Simulated Solar Irradiance Research Articles

In-situ electrical characterisation of a photodiode during nano-structuring with a focussed ion beam

We study the fabrication and power conversion efficiency of GaAs photodiodes, which have been nano-structured and covered with colloidal quantum dots. A focussed ion beam is used to etch vertical channels into the photodiodes and the detrimental effects of this treatment are characterised in-situ during the fabrication process. A novel experimental configuration allows the electrical characterization of the photodiodes under laser illumination during the nano-fabrication process and reveals the gradual decrease of the photodiodes’ shunt resistance with increasing laterally revealed surface along the etched channels. This is interpreted as evidence for leakage currents through redeposited material and surface states on the lateral channel surface. After the fabrication step the channels are filled with colloidal quantum dots, which upon absorption of light transfer electronic excitations to the photodiode via resonance energy transfer. It is found that after the addition of quantum dots the nano-structured photodiodes show larger enhancements of the energy conversion efficiency under simulated solar irradiance than the pristine photodiodes. Nevertheless, the device degradation induced by the ion beam treatment itself cannot be compensated for.

Application of Poly(3‐hexylthiophene) Functionalized with an Anchoring Group in Dye‐sensitized Solar Cells

A series of three poly(3-hexylthiophene) functionalized either with a cyanoacetic acid (CA) or a rhodanine-3-acetic acid anchoring groups were synthesized and characterized. The TiO(2) based dye-sensitized solar cells have been fabricated and performances were tested. We show that shorter chain length (15 thiophene units) linked to CA binding group gives good performances as J(sc) , V(oc) , FF and η(%) were 6.93(mA · cm(-2) ), 0.65(V), 0.67 and 3.02%, respectively. A maximum IPCE of ≈50% at 500 nm was recorded with a liquid electrolyte, under AM 1.5 simulated solar irradiance.

Photobleaching kinetics of chromophoric dissolved organic matter derived from mangrove leaf litter and floating Sargassum colonies

We examined the photoreactivity of chromophoric dissolved organic matter (CDOM) derived from Rhizophora mangle (red mangrove) leaf litter and floating Sargassum colonies as these marine plants can be important contributors to coastal and open ocean CDOM pools, respectively. Mangrove and Sargassum CDOM readily degraded when exposed to simulated solar irradiance (CPS SunTest solar simulator exposures). CDOM produced from brown mangrove leaves (representative of substantial senescence) exhibited shorter photobleaching half-lives ( a 305 t 1/2 < 50 h) than CDOM produced from yellow and orange (early and mid senescence) leaves ( a 305 t 1/2 ∼ 60–90 h). Mangrove CDOM photobleaching rates were higher in the mid-UVA ( a 350) than in the UVB ( a 305) spectral region. Photobleaching half-lives of Sargassum CDOM were mostly < 40 h and more consistent across UVB ( a 305) and UVA ( a 350) wavelengths. Sargassum CDOM photomineralized during simulated solar irradiation producing DIC at rates exceeding 2500 nmol m l – 1 h – 1 , indicating that regions of the surface ocean with large concentrations of this plant may provide a strong CO 2 source to the atmosphere. Sargassum CDOM photoreactions also produced CO more efficiently than terrestrial CDOM and much more efficiently than ambient CDOM in the open ocean. Thus, biological production of CDOM may be the rate-limiting step for photoproduction of DIC from Sargassum and other sources in the open ocean. An examination of CDOM photobleaching in Florida Keys coastal waters indicates that one month of summertime solar radiation may substantially increase UVB and UVA exposure to corals in shallow waters (< 4 m), especially along the offshore reef tract. But, our results also indicate that when ambient CDOM levels are high, the corals are well-buffered against increases in ultraviolet radiation (UV-R) exposure even after periods of extended CDOM photobleaching.

Photoelectrochemical Analysis of Anion-Doped TiO2 Colloidal and Powder Thin-Film Electrodes

The photoelectrochemical characteristics of anion-doped powder and colloidal electrodes were investigated under UV and visible illumination. The solar absorption of was improved by synthesizing reduced forms of using anions of the main group elements (C, N, and P) to substitute for oxygen in the titania lattice. Analytical methods, including scanning electron microscopy, X-ray diffraction, elemental analysis, Raman, and UV–visible spectroscopy were employed to characterize these materials. The photoactivity of the electrodes was evaluated using a three-electrode configuration quartz photoelectrochemical cell using simulated solar irradiance. All anion-doped electrodes investigated, specifically C-, N-, and P-doped, increased the visible absorption of n-, leading to higher photoactivity under solar light. The addition of methanol to the electrolyte reduced the rapid charge recombination and hence enhanced the photocurrents. Although the efficiency is not yet comparable to single-crystal n-, optimization of the parameters studied here showed that significant increases in photoactivity could be achieved over the native powder.

