Concentrating photovoltaic (CPV) technology recently gained interest based on its expected low levelized cost of electricity, high efficiency, and scalability. Many CPV systems employ Fresnel lenses composed of poly(methyl methacrylate) (PMMA) to obtain a high optical flux density on the cell. The optical and mechanical durability of these lenses, however, is not well established relative to the desired surface life of 30 years. Our research aims to quantify the expected lifetime of PMMA in key market locations (FL, AZ, and CO).

This presentation is an update on the Gearbox Reliability Collaborative (GRC) for the AWEA Wind Project Operations, Maintenance & Reliability Seminar. GRC accomplishments are: (1) Failure database software deployed - partners see business value for themselves and customers; (2) Designed, built, instrumented, and tested two gearboxes - (a) Generated unprecedented public domain test data from both field testing and dynamometer testing, (b) Different responses from 'identical' gearboxes, (c) Demonstrated importance of non-torque loading and modeling approach; and (3) Active collaborative, with wide industry support, leveraging DOE funding - Modeling round robin and Condition Monitoring round robin.

This presentation describes a National Renewable Energy Laboratory project to collect and analyze commercial fleet deployment data from medium-duty plug-in hybrid electric and all-electric vehicles that were deployed using funds from the American Recovery and Reinvestment Act. This work supports the Department of Energy's Vehicle Technologies Program and its Advanced Vehicle Testing Activity.

This presentation discusses the Building America Program. This presentation discusses the background and goals of the program. A few hot topic technologies are discussed. Outreach activities are discussed as well.

This presentation describes the current status of the DOE's Energy Storage R and D program, including modeling and design tools and the Computer-Aided Engineering for Automotive Batteries (CAEBAT) program.

Description and history of the IEC 61215 qualification test, what it accomplishes, and what it does not accomplish that would be useful to the community. The commercial success of PV is based on long term reliability of the PV modules. Today's modules are typically qualified/certified to: (1) IEC 61215 for Crystalline Silicon Modules; (2) IEC 61646 for Thin Film Modules; and (3) IEC 62108 for CPV Modules. These qualification tests do an excellent job of identifying design, materials and process flaws that could lead to premature field failures. This talk will provide a summary of how IEC 61215 was developed, how well it works and what its limitations are.

This presentation covers modeling metal fatigue as a key step in photovoltaic (PV) module lifetime predictions. Described are time-dependent and time-independent case studies.

Description of how to make PV modules so that they are less likely to turn into safety hazards. Making modules inherently safer with minimum additional cost is the preferred approach for PV. Safety starts with module design to ensure redundancy within the electrical circuitry to minimize open circuits and proper mounting instructions to prevent installation related ground faults. Module manufacturers must control the raw materials and processes to ensure that that every module is built like those qualified through the safety tests. This is the reason behind the QA task force effort to develop a 'Guideline for PV Module Manufacturing QA'. Periodic accelerated stress testing of production products is critical to validate the safety of the product. Combining safer PV modules with better systems designs is the ultimate goal. This should be especially true for PV arrays on buildings. Use of lower voltage dc circuits - AC modules, DC-DC converters. Use of arc detectors and interrupters to detect arcs and open the circuits to extinguish the arcs.

This presentation discusses U.S. DOE Learning Demonstration Project goals, fuel cell vehicle and H2 station deployment status, and technical highlights of vehicle and infrastructure analysis results and progress.

Engineering robust adhesion of the junction-box (j-box) is a hurdle typically encountered by photovoltaic (PV) module manufacturers during product development. Furthermore, there are historical incidences of adverse effects (e.g., fires) caused when the j-box/adhesive/module system has failed in the field. The addition of a weight to the j-box during the 'damp heat' IEC qualification test is proposed to verify the basic robustness of the j-box adhesion system. The details of the proposed test are described, in addition to the preliminary results conducted using representative materials and components.

Recently there has been an interest in the use of thermoplastic encapsulant materials in photovoltaic modules to replace chemically crosslinked materials, e.g., ethylene-vinyl acetate. The related motivations include the desire to: reduce lamination time or temperature; use less moisture-permeable materials; or use materials with better corrosion characteristics. However, the use of any thermoplastic material in a high-temperature environment raises safety and performance concerns, as the standardized tests currently do not expose the modules to temperatures in excess of 85C, yet modules may experience temperatures above 100C in operation. Here we constructed eight pairs of crystalline-silicon modules and eight pairs of glass/encapsulation/glass mock modules using different encapsulation materials of which only two were designed to chemically crosslink. One module set was exposed outdoors with insulation on the back side in Arizona in the summer, and an identical set was exposed in environmental chambers. High precision creep measurements and performance measurements indicate that despite many of these polymeric materials being in the melt state at some of the highest outdoor temperatures achievable, very little creep was seen because of their high viscosity, temperature heterogeneity across the modules, and in the case of the crystalline-silicon modules, the physical restraint of the backsheet. These …

Presentation given at the 2012 Department of Homeland Security Renewable Energy Roundtable on Algal Fuels.

