Steady state analysis of a storage integrated solar thermophotovoltaic (SISTPV) system

This paper presents the theoretical analysis of a storage integrated solar thermophotovoltaic (SISTPV) system operating in steady state. These systems combine thermophotovoltaic (TPV) technology and high temperature thermal storage phase-change materials (PCM) in the same unit, providing a great potential in terms of efficiency, cost reduction and storage energy density. The main attraction in the proposed system is its simplicity and modularity compared to conventional Concentrated Solar Power (CSP) technologies. This is mainly due to the absence of moving parts. In this paper we analyze the use of Silicon as the phase change material (PCM). Silicon is an excellent candidate because of its high melting point (1680 K) and its very high latent heat of fusion of 1800 kJ/kg, which is about ten times greater than the conventional PCMs like molten salts. For a simple system configuration, we have demonstrated that overall conversion efficiencies up to ?35% are approachable. Although higher efficiencies are expected by incorporating more advanced devices like multijunction TPV cells, narrow band selective emitters or adopting near-field TPV configurations as well as by enhancing the convective/conductive heat transfer within the PCM. In this paper, we also discuss about the optimum system configurations and provide the general guidelines for designing these systems. Preliminary estimates of night time operations indicate it is possible to achieve over 10 h of operation with a relatively small quantity of Silicon.

Laser induced forward transfer of silver pastes for printing of fingers in c-si cells.

The main objective of this work is to adapt the Laser Induced Forward Techniques (LIFT), a well- known laser direct writing technique for material transfer, to define metallic contacts (fingers and busbars) onto c-Si cells. The silver paste (with viscosity around 30-50 kcPs) is applied over a glass substrate using a coater. The thickness of the paste can be control changing the deposit parameters. The glass with the silver paste is set at a controlled gap over the c-Si cell. A solid state pulsed laser (532 nm) is focused at the glass/silver interface producing a droplet of silver that it is transferred to the c-Si cell. A scanner is used to print lines. The process parameters (silver paste thickness, gap and laser parameters -spot size, pulse energy and overlapping of pulses) are modified and the morphology of the lines is studied using confocal microscopy. Long lines are printed and the uniformity (in thickness and height) is studied. Some examples of metallization of larger areas (up to 10 cm x 10 cm) are presented.

Reduction of front-metallization grid shading in concentrator cells through laser micro-grooved cover glass

Concentrator solar cell front-grid metallizations are designed so that the trade-off between series resistance and shading factor (SF) is optimized for a particular irradiance. High concentrator photovoltaics (CPV) typically requires a metallic electrode pattern that covers up to 10% of the cell surface. The shading effect produced by this front electrode results in a significant reduction in short-circuit current (I SC) and hence, in a significant efficiency loss. In this work we present a cover glass (originally meant to protect the cell surface) that is laser-grooved with a micrometric pattern that redirects the incident solar light towards interfinger regions and away from the metallic electrodes, where they would be wasted in terms of photovoltaic generation. Quantum efficiency (QE) and current (I)-voltage (V) characterization under concentration validate the proof-of-concept, showing great potential for CPV applications

The inhibition of antigen-presenting activity of dendritic cells resulting from UV irradiation of murine skin is restored by in vitro photorepair of cyclobutane pyrimidine dimers

Exposing skin to UVB (280–320 nm) radiation suppresses contact hypersensitivity by a mechanism that involves an alteration in the activity of cutaneous antigen-presenting cells (APC). UV-induced DNA damage appears to be an important molecular trigger for this effect. The specific target cells in the skin that sustain DNA damage relevant to the immunosuppressive effect have yet to be identified. We tested the hypothesis that UV-induced DNA damage in the cutaneous APC was responsible for their impaired ability to present antigen after in vivo UV irradiation. Cutaneous APC were collected from the draining lymph nodes of UVB-irradiated, hapten-sensitized mice and incubated in vitro with liposomes containing a photolyase (Photosomes; Applied Genetics, Freeport, NY), which, upon absorption of photoreactivating light, splits UV-induced cyclobutane pyrimidine dimers. Photosome treatment followed by photoreactivating light reduced the number of dimer-containing APC, restored the in vivo antigen-presenting activity of the draining lymph node cells, and blocked the induction of suppressor T cells. Neither Photosomes nor photoreactivating light alone, nor photoreactivating light given before Photosomes, restored APC activity, and Photosome treatment did not reverse the impairment of APC function when isopsoralen plus UVA (320–400 nm) radiation was used instead of UVB. These controls indicate that the restoration of APC function matched the requirements of Photosome-mediated DNA repair for dimers and post-treatment photoreactivating light. These results provide compelling evidence that it is UV-induced DNA damage in cutaneous APC that leads to reduced immune function.

