Effect Of Radiation Intensity Research Articles

The Effect of Radiation Intensity on the Performance of Direct-Expansion Solar PVT Heat Pump Systems

The objective of this study was to investigate the impact of solar radiation intensity on the performance of direct-expansion solar PVT heat pump systems. To this end, an experimental setup was constructed for direct-expansion photovoltaic (PVT) solar heat pump water heating systems and photovoltaic (PV) power generation systems. The system performance and main parameters were analyzed and discussed under different solar radiation intensities. The winter experiments in southern China revealed that the exhaust temperature of the heat pump unit varied considerably under clear conditions, while the back temperature remained stable, fluctuating between approximately −13.5 °C and 24 °C. In contrast, the power generation of PVT panels increased with the increase in radiation intensity, from 78.33 W to 122.68 W, for an increase of 56.6%. Furthermore, the total electricity generation of the PVT panels was higher than that of PV panels, with an increase of 8.7–8.3%. Nevertheless, discrepancies between experimental and theoretical data were observed, particularly under overcast conditions, where the back panel temperature error was pronounced. Additionally, the system exhibited enhanced stability at elevated temperatures in comparable environments, accompanied by an improvement in the system’s coefficient of performance (COP) by 5.67%.

Thermodynamics Investigation and Artificial Neural Network Prediction of Energy, Exergy, and Hydrogen Production from a Solar Thermochemical Plant Using a Polymer Membrane Electrolyzer

Hydrogen production using polymer membrane electrolyzers is an effective and valuable way of generating an environmentally friendly energy source. Hydrogen and oxygen generated by electrolyzers can power drone fuel cells. The thermodynamic analysis of polymer membrane electrolyzers to identify key losses and optimize their performance is fundamental and necessary. In this article, the process of the electrolysis of water by a polymer membrane electrolyzer in combination with a concentrated solar system in order to generate power and hydrogen was studied, and the effect of radiation intensity, current density, and other functional variables on the hydrogen production was investigated. It was shown that with an increasing current density, the voltage generation of the electrolyzer increased, and the energy efficiency and exergy of the electrolyzer decreased. Additionally, as the temperature rose, the pressure dropped, the thickness of the Nafion membrane increased, the voltage decreased, and the electrolyzer performed better. By increasing the intensity of the incoming radiation from 125 W/m2 to 320 W/m2, the hydrogen production increased by 111%, and the energy efficiency and exergy of the electrolyzer both decreased by 14% due to the higher ratio of input electric current to output hydrogen. Finally, machine-learning-based predictions were conducted to forecast the energy efficiency, exergy efficiency, voltage, and hydrogen production rate in different scenarios. The results proved to be very accurate compared to the analytical results. Hyperparameter tuning was utilized to adjust the model parameters, and the models' results showed an MAE lower than 1.98% and an R2 higher than 0.98.

Effect of radiation intensity on the fragmentation of furan through multiphoton ionization at 532 and 355 nm

The effect of radiation on the multiphoton ionization/dissociation of furan was studied at wavelengths of 532 nm and 355 nm. The relative abundance of the ions that were produced is presented for each wavelength; it was observed that the ion C2H2+ (m/z = 26) was the most abundant at 532 nm, while the parent ion C4H4O+ (m/z = 68) was the most abundant at 355 nm. These results differ from those of previous studies that used different ionization methods. The fragmentation mechanisms found in this study suggest that isomerization of the molecule occurs while it breaks down into smaller fragments, in which the migrations of H are included. In addition, an effect on the kinetic energy of the produced ions related to the intensity of radiation was observed, which seemed to indicate a type of multiphoton resonance.

Photocatalytic degradation of cefixime using visible light-driven Z-scheme ZnO nanorod/Zn2TiO4/GO heterostructure

