Photovoltaics International Papers

Because most of the costs of developing a PV power plant are paid before any energy is generated, optimizing the energy production from the plant is critical during plant design. Lost energy and increased operations costs due to non-optimal site characterization, technology choice, plant design, installation and other factors result in lower energy production and a higher levelized cost of energy (LCOE). Many design decisions are based on results from PV performance models. Current PV performance models can represent only some of the differences between sites, technologies, designs and operations choices. This paper provides a description of what is currently known about some of the performance tradeoffs faced by PV plant designers and operators. It presents a vision for improving PV performance models so that in the near future a full optimization can be carried out to improve the performance and lower the costs of PV plants. This will hasten the adoption of clean energy production from the sun.

Economics will always play a crucial role in the way PV technology advances. However, the current generation of products is facing substantial business challenges in the attempt to scale the product technologies. This paper is the fifth in a series covering business analysis for PV processes. The methods applied in these papers fall into two categories: cost of ownership (COO) modelling and cost and resource modelling. Both methods examine the business considerations associated with the adoption of new processes, tools or materials. This is more critical than ever. Nearterm issues – in some cases the survival of the business – heavily influence today's decision processes. This paper tries to identify the areas that it is thought will produce the largest near-term paybacks. The areas identified are n-type wafers, Al2O3 passivation and copper metallization.

To achieve project cash flow expectations, it is necessary to operate, maintain and optimize the performance of a PV power asset to meet or exceed the pro forma operating assumptions. To assume as given the achievement of these model assumptions is both naive and risky. Experience in operating the largest fleet of solar PV power plants in the world has demonstrated that project financial hurdle rates can be missed by as much as 25% if the plant is not well maintained and its performance is not optimized. Conversely, an optimized PV asset can generate cash flows 2–10% higher than expected if the optimization approach described in this paper is implemented.

The rapid growth of the PV market during the last five to seven years entailed a considerable expansion of the encapsulation material market, which temporarily led to shortages in the supply chain. Simultaneously, module prices decreased significantly, which resulted in intense pressure on production costs and the cost of PV module components, inducing changes in the encapsulation material market towards new materials and suppliers. This pressure – together with the huge impact of the encapsulation material on module efficiency, stability and reliability – makes the selection of encapsulation technologies and materials a very important and critical decision in the module design process. This paper presents an overview of the different materials currently on the market, the general requirements of PV module encapsulation materials, and the interactions of these materials with other module components.

This paper provides an overview of reducing the ‘soft costs’ of solar, with a focus on driving down the cost of balance of system (BOS) and operations, primarily in commercial-scale installations. Attention is drawn to the internal data and information on specific case studies/best practices that can be replicated by other companies. Mainstream Energy (which supports three business units – REC Solar, AEE Solar and SnapNRack) aims to simplify system design and configuration by utilizing new technologies and streamlining internal processes to reduce total system cost – and take solar to the mainstream.

This paper provides an overview of reducing the ‘soft costs’ of solar, with a focus on driving down the cost of balance of system (BOS) and operations, primarily in commercial-scale installations. Attention is drawn to the internal data and information on specific case studies/best practices that can be replicated by other companies. Mainstream Energy (which supports three business units – REC Solar, AEE Solar and SnapNRack) aims to simplify system design and configuration by utilizing new technologies and streamlining internal processes to reduce total system cost – and take solar to the mainstream.

Economic success in operating PV systems depends essentially on the likelihood of their long-term operation and their delivery of the expected energy yield. These requirements, for which a lifetime of 20–25 years is often assumed, are demanding and cannot be met without preparation. Preconditions are the acceptable quality and long-term stability of the products employed (particularly the PV modules, but also all other components and materials) and the absence of damage to these items during transport and handling. Moreover, PV systems must be professionally planned and properly implemented. This includes considering energy yield assessments not only in the initial estimation of the energy yield, but also in the subsequent planning for concrete implementation. In addition, professional operational management and appropriate maintenance measures will ensure operation with maximum availability. Yield insurance policies can safeguard profitability and render the risks calculable; various models exist for this purpose and these must be carefully tested. It is important that the insurances services also cover the possible insolvency of the responsible system and component suppliers.

Electroluminescence (EL) imaging for photovoltaic applications has been widely discussed over the last few years. This paper presents the results of a thorough evaluation of this technique in regard to defect detection in photovoltaic modules, as well as for quality assessment. The ability of an EL system to detect failures and deficiencies in both crystalline Si and thin-film PV modules (CdTe and CIGS) is thoroughly analyzed, and a comprehensive catalogue of defects is established. For crystalline silicon devices, cell breakages resulting from micro-cracks were shown to pose the main problem and to significantly affect the module performance. A linear correlation between the size of the breakages and the power drop in the module was established. Moreover, mechanical stress and temperature change were identified as the major causes of the proliferation of cracks and breakages. For thin-film modules, EL imaging proved the existence of an impressive reduction in the size of localized shunts under the effect of light-soaking (together with a performance improvement of up to 8%). Aside from that, the system voltage was applied in order to monitor transparent conductive oxide (TCO) corrosion effects and laser-scribing-induced failures, as well as several problems related to the module junction box in respect of its sealing and the quality of its electric connectors.

Because potential-induced degradation (PID) can cause power losses of more than 30% for modules out in the field, there has already been an extensive effort placed on avoiding this adverse phenomenon. A key feature at the cell level is the silicon nitride (SiNx) anti-reflective coating (ARC). Apart from the known dependency of PID susceptibility on the refractive index, the impact of the deposition parameters has also been under investigation. This paper illustrates the influence of different silicon nitrite layers and their ability to prevent PID. A large number of cells and modules were therefore manufactured, differing only in the type of ARC. The modules were subsequently PID tested under three different climatic conditions, and acceleration factors and activation energies were determined from these tests. In addition this paper presents the results of addressing the weak-light performance and the hot-spot risk of panels after PID exposure. Finally, the reversibility of PID was also investigated in relation to the state of degradation of these samples.

Since the demonstration of the first CuInSe2 solar cell in 1974 by scientists at Bell Laboratories, a lot of effort has been put into the development of cost-effective processes for highly efficient Cu(In,Ga)(Se,S)2 – or CIGS – solar cell devices. In 2012 these efforts led to the first gigawatt CIGS solar module production facility operated by Solar Frontier, a company that has a long history in R&D and originates from ARCO Solar, who developed the first commercial CIGS solar modules at the beginning of the 1990s. However, several start-up companies employing CIGS technology are presently struggling in the currently harsh market environment. Even though world-record laboratory solar cells now demonstrate 20.3% efficiency using a three-stage co-evaporation process, and full-size modules achieve 14.6% employing a similar method, efforts in research and development are more important than ever in order to increase cell efficiency, to bridge the gap between cell and module efficiencies, and to develop cost-effective and robust manufacturing processes. This paper gives an overview of current research topics under investigation by research institutes and industry, with a main focus on CIGS absorber formation. Along with other research results published by groups all over the world, this paper covers recent research results obtained at the Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) and briefly mentions the work of the Photovoltaic Competence Center Berlin (PVcomB), a joint initiative of the Technical University of Berlin (TU Berlin) and HZB.