• Energy Research

AbstractIn this work, we show the integration of polysilicon‐based passivating contacts in plated bifacial n‐type PERT (passivated emitter and rear totally diffused) solar cells. We show the viability of n‐PERT cells using two‐side passivating contacts with two‐side plated nickel/silver metallization. Compared with commercially available “TOPCon” cells with rear side passivated contacts only, n‐PERT cells with both side passivated contacts should enable the exploitation of the full potential of passivated contacts. We show that both n‐poly and p‐poly were applied and co‐plated successfully on both sides of n‐PERT solar cells. Considering the potential parasitic absorption losses on the front side of the device originating from p‐poly, we applied selective p‐poly by patterning. We compared two patterning methods for front side polysilicon: the masking and etch approach using inkjet printing and a simple and cost‐effective patterning method using UV laser oxidation. A best efficiency of 22.7% has been achieved with these cells so far on large area (244.3 cm2) n‐type Cz, with a potential efficiency above 24%. Some of these co‐plated bifacial cells have been processed into one‐cell laminates using smart wire interconnection (SWCT) technology. These have passed thermal cycling (TC) tests as defined in IEC61215.

ABSTRACTThe incidence angle effect causes a decrease in the photogenerated current of PV modules when they are subject to incident irradiance at wide angles: Its relevance should be quantified for accurate energy yield purposes and has recently gained significance due to the rising interest in novel integrated PV applications, where vertical or nonoptimal tilt are favored (e.g., in urban structures, in agrivoltaics, and vehicles). The international standard IEC 61853‐2 presents both outdoor and indoor measurement methods: However, the indoor measurement method for commercial‐size modules is often impractical due to irradiance uniformity limitations on the volume spanned by the tested module upon rotation in most of the solar simulators available on the market. In recent years, new solutions have been proposed to overcome these limitations and allow wider adoption of this standard: However, method validations and interlaboratory comparisons have been conducted so far only on small‐area samples, and a real validation on commercial‐size modules is still missing. In this work, we aim at filling this gap, reporting the results of an interlaboratory comparison conducted within the international project team that is currently working at the new edition of IEC 61853‐2. The results show a remarkable agreement between different measurement methods, thus validating more options for the evaluation of this important effect.

AbstractSince massive numbers of photovoltaic (PV) modules are expected to be discarded in the next decades, it is important to think about end‐of‐life management for those PV modules and to include re‐use next to recycling. However, the re‐use of decommissioned PV modules is a quite complex subject since there are requirements from technical, economic, environmental and legislative point of view. An evaluation of possible applications for second‐hand PV modules showed that currently, the use of these PV modules in high‐income countries is only interesting for specific applications. These are the replacement of some defect modules to repair PV systems (that usually still receive feed‐in tariff) or the replacement of all PV modules for either a low‐cost extension of system lifetime or the repowering of severely underperforming systems. For low‐income countries, second‐hand PV modules are interesting to build new small to medium size PV systems (often off‐grid). The typical decommissioned PV module is a crystalline silicon glass‐backsheet module from a utility power plant. Most PV modules originate from plants that have been partly damaged by severe weather or from repowered plants that did not receive feed‐in tariff (anymore). Currently, technical requirements to qualify potentially re‐usable PV modules for re‐use are lacking. In the legislation also, a clear criterion for a PV module to be considered functional is needed, since it is not an easy yes/no situation like for a typical electronic device. In this paper, guidelines for a low‐cost quality inspection and cost‐effective PV module repair are given. It is proposed to set a clear performance threshold at 70% of the original power for a PV module to be not considered as waste. With this paper, we aim to open the dialogue on a commonly accepted re‐certification protocol and threshold values. Currently, the worldwide re‐use market size is estimated to be around 1 GWp/year, of which 0.3 GWp/year is originating from Europe (mainly Germany, with Italy rapidly coming up). Many second‐hand PV modules are shipped to developing countries without recycling facilities which might create the risk of disposal on the longer term. To create a healthy and sustainable market for second‐hand PV modules, it will be important that evaluation standards for potentially re‐usable PV modules become available and that the existing electronic waste legislation will be adapted for energy‐generating products like PV modules.