The presentation shows a brief status report on the development of a specification being considered by IEC TC82 WG7 for a concentrator cell data sheet and solicits suggestions from the community.

This is a general overview of CIGS material and device fundamentals. In the first part, the basic features of high efficiency CIGS absorbers and devices are described. In the second part, some examples of previous collaboration with Shell Solar CIGSS graded absorbers and devices are shown to illustrate how process information was used to correct deviations and improve the performance and stability.

Concentrating photovoltaic (CPV) cell assemblies can fail due to thermomechanical fatigue in the die-attach layer. In this presentation, we show the latest results from our computational model of thermomechanical fatigue. The model is used to estimate the relative lifetime of cell assemblies exposed to various temperature histories consistent with service and with accelerated testing. We also present early results from thermal cycling experiments designed to help validate the computational model.

Over the past decade, there have been observations of module degradation and power loss because of the stress that system voltage bias exerts. This results in part from qualification tests and standards note adequately evaluating for the durability of modules to the long-term effects of high voltage bias that they experience in fielded arrays. This talk deals with factors for consideration, progress, and information still needed for a standardized test for degradation due to system voltage stress.

Many concentrating photovoltaic (CPV) systems use a polymeric encapsulant to couple and optical component and/or coverglass to the cell. In that location, the encapsulation improves the transmission of concentrated optical flux through interface(s), while protecting the cell from the environment. The durability of encapsulation materials, however, is not well established relative to the desired service life of 30 years. Therefore, we have initiated a screen test to identify the field-induced failure modes for a variety of popular PV encapsulation materials. An existing CPV module (with no PV cells present) was modified to accommodate encapsulation specimens. The module (where nominal concentration of solar flux is 500x for the domed-Fresnel design) has been mounted on a tracker in Golden, CO (elevation 1.79 km). Initial results are reported here for 18 months cumulative exposure, including the hottest and coldest months of the past year. Characteristics observed at intervals during that time include: visual appearance, direct and hemispherical transmittance, and mass. Degradation may be assessed from subsequent analysis (including yellowness index and cut-on frequency) relative to the ambient conditions present during field exposure. The fluorescence signature observed of all the silicone specimens is examined here, including possible factors of causation -- the platinum catalyst …

Presentation given at the 2012 Department of Homeland Security Renewable Energy Roundtable on Energy Savings Performance Contracts (ESPCs) and Power Purchase Agreements (PPAs) for Renewable Energy (RE)

The failures and performance issues associated with three years of on-sun testing of CPV modules are discussed. Pictures of various failure mechanisms and performance issues are presented. A wide array of CPV module failures and performance issues have been experienced at NREL. Many of the modules are prototypes and have not been through qualification testing. It is assumed that the qualification test would have captured many of the problems. Internal lens soiling due to condensation is not currently captured by the qualification test. Lens temperature dependence can be built into modeling if CPV is to operate in cold locations.

Presentation given at the 2012 Department of Homeland Security Renewable Energy Roundtable on Energy Savings Performance Contracts (ESPCs) and Power Purchase Agreements (PPAs) for Renewable Energy (RE).

The presentation describes the composition of and motivation for the International PV QA Task Force, then describes the presentations and discussion that occurred at the workshop on Feb. 29th, 2012.

This presentation summarizes NREL's development of a HPWH model for use in hourly building energy simulation programs, such as BEopt; this presentation was given at the Building America Stakeholder meeting on March 1, 2012, in Austin, Texas.

An update is given on the work of the PV Quality Assurance Task Force; Group 3: studying the effects of humidity, temperature, and voltage bias.

A new approach to modeling residential air conditioners and heat pumps allows users to model systems by specifying only the more readily-available SEER/EER/HSPF-type metrics. Manufacturer data was used to generate full sets of model inputs for over 450 heat pumps and air conditioners. A sensitivity analysis identified which inputs can be safely defaulted 'behind-the-scenes' without negatively impacting the reliability of energy simulations.