Proposed photovoltaic module form factor to reduce levelized cost of energy
This paper discusses a proposed photovoltaic (PV) module form factor designed for utility-scale, one-axis tracking projects. The purpose of the form factor is to: 1) reduce total installed costs for utility-scale projects; 2) improve module reliability; 3) reduce operating and maintenance (O&M) costs, and 4) improve the project return on investment. The proposed module uses a double-glass construction to improve reliability and service lifetime in a form factor that is longer and narrower than existing 60-cell modules. This form factor places more module area per linear meter of torque tube when used with single-axis trackers. These changes are expected to lower the levelized cost of energy.
The effect of cell thickness on module reliability
This paper addresses the issue of the reliability of modules using ultra-thin crystalline silicon cells. Do thin cells have a greater likelihood of cracking during production, transport, installation or use and if so does this result in long term degradation of the power? The present qualification test sequence, IEC 61215 does not adequately address this issue, The only mechanical test in IEC 61215 is a static mechanical load test consisting of three load cycles that are performed after the accelerated stress tests. So even if this mechanical load test does break cells, it is unlikely to result in significant power loss. BP Solar has developed a test sequence for evaluation of cracked cells in PV modules. The test sequence incorporates a dynamic mechanical load test performed before the 50 thermal cycles/10 humidity freeze cycles of IEC 61215. Usually there is no significant power loss after the dynamic load testing. However, the subsequent thermal cycling opens up the cracks that propagated during the dynamic load test resulting in significant power loss. Having a test sequence that identifies damaged cells allows us to develop processes and handling procedures to minimize or eliminate damage to the ultra-thin cells, resulting in reliable modules.
Effect of dynamic cross-linking on phase morphology and dynamic mechanical properties of polyamide 12/ethylene vinyl acetate copolymer blends
Dynamic cross-linking of polyamide 12 (PA12) and ethylene vinyl acetate copolymer (EVA) blends in the mixing chamber of a torque rheometer was investigated. EVA was selectively cross-linked within the PA12 phase through free radical reactions using dicumyl peroxide. The torque level and temperature in the torque rheometer chamber were monitored to follow the evolution of the EVA cross-linking during the dynamic cross-linking process. The degree of cross-linking of EVA in the PA12/EVA materials was estimated based on the gel content (insoluble EVA fraction). The PA12/EVA phase morphology was investigated by scanning electron microscopy. The solid viscoelastic properties were investigated by dynamic mechanical thermal analysis (DMTA). The morphology, interfacial tension and viscoelastic results showed the immiscible nature of this system. The morphology of the blends was observed and the results revealed a two-phase system. The PA12/EVA 70/30 showed disperse-phase morphology, however a co-continuous phase was observed in blend ratios of 50/50 and 60/40. The dynamic cross-linking process resulted in a more stable EVA phase morphology with disperse and interconnected structures in the thermoplastic PA12 domains.