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In the context of global warming and a reduction in fresh water availability, this study presents the evolution of dew, rain and evapotranspiration in the North-West (NW) of Africa. This study is followed by a chemical analysis of dew and rain data in a representative site. The time periods are concerned with the years 2005–2020 using existing data, and years 2020–2100 using the low and high emissions representative concentration pathway scenarios RCP 2.6/8.5 from the coordinated regional climate downscaling experiment database. A continuous decrease in rain precipitation is observed, on the order of −14 mm·decade−1 for the more credible scenario RCP 8.5. The amplitude is maximum on the coast and on the foothills of Atlas. A clear decrease in dew yields (up to 7%) is also observed along a NW/SE axis. It is strongly correlated with a corresponding decrease in relative humidity. Chemical dew and rain data in the representative site of Mirleft correspond to the major cations of Na+ > Ca2+ > Mg2+ > K+, similar to local spring water. The concentrations in rain are about two times less than in dew water. Ionic concentrations are compatible with the World Health Organization standards. The seasonal variations of the ionic concentrations in dew and rain follow a volume dilution dependence. In the future, the expected diminution in dew and rain volumes according to the RCPs 2.6 and 8.5 should increase the dew and rain ionic concentrations. [ABSTRACT FROM AUTHOR]

Several post-processing methods have been developed over the last years in order to take into consideration topography within satellite-based solar radiation maps using digital elevation models (DEM). If the main part of these procedures is to estimate the obstructed horizon around each DEM point of a given region so as to consider terrain-based shading effects, the size of the area can also limit this implementation. That is why we have developed a new efficient horizon model based on the DEM retrieved during the Shuttle Radar Topography Mission (SRTM). In order to be usable at any world location with the same expected accuracy, this model is only derived from mathematical statements without any kind of empirical approximation. Validation against in situ horizons and comparison with some other models have finally shown this one presents both better accuracy (RMSE of 1.555 ° against 1.712 ° or more) and lower computation time (at least 4 times faster). Furthermore, in the case of very large areas, we propose an optimization procedure allowing the user to knowingly alter the modeling error in order to reduce processing time. Finally, using in situ data, we have also developed a method for predicting the repercussion of the original SRTM DEM error on the final horizon precision. [ABSTRACT FROM AUTHOR]

As well as for Sub-Saharan Africa, solar energy presents many relevant standalone applications for remote populations of the Republic of Djibouti. Therefore, in order to estimate the significance and the distribution of the solar resource throughout the country, we have retrieved the first hourly global irradiation maps of the country, at 0.05 ° resolution and for the period 2008–2014, using the OSI SAF satellite-derived model. To assess the accuracy of this solar atlas , we have then compared estimates with ground measurements collected between 2010 and 2013 by temporary weather stations carried out on 4 different sites. The results of this comparison have shown a good precision of the global process, with for the daily irradiation a maximum relative error of 8.05% and a minimum correlation coefficient of 0.8892. Finally, the solar irradiation maps extracted from the atlas show the solar potential is substantial with a daily mean irradiation equal to 5.92 kW h / m 2 , and also spatially and temporally consistent, with a daily standard deviation of 0.216 kW h / m 2 and a yearly range between 5.08 kW h / m 2 day and 6.69 kW h / m 2 day . [ABSTRACT FROM AUTHOR]

Physical, Chemical and Biological Characteristics of Dew and Rainwater during the Dry Season of Tropical Islands. Reference 1 Muselli M., Clus O., Ortega P., Milimouk I., Beysens D. Physical, Chemical and Biological Characteristics of Dew and Rainwater during the Dry Season of Tropical Islands. A correction has been made to Equation (4): (4) HT ht It means that when I V i > I V i SB 0 sb , the negative contribution of heat losses are so important that the dew yield becomes negative and should be discarded. [Extracted from the article]

