[en] An ultraviolet index appropriate for its use in Spain is studied on the basis of those already available in other countries. The suitability of this index to characterise ultraviolet solar radiation and, particularly, the potential risks to human health are discussed. Finally, the main factors affecting this index are identified and their influence is studied. (Author) 43 refs

[en] Unspec and SMARTS2 models have been used to estimate the UV spectral irradiance values in Valencia, Spain, and the results of these estimations have been compared with experimental measurements of direct irradiance at normal incidence obtained using an Optronic OL 754 in the 300-400 nm range. The relative RMSD and MBD parameters have been used to estimate the deviations of the modelled values with respect to the experimental values. The results indicate that the deviations are smaller when the SMARTS2 model is used with the appropriate aerosol coefficients. (author)

[en] The Solar Radiation Group of the University of Valencia, in collaboration with the National Institute of Meteorology (INM), recently began a database of erythemal UV irradiance measurements. Such measurements are obtained by a YES UVB-1 pyranometer (280-330 nm) that measures continuously, integrates the values and stores them in a database. The measured values are being compared with those obtained by the integration of the data registered by an Optronic OL 754 spectroradiometer (250-800 nm) considering clear days and different solar zenith angles. For the present study only the data corresponding to the summer (1999) are being considered because these are the days of the year with the higher erythemal values and also the season when people enjoy sunbathing. The results are used to deduce the ultraviolet index (UVI) related to the erythemal doses and the sunburn time. (author)

[en] We present the first multiyear set of simultaneous measurements of the global ultraviolet-B radiation and its two components: direct and diffuse. The measurements have been taken with four YES-UVB-1 radiometers: two radiometers to measure the diffuse radiation, one provided with a shadow band and the other with a shadow disk on a Sun tracker; a radiometer to measure the global horizontal radiation; and a Sun-tracking radiometer to measure the direct radiation with an especially designed radiance collimator. The diffuse minute-values measured with both instruments agree within a coefficient correlation of 1.00. The diffuse component represents at least 50% of the global UVB (ultraviolet-B) radiation. The minute values of global UVB irradiance obtained by adding the direct and diffuse components concur with the measured global irradiance. Therefore, the measurement of the direct irradiance enables the estimation of the diffuse component, and gives an insight into the factors that affect its value, especially aerosols. - Highlights: • Simultaneous measurements of global, direct and diffuse UVB (ultraviolet-B) radiation. • The diffuse minute-values are at least 50% of the global ones. • The diffuse measurements are highly correlated to the aerosol load. • The sum of direct + diffuse radiation concur with the measured global.

[en] Highlights: • We have evaluated the aerosol radiative impact on the performance of a solar photovoltaic plant. • Aerosols cause a great reduction of the photovoltaic power, that is driven by the aerosol load and type. • We use a simple and empirical method that assures results of high level of confidence and accuracy. • Better understanding of aerosol impact on solar photovoltaics would improve the energy forecasts. -- Abstract: We have estimated the radiative impact produced by an unusually extreme dust and wildfire episode on the performance of a photovoltaic (PV) plant. The dust and wildfire events were mostly active on 26–28 and 29–30 June 2012, respectively. We took advantage of the consecutiveness of both events to separate and derive empirically the radiative effect of dust and smoke aerosols. With this purpose, we employed measurements of aerosol load, radiation and PV power output from a collocated atmospheric station and PV plant located at Burjassot (Valencia, Spain). The empirical estimates were obtained by direct comparison with a summer background day, happened right before the two consecutive case studies. The whole episode is characterized by high aerosol optical depth (AOD) at 500 nm, reaching values up to 1 and 6 for dust and smoke, respectively. Our analysis shows an average daily energy loss of −132 kWh, that represents a fraction of 20% of the energy generated by the PV plant on the reference summer background day. A significant fraction of the energy lost was due to smoke, with a daily maximum of 43% and a daily average of 34%. In case of dust, the energy reduction was moderated, with a daily average of 6%. In terms of instantaneous power reduction, we have obtained peaks of 8 and 51% for dust and smoke, respectively. The energy reduction due to aerosols is strongly dependent on AOD. Further, we have found that the power loss per unit of AOD at 870 nm is useful to separate the radiative impact of different aerosol types. Essentially, the efficiency of smoke to reduce the energy generated by the PV plant is much greater than that of dust. This effect is mainly due to the different optical properties in the near infrared that result in a daily Power Aerosol Forcing Efficiency at 870 nm of −5.7 and −19.1 kW, for dust and smoke, respectively. Our results indicate that both the AOD and aerosol type drive the radiative impact of aerosols on the PV output, confirming that extreme aerosol events may drastically reduce the power generated by operative PV plants. This reduction may be as large as that reported for particle soiling. Therefore, considering both amount and type of aerosols in the PV power analyses is mandatory in order to obtain accurate forecast scenarios and improve the grid integration, especially during extreme episodes.

[en] Highlights: • I_UVER and I_T (irradiation) have been measured at three high altitude sites. • I_UVER can be estimated from the linear regression between I_UVER and I_T. • The I_UVER/I_T ratio increases with altitude about 0.32/km. • The clearness indices for both ranges, k_T and k_TUVER, increase with altitude. • K_TUVER can be estimated as a function of the solar zenith angle, θ_z, and k_T. An analysis of the broadband solar irradiation, I_T, and the erythemal UV irradiation, I_UVER, has been performed using the measurements made from 2013 to 2015 at three sites located at altitudes over 1000 m a.s.l. In Northwestern Argentina (Salta, El Rosal, and Tolar Grande). The main objective of this paper is to determine a relationship between I_T and I_UVER, which would allow to estimate I_UVER from I_T in places with few I_UVER measurements available, and especially in those where is important to establish adequate photoprotection measures given their dense population and location at high altitude. The relationship between the daily values of I_UVER and I_T has been fitted to a linear regression (I_UVER = m I_T + n), showing good correlation in the three measurement sites (R² ≥ 0.77). Besides, the I_UVER/I_T ratio shows an increase with altitude of 0.32 ± 0.03 units per km, indicating a more significant influence of altitude on I_UVER than on I_T. Total ozone column also attenuates more I_UVER than I_T. In order to reduce the local nature of the relationship between I_UVER and I_T, the clearness indices k_T and k_TUVER have been used to obtain a multivariable linear regression of k_TUVER as a function of the solar zenith angle, θ_z, and k_T, which shows good correlation (R² ≥ 0.89) for the three measurement sites.