Abstract. In this study, two different methodologies are used to develop two models for estimating daily solar UV radiation. The first is based on traditional statistical techniques whereas the second is based on artificial neural network methods. Both models use daily solar global broadband radiation as the only measured input. The statistical model is derived from a relationship between the daily UV and the global clearness indices but modulated by the relative optical air mass. The inputs to the neural network model were determined from a large number of radiometric and atmospheric parameters using the automatic relevance determination method, although only the daily solar global irradiation, daily global clearness index and relative optical air mass were shown to be the optimal input variables. Both statistical and neural network models were developed using data measured at Almería (Spain), a semiarid and coastal climate, and tested against data from Table Mountain (Golden, CO, USA), a mountainous and dry environment. Results show that the statistical model performs adequately in both sites for all weather conditions, especially when only snow-free days at Golden were considered (RMSE=4.6%, MBE= -0.1%). The neural network based model provides the best overall estimates in the site where it has been trained, but presents an inadequate performance for the Golden site when snow-covered days are included (RMSE=6.5%, MBE= -3.0%). This result confirms that the neural network model does not adequately respond on those ranges of the input parameters which were not used for its development.
Nowadays, the evaluation of sustainability is an important aspect in the study of agricultural systems and the number of projects and methods for impact assessment of food production systems is increasing. In this work, we initially carried out a survey to know the status of the artificial lighting establishment in horticultural seedling nurseries in southern Spain. Taking into account the data obtained in the survey, we conducted an experiment with different types of fluorescent lamps (TLD-18, CF, TL5, TLD-56), light-emitting diodes (LEDs) and their combinations along with the novelty white LEDs lamps and XTRASUN LEDs to evaluate their technical parameters and spectral light qualities. In addition, the effectiveness of light irradiance (ELIplant) and the use of irradiance (UI) by cucumber and tomato seedling plants were estimated considering their light absorbance capacity previously analyzed. The results showed that TLD-18 lamps and their combinations, CF and XTRASUN LEDs, had a limited value of energy efficiency (VEEI) ≤ 2. The lamps essayed with the lowest total irradiance were LEDs (B, R, V, W) and the ones with the highest values were TLD58-6 lamps. The effectiveness of light irradiance (ELIplant) and the UI were slightly higher in the case of cucumber than that of the tomato for all essayed lamps. Considering the effectiveness of the light irradiance (ELIplant), TL5-6 lamps showed the highest values. On the other hand, considering the use of irradiance, XTRASUN LEDs on the mode of vegetative growth (VG) showed the highest values.
Inch (Tradescantia zebrina) and spider (Chlorophytum comosum) plants were grown in a growth chamber for two months in plastic containers to evaluate the effects of different light treatments (T O Tube luminescent Dunn (TLD) lamps or control), T B (TLD lamps + blue light emitting diodes (LEDs)), T R (TLD lamps + red LEDs), and T BR (TLD lamps + blue and red LEDs) on biomass, photosynthesis, and physiological parameters. Total dry weight and water content were evaluated at the end of the experimental period. After two months, pigment concentrations and the photosynthetic rate were assessed in both species. The total soluble sugar, starch, and proline concentrations in the leaf as physiological parameters were studied at the end of the experiment. Both species had increased root, shoot, and total dry weight under blue LEDs conditions. The chlorophyll concentration showed a specific response in each species under monochromic or mixed red-blue LEDs. The highest photosynthetic rate was measured under the addition of mixed red-blue LEDs with TLD lamps. At the physiological level, each species triggered different responses with respect to total soluble sugars and the proline concentration in leaves under monochromic or mixed red-blue LEDs. Our study demonstrated that the addition of blue LEDs is advisable for the production of these ornamental foliage species.
As part of the research for techniques to control the final energy reaching the receivers of central solar power plants, this work combines two contrasting methods in a novel way as a first step towards integrating such systems in solar plants. To determine the effective power reaching the receiver, the direct normal irradiance was predicted at ground level using a total sky camera, TSI-880 model. Subsequently, these DNI values were used as the inputs for a heliostat model (Fiat-Lux) to trace the sunlight’s path according to the mirror features. The predicted valuex of flux, obtained from these simulations, differ of less than 20% from the real values. This represents a significant advance in integrating different technologies to quantify the losses produced in the path from the heliostats to the central receiver, which are normally caused by the presence of atmospheric attenuation factors.
The most common sensors used for the measurement of high solar irradiance are the Gardon gauges, which are usually calibrated using a black body at a certain temperature as the radiant source. This calibration procedure is assumed to produce a systematic error when solar irradiance measurements are taken using these sensors. This paper demonstrates a calorimetric method for calibrating these high-heat-flux gauges in a solar furnace. This procedure has enabled these sensors to be calibrated under concentrated solar radiation at higher irradiances under non-laboratory conditions in the CIEMAT solar furnace at the Plataforma Solar de Almería. Working at higher irradiances has allowed the uncertainty in the calibration constant of these sensors to be reduced. This work experimentally confirms the predicted systematic errors committed when measuring high solar irradiances using Gardon sensors calibrated with a black body.
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