Abstract: Nowadays, energy supply is a major challenge for developing countries. In Sub-Saharan Africa, about only one-third of the population is connected to the electrical network and the use of classical energy resources presents economical and environmental problems. As many other African countries, the Djiboutian government looks for installing power systems using renewable energies, including solar systems, in order to overcome power supply difficulties in their energetic strategy. Therefore, the aim of this study is the creation of the first solar atlas in Djibouti, including assessment and improvement, for helping to establish an energy planning. To realize this atlas, a satellite-based irradiance model is used (EUMETSAT O&SI SAF). To validate this model over Djibouti, we installed 2 pyranometric weather stations during the year 2010 and we compared hourly, daily and monthly irradiation estimates against ground measurements. Results showed a good agreement between measurements and estimates, with, for the whole hourly sets, an RRMSE equal to 10.88% and 15.29%, and a bias of 0.61% and −2.17%. Then, to improve accuracy of irradiation estimates, we disaggregated irradiation maps with a 3 arc second (∼ 90 m at the equator) Digital Elevation Model (DEM), in order to take into consideration topography and elevation effects. As current software does not allow downscaling of pre-processed maps, we performed this work by computing our own global model, combination of horizon, elevation correction and irradiance splitting models. By comparing horizon estimates against measured horizons, we observed that error probability on irradiation increased over high mountainous areas, mainly due to the original DEM error. Finally, according to the final computed atlas, during the year 2010, mean irradiation all over the country was around 2100 kWh/m² and about 82% of the country received over 2000 kWh/m². Furthermore, the solar radiation reaching Djibouti corresponded to 20,000 times the total yearly energy consumption of the country in 2005. With the first solar atlas of Djibouti, this study shows how reliable the solar potential in the country is and presents an accurate decision-making tool for sizing future solar systems across the country. [Copyright &y& Elsevier]

The metal surfaces of a car exhibit favorable properties for the passive condensation of atmospheric water. Under certain nocturnal climatic conditions (high relative humidity, weak windspeed, and total nebulosity), dew is often observed on cars, and it is appropriate to ask the question of using a vehicle as a standard condenser for estimating the dew yield. In order to see whether cars can be used as reference dew condensers, we report a detailed study of radiative cooling and dew formation on cars in the presence of radiating obstacles and for various windspeeds. Measurements of temperature and condensed dew mass on different car parts (rooftop, front and back hoods, windshield, lateral and back windows, inside and outside air) are compared with the same data obtained on a horizontal, thermally isolated planar film. The paper concludes that heat transfer coefficients, evaluated from temperature and dew yield measurements, are found nearly independent of windspeed and tilt angles. Moreover, this work describes the relation between cooling and dew condensation with the presence or not of thermal isolation. This dependence varies with the surface tilt angle according to the angular dependence of the atmosphere radiation. This work also confirms that cars can be used to estimate the dew yields in a given site. A visual observation scale h = Kn, with h the dew yield (mm) and n = 0, 1 2, 3 an index, which depends whether dew forms or not on rooftop, windshield, and lateral windows, is successfully tested with 8 different cars in 5 sites with three different climates, using K = (0.067 ± 0.0036) mm·day−1. [ABSTRACT FROM AUTHOR]

