Reliability Improvement in III-V Concentrator Solar Cells by Means of Perimeter Protection

This paper presents the evolution in the strategy to assess the reliability of III-V solar cells and a new thermal ageing test carried out over GaAs single junction solar cells at three different temperatures (130, 150 and 170° C). The perimeter of the solar cells has been protected with silicone, which seems to be an effective way of enhancing the reliability of the solar cells. A preliminary analysis of the results indicates a mean time to failure (MTTF) one order of magnitude larger than the one obtained in a previous thermal test with the perimeter uncoated

Reliability of III-V concentrator solar cells

III–V concentrator solar cells are starting to be commercialized. However, no complete studies about their reliability have been carried out. A review about both the accelerated ageing tests and real time tests developed till now is presented. A proposal about the required tests is also done. In this stage, the tests show that III–V concentrator cells are robust devices with MTTFs well over the expected ones (30 years)

Instrumentation for accelerated life tests of concentrator solar cells

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

Case study in failure analysis of accelerated life tests (ALT) on III-V commercial triple-junction concentrator solar cells

In this work the failure analysis carried out in III-V concentrator multijunction solar cells after a temperature accelerated life test is presented. All the failures appeared have been catastrophic since all the solar cells turned into low shunt resistances. A case study in failure analysis based on characterization by optical microscope, SEM, EDX, EQE and XPS is presented in this paper, revealing metal deterioration in the bus bar and fingers as well as cracks in the semiconductor structure beneath or next to the bus bar. In fact, in regions far from the bus bar the semiconductor structure seems not to be damaged. SEM images have dismissed the presence of metal spikes inside the solar cell structure. Therefore, we think that for these particular solar cells, failures appear mainly as a consequence of a deficient electrolytic growth of the front metallization which also results in failures in the semiconductor structure close to the bus bars

Concentrated Photovoltaics

70 σ.Στόχος της παρούσας διπλωματικής είναι η βιβλιογραφική ανασκόπηση της τεχνολογίας των συγκεντρωτικών φωτοβολταϊκών (CPV) και στη συνέχεια η μελέτη του ρόλου που μπορούν να παίξουν στην παραγωγή πράσινης, φθηνής ηλεκτρικής ενέργειας σε μεγάλη κλίμακα. Αρχικά, γίνεται μία σύντομη ιστορική αναδρομή στην ιστορία της φωτοβολταϊκής τεχνολογίας, και στη συνέχεια παρουσιάζεται αναλυτικά η τεχνολογία των συγκεντρωτικών φωτοβολταϊκών δίνοντας έμφαση στις διαφορές τους με τα συμβατικά κύτταρα πυριτίου. Έπειτα, παρουσιάζονται οι πιο σημαντικές κατασκευαστικές διαδικασίες (LPE και MOCVD) καθώς και επίκαιρα ζητήματα που αφορούν τις διαδικασίες αυτές. Ειδικό βάρος δίνεται στις τρέχουσες και μελλοντικές δυνατότητες εμπορικής ανάπτυξης των CPV: Παρουσιάζονται σενάρια μελλοντικής υλοποίησης της τεχνολογίας των CPV, καθώς και το τι έχει γίνει μέχρι σήμερα. Αναδεικνύεται ειδικά ο ρόλος των πολυσυνδετικών ηλιακών κελιών(multi-junction solar cells) σαν καταλύτης στη παραγωγή ηλεκτρικής ενέργειας που μπορεί να ανταγωνιστεί ευθέως τις συμβατικές πηγές (άνθρακας, υγραέριο, πυρηνικά καύσιμα). Στο τέλος, αναφέρονται συνοπτικά εφαρμογές μεγάλης κλίμακας. ΘεόδωροςThis diploma thesis is a bibliographical review about Concentrated Photovoltaics (CPV) and the major role they could play in generating solar power on an industrial-size scale. So far, there hasn't been any greek bibliography concerning concentrated photovoltaics and this thesis aims to close that gap. Initially, a small introduction about photovoltaics in general is made, and consenquently CPV technology is explained in detail. Special emphasis is given on its differences with conventional silicon cells. Afterwards, the most important and promising manufactoring processes and techniques are presented(such as LPE and MOCVD) and current challenges and difficulties concerning those techniques are pointed out. Its current and future economic prospects are laid down, especially in comparison to conventional solar cells. Also, we explain in detail why multijunction solar cell technology is an enabler for low cost power generation using concentrated photovoltaic systems. Finally, several current, large scale applications are presented.Θεόδωρος Μ. Μπέλλο

Index to 1981 NASA Tech Briefs, volume 6, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1981 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Phase 1 of the First Solar Small Power System Experiment (experimental System No. 1). Volume 2: Appendix A - D

Recommended conceptual designs for the baseline solar concentrator and electrical subsystems are defined, and trade offs that were evaluated to arrive at the baseline systems are presented. In addition, the developmental history of the Stirling engine is reviewed, the U4 configuration is described, and a Stirling engine heat pipe system is evaluated for solar application where sodium vapor is used as the heat source. An organic Rankine cycle engine is also evaluated for solar small power system application