Critical contribution of liver natural killer T cells to a murine model of hepatitis

Natural killer T (NKT) cells constitute a distinct subpopulation of T cells with a unique antigen specificity, prompt effector functions, and an unusual tissue distribution. NKT cells are especially abundant in the liver, but their physiological function in this organ remains unclear. In the present study, we examined the possible contribution of NKT cells to a murine model of hepatitis induced by i.v. injection of Con A. CD1-deficient mice lacking NKT cells were highly resistant to Con A-induced hepatitis. Adoptive transfer of hepatic NKT cells isolated from wild-type mice, but not from FasL-deficient gld mice, sensitized CD1-deficient mice to Con A-induced hepatitis. Furthermore, adoptive transfer of hepatic mononuclear cells from wild-type mice, but not from CD1-deficient mice, sensitized gld mice to Con A-induced hepatitis. Upon Con A administration, hepatic NKT cells rapidly up-regulated cell surface FasL expression and FasL-mediated cytotoxicity. At the same time, NKT cells underwent apoptosis leading to their rapid disappearance in the liver. These results implicated FasL expression on liver NKT cells in the pathogenesis of Con A-induced hepatitis, suggesting a similar pathogenic role in human liver diseases such as autoimmune hepatitis.

Enhanced somatic mutation rates induced in stem cells of mice by low chronic exposure to ethylnitrosourea.

We have found that the somatic mutation rate at the Dlb-1 locus increases exponentially during low daily exposure to ethylnitrosourea over 4 months. This effect, enhanced mutagenesis, was not observed at a lacI transgene in the same tissue, although the two loci respond very similarly to acute doses. Since both mutations are neutral, the mutant frequency was expected to increase linearly with time in response to a constant mutagenic exposure, as it did for lacI. Enhanced mutagenesis does not result from an overall sensitization of the animals, since mice that had first been treated with a low daily dose for 90 days and then challenged with a large acute dose were not sensitized to the acute dose. Nor was the increased mutant frequency due to selection, since animals that were treated for 90 days and then left untreated for up to 60 days showed little change from the 90-day frequency. The effect is substantial: about 8 times as many Dlb-1 mutants were induced between 90 and 120 days as in the first 30 days. This resulted in a reverse dose rate effect such that 90 mg/kg induced more mutants when delivered at 1 mg/kg per day than at 3 mg/kg per day. We postulate that enhanced mutagenesis arises from increased stem cell proliferation and the preferential repair of transcribed genes. Enhanced mutagenesis may be important for risk evaluation, as the results show that chronic exposures can be more mutagenic than acute ones and raise the possibility of synergism between chemicals at low doses.

Regulatory T Cells Accumulate in the Lung Allergic Inflammation and Efficiently Suppress T-Cell Proliferation but Not Th2 Cytokine Production

Foxp3(+)CD25(+)CD4(+) regulatory T cells are vital for peripheral tolerance and control of tissue inflammation. In this study, we characterized the phenotype and monitored the migration and activity of regulatory T cells present in the airways of allergic or tolerant mice after allergen challenge. To induce lung allergic inflammation, mice were sensitized twice with ovalbumin/aluminum hydroxide gel and challenged twice with intranasal ovalbumin. Tolerance was induced by oral administration of ovalbumin for 5 consecutive days prior to OVA sensitization and challenge. We detected regulatory T cells (Foxp3(+)CD25(+)CD4(+) T cells) in the airways of allergic and tolerant mice; however, the number of regulatory T cells was more than 40-fold higher in allergic mice than in tolerant mice. Lung regulatory T cells expressed an effector/memory phenotype (CCR4(high)CD62L(low)CD44(high)CD54(high)CD69(+)) that distinguished them from naive regulatory T cells (CCR4(int)CD62L(high)CD44(int)CD54(int)CD69(-)). These regulatory T cells efficiently suppressed pulmonary T-cell proliferation but not Th2 cytokine production.

Low-cost sprayed CdTe solar-cell research : third quarterly progress report for period February 15 - May 14, 1980 /

"Work Performed Under Contract No. AC02-77CH00178."

Electrochemical photovoltaic cells : quarterly technical progress report for April 15 - July 31, 1980 /

"Work Performed Under Contract No. AC02-77CH00178."

Electrochemical photovoltaic cells/stabilization and optimization of II-VI semiconductors : first technical progress report for April 15 - June 30, 1980 /

"Work Performed Under Contract No. AC02-77CH00178."

Analysis of the application of thermogalvanic cells to the conversion of low grade heat to electricity /

"Work Performed Under Contract No. AC02-77CH00178."

Electrochemical photovoltaic cells : project 65021 final technical progess report for the period April 15, 1979, through April 17, 1980 /

"September 1980."

Electrochemical photovoltaic cells CdSe thin film electrodes : final report, June 1979-June 1980 /

"Contract No. AC02-77CH00178."

Solar cell and photocell handbook.

"No. 3 of a series of technical handbooks."

Investigation of silicon photocells as converters of solar radiation (Issledovaniye kremniyevykh fotoelementov kak preobrazovately solnechnogo izlucheniya)

"This translation was prepared under the auspices of the Liaison Office, Technical Information Center, Wright-Patterson AFB, Ohio."