Abstract: Nowadays, energy supply of rural populations is one of the most important challenges in African developing countries, and more particularly in Sub-Saharan Africa. With only one third of the population connected to the grid and the high economical and environmental cost of classical energy resources, the use of renewable energies within the rural energy supply pattern is a reliable alternative solution to improve human development of remote populations. Djibouti is a little poor country of Sub-Saharan Africa which perfectly symbolizes this way of life. Electrification rate is only about 30% and the important scattering of rural peoples throughout the country makes grid extension and fuel transportation unsuitable economic solutions to carry energy. The geographically diffused solar resource can therefore be an interesting mean to produce energy where it is consumed. The aim of this study was the creation of the first Djibouti’s global horizontal irradiation atlas, including assessment and improvement. To realize this atlas, a satellite-derived irradiance model was used (EUMETSAT O&SI SAF). To validate this model over Djibouti, we installed two temporary weather stations during the year 2010 in Djibouti-city and Dikhil and we compared hourly, daily and monthly irradiation estimates against ground-based measurements. Results showed a good agreement between measures and estimates, with a maximum Relative Root Mean Squared Error (RRMSE) over the hourly solar atlas of 12.43% and 15.44%, for Dikhil and Djibouti-city respectively. In order to improve geographic information and accuracy of this solar atlas, we then disaggregated irradiation maps with a 3arcsec (∼90m at the equator) Digital Elevation Model (DEM), by taking into consideration terrain-related shading effects and elevation gradient. As current software solutions do not allow downscaling of preprocessed maps, we performed this work by computing our own global model, combination of horizon, elevation correction and irradiance splitting models. The horizon model we developed was assessed and compared with other existing models by using a theodolite in mountainous areas of Corsica. Finally, according to the final computed atlas, during the year 2010, mean irradiation all over the country was around 2100kWh/m2 and about 82% of the country received over 2000kWh/m2. Furthermore, the solar radiation reaching Djibouti corresponded to 20,000 times the total yearly energy consumption of the country in 2005. The retrieved irradiation maps can be used to evaluate relevance of the solar resource over rural areas of the country, and implemented within energy models in order to size stand-alone solar systems. [Copyright &y& Elsevier]

Abstract: The renewable energies prediction and particularly global radiation forecasting is a challenge studied by a growing number of research teams. This paper proposes an original technique to model the insolation time series based on combining Artificial Neural Network (ANN) and Auto-Regressive and Moving Average (ARMA) model. While ANN by its non-linear nature is effective to predict cloudy days, ARMA techniques are more dedicated to sunny days without cloud occurrences. Thus, three hybrids models are suggested: the first proposes simply to use ARMA for 6 months in spring and summer and to use an optimized ANN for the other part of the year; the second model is equivalent to the first but with a seasonal learning; the last model depends on the error occurred the previous hour. These models were used to forecast the hourly global radiation for five places in Mediterranean area. The forecasting performance was compared among several models: the 3 above mentioned models, the best ANN and ARMA for each location. In the best configuration, the coupling of ANN and ARMA allows an improvement of more than 1%, with a maximum in autumn (3.4%) and a minimum in winter (0.9%) where ANN alone is the best. [Copyright &y& Elsevier]

The EU's hydrogen strategy consists of studying the potential for renewable hydrogen to help decarbonize the EU in a cost-effective way. Today, hydrogen accounts for less than 2% of Europe's energy consumption. It is primarily used to produce chemical products. However, 96% of this hydrogen production is through natural gas, leading to significant amounts of CO2 emissions. In this paper, we investigated PV electrolysis H2 gas (noted H2(g)) production for mapping this resource at Europe's scale. The Cordex/Copernicus RCPs scenarios allow for evaluating the impact of climate changes on the H2-produced mass and the equivalent energy, according to both extreme RCPs scenarios. New linear regressions are investigated to study the great dependence in H2(g) produced masses (kg·yr−1) and equivalent energies (MWh·yr−1) for European countries. Computational scenarios are investigated from a reference year (2005) to the end of the century (2100) by steps of 5 years. According to RCPs 2.6 (favorable)/8.5 (extreme), 31.7% and 77.4% of Europe's area presents a decrease of H2(g)-produced masses between 2005 and 2100. For the unfavorable scenario (8.5), only a few regions located in the northeast of France, Germany, Austria, Romania, Bulgaria and Greece present a positive balance in H2(g) production for supplying remote houses or smart grids in electricity and heat energy. [ABSTRACT FROM AUTHOR]

