PV Modules

Photovoltaic (PV) modules and components are products which have to withstand the diverse effects of extreme conditions during their lifetime. The wide range of climatic conditions and possible mechanical stresses must be taken into account when designing a PV component. To assess whether the quality of a product is sufficient to withstand such influences, some international standards have been developed. TÜV Rheinland operates several ISO 17025-accredited laboratories worldwide for type approval testing of PV components – such as junction boxes, connectors and cables – as well as concentrating PV modules, flat-plate modules and solar thermal systems. Experience of testing PV components has been gained over the last 12 years, and even over the last 20 years in the case of PV modules. New developments in photovoltaics mean that continuous development and review of standards is necessary.

Solar enterprises will each be faced with the occasional surplus or lack of solar modules in their lifetimes. In these instances, it is useful to adjust stock levels for modules at short notice, thus creating a spot market. Spot markets serve the short-term trade in different products, by enabling the seller to permanently or temporarily offload surplus, while buyers are able to access attractive offers on surplus stocks and supplement existing supply arrangements as a last resort.

With new industrial challenges faced by the PV industry – such as the striking development of Chinese manufacturers, and ever more demanding investors and financial institutions – the quality of PV modules has never been as important as it is today. Because normative requirements are not matching the buyers’ expectations, the questions of what the real quality of a PV module is and how to assess it still remain. This paper analyzes the current situation in terms of quality and the causes of problems, and proposes some ways of addressing the issues in order for the industry to progress on the long path to excellence.

By definition, PV module certification is simply based on conformance to standards. The IEC norms for PV modules are considered to be adequate quality requirements for guaranteeing initial quality. However, it is commonly understood that two products A and B may meet the standard’s requirements, but overall qualty – considering long-term stability, performance and safety – can still be quite different. PV module testing should therefore be carried out more frequently and beyond IEC requirements. A factory inspection once a year – as suggested by most certification bodies to ensure continuous quality of certified crystalline modules – may not be sufficient. The need for additional control is demonstrated in this paper, with reference to our experience from PV module testing and quality assurance activities for wholesalers and project developers. We present the necessity of additional measurements under standard test conditions (STC) and advanced testing methods, which are becoming essential for reliability.

Solar enterprises will each be faced with the occasional surplus or lack of solar modules in their lifetimes. In these instances, it is useful to adjust stock levels for modules at short notice, thus creating a spot market. Spot markets serve the short-term trade in different products, where the seller is able to permanently or temporarily offset surplus, while buyers are able to access attractive offers on surplus stocks and supplement existing supply arrangements as a last resort.

After the encapsulation step, a c-Si solar module’s output is usually decreased, in comparison to its cells’ power, which is referred to as ‘power loss’. This paper focuses on the various factors that can impact power loss of solar modules, such as solar cell classification, encapsulation material, match of solar cells, the encapsulation process used, and so on. The conclusion indicates that power loss in solar modules can be significantly decreased with a resulting increment of a module’s output by appropriately optimizing those factors.

Solar enterprises will each be faced with the occasional surplus or lack of solar modules in their lifetimes. In these instances, it is useful to adjust these stock levels at short notice, thus creating a spot market. Spot markets serve the short-term trade of different products, where the seller is able to permanently or temporarily offset surplus, while buyers are able to access attractive offers on surplus stocks and supplement existing supplyarrangements as a last resort.

Since the 1980s, ethylene-vinyl acetate (EVA) has been the standard encapsulation material for crystalline photovoltaic modules. From a mechanical point of view, the encapsulant takes the function of a compliant buffer layer surrounding the solar cells. Therefore, understanding its complex mechanical properties is essential for a robust module design that withstands thermal and mechanical loads. In the cured state after lamination, its stiffness features a high sensitivity to temperature especially in the glass transition region around -35°C, and a dependence on time which becomes obvious in relaxation and creep behaviour. This paper outlines the viscoelastic properties of EVA and the corresponding standard experimental methods, as well as the impact on the accuracy of wind and snow load test procedures for PV modules.

Ammonia, a gas which has its roots in livestock farming, can have potentially detrimental effects on the lifetime and reliability of PV modules. Research into the degree of corrosive effects of this gas on modules is of utmost importance for any module manufacturer guaranteeing a certain specific lifetime for their product. Researchers from SCHOTT and SCHOTT Solar together with the DLG (Deutsche Landwirtschafts-Gesellschaft/German agricultural society) developed a test design involving humidity, temperature and ammonia gas. This design is based on permeation testing and microscopic analysis of samples aged under a controlled atmosphere or from outdoor exposure. Additionally, a highly accelerated test is presented which allows screening materials for use in PV modules within 84 hours. An Arrhenius type of model is used to calculate the acceleration factors involved. Based on this model, the proposed test design is equivalent to more than 20 years of outdoor exposure in the rural environment (in Central Europe).

Savvy solar panel manufacturers understand that wringing excess costs from every stage of the value chain is simply the price of admission to today’s crowded market. They also know that reliability and quality are not only critical for delivering on a 25-year warranty promise, but also drive the true cost of energy over the lifetime of the system. This factor is becoming increasingly apparent, especially in industrial- and utility-scale solar projects, as they age and the power output of many lower quality systems begins to degrade to unexpected levels. Many of those systems used UL or IEC certifications as a proxy for good reliability. Unfortunately, UL certification is primarily concerned with user safety, and even the IEC requirements are not rigorous enough to ensure trouble-free operation throughout the system lifetime. High reliability and quality require testing and manufacturing methods that go far beyond the certification tests.