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PSL Projects : Novel Solar Array Configuration for Enhanced Power Generation
This project develops novel and optimum solar array and power converter configurations that significantly enhance the power available for portable systems that are used under partially shaded conditions such as solar jackets and backpacks. Study results demonstrated that the power produced is increased by a typical factor of two and no extra cost is added.
In photovoltaic solar arrays, the cells are generally connected in series to obtain the desired voltage, and diodes are added to bypass groups of mismatched cells or shaded cells. For example, as shown in Fig. 1, a traditional solar panel is connected with 20 cells in series then 3 strings in parallel, and a bypass diode is added to every 5 solar cells.
Fig. 1 Solar panel connected with a traditional configuration.
Solar arrays are often subject to partially shading or continuously changing shadow conditions whether they are mounted outdoors or moving with equipment that uses them. The partially shaded cells generate a certain amount of energy but that energy cannot be collected by the widely used designs where bypass diodes are used, thus this part of the energy is wasted. This problem is not a significant problem in high voltage systems or in stationary systems that do not have obstructions. It is a significant problem in low voltage systems and in systems where partial shading occurs. Therefore, it is necessary to find out an optimum array configuration in terms of cell connections to maximize the array power generation.
Addressing this problem, opitimum array configurations were proposed and
validated in this project. Fig. 2 shows the prototype of the solar panel using
an optimium array configuration with a power
converter to regulate the output
Fig. 2. Prototype of solar panel using optimum configuration and its power
converter.
Fig. 3 illustrates the comparison of power generation between the optimum configuration and the traditional configuration. Total seven experimental tests were taken, in which the first five tests were done out-of-doors and the last two were taken in laboratory. In each test, the power generated by the optimum configuration is first normalized to 100% and then it is used to calculate the relative power generated by the traditional configuration. It can be seen that, from Fig. 2, the optimum configured solar panel has better performance and its power generation capability is enhanced by a typical factor of 2 at partially shaded conditions. Table 1 lists the descriptions of test conditions.
Fig. 3. Comparison of power generation between optimum and traditional
configurations.
Table. 1. Description of test condition
|
Test No. |
Place |
Test Description |
|
1 |
Out-of-doors |
* Area has no shade * Panels stationary * Panels positioned
horizontally |
|
2 |
Out-of-doors |
* Area shaded by trees * Panels constant movement * Panels positioned
horizontally |
|
3 |
Out-of-doors |
* Area shaded by trees * Panels constant movement * Panels positioned about
70 degrees to the horizontal |
|
4 |
Out-of-doors |
* Area shaded by trees * Panels constant movement * Panels positioned about
70 degrees to the horizontal |
|
5 |
Out-of-doors |
* Area shaded by railing * Panels stationary * Panels positioned
horizontally |
|
6 |
Laboratory |
* 300 W artificial
illumination source * Panels stationary * Constant swing of
artificial shade |
|
7 |
Laboratory |
* 300 W artificial
illumination source * Panels stationary * Constant swing of
artificial shade |
Fig. 4 shows the pictures of experimental tests in both Laboratory and out-of-doors.
Fig. 4 Photos of experimental tests.
