This paper presents a summary of the status of bifacial PV in respect of the technology in mass production, the installed PV systems, and the costs relating both to module production (cost of ownership – COO) and to electricity (levelized cost of energy – LCOE). Since the first bifacial workshop, organized by ISC Konstanz and the University of Konstanz, in 2012, many things have changed. Bifacial cells and modules have become cost effective, with installed systems now adding up to more than 120MWp and the technology becoming bankable. Large electricity providers have recognized the beauty of bifacial installations, as the lowest costs per kWh are attainable with these systems. The authors are sure that by the end of 2017, bifacial PV systems amounting to around 500MWp will have been installed, and that by 2025 this type of system will become the major technology in large ground-mounted installations.
Even though it is now more than five years since potential-induced degradation (PID) began to proliferate, and despite the fact that solutions are under development, it is currently still the most discussed mode of degradation associated with cracking in PV modules.
Conventional ribbons used for interconnecting solar cells in PV modules act like mirrors, causing a large proportion of incident light to be lost. Experimental results indicate that only around 5% of the perpendicular
incident light on the connections can be reused; as a result, this area contributes very little, if at all, to the current generation.
PV Tech can reveal the preliminary top 5 solar module manufacturers in 2016, based as usual on final shipment guidance from third quarter financial results.
PV manufacturing capacity expansions planned this year are expected to push production levels beyond anticipated demand in 2016, creating further cost pressures for suppliers.
The output power of a solar module is the sum of the powers of all the individual cells in the module multiplied by the cell-to-module (CTM) power ratio. The CTM ratio is determined by interacting optical losses and gains as well as by electrical losses. Higher efficiency and output power at the module level can be achieved by using novel ideas in module technology. This paper reviews methods for reducing different optical and electrical loss mechanisms in PV modules and for increasing the optical gains in order to achieve higher CTM ratios. Various solutions for optimizing PV modules by means of simulations and experimental prototypes are recommended. Finally, it is shown that designing PV modules on the basis of standard test conditions (STC) alone is not adequate, and that, to achieve higher CTM ratios by improving the module designs in respect of environmental conditions, an energy yield analysis is essential.
The back-contact (BC) technology currently available on the market is considered to be either highly efficient but extremely expensive (interdigitated back contact – IBC – from SunPower) or, if cost-effective, not very
efficient (metal wrap-through – MWT) compared with what is becoming today’s new standard: passivated emitter and rear contact (PERC) technology. Something in between, such as low-cost, high-efficiency IBC cells
and modules, would therefore be desirable. This paper briefly describes the past, focuses on the present, and forecasts the possible future developments of BC technology in respect of efficiencies, costs and applications.
Potential-induced degradation can cause significant power loss in modules if the appropriate precautions are not taken. In the first part of a new series in PV Tech Power on module failure, Peter Hacke and Steve Johnston assess the current state-of-the-art in detecting, avoiding and mitigating the worst effects of PID.
‘Silicon Module Super League’ (SMSL) member Jinko Solar has reported the second consecutive quarter of solar module shipments that were higher than leading SMSL rival, Trina Solar.
The continual increase in cell efficiency of passivated emitter and rear cells (PERCs), as well as the optimization of the module processes, has led to significant advances in module power and efficiency. To achieve the
highest module power output, one important aspect to consider is the optimization of the solar cell front metallization and the cell interconnection.
Cell-to-module (CtM) loss is the loss in power when a number of cells are interconnected and laminated in the creation of a PV module. These losses can be differentiated into optical losses, leading to a lower
photogenerated current, and resistive losses, leading to a decrease in fill factor. However, since the application of anti-reflection (AR) coatings and other optical ‘tricks’ can sometimes increase the Isc of the module with respect to the average cell Isc, the CtM loss in such cases needs to be expressed as a negative value, which gives rise to confusion. It is proposed to use the CtM change, where a negative value corresponds to a loss in current or power, and a positive value to a gain. In this paper, the CtM changes for back-contact modules utilizing a conductive foil are described and compared with other mature module technologies. A detailed analysis of the CtM change for a full-size metal-wrap-through (MWT) module is presented.
Higher power generation yield is the prime objective of any solar power plant developer. The quality and reliability of the modules used are therefore a key aspect, with customers placing stringent criteria on cell and
module manufacturers with regard to product quality. Electroluminescence (EL) image monitoring, which gives a clear picture of defect distribution across a module, is an increasingly popular quality criterion.
Double-glass PV modules are emerging as a technology which can deliver excellent performance and excellent durability at a competitive cost. In this paper a glass–glass module technology that uses liquid silicone encapsulation is described. The combination of the glass–glass structure and silicone is shown to lead to exceptional durability. The concept enables safe module operation at a system voltage of 1,500V, as well as innovative, low-cost module mounting through pad bonding.
We are always hearing about champion cells demonstrating efficiencies of 24% or higher, yet only 20 or 21% can be obtained at the module level. This paper highlights the different loss mechanisms in a module, and how they can be quantified. Once it is known where photons and electrons are lost, it is possible to develop strategies to avoid this happening.
The backsheet is the first barrier for ensuring the reliability and durability of PV modules for 25+ years. To reduce cost, backsheets with a variety of compositions and constructions have been developed and introduced in PV modules. For PV module manufacturers, a major challenge is choosing a low-cost backsheet that can maintain the current levels of high reliability and durability performance. In the work reported in this paper, the properties of several backsheets of various compositions and constructions were compared.