Solar disinfection of poliovirus and Acanthamoeba polyphaga cysts in water – a laboratory study using simulated sunlight

To determine the efficacy of solar disinfection (SODIS) in disinfecting water contaminated with poliovirus and Acanthamoeba polyphaga cysts. Organisms were subjected to a simulated global solar irradiance of 850 Wm(-2) in water temperatures between 25 and 55 degrees C. SODIS at 25 degrees C totally inactivated poliovirus after 6-h exposure (reduction of 4.4 log units). No SODIS-induced reduction in A. polyphaga cyst viability was observed for sample temperatures below 45 degrees C. Total cyst inactivation was only observed after 6-h SODIS exposure at 50 degrees C (3.6 log unit reduction) and after 4 h at 55 degrees C (3.3 log unit reduction). SODIS is an effective means of disinfecting water contaminated with poliovirus and A. polyphaga cysts, provided water temperatures of 50-55 degrees C are attained in the latter case. This research presents the first SODIS inactivation curve for poliovirus and provides further evidence that batch SODIS provides effective protection against waterborne protozoan cysts.

Simulation of daily solar irradiance

Solar irradiance is an important input parameter for many simulation models dealing with plant responses to the environment and is not measured in as many locations as temperature and precipitation. This situation has led to the development of algorithms to simulate solar irradiance with measured temperature and precipitation. The objectives of this research effort were two-fold: (1) to determine if a location-specific algorithm to simulate solar irradiance (based on temperature and precipitation) developed in the central Great Plains of the US could be used in other locations and (2) to determine if these results could then be used to develop a generalized algorithm. Data (temperature, precipitation, and solar irradiance) from a wide variety of locations (climates) were used to develop the location-specific and generalized algorithm. Simulated values of solar irradiance from both algorithms were evaluated with independent data from the same locations. A second independent data set was used to evaluate the generalized algorithm. For the first independent data set using the location-specific algorithm, root mean square errors (RMSE) varied from 2.6 to 5.5 MJ m −2 per day. Using the generalized algorithm, RMSE varied from 3.2 to 5.5 MJ m −2 per day, excluding Barrow, AK, which had an RMSE of 6.8 MJ m −2 per day. For the second independent data set using the generalized algorithm, RMSE ranged from 4.0 to 5.8 MJ m −2 per day. The RMSE for simulated solar irradiance was relatively large when the mean annual temperature term (Δ T), which is used in the generalized algorithm, was relatively small and precipitation was relatively high. With this caveat, the generalized algorithm can be used to simulate solar irradiance at locations where only daily values of temperature and precipitation are measured. The RMSE values reported in this study compare favorably to results for other algorithms used to simulate solar irradiance. An advantage of this approach is its relative simplicity and ease of use.

Photoenhanced toxicity of weathered oil to Mysidopsis bahia

The toxicity of a water-accommodated fraction (WAF) prepared from weathered oil was assessed in a 7-day static renewal test with Mysidopsis bahia. Weathered oil was collected from the 5× monitoring well at the Guadalupe oil field. Solar ultraviolet and visible light intensities were measured in various habitats in the vicinity of the weathered oil sample collection site, and the resultant measurements were used to produce laboratory light treatments that were representative of the on-site quality and intensity of natural solar radiation. Each of five WAF dilutions and a control without WAF was tested under three different simulated solar radiation intensities. During the test, survival and growth of the mysids, irradiance, and total petroleum hydrocarbon (TPH) concentrations in the test treatments were measured. Significant increases ( P≤0.05) in mortality occurred among mysids exposed to 0.57 and 1.30 mg TPH/l and the effects were potentiated as irradiance increased. Seven-day LC50 (0.92–0.42 mg TPH/l) and LC20 (0.58–0.15 mg TPH/l) values decreased as the simulated solar irradiance increased. Calculated EC20 and EC50 values for mysid growth indicate that surviving mysids exposed to 0.1–1.0 mg TPH/l would incur significant reductions ( P≤0.05) in productivity (biomass). Results of the present study indicate that effects elicited through the interaction of WAF of weathered oil and solar radiation will substantially increase the toxicity of weathered oil. Further, the photomediated effects of petroleum compounds measured as TPH on mysid survival and growth demonstrate a need to consider the interactions of ultraviolet light and contaminant to avoid under estimating toxicity that might occur in the environment.

Multiple Channel Interferometer for Metrology

A multiple channel interferometer was developed and used for the remote monitoring of the dynamic behavior of a large-diameter antenna experiencing simulated solar irradiance in a space simulation chamber. Reversible fringe-counting techniques were employed to measure changes in the distance between the equipment located outside the chamber and each of seven optical retroreflectors mounted on the face of the antenna. After the initial measurement program was completed, the equipment was modified to improve its performance.

Solar Simulators at the Jet Propulsion Laboratory

The large JPL solar simulation systems are unique in their ability to furnish well collimated light over large areas with good uniformity and high efficiency/intensity. These systems furnish simulated solar irradiance to 10-ft (3-m) and 25-ft (7.6-m) space simulation chambers. The discussion is divided into two parts. In the first part (Sec. II) the existing facilities are described and some potential improvements discussed. In the second part (Sec. III) some results of a high-intensity lamp development program are presented.