Abstract: We propose in this paper an original technique to predict global radiation using a hybrid ARMA/ANN model and data issued from a numerical weather prediction model (NWP). We particularly look at the multi-layer perceptron (MLP). After optimizing our architecture with NWP and endogenous data previously made stationary and using an innovative pre-input layer selection method, we combined it to an ARMA model from a rule based on the analysis of hourly data series. This model has been used to forecast the hourly global radiation for five places in Mediterranean area. Our technique outperforms classical models for all the places. The nRMSE for our hybrid model MLP/ARMA is 14.9% compared to 26.2% for the naïve persistence predictor. Note that in the standalone ANN case the nRMSE is 18.4%. Finally, in order to discuss the reliability of the forecaster outputs, a complementary study concerning the confidence interval of each prediction is proposed. [Copyright &y& Elsevier]

Abstract: This paper presents an application of Artificial Neural Networks (ANNs) to predict daily solar radiation. We look at the Multi-Layer Perceptron (MLP) network which is the most used of ANNs architectures. In previous studies, we have developed an ad-hoc time series preprocessing and optimized a MLP with endogenous inputs in order to forecast the solar radiation on a horizontal surface. We propose in this paper to study the contribution of exogenous meteorological data (multivariate method) as time series to our optimized MLP and compare with different forecasting methods: a naïve forecaster (persistence), ARIMA reference predictor, an ANN with preprocessing using only endogenous inputs (univariate method) and an ANN with preprocessing using endogenous and exogenous inputs. The use of exogenous data generates an nRMSE decrease between 0.5% and 1% for two stations during 2006 and 2007 (Corsica Island, France). The prediction results are also relevant for the concrete case of a tilted PV wall (1.175 kWp). The addition of endogenous and exogenous data allows a 1% decrease of the nRMSE over a 6 months-cloudy period for the power production. While the use of exogenous data shows an interest in winter, endogenous data as inputs on a preprocessed ANN seem sufficient in summer. [ABSTRACT FROM AUTHOR]

Abstract: Passive cooling is considered as an alternative technology to avoid unwanted heat gains, to reduce urban heat islands and to generate cooling potential for buildings (limiting air-conditioning energy). According to materials and surface treatments, the roof can represent to be a major heat gain source from opaque elements of the building fabric, heating up the outer surface and increasing heat flow by conduction. This paper presents low-cost new radiative materials (1∉/m2) allowing to limit heat gains during diurnal cycle for hot seasons. To evaluate the relevance of these new substrates, their reflective UV–VIS–IR behavior are studied and compared to classical roofed materials available in industrial and developing countries. A 48m2 experimental roof having different surfaces (plate steel sheets, fiber cement, terra cotta tiles and corrugated sheets) allows to determine the temperature ratio δ between uncoated and coated materials. Up to 34% surface temperature gains are obtained for white coated CS, 25% for FC and ∼18% for TCT and PSS. According to uncoated materials for a surface temperature T 0 =60°C, simulations showed that the low-cost white opaque reflective roofs (50m2) presented in this study would reduce cooling energy consumption by 26–49%. [Copyright &y& Elsevier]

Abstract: Dew water was collected from several passive foil-based radiative condensers established in a variety of geographic settings: continental (Grenoble, in an alpine valley, and Brive-la-Gaillarde, in the Central Massif volcanic area, both in France), French Atlantic coast (Bordeaux), eastern Mediterranean (Jerusalem, Israel), and the island of Corsica (Ajaccio, France) in the Mediterranean Sea. In Ajaccio two large 30m2 condensers have been operating since 2000. Additional semi-quantitative dew measurements were also carried out for Komiža, island of Vis (Croatia) in the Adriatic Sea, and in Mediterranean Zadar and Dubrovnik (both in Croatia). Dew potential was calculated for the Pacific Ocean island of Tahiti (French Polynesia). The data show that significant amounts of dew water can be collected. Selected chemical and biological analyses established that dew is, in general, potable. Continued research is required for new and inexpensive materials that can enhance dew condensation. [Copyright &y& Elsevier]

