Gary Lavigne

Investigation of the degradation and stabilization of EVA-based encapsulant in field-aged solar energy modules

Abstract The discoloration of EVA-based encapsulant in some solar photovoltaic modules, most notably a mirror-enhanced module and others recovered from Carrisa Plains, CA, has been investigated in order to understand the causes of the phenomenon and to find solutions to the problem of reduced electrical output. The discoloration has been found to be due to interactions between cross-linking peroxide and some stabilizing additives, and is also likely to be due to oxidation of the encapsulant. No evidence could be found in field-aged, discolored EVA encapsulant for conjugated double bonds, which has been implicated as the cause of discoloration in earlier publications. Reformulated encapsulant and the use of cerium-oxide-containing glass as the top cover of PV modules have dramatically reduced discoloration. Additional benefit should be derived by excluding oxygen from the modules.

Use of herbivore-induced plant volatiles as search cues by Tiphia vernalis and Tiphia popilliavora to locate their below-ground scarabaeid hosts.

Japanese beetle, Popillia japonica Newman, and oriental beetle, Anomala orientalis (Waterhouse) (both Coleoptera: Scarabaeidae) are considered invasive species and have been reported as key pests of urban landscapes in the Northeastern USA. Tiphia vernalis Rohwer and Tiphia popilliavora Rohwer (Hymenoptera: Tiphiidae) were introduced as biocontrol agents against these beetles. These parasitic wasps burrow into the soil and search for grubs. When a host is found, the wasp attaches an egg in a location that is specific for the wasp species. It is unknown if these wasps can detect patches of concealed hosts from a distance above ground and what role, if any, herbivore‐induced plant volatiles play in their host location. This study evaluated the responses of female T. vernalis and T. popilliavora to grub‐infested and healthy plants in Y‐tube olfactometer bioassays. Also the effect of root herbivory on the composition of turfgrass (Poaceae) volatile profiles was investigated by collecting volatiles from healthy and grub‐infested grasses. Tiphia wasps were highly attracted to volatiles emitted by grub‐infested tall fescue (Festuca arundinacea Schreb.) and Kentucky bluegrass (Poa pratensis L.) over healthy grasses. In contrast, wasps did not exhibit a significant preference for grub‐infested perennial ryegrass (Lolium perenne L.) as compared with the control plants. The terpene levels emitted by grub‐infested Kentucky bluegrass and tall fescue were greater than that of control plants. Low levels of terpenes were observed for both test and control perennial ryegrass. The elevated levels of terpenes emitted by grub‐infested Kentucky bluegrass and tall fescue coincided with the attractiveness to the tiphiid wasps. Here, we provide evidence that plant exposure to root‐feeding insects P. japonica and A. orientalis resulted in an increase in terpenoid levels in turfgrasses, which strongly attracts their above‐ground parasitoids.

Advanced development of non-discoloring EVA-based PV encapsulants

The purpose of this investigation was to better define the problem of field yellowing of EVA‐based PV encapsulant, through laboratory study of probable chemical mechanisms and the development of stabilization strategies for protecting EVA from discoloration. EVA from fielded modules was analyzed for vinyl acetate content, unsaturation, and additive levels. These test results were then compared to results from Xenon Arc Weather‐Ometer aged glass/EVA/glass laminates made in the laboratory. Variables evaluated in Weather‐Ometer aged laminates included ‘‘standard‐cure’’ A9918P EVA, ‘‘fast‐cure’’ 15295P EVA, low iron glass superstrate containing cerium oxide, and systematic elimination or addition of specific additives. Six significant findings were revealed: 1) Improved ‘‘standard‐cure’’ and ‘‘fast‐cure’’ type EVA encapsulants, formulations X9903P and X15303P, respectively, showed little or no yellowing after extended Weather‐Ometer exposure; 2) The use of ‘‘fast‐cure’’ EVA reduced discoloration when compared...

A Method to Analyze the Surface of Microcapsules Using Diffuse Reflectance

AbstractThe diffuse reflectance of infra-red energy from microcapsules was shown to be a useful analytical technique to study the structural properties of microcapsules. The technique of diffuse reflectance is unique in that the anisotropic nature of reflected light enables spectral differences to be explained on the basis of molecular orientation. As a result of the collection and analysis of diffuse spectra, spectral differences that may correspond to structural differences in the capsule wall structure were found to be dependent on the core material. More specifically, in microcapsules of kaolin and talc, produced with a block copolymer of d-tartaric acid and 1,8-octanediol, the relative orientation of hydroxyl functional groups for the respective core materials differed by forty-nine degrees while carbonyl groups differed by 15 degrees.