ZnO nanorod along with a Zn2TiO4/GO heterostructure with enhanced charge transfer capability was synthesized by a facile sol-gel method. FT-IR, XRD, XPS, TEM, SEM, EDX, UV–Vis DRS, photocurrent response and PL analyses were applied to characterize the as-prepared photocatalysts. To investigate the photocatalytic activity of the composite, Cefixime (CEF) removal under visible light was evaluated. The ZnO nanorod/Zn2TiO4/GO, including 65 wt% ZnO and 3 wt% graphene oxide, showed the highest CEF degradation and was selected as the optimal ternary composite. Reduction of electron-hole pair recombination rate, successful interfacial charge transfers, and more visible light reception in the Z-scheme system were the important reasons for improving the photocatalytic properties of ZnO nanorod/Zn2TiO4/GO. Effective operating parameters in the CEF photocatalytic removal process were optimized employing the response surface method and were as follows: photocatalyst dosage = 0.88 g/L, pH = 5, radiation time = 115 min, and CEF concentration = 10 ppm. The photocatalytic degradation% of CEF and total organic carbon (TOC) removal% under the optimal conditions were 71.4 and 57.5%, respectively, for the three-component composite indicating the production of intermediate species during the process. This photocatalytic reaction confirmed the first-order kinetic and using the ZnO nanorod/Zn2TiO4/GO composite was able to improve the reaction rate by about 2.7 and 6.2 times more than ZnO nanorod/Zn2TiO4 and ZnO, respectively. The effects of radiation intensity and temperature were investigated and 175 W/m2 and 35 °C were obtained as optimum values. Eventually, according to the trapping test, h+, superoxide radical, and hydroxyl radical are the most effective active species in this photocatalytic reaction, respectively.

Simulation of the impact of solar radiation intensity on the performance of economical solar water desalination still in Semnan province

Semnan province with a total area of 97000 km2 is the sixth biggest province in Iran. The evaporation rate in this province is high and can be. The index of the urban and rural water networks in this province is much higher than the global average, but according to the goals set for water supply to all people in all cities and villages, using new technologies is an effective way. High potential evaporation intensity in Semnan province, which reaches 1000-3000 (mm) per year, can be converted from a threat to an opportunity by using it as a new source of energy for a sustainable safe drinking water supply. In order to use of evaporation capacity, in this paper the impact of solar radiation intensity on the performance of single-slope solar still is investigated. The solar radiative flux depends on geographical location, season, and time. In this study, the dimension and temperature of the basin are constant and the effect of radiation intensity on water productivity of solar stills is investigated as a function of time, month (April) and location (Semnan province). The accuracy of the numerical method has been evaluated using different models and experimental data for the average Nusselt number on water surface and production rate of water. Results also indicate that the variation trends for radiation intensity are similar to the production rate. The maximum water production rate belongs to 12 o'clock with a 5.6% increase in comparison with 7:00 a.m., which has the lowest evaporation rate in the bell shaped curve.

Effects of Radiation Intensity, Mineral Matrix, and Pre-Irradiation on the Bacterial Resistance to Gamma Irradiation under Low Temperature Conditions.

Ionizing radiation is one of the main factors limiting the survival of microorganisms in extraterrestrial conditions. The survivability of microorganisms under irradiation depends significantly on the conditions, in which the irradiation occurs. In particular, temperature, pressure, oxygen and water concentrations are of great influence. However, the influence of factors such as the radiation intensity (in low-temperature conditions) and the type of mineral matrix, in which microorganisms are located, has been practically unstudied. It has been shown that the radioresistance of bacteria can increase after their exposure to sublethal doses and subsequent repair of damage under favorable conditions, however, such studies are also few and the influence of other factors of extraterrestrial space (temperature, pressure) was not studied in them. The viability of bacteria Arthrobacter polychromogenes, Kocuria rosea and Xanthomonas sp. after irradiation with gamma radiation at a dose of 1 kGy under conditions of low pressure (1 Torr) and low temperature (−50 °C) at different radiation intensities (4 vs. 0.8 kGy/h) with immobilization of bacteria on various mineral matrices (montmorillonite vs. analogue of lunar dust) has been studied. Native, previously non-irradiated strains, and strains that were previously irradiated with gamma radiation and subjected to 10 passages of cultivation on solid media were irradiated. The number of survived cells was determined by culturing on a solid medium. It has been shown that the radioresistance of bacteria depends significantly on the type of mineral matrix, on which they are immobilized, wherein montmorillonite contributes to an increased survivability in comparison with a silicate matrix. Survivability of the studied bacteria was found to increase with decreasing radiation intensity, despite the impossibility of active reparation processes under experimental conditions. Considering the low intensity of radiation on various space objects in comparison with radiobiological experiments, this suggests a longer preservation of the viable microorganisms outside the Earth than is commonly believed. An increase in bacterial radioresistance was revealed even after one cycle of irradiation of the strains and their subsequent cultivation under favourable conditions. This indicates the possibility of hypothetical microorganisms on Mars increasing their radioresistance.