We report on the development of an inexpensive radiative condenser for collecting atmospheric vapor. Based on the experience gained using a small working model in Grenoble (France), a prototype of 10×3 m2 was established in Ajaccio (Corsica, France). The condensing surface is a rectangular foil made of TiO2 and BaSO4 microspheres embedded in polyethylene and has an angle of 30° with respect to horizontal. The hollow part of the device, thermally isolated, faces the direction of the dominant nocturnal wind. Dew measurements were correlated with meteorological data and compared to dew condensed on a horizontal polymethylmethacrylate (PMMA, Plexiglas) reference plate. The plate served as a reference standard unit and was located nearby. Between July 22, 2000 and November 11, 2001 (478 days), there were 145 dew days for the reference plate (30%), but 214 dew days for the condenser (45%). This yield corresponds to 767 l (3.6 l, on average, per dew day). The maximum yield in the period was 11.4 l/day. Dew mass can be fitted to a simple model that predicts dew production from simple meteorological data (temperature, humidity, wind velocity, cloud cover). Chemical analyses of the water collected from the plate were performed from October 16, 1999 to July 16, 2000 and from the condenser, from July 17, 2000 to March 17, 2001. The following parameters were investigated: suspended solids, pH, concentration of SO42−, Cl−, K+, Ca2+ ions. Only Cl− and SO42− ions were sometimes found significant. Wind direction analyses revealed that Cl− is due to the sea spray and SO42− to the combustion of fuel by an electrical plant located in the Ajaccio Gulf. Except for a weak acidity (average pH≈6) and high concentration of suspended solids, dew water fits the requirements for potable water in France with reference to the above ions. [Copyright &y& Elsevier]

In order to establish data to be used for comparison with future evolution related to climate change, physical, chemical and biological characteristics of dew and rainwater as collected during the 2005 dry season (plus a few data during the 2004 dry season) are reported. They have been collected in two characteristic tropical islands of French Polynesia, Tikehau (TKH), a low-lying coral atoll in the Tuamotu Archipelago, and the mountainous Tahiti island at the University of French Polynesia (TAH). Trade winds dominate the trajectory of air masses, ensuring constant temperature and humidity to the lower layers of the atmosphere where dew forms. In addition to the comparison of dew yields with a physical model using simple meteorological data (air and dew point temperatures, windspeed, cloud cover), the following parameters were studied: pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness, suspended matter, ion concentration with major cations (Ca2+, K+, Na+, Mg2+, NH4+) and major anions (Cl−, SO42−, NO3−), reviviscible aerobe microorganisms and compared to two Polynesian spring waters ("Eau Royale" and "Vaimato"). Dew, with a chemical composition mainly consisting of Na+, Ca2+, Mg2+, Cl− and SO42−, exhibits much higher ion concentration than rain and compares well with the composition of local spring waters. The values of pH, EC and TDS are larger in dew than in rainwater. At TAH, the volume weighted mean (VWM) pH values of dew were 6.05 in 2004 and 5.23 in 2005, larger than the pH of rain (4.69). The VWM dew EC (at TAH, 203 μS·cm−1 in 2004 and 237 μS·cm−1 in 2005; 321 μS·cm−1 at TKH in 2005) and dew TDS (152 mg·L−1 at TAH and 225 mg·L−1 at TKH) were higher than the corresponding quantities in rain. Mean total hardness (TH) values of dew water are much higher than in rainwater (2.8 for dew versus 0.5 for rain at TAH and 5.7 for dew versus 0.5 for rain at TKH). Ions Na+, Mg2+ and Cl− are clearly of sea origin while the presence of Ca2+ is due to coral particles. From their chemical characteristics, dew and rainwater could be used as an alternative source of water in dry season but, due to the presence of reviviscible aerobe microorganisms at 22 °C and 36 °C (>300 CFU·mL−1), water must be disinfected to be potable. [ABSTRACT FROM AUTHOR]

