Instrumentation for accelerated life tests of concentrator solar cells

Abstract

Concentrator photovoltaic is an emergent technology that may be a good economical and efficient alternative for the generation of electricity at a competitive cost. However, the reliability of these new solar cells and systems is still an open issue due to the high-irradiation level they are subjected to as well as the electrical and thermal stresses that they are expected to endure. To evaluate the reliability in a short period of time, accelerated aging tests are essential. Thermal aging tests for concentrator photovoltaic solar cells and systems under illumination are not available because no technical solution to the problem of reaching the working concentration inside a climatic chamber has been available. This work presents an automatic instrumentation system that overcomes the aforementioned limitation. Working conditions have been simulated by forward biasing the solar cells to the current they would handle at the working concentration (in this case, 700 and 1050 times the irradiance at one standard sun). The instrumentation system has been deployed for more than 10 000 h in a thermal aging test for III-V concentrator solar cells, in which the generated power evolution at different temperatures has been monitored. As a result of this test, the acceleration factor has been calculated, thus allowing for the degradation evolution at any temperature in addition to normal working conditions to be obtained.

Evaluation of the reliability of high concentrator GaAs solar cells by means of temperature accelerated aging tests

“…As mentioned in the previous section, the DBC substrate material used to assemble the cells was selected for its good thermal conductivity and resistance to the high temperatures at which these tests were conducted. The measurement method setup used to emulate the working conditions and the method used to determine the solar cell junction temperature during tests are described in detail in [13]. Table I shows the testing temperatures and the total test duration, together with the number of cells tested at each concentration for each temperature (for the sake of simplicity, 0X indicates the emulated dark condition, i.e., no illumination, and no bias was applied).…”

“…These two types of tests are described in detail in . A new data acquisition system was designed and built. Its full description can be found elsewhere . A new method for encapsulating solar cells using direct bonded copper substrates (DBC) was implemented. This encapsulation technique provided good thermal management and minimized the risks associated with failure of elements not in the solar cells. Three temperatures and two concentration ratios were applied.…”

“…As mentioned in the previous section, the DBC substrate material used to assemble the cells was selected for its good thermal conductivity and resistance to the high temperatures at which these tests were conducted. The measurement method setup used to emulate the working conditions and the method used to determine the solar cell junction temperature during tests are described in detail in .…”

“…Accordingly, the suitable period was determined experimentally, 18 h for the 130°C test and 3 h for the 170°C test. Additional details are provided in .…”

“…The temperature difference between the sets of solar cells emulated at each concentration (700X and 1050X) was only 2°C because the solar cell circuit boards used in these tests were prepared using good thermal designs. Forever, the emulated concentration is basically the only difference between the two set of solar cells.…”