Leveraging Controlled-Environment Agriculture to Increase Key Basil Terpenoid and Phenylpropanoid Concentrations: The Effects of Radiation Intensity and CO2 Concentration on Consumer Preference.

Altering the radiation intensity in controlled environments can influence volatile organic compound (VOC) biosynthetic pathways, including those of terpenoids and phenylpropanoids. In turn, the concentrations of these compounds can have a profound effect on flavor and sensory attributes. Because sweet basil (Ocimum basilicum) is a popular culinary herb, our objectives were to (1) determine the extent radiation intensity and carbon dioxide (CO2) concentration influence seedling terpenoid and phenylpropanoid concentrations; (2) determine if differences in phenylpropanoid and terpenoid concentrations influence consumer preference; and (3) characterize consumer preferences to better inform production and marketing strategies. “Nufar” sweet basil was grown with CO2 concentrations of 500 or 1,000 μmol ⋅ mol–1 under sole-source radiation intensities of 100, 200, 400, or 600 μmol ⋅ m–2 ⋅ s–1 with a 16 h photoperiod to create daily light integrals of 6, 12, 23, and 35 mol ⋅ m–2 ⋅ d–1. After 2 weeks, concentrations of the terpenoids 1,8 cineole and linalool and the phenylpropanoids eugenol and methyl chavicol were quantified, and consumer sensory panel evaluations were conducted to quantify preferences. Overall, increasing radiation intensity from 100 to 600 μmol ⋅ m–2 ⋅ s–1 increased 1,8 cineole, linalool, and eugenol concentrations 2. 4-, 8. 8-, and 3.3-fold, respectively, whereas CO2 concentration did not influence VOCs. Contrary to our hypothesis, increased VOC concentrations were not correlated with consumer preference. However, overall liking was correlated with aftertaste and flavor. The conclusion that consumer preference is dependent on flavor can be drawn. However, increasing VOC concentrations to increase flavor did not improve flavor preference. Many consumer sensory preference characteristics (favorable preference for aftertaste, bitterness/sweetness, color, flavor, overall liking, and texture) were correlated with basil grown under a radiation intensity of 200 μmol ⋅ m–2 ⋅ s–1. This led us to determine that consumers prefer to detect the characteristic basil flavor made up of 1,8 cineole, eugenol, and linalool, which was not as prevalent in basil grown under 100 μmol ⋅ m–2 ⋅ s–1, but too high in basil grown under 400 and 600 μmol ⋅ m–2 ⋅ s–1, which led to lower consumer preference.

Performance of a bridge deck as solar collector in a thermal energy storage system

Solar energy can be stored in subsurface and extracted to melt snow and deice in winter. In summer, the bridge deck heat element in a bridge deicing system could serve as a solar energy collector without additional cost. Numerical models were developed in this study to investigate the performance of a bridge deck solar collector. The effects of radiation intensity and wind speed on the solar energy collection efficiency of a bridge deck solar energy collector were discussed and analyzed. The results show that the temperature of the slab was decreased during the solar collection process, and the solar energy collection efficiency of the bridge deck solar collector was about 26~47%. The collection efficiency of solar energy at a given wind speed was increased with the decreasing of the radiation energy, and this effect was more pronounced when the wind speed was higher. The solar energy collection was beneficial to the durability of the top asphalt layer as well as the structural response of the bridge because the magnitude and gradient of the slab temperature were much lower when the bridge deck served as a solar energy collector.

Analysis of the charge state of nitrogen-vacancy centers in diamond driven by an infrared laser field

The methods of controlling the charge state of nitrogen–vacancy centers using pulsed infrared laser field are studied. The effect of radiation intensity at a wavelength of about 1 μm on the ionization of these color centers was shown. The obtained results can be useful for multiphoton microscopy of biological objects, high-resolution microscopy and sensory applications.