Highlights: [•] Global radiation prediction using satellites data and time series analysis. [•] Optimized artificial neural networks using the mutual information. [•] New tool of solar radiation maps comparison related to “the distance to agreement” are exposed: the gamma index. [Copyright &y& Elsevier]

Highlights: [•] Global radiation prediction and PV energy integration. [•] Artificial intelligence and stochastic modeling in order to use the time series formalism. [•] Using Bayesian rules to select models. [•] MLP and ARMA forecasters are equivalent (nRMSE close to 40.5% for the both). [•] The hybridization of the three predictors (ARMA, MLP and persistence) induces very good results (nRMSE=36.6%). [Copyright &y& Elsevier]

Abstract: Considering the grid manager′s point of view, needs in terms of prediction of intermittent energy like the photovoltaic resource can be distinguished according to the considered horizon: following days (d+1, d+2 and d+3), next day by hourly step (h+24), next hour (h+1) and next few minutes (m+5 e.g.). Through this work, we have identified methodologies using time series models for the prediction horizon of global radiation and photovoltaic power. What we present here is a comparison of different predictors developed and tested to propose a hierarchy. For horizons d+1 and h+1, without advanced ad hoc time series pre-processing (stationarity) we find it is not easy to differentiate between autoregressive moving average (ARMA) and multilayer perceptron (MLP). However we observed that using exogenous variables improves significantly the results for MLP. We have shown that the MLP were more adapted for horizons h+24 and m+5. In summary, our results are complementary and improve the existing prediction techniques with innovative tools: stationarity, numerical weather prediction combination, MLP and ARMA hybridization, multivariate analysis, time index, etc. [Copyright &y& Elsevier]

Summary: Two coastal sites were investigated in an arid region of southwest Morocco to determine the amount of dew, fog and rain that could be collected from rooftops for household use. Systematic measurements were performed in Mirleft (43m asl, 200m from the coast) for 1year (May 1, 2007 to April 30, 2008) and in Id Ouasskssou (240m asl, 8km from the coast) for three summer months (July 1, 2007 to September 30, 2007). Dew water was collected using standard passive dew condensers and fog water by utilizing planar fog collectors. The wind flow was simulated on the rooftop to establish the location of the fog collector. At both sites, dew yields and, to a lesser extent, fog water yields, were found to be significant in comparison to rain events. Mirleft had 178 dew events (48.6% of the year, 18±2Lm−2 cumulated amount) and 20 fog episodes (5.5% of the year, 1.4Lm−2 with uncertainty −0.2/+0.4Lm−2 cumulated amount), corresponding to almost 40% of the yearly rain contribution (31 rain events, 8.5% of the year, 49±7mm cumulated amount). At Id Ouasskssou there were 50 dew events (7.1±0.3Lm−2, 54.3% frequency), 16 fog events (6.5Lm−2 with uncertainty −0.1/+1.8Lm−2, 17.4% frequency) and six rain events (16±2mm, 6.5% frequency). Meteorological data (air and dew point temperature and/or relative humidity, wind speed and wind direction, cloud cover) were recorded continuously at Mirleft to assess the influence of local meteorological conditions on dew and fog formation. Using the set of collected data, a new model for dew yield prediction based on artificial neural networks was developed and tested for the Mirleft site. This model was then extrapolated to 15 major cities in Morocco to assess their potential for dew water collection. It was found that the location of the cities with respect to the Atlas mountain chain, which controls the circulation of the humid marine air, is the main factor that influences dew production. [Copyright &y& Elsevier]

