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.

The presentation describes the test-to-failure protocol that was developed and piloted at NREL, stressing PV modules with multiple applications of damp heat (with bias) and thermal cycling until they fail.

An update is given on the IEC WG7's progress to write and publish a tracker design qualification standard.

Edge seal materials were evaluated using a 100-nm film of Ca deposited on glass and laminated to another glass substrate. As moisture penetrates the package it converts the Ca metal to transparent CaOH2 giving a clear indication of the depth to which moisture has entered. Using this method, we have exposed test samples to a variety of temperature and humidity conditions ranging from 45C and 10% RH up to 85C and 85% RH, to ultraviolet radiation and to mechanical stress. We are able to show that edge seal materials are capable of keeping moisture away from sensitive cell materials for the life of a module.

Presentation given at the 2012 Department of Homeland Security Renewable Energy Roundtable as an introduction to renewable technologies and applications.