Effect of Radiation Intensity, Water Temperature and Support-Base Materials on the Inactivation Efficiency of Solar Water Disinfection (SODIS)

Solar water disinfection (SODIS) harnesses energy from the sun to kill pathogenic microorganism in drinking water, thus making it safe for consumption. The effects of local conditions and materials on the efficiency of SODIS were investigated in this study for a period of five months. Waste polyethylene terephthalate (PET) bottles with varying optical properties were used as SODIS reactors. Water samples from deep well, shallow well, rainfall and spring were used for the study. SODIS reactors were exposed to sunlight for a period of 8 h under varying conditions of temperature and solar radiation. The study revealed that solar radiation intensity of 500–650 W/m2 and water temperature of 45–55 °C, were effective in destroying pathogens. Analysis of variance (ANOVA) confirmed statistically significant difference (p < 0.000) in water temperature of the reactors and support base materials used. However, this did not translate to significant difference in microbial population after 8 h of exposure to sunlight. Over 3 Log reduction in faecal coliform was recorded at a temperature of 55.5 °C within 3 h of exposure. At temperatures below 45 °C, 3 log inactivation of bacteria was not attained even after 8 h of exposure to sunlight. Hence, SODIS can be employed to address the immediate water quality needs of the most disadvantaged communities of Nigeria.

Simulation study on performance of a dual-source hybrid heat pump unit with alternative refrigerants

Abstract To solve the problems of single heat source heat pump systems in severe cold regions, a dual-source hybrid heat pump unit (DSHHPU) is proposed. The mathematical models of the DSHHPU when charging R134a or its alternative refrigerants R32, R290 and R600a were established respectively, and the performance was simulated and analysed. The results showed that the four refrigerants have different performance characteristics in different aspects. In heat pipe mode, the heating capacity and evaporating pressure of R32 are 36.94% and 59.94% higher than those of R134a. The heating capacity and evaporating pressure of R290 are 5.73% and 22.99% lower than those of R134a. The heating capacity and evaporating pressure of R600a are 43.29% and 68.08% lower than those of R134a. In vapour compression heating mode, the discharge temperature of R32, R290 and R600a are 184.88, 72.98 and 66.44% of that of R134a. The coefficient of performance (COP) of R32, R290 and R600a are 72.65, 111.59 and 117.94% of that of R134a. Finally, the effects of radiation intensity and ambient temperature on key performance parameters of the different refrigerants were analysed. The research results provide a reference for research on refrigerant replacements for multi-heat source composite heat pump systems.

The Solar Panel’s Performance Dependence on Incident Radiation Intensity and its Surface Temperature

The effect of radiation intensity and temperature on the performance parameters of a solar panel is investigated experimentally using an indoor experimental setup, designed and constructed locally at Higher Institute for Applied Sciences and Technology, Damascus. The experiments have been carried out under various intensity levels of radiation in the range of 700- 2000W/m2. The experimental results indicate that, radiation intensity has a dominant effect on current parameters. It is found that photocurrent; short circuit current and maximum current have been increased linearly with increasing radiation intensity. So, concentrating system may be regarded as a best choice to enhance the power output of solar system. The power density of the solar panel at 30oC increased from 1.86 mW/cm2 at 1300W/m2 to 3.59 mW/cm2 at 2000W/m2. The role of temperature on the electric parameters of solar panel is also considered. The practical local possible solar panel’s temperature was considered to be in the range of 10–70oC. The experiments cover this temperature range. Experimental results show that all electrical parameters of solar panel such as maximum output power, open circuit voltage, short circuit current, efficiency and fill factor have changed with temperature variation. As well as the amount of changes in these parameters in terms of temperature value have been obtained. According to results, the most significant is the temperature dependence of the voltage which decreases with increasing temperature while the current of the solar panel slightly increases by temperature. On the other hand, it has been observed that solar panel’s temperature has a dramatic effect on voltage parameters. Open circuit voltage and maximum voltage are decrease with increasing solar panel’s temperature. So, the maximum power density of the mono-crystalline and poly-crystalline silicon solar module decreased from 43.4 and 48.76/cm2 to 36.32 and 41.88mW/cm2 for temperature 10oC and 70oC respectively. When testing the effect of temperature on French Photo watt solar cells, obtained 20 years ago and encapsulated in a solar panel locally, in the temperature range of 10–90oC, it was found that, the open circuit voltage decreases by 1.87mV/ oC which is equivalent to 0.3% of the nominal value. The short circuit current intensity decreases by 20mA/oC which is equivalent to 1% of the nominal value. When comparing these values with those of the company presented at its electronic cite, Isc = +0,06%/°C; Voc = -0,34%/°C, one can conclude that aging effect is important on short circuit current intensity.