Abstract: In this paper, we present an application of Artificial Neural Networks (ANNs) in the renewable energy domain. We particularly look at the Multi-Layer Perceptron (MLP) network which has been the most used of ANNs architectures both in the renewable energy domain and in the time series forecasting. We have used a MLP and an ad hoc time series pre-processing to develop a methodology for the daily prediction of global solar radiation on a horizontal surface. First results are promising with nRMSE∼21% and RMSE∼3.59MJ/m2. The optimized MLP presents predictions similar to or even better than conventional and reference methods such as ARIMA techniques, Bayesian inference, Markov chains and k-Nearest-Neighbors. Moreover we found that the data pre-processing approach proposed can reduce significantly forecasting errors of about 6% compared to conventional prediction methods such as Markov chains or Bayesian inference. The simulator proposed has been obtained using 19years of available data from the meteorological station of Ajaccio (Corsica Island, France, 41°55′N, 8°44′E, 4m above mean sea level). The predicted whole methodology has been validated on a 1.175kWc mono-Si PV power grid. Six prediction methods (ANN, clear sky model, combination…) allow to predict the best daily DC PV power production at horizon d +1. The cumulated DC PV energy on a 6-months period shows a great agreement between simulated and measured data (R 2 >0.99 and nRMSE<2%). [ABSTRACT FROM AUTHOR]

Abstract: Dew and rain water were collected and analyzed during 3years (2004–2006) in Zadar, Croatia. The goal was to characterize the chemical properties of dew water versus rain water (and the atmosphere in which they form) and to determine the extent to which they can be used as potable water. The corresponding parameters were measured: pH, electrical conductivity (EC), major anions (HCO3 −, Cl−, SO4 2−, NO3 −), and major cations (NH4 +, Na+, K+, Ca2+, Mg2+). The mean pH and EC values were comparable for both dew and rain water, pH=6.7 (dew) and pH=6.35 (rain), EC=195µScm−1 (dew) and EC=178µScm−1 (rain). The ratio (SO4 2− +NO3 −)/(Ca2 + +Mg2+) was lower than 1, indicating the alkaline nature of both dew and rain water. Both dew and rain water exhibited low mineralization. The analysis of the major ions showed that the concentration of cations is high compared to that of anions (presumably because the NO2 −, HCOO− and CH3COO− ions were not measured), with Ca²+, Na+ and Mg2+ as the main ions. In order to discriminate between the marine and non-marine origin of ions, the sea-salt fraction (SSF) was calculated by taking Na+ as a reference. The small SSF value in dew suggests a considerable contribution of non-marine origin for components Ca²+, K+, SO4 2− and NO3 −, except Cl−. In contrast, in rain water, the values of the non sea-salt fraction (NSSF) indicate that only Ca²+ and NO3 − are not influenced by sea proximity. The study of the neutralization factor, NF, reveals the descending order of the cations in dew and rain water, NFCa ²+ >NFMg²+ >NFK+ >NFNH4+. The dew and rain water are in conformity with the World Health Organization directives for potability, except for Mg2+. [Copyright &y& Elsevier]

[Display omitted] • A great controversy exists whether biocrust use non-rainfall water (NRW) for growth. • NRW was measured at 1 m-height, cobbles, rock and soil and compared to MET model. • A good fit was found between the model and 1 m-height. • NRW was much lower at the soil, explained by a steep temperature gradient with height. • NRW did not reach the necessary threshold for net photosynthesis by soil biocrust. Knowledge regarding the distribution of non-rainfall water (NRW) and particularly dew has great ecological importance. Nevertheless, the role of NRW as a water source for biocrusts is controversial, with most scholars attributing a central role to NRW as water source for biocrusts. Estimating the amounts of NRW and particularly dew is indeed challenging due to the interrelationship between vapor, temperature and wind. Recently, the use of NRW by biocrusts was also suggested following a meteorological model. Here we compare the amounts obtained by model calculation to the amounts of NRW as measured at 1 m-height above ground (used for meteorological models), and on cobbles, rocks and the soil surface in the Negev. While field measurements at 1 m-height above ground (averaging 0.144 mm/day) showed a fairly good fit (r = 0.52) with model calculation (averaging 0.147 mm/day), and the NRW measurements surpassed the threshold for net photosynthesis for lichens (0.05 mm) and occasionally for cyanobacteria (0.1 mm) on the rocky surfaces (averaging 0.093 mm/day for the cobbles and 0.042 mm/day for the rock slabs), it was substantially below these thresholds at the soil surface (averaging 0.009 mm/day). Our data imply that the amount of NRW reaching the soil surface is too low to provide the soil microorganisms sufficient water for net photosynthesis. With 0.5 mm/day marking the maximum theoretical dew value, the 16.9-fold lower amounts obtained by us at the soil surface in comparison to 1 m-height above ground (used by meteorological models) indicates only 0.03 mm/day at the soil surface, substantially below the required amounts for net photosynthesis by biocrusts. When estimating the amounts of NRW available for biocrusts, meteorological models must be adjusted in accordance with height above ground. [ABSTRACT FROM AUTHOR]

