inclination angle were investigated.Fig.3shows the current increas obrved in relation to the inclination angle of the module.The current increa rate ro as the inclination angle incread.
This is becau the relative incident angle of the sun is lower and the amount of reflected sunlight increas with an increa in the effective reflective area.Approximately the same current as that of the conventional module was obtained at an inclination of 201,even though the incident angle was 701.
This means that a higher output current than that of the conventional module can be obtained by placing the module at an angle of around 201throughout the year,becau the sun’s altitude is only at such a high angle in the summer.3.2.Characteristics under actual sunlight
Characteristic tests were carried out outside under actual sunlight by using a small test module of the propod concentrating module in order to ascertain the current
Propod module (Inclination angle)
Conventional module
(Tilt angle: 20°)
S h o r t -c i r c u i t c u r r e n t (I s c ) [ −] R e l a t i v e V a l u e :
1
2
Fig.3.Effects of inclination angle on the generation characteristics of propod module (sunlight:artificial standard sunlight,solar panel:two 125-mm-square cells).
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rate at noon.As shown in Fig.4(a),the rate of current increa reached 1.8times that of conventional panels at noon when sunlight was projected from the front (sun altitude:361,irradiation:919W/m 2).Current increas due to the inclination of the module were also obrved (Fig.4(b)).The current i
ncrea rate was 1.4times compared to the conventional panel when the module was placed horizontally,and the rate incread to 1.7times when the module was slanted at an angle of 201(sun altitude:441,irradiation:769W/m 2).The results are in good agreement with the
Current increa
Effects of inclination angle on current increa
1
2
S h o r t -c i r c u i t c u r r e n t ( I s c )
敬老爱老手抄报
8 9 10 11 12 13 14 15 16
Time of day
S h o r t -c i r c u i t c u r r e n t ( I s c ) [ −] (R e l a t i v e V a l u e )
Conventional module
(Tilt angle: 20°)
Propod module
Solar altitude: 36°故土难离
2
生命中的过客1
8 9 10 11 12 13 14 15 16
Time of day
[ −] (R e l a t i v e V a l u e )
(a)
(b)
Fig.4.Generation characteristics of a small concentrating module under actual sunlight (modules:two 125-mm-square cell module).
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results shown in Fig.3.Our concentrating module thus increas short-circuit currents under actual sunlight.The current curves on the concentrating module have a slightly sharp shape than expectation.This is becau as the reflector is installed just in front of the cells,only the sunlight that reached the reflector was reflected and projected throughout the day.As for cell temperature,approximately 151C ri was obrved at noon,but this temperature ri is suppod to be not harmful for generation characteristics.In addition,the concentration ratio in this module is so small;approximately below 2,so that short-circuit current is magnified in accordance withth e concentrating ratio.
A full-size prototype was constructed in order to measure the fundamental characteristics for a long duration,including the effects of asonal weather conditions.It was constructed from three 75-W panels and reflectors by installing them so as to make a right angle.The size of the solar panel is 490(H)Â1240(W)and reflector 1350(H)Â1350(W)(mm).The module was ttled with an inclination angle of 201.The concentrating module is so constructed that the reflected sun light can be projected onto the panel in the range over 401altitude and under 7451azimuth.This effective reflection area can be varied by lecting the appropriate reflector size.Edge effects can be solved by installing additional reflectors on both sides of the strings of module.(On this prototype module,such additional reflectors are not provided.)Fig.5shows its external view and the test results in terms of irradiance on the panels.Irradiance was measured by the pyrano-meter installed on the top of the central panel with same angle as the panel.As Fig.5(b)clearly shows,irradiance on the concentrating module was incread and exceeded in the time between 9:00and 15:00than that of the conventional one,and the concentration ratio reached 1.6times that of the conventional panel at noon.Output current from our concentrating module was also obrved to increa and exceeded that of the conventional one becau of the incread amount of sunlight projected.The test results demonstrate the ufulness of this module concept from the viewpoint of improvement of the generation characteristics.
4.Comparison of the generation characteristics
小儿疳积糖The propod module has great effects on the improvement of the generation characteristics by a factor of 1.8times at most,compared to the conventional panel.As sun altitude varies in each month,generation characteristics in each monthwere calculated and compared on th e conventional and concentrating module in order to clarify the sun altitude effects on the characteristics of this new module.The generation characteristics at noon were lected and calculated for the easy comparison.At first,irradiance on each panel was calculated,then the generated electricity was estimated at noon.Modules with the structure shown in Fig.6were applied for the comparison.What should be emphasized is that the area of the solar panels for our concentrating module was 1/2that of conventional ones.The following calculations were made for each
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