Engineering sciences area and module performance and failure analysis area

Photovoltaic-array/power-conditioner interface studies are updated. An experiment conducted to evaluate different operating-point strategies, such as constant voltage and pilot cells, and to determine array energy losses when the array is operated off the maximum power points is described. Initial results over a test period of three and a half weeks showed a 2% energy loss when the array is operated at a fixed voltage. Degraded-array studies conducted at NE RES that used a range of simulated common types of degraded I-V curves are reviewed. The instrumentation installed at the JPL field-test site to obtain the irradiance data was described. Experiments using an optical filter to adjust the spectral irradiance of the large-area pulsed solar simulator (LAPSS) to AM1.5 are described. Residential-array research activity is reviewed. Voltage isolation test results are described. Experiments performed on one type of module to determine the relationship between leakage current and temperature are reviewed. An encapsulated-cell testing approach is explained. The test program, data reduction methods, and initial results of long-duration module testing are described

Campus Vol IV N 4

Lang, Pete. The Rain . Prose. 2. Chase Jr., Richard and Jack K. Matthews Jr. Fitz and the Field house . Picture. 3. Gould, Jim. After Graduation day . Prose. 4. Runkle, Pete. As We Danced Off Both our Shoes . Prose. 5. Hawk, Bob. Fields of Concentration For Seniors! . Cartoon. 6. De Lackner, Barbara. Spring fever . Poem. 8. Goodwin, Joyce. Would That Time Were A . Poem. 8. Ward, Nancy. It Was Fall . Poem. 8. Rounds, Dave. Untitled. Cartoon. 8. Johnston, Ed. Campus Casuals . Prose. 9. Gilbert, Ralph. Campus Progress Report . Picture. 10. Rounds, Dave. Untitled. cartoon. 12

Large-scale synchrony of gap dynamics and the distribution of understory tree species in maple-beech forests

Large-scale synchronous variations in community dynamics are well documented for a vast array of organisms, but are considerably less understood for forest trees. Because of temporal variations in canopy gap dynamics, forest communities—even old-growth ones—are never at equilibrium at the stand scale. This paucity of equilibrium may also be true at the regional scale. Our objectives were to determine (1) if nonequilibrium dynamics caused by temporal variations in the formation of canopy gaps are regionally synchronized, and (2) if spatiotemporal variations in canopy gap formation aVect the relative abundance of tree species in the understory. We examined these questions by analyzing variations in the suppression and release history of Acer saccharum Marsh. and Fagus grandifolia Ehrh. from 481 growth series of understory saplings taken from 34 mature stands. We observed that (1) the proportion of stems in release as a function of time exhibited a U-shaped pattern over the last 35 years, with the lowest levels occurring during 1975–1985, and that (2) the response to this in terms of species composition was that A. saccharum became more abundant at sites that had the highest proportion of stems in release during 1975–1985. We concluded that the understory dynamics, typically thought of as a stand-scale process, may be regionally synchronized

The effects of size of opening in vegetation and litter cover on seedling establishment of goldenrods ( Solidago spp.)

We investigated the effects of size of opening in the vegetation and litter cover on seedling establishment of two species of goldenrods ( Solidago spp.) in an abandoned field in southwestern Michigan, U.S.A. Seeds of S. canadensis and S. juncea were sown into clipped plots, ranging from 0 cm (control, unclipped) to 100 cm in diameter, with and without litter. Seedling emergence, survival and growth were followed for one year. Soil moisture was not significantly different among the opening sizes, but, within a size, tended to be lower when litter was removed. Light intensity at the soil surface was positively related to opening size early in the growing season, but later in the growing season reached a maximum in intermediate-sized openings and then leveled off.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47747/1/442_2004_Article_BF00379516.pd

Temporal changes in height and diameter growth for two Nothofagus species in New Zealand

We examined whether the growth dynamics of two species can explain their coexistence. In particular, we examined New Zealand forests dominated by Nothofagus fusca and N. menziesii to determine whether both species can reach the canopy in tree-fall gaps. Stems in a gap and other stems (in pairs: one of each species, close together) were destructively sampled and aged at their bases and at heights of 1.4 m and 3 m, and at 2 m intervals thereafter as high as possible. For additional pairs of adjacent, similarly sized stems, one of each species, ring widths were analyzed for responsiveness to environmental changes. In general the faster growth rates of N. fusca were sufficient to balance the greater abundance of N. menziesii in the understory, such that both species were able to reach the canopy. Stems of both species grew at similar rates for decades. Both species were able to tolerate some periods of suppression and to respond to opportunities (climatic or due to mild disturbances)

Delta‐Flux: An Eddy Covariance Network for a Climate‐Smart Lower Mississippi Basin

Networks of remotely monitored research sites are increasingly the tool used to study regional agricultural impacts on carbon and water fluxes. However, key national networks such as the National Ecological Observatory Network and AmeriFlux lack contributions from the Lower Mississippi River Basin (LMRB), a highly productive agricultural area with opportunities for soil carbon sequestration through conservation practices. The authors describe the rationale to create the new Delta‐Flux network, which will coordinate efforts to quantify carbon and water budgets at seventeen eddy covariance flux tower sites in the LMRB. The network structure will facilitate climate‐smart management strategies based on production‐scale and continuous measurements of carbon and water fluxes from the landscape to the atmosphere under different soil and water management conditions. The seventeen instrumented field sites are expected to monitor fluxes within the most characteristic landscapes of the target area: row‐crop fields, pasture, grasslands, forests, and marshes. The network participants are committed to open collaboration and efficient regionalization of site‐level findings to support sustainable agricultural and forestry management and conservation of natural resources