Experimental Investigation of the Transpired Solar Air Collectors and Metal Corrugated Packing Solar Air Collectors

The thermal performance of three novel solar air collectors with perforating corrugated plate, slit-perforated plate, and corrugated packing were experimentally studied in this paper. Experiments were conducted in Tianjin to study the thermal and dynamic performance of the collectors in cold and severe cold regions. A chamber with a PID (Proportion Integration Differentiation) temperature controller was designed to control the inlet air temperature of the three collectors. Effects of radiation intensity, inlet air temperature, and flow rate on the thermal efficiency and outlet air temperature were experimentally studied. The results indicated that the thermal efficiency of the three collectors in severe cold regions could be much higher than 50% and the collector with perforating corrugated plate had the highest thermal efficiency. The inlet air flow rate had significant effects on the thermal comfort of buildings in cold and severe cold regions and it should be lower than 45 m3/h. The results indicated that the pressure drops of collectors with perforating corrugated plate were a little larger than the collectors with slit-perforated plate, but the thermal efficiency and outlet air temperature was higher. Therefore, the collector with perforating corrugated plate was more suitable to use in cold and severe cold regions.

Effect of Microwave treatment on longitudinal air permeability and preservative uptake characteristics of chir pine wood

Low permeability of many wood species due to their anatomical properties causes problems during timber drying as well as impregnating with preservatives and resins. Microwave (MW) treatment influences heartwood permeability and improves preservative uptake and distribution. In the present study, microwave treatment of chir pine (Pinus roxburghii) wood was done at 2,45 GHz frequency at different level of intensity and radiation time. The gas permeability of chir pine wood was measured in an in-house built apparatus. Preservative uptake was tested using acid copper chromate (ACC) preservative by a dipping process. The effect of radiation intensity and time on preservative uptake and air permeability were studied. The results revealed remarkable increase in longitudinal wood air permeability and preservative uptake with the increase of intensity and time of treatment. The results indicate that this technology can be tested and applied on pilot scale for application in wood preservation industry.

Effect of microwave treatment on air permeability and preservative impregnation of Eucalyptus tereticornis wood

Low permeability of many wood species causes problems during timber drying as well as impregnating with preservatives and resins. In the present study, microwave treatment of Eucalyptus tereticornis Sm. wood which is difficult to treat, was done at 2.45 GHz frequency at different levels of intensity and radiation time. The gas permeability of E. tereticornis wood was measured in an in-house built apparatus. Preservative uptake/retention was tested using Acid Copper Chrome preservative by dipping method. The effect of radiation intensity and time was studied with respect to air permeability and preservative uptake. The results revealed remarkable increase in longitudinal wood air permeability and preservative uptake with the increase of intensity and time of treatment. The results indicate that this technology could be tested and applied on pilot scale for application in wood preservation industry.

Effect of radiation intensity on the outcome of postharvest UV-C treatments

Studies on the use of UV-C radiation of fresh produce have focused on the selection of appropriate doses (energy per unit area) for different commodities, but little attention has been placed on the effect of radiation intensity (dose per unit time). In this study, tomatoes (Solanum lycopersicum cv. Elpida) and strawberries (Fragaria×ananassa cv. Camarosa), were harvested (breaker and 100% of surface red color respectively) and treated with 4kJm−2 of UV-C, at low (3Wm−2) or high (33Wm−2) radiation intensities. Untreated fruits were used as controls. After the treatments and at different storage times the incidence of postharvest rots and the changes in fruit physical and chemical properties were determined. UV-C treatments reduced decay, with the effects being were more marked in fruit exposed to high intensities. Mold counts were unaffected by the treatments, suggesting that improved disease control did not result from greater germicide effect. In both fruit species exposure to UV-C radiation delayed ripening, evidenced as lower color development, pigment accumulation and softening. UV-C-treated fruit maintained better quality than the control. In strawberry, high intensity treatments were more effective to prevent deterioration than in tomato where the differences between UV-C treatments were subtler. Soluble solids, titratable acidity and ethanol soluble antioxidants were not affected regardless of the UV-C intensity. Consumer tests showed higher preference of fruit treated at high UV-C intensity. Results show that in addition to the applied dose, radiation intensity is a main factor determining the effectiveness of UV-C treatments and should not be over-sighted. For a given dose, increasing radiation intensity may in some cases maximize the benefits of UV-C on fruit quality, while significantly reducing the treatments time.

