This work treats the thermal and mechanical performances of gas-filled, flat plate solar collectors in order to achieve a better performance than that of air filled collectors. The gases examined are argon, krypton and xenon which all have lower thermal conductivity than air. The absorber is formed as a tray connected to the glass. The pressure of the gas inside is near to the ambient and since the gas volume will vary as the temperature changes, there are potential risks for fatigue in the material. One heat transfer model and one mechanical model were built. The mechanical model gave stresses and information on the movements. The factors of safety were calculated from the stresses, and the movements were used as input for the heat transfer model where the thermal performance was calculated. It is shown that gas-filled, flat plate solar collectors can be designed to achieve good thermal performance at a competitive cost. The best yield is achieved with a xenon gas filling together with a normal thick absorber, where normal thick means a 0.25 mm copper absorber. However, a great deal of energy is needed to produce the xenon gas, and if this aspect is taken into account, the krypton filling is better. Good thermal performance can also be achieved using less material; a collector with a 0.1 mm thick copper absorber and the third best gas, which is argon, still gives a better operating performance than a common, commercially produced, air filled collector with a 0.25 mm absorber. When manufacturing gas-filled flat plate solar collectors, one way of decreasing the total material costs significantly, is by changing absorber material from copper to aluminium. Best yield per monetary outlay is given by a thin (0.3 mm) alu-minium absorber with an argon filling. A high factor of safety is achieved with thin absorbers, large absorber areas, rectangular constructions with long tubes and short distances between glass and absorber. The latter will also give a thin layer of gas which gives good thermal performance. The only doubtii ful construction is an argon filled collector with a normal thick (> 0.50 mm) aluminium absorber. In general, an assessment of the stresses for the proposed construction together with appropriate tests are recommended before manufacturing, since it is hard to predict the factor of safety; if one part is reinforced, some other parts can experience more stress and the factor of safety actually drops.

The major objective of this study was to analytically determine the effects of small transverse solar tracking errors on the concentrated intensity profile generated by a 22-inch wide, f-number one, linear Fresnel model lens. Transverse tracking error is caused by the misalignment of the lens optic axis and the center of the sun in a direction perpendicular to the lens optic axis. The analytical method consisted of extending an earlier theoretical model developed by Cosby3 in which the solar disk was perfectly tracked; thus the tracking error problem is treated as a perturbation of the basic theory. Data was obtained using extensive computer calculations.Results indicated that in the presence of transverse tracking error, lens serrations (upper half serrations) on the same side of the lens optic axis as the sun differ significantly from the lens serrations (lower half serrations) on the opposite side of the lens optic axis in their concentration characteristics. Incident angles of sunlight are greater for upper half serrations causing greater angles of refraction at the second surface. The peak concentration ratio values are observed to shift in the negative intercept direction in a linear relationship with tracking error angle. It was observed that the 90% target width monotonically increased, e.g., by 100% and 700% for transverse tracking errors of 1/2° and 2-1/2°, respectively. It is concluded that the dominant cause for the 90% target width increase is the intensity profile shift itself. Some lesser influence results from increasing intensity profile skewness and profile broadening for IR wavelengths caused by greater IR refraction with increased transverse tracking error.Ball State UniversityMuncie, IN 47306

The flat-plate solar collector is the most commonly used device for the direct utilization of solar energy, but its applicability in some places is still debatable. The performance of the solar collector varies with changes in environmental and operational conditions. In this thesis the performance ice of a flat-plate solar collector was examined in order to determine the feasibility of utilizing solar energy s an alternative energy resource for residential water and space heating purposes in East Central Indiana.Various environmental and operational data pertinent to the performance of the solar collector were collected over a period of 76 days (March 26 through June 10). Analysis of the data showed that the efficiency of the collector varies with changes in climatic and operational conditions. Negative relationships were observed between efficiency and fluid inlet temperature, wind speed, cloud cover and precipitation, while relationships between the collector efficiency and ambient temperature, solar radiation and fluid flow rate were found to be positive. Further analysis of the collector performance findings and the average energy consumption in i-iuncie, Indiana produced encouraging evidence for the utilization of solar energy for residential crater heating and space heating purposes in the area.Ball State UniversityMuncie, IN 47306