This paper focuses on a full-scale experiment to assess and model the airflow rate in a naturally ventilated room using different approaches. The building studied is located in a coastal area of Corsica and mostly affected by thermal breezes phenomena which lead to high airflow rate during day (between 8 and 30 ACH ) and lower during night (between 2 and 8 ACH ). The first aim of this work is to set up a method in order to measure continuously the airflow rate in cross ventilation configuration using a minimal number of sensors. Our methodology involves direct measurements of velocity on a mesh and use of statistical methods. The second objective is to develop and evaluate different airflow modeling approach in cross natural ventilation configuration. Various levels of complexity are tested and compared: empirical modeling, model calibration and behavioral modeling based on artificial neural networks. In terms of error, the artificial neural network appears to be the best compromise to model the airflow rate and allow to reach a MAE of 1.75 ACH with a one minute time step. Suggested model in this paper can be coupled with a thermal model and is suitable for model based natural ventilation control. [ABSTRACT FROM AUTHOR]

ABSTRACT The grid integration of variable renewable energy sources implies that their effective production could be predicted, at different times ahead. In the case of solar plants, the driving factor is the global solar irradiation (sum of direct and diffuse solar radiation projected on a plane (Wh m−2)). This paper focuses on the 24 h ahead forecast of global solar irradiation (i.e. hourly solar irradiation prediction for the day after). A method based on artificial intelligence using artificial neural network ( ANN) is reported. The ANN hereafter considered is a multi-layer perceptron ( MLP) applied to a pre-treated time series ( TS). Two architectures are tested; it is shown that the most relevant is based on a multi-output MLP using endogenous and exogenous input data. A real case 2 years TS is computed and the ANN results are compared with both a statistical approach (autoregressive-moving average model; ARMA) and a reference persistent approach. Results show that the prediction error estimate ( nRMSE) can be reduced by 1.3 points with an ANN compared to ARMA) and by 7.8 points compared to the naïve persistence. Copyright © 2013 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Highlights: [•] Interest of thermal breezes for natural cross ventilation. [•] Proposition of climate indicators to assess natural ventilation potential. [•] Methodology applied with meteorological data from Corsica (France). [•] Airflow rate of a seaside building studied by tracer gas measurements. [•] Interest of controlling system studied with an empirical model. [ABSTRACT FROM AUTHOR]

An inexpensive radiative condenser for collecting atmospheric vapor (dew) was tested in Grenoble (France). The surface temperature measurements are correlated with meteorological data (wind velocity, air temperature) and compared to the corresponding surface temperature of a horizontal Polymethylmethacrylate (Plexiglas) reference plate located nearby. The condenser surface is a rectangular foil (1×0.3 m2) made of TiO2 and BaSO4 microspheres embedded in polyethylene. The foil has an angle θ with respect to horizontal. The under-side of the device, thermally isolated, faces the direction of the dominant nocturnal wind. Both a 2D numerical simulation of the air circulation around the foil and experimental measurements shows that the angle θ=30° is a good compromise between weak wind influence, large light-emission solid angle and easy drop collection. The study was conducted from November 25, 1999 to January 23, 2001. In comparison to the reference plate, it is found that water yield can be increased by up to 20% and water collection greatly facilitated. [Copyright &y& Elsevier]