Nonlinear Optical Properties of Si Nanodot in ${\rm Al}_{2}{\rm O}_{3}$ Matrix

The linear and the third-order nonlinear optical properties associated with intersubband transitions are studied for spherical Si nanodot embedded in an amorphous matrix. The effect of radiation intensity and the change in the size of the dot are investigated on the nonlinear photoabsorption coefficient, refractive index change, and the third-order nonlinear optical susceptibility for transitions from ground state (1s-1p) and excited states (1p-1d, 2s-2p). The oscillator strength is also calculated for these transitions along with the photoelectric cross sections from the initial 1s and 2s states of the dot. It is noted that a decrease in the size of the dot leads to blue shift in peak positions of photoabsorption coefficient, refractive index change, and third-order nonlinear susceptibility involving transitions from the ground and excited states.

Photopolymerization of Vinyl Ether Networks Using an Iodonium Initiator: Effect of Radiation Intensity and Iodonium Concentration

Photo-differential scanning calorimetry (photo-DSC) was used to investigate the photocuring kinetics of visible light initiated cationic photopolymerization of triethylene glycol divinyl ether (TEGDVE) with a diphenyl iodonium salt initiator and the three photosensitizers: 1-chloro-4-propoxy-9H-thioxanthen-9-one (CPTXO), camphorquinone (CQ), and acridine orange (AO). The effects of water, a tertiary amine, and a radical scavenger were used to probe the photocuring mechanism. The rate of photopolymerization was approximately proportional to the incident light intensity, and in each system, the final conversions, as measured by photo-DSC, also increased with raised incident light intensity. The power-law dependence of the reaction rate on the concentration of iodonium salt with CPTXO and AO was ∼1.5, while the order is nearly unity with CQ as the photosensitizer, suggesting that these photosensitizers do not follow the same sensitization mechanism. For the three photosensitizers, the final conversions all increased with higher iodonium salt concentrations. After cessation of irradiation, a dark reaction was observed—although the rate of this process decreased rapidly with time (as shown by photo-DSC), the polymerization continued very slowly over a long period of time.

Numerical Modeling of Thaw Penetration in Frozen Ground Subject to Low-Intensity Infrared Heating

This research investigated the efficacy of low-intensity, radiant, infrared heating for inducing thawing in frozen ground. Specifically, the performance characteristics of a 22 kW infrared tube heater were evaluated. A commercial building site in Park City, Utah, was instrumented with thermocouple piers for field testing over a period of approximately 5 days. The experimental data were used to calibrate a numerical model of the infrared heating process, and several numerical simulations were then performed. The simulations facilitated evaluation of the effects of radiation intensity, air temperature, and ice content on thaw penetration rates achieved using infrared heating. While ice content has a marked influence on thaw penetration rates in all the simulations, the air temperature becomes less important with increasing infrared radiation intensity. The results of the testing also indicate that the tube heater exhibits a steady reduction in emitted radiation between propane tank exchanges and that the he...

Effects on photovoltaic solar module performance in the UK climate

SYNOPSIS Presently, PV devices are rated on the basis of a standard test condition (STC) efficiency and not on their energy production, which would be a much better parameter for their cost per generated kwh. There is a lack of knowledge of factors affecting performance of thin film PV devices, especially operating in maritime climates such as the UK's. Modules studied in this investigation include crystalline, polycrystalline and amorphous silicon, cadmium telluride and copper indium diselenide. The different factors affecting the performance of PV modules operated in the UK climate are investigated. The main effects identified are changes in the spectrum, operating temperature and irradiance, each affecting device performance according to the type of cell material. The spectral effect is predictably more pronounced for the wider band gap materials (amorphous silicon and cadmium telluride) and includes two separate identifiable effects, termed primary and secondary. The primary spectral effect depends on the availability of spectrally useful irradiance and is more pronounced for the amorphous silicon (a-Si) single junctions, where it varies by + 5% to—9% with respect to the annual average. There is also evidence of a secondary effect in the a-Si multi-junctions, due to mismatch of current between the series connected sub-cells, the magnitude of which is much less than the primary spectral effect, but is noticeable nevertheless. The materials with narrower band gaps (polycrystalline, crystalline and copper indium diselenide) suffer more significantly from thermal effects and less from spectral effects than do devices with a wider band gap. The effect of radiation intensity is device-specific; some devices (crystalline and polycrystalline) benefit from increased irradiance, although some thin films show a deterioration of efficiency with increasing irradiance. The importance of shunt and series resistance is discussed in this context.