The planting of native species is a common strategy for the conservation of biodiversity; it not only allows for the restoration of degraded habitat both within conservation reserves and the matrix lands between reserves, it supplements the populations of the floral species which are planted. These supplemental populations may play an important role in providing demographic security for rare species. However, the conservation of rare species depends on more than simply maintaining adequate numbers of the species: the diversity within the species must also be conserved. Although maintaining genetic diversity is increasingly a concern for formal species recovery efforts, there has been very little research done about the diversity within plantings by non-state actors. This research was undertaken to address this knowledge gap by studying the provenances of planted rare species and the activities of those who collect and grow these plants. This research was undertaken in the Carolinian zone of southern Ontario, a region with a large number of rare plant species and a large human population. Part of this study utilized semi-structured interviews with commercial seed collectors, commercial native plant growers, and non-commercial, hobbyist growers. A variety of factors limited the diversity with the seeds collected by commercial collectors. Due to difficulty in accessing information about the natural occurrences of rare species, collectors typically collected from the same, limited number of source plants. Trespassing on private property or protected lands was common to access these seed sources, although their preference for easily accessible, reliably fecund source plants on flat, mowed sites also meant that horticultural specimens were also desired. Many of these biases were passed on to commercial growers when the seed was sold by the commercial collectors. Commercial growers shared many collection practices with commercial collectors, creating similar restrictions on the diversity within their collections. However, further limitations in diversity were also created by the growers’ establishment of small populations of seed plants and by the trading of seeds and plants between growers. One boutique grower was a dominant source of seeds and plants in these trades. The limitations in the diversity within these rare species were passed onto those who purchased and planted them. This study also focused on enthusiastic native plant hobbyists and found that they not only purchased plants but collected and grew their own plants. They also traded with other hobbyists. Much of the information about where to collect seed or plants, as well as much of the seed or plants traded between hobbyists, originated with a key individual. Thus, this champion hobbyist plays a significant role in the character of planted examples of rare plant species and the genetics of the champion’s plants are heavily represented with other planted occurrences. The practices of commercial seed collectors, growers and native plant hobbyists create biases which limit the diversity within plantings of rare species. Although these plantings provide demographic security for these species, they do not represent the diversity within their remnant “wild” populations. Thus, important questions must be raised about the conservation value of these plantings. Since many of the practices of seed collectors and growers are also used when growing more common species, the diversity within plantings of these species should also be suspect. Although the lack of diversity within common species may not threaten the regional survival of the species in the short term, it may impact the ultimate success of restoration projects.

The planting of native species is a common strategy for the conservation of biodiversity; it not only allows for the restoration of degraded habitat both within conservation reserves and the matrix lands between reserves, it supplements the populations of the floral species which are planted. These supplemental populations may play an important role in providing demographic security for rare species. However, the conservation of rare species depends on more than simply maintaining adequate numbers of the species: the diversity within the species must also be conserved. Although maintaining genetic diversity is increasingly a concern for formal species recovery efforts, there has been very little research done about the diversity within plantings by non-state actors. This research was undertaken to address this knowledge gap by studying the provenances of planted rare species and the activities of those who collect and grow these plants. This research was undertaken in the Carolinian zone of southern Ontario, a region with a large number of rare plant species and a large human population. Part of this study utilized semi-structured interviews with commercial seed collectors, commercial native plant growers, and non-commercial, hobbyist growers. A variety of factors limited the diversity with the seeds collected by commercial collectors. Due to difficulty in accessing information about the natural occurrences of rare species, collectors typically collected from the same, limited number of source plants. Trespassing on private property or protected lands was common to access these seed sources, although their preference for easily accessible, reliably fecund source plants on flat, mowed sites also meant that horticultural specimens were also desired. Many of these biases were passed on to commercial growers when the seed was sold by the commercial collectors. Commercial growers shared many collection practices with commercial collectors, creating similar restrictions on the diversity within their collections. However, further limitations in diversity were also created by the growers’ establishment of small populations of seed plants and by the trading of seeds and plants between growers. One boutique grower was a dominant source of seeds and plants in these trades. The limitations in the diversity within these rare species were passed onto those who purchased and planted them. This study also focused on enthusiastic native plant hobbyists and found that they not only purchased plants but collected and grew their own plants. They also traded with other hobbyists. Much of the information about where to collect seed or plants, as well as much of the seed or plants traded between hobbyists, originated with a key individual. Thus, this champion hobbyist plays a significant role in the character of planted examples of rare plant species and the genetics of the champion’s plants are heavily represented with other planted occurrences. The practices of commercial seed collectors, growers and native plant hobbyists create biases which limit the diversity within plantings of rare species. Although these plantings provide demographic security for these species, they do not represent the diversity within their remnant “wild” populations. Thus, important questions must be raised about the conservation value of these plantings. Since many of the practices of seed collectors and growers are also used when growing more common species, the diversity within plantings of these species should also be suspect. Although the lack of diversity within common species may not threaten the regional survival of the species in the short term, it may impact the ultimate success of restoration projects.

No description available.

Thesis (M.F.A.)--Rochester Institute of Technology, 2008. / Typescript. Includes bibliographical references (leaves 39-40).

Thesis (doctoral)--Göteborgs universitet. / Extra t.p. with thesis statement inserted. Summary in English. Includes bibliographical references (p. 329-343) and index.

Thesis (Ph.D.)--University of Edinburgh, 1988.

Thesis (doctoral)--Göteborgs universitet. / Extra t.p. with thesis statement inserted. Summary in English. Includes bibliographical references (p. 329-343) and index.