Argimiro de Miguel

Test Reference Year Generation and Evaluation Methods in the Continental Mediterranean Area

Different meteorological data series called multiyear data, long-term average measured data series, or test reference years (TRYs) are required for solar energy system simulation. It is known that the use of the multiyear data approach requires a great effort in time and computation, long-term average measured data do not have the extreme values of weather data given along the year, and TRYs represent typical references rather than extreme conditions and facilitate the comparison in the performance of energy systems. In this paper, TRYs have been generated, using three different methodologies, from hourly meteorological data measured in two cities, Madrid and Valladolid (Spain). In order to evaluate them, the performance simulation of three solar energy systems (thermal, passive, and photovoltaic) with long-term measured meteorological data has been compared with estimated performance simulations with TRYs. Root-mean-square and mean bias errors and relative differences have been used as estimators to measure the performance deviation of TRYs from long-term measured meteorological data series. Results of the comparison show that the most appropriate method for generating test reference year depends on the characteristics of the station and varies from month to month. The Danish method (TRY5) gives better results in Valladolid than in Madrid for the photovoltaic and passive systems; the Argirious method (TRY6) gives better results in Madrid than in Valladolid for the photovoltaic system. The Pissimanis method (TRY4) is the best for simulating thermal and photovoltaic systems in summer.

Estimation of Daylight Downward Longwave Atmospheric Irradiance under Clear-Sky and All-Sky Conditions

Abstract Daylight downward longwave irradiance data recorded over a flat place for the period between April 2001 and December 2004 in Valladolid, Spain, have been compared with estimates generated using four different schemes. The parameterization schemes of Brutsaert, Swinbank, Idso, and Brunt have been considered and calibrated for the comparison. Root-mean-square errors (rmse), mean bias errors, and linear regression correlations have been used to compare measured and estimated values. The results of this comparison show that, for clear-sky conditions, rmse values range between 19.57 and 8.85 W m−2 for calibrated schemes and between 39.78 and 11.13 W m−2 for original ones. The Idso and Brunt schemes give the best results with calibrated coefficients, and the Brunt scheme performs the best with original coefficients. A new scheme for estimating daylight downward longwave irradiance under “all-sky” conditions has been developed based on clear-sky schemes and solar global shortwave irradiance, and, after ...

Air Temperature Model Evaluation in the North Mediterranean Belt Area

Abstract A comparative assessment of air temperature models, using hourly and daily air temperature measurements in 34 different stations in the north Mediterranean belt, is presented. Four air temperature models were used to estimate hourly and daily mean air temperature from daily maximum, daily minimum, and monthly mean air temperature. Root-mean-square error (rmse), scatter graphs, and cumulative frequency curves were used to determine the performance of each model. The best overall performance for estimating hourly air temperature from monthly mean values was presented by Erbss model; the “standard” model gave the best performance for estimating daily mean air temperature from daily minimum and maximum air temperature values. The results show that the Erbs and standard models are the best for all stations used. A new Climatic Synthetic Time Series for the Mediterranean Belt Temperature Model (CLIMEDTEM) for estimating daily air temperature was developed by the authors with the help of available data...

Uncertainty of different atmospheric ozone retrievals and its effect on temporal trends and radiative transfer simulations in the Iberian Peninsula

Uncertainty in total ozone column (TOC) values is quantified for eight different databases through a direct comparison with ground-based data at three Spanish locations, the maximum uncertainty being about 10.5 Dobson unit. A long-term TOC series is constructed using the mentioned databases from 1950 to 2011 for nine locations in the Iberian Peninsula. The monthly TOC climatology in the nine locations is presented. An exhaustive analysis is performed of TOC series trends and their statistical significance in the periods 1950–2011, 1950–1984, and 1985–2011. A significant ozone reduction between 1950 and 2011 appears in the Iberian Peninsula with a strong reduction from the late 1970s to the mid-1990s and with more or less constant or slightly increasing levels in the last 17 year. These trends are recalculated taking into account of uncertainty in the TOC values of the series, with a decrease in the number of statistically significant trends emerging. The statistically significant trends in annual and in the averaged Iberian Peninsula series are usually still significant even considering the uncertainty. Finally, a study is carried out of the uncertainty caused by TOC uncertainty in total shortwave and erythemal ultraviolet irradiances simulated under cloudless skies using a radiative transfer model.

Contribution to the Analysis of Global, Diffuse and UVB Solar Irradiance Components, in Spain

Measurements of solar ultraviolet-B, global and diffuse irradiances were made at Low Atmosphere Research Centre, (CIBA), Valladolid, Spain, using a YES UVB-1 and two Kipp-Zonen CM6 sensors respectively. Before using data, some necessary quality control tests were performed. An parameterization was established to estimate UV-B solar radiation on horizontal surface from horizontal global and diffuse radiation and solar zenith angle. Measured and calculated UV-B values were compared and root mean square errors (rmse) and mean bias errors (mbe) are used to determine the intrinsic performance of the models. From the results it can be observed that for small zenith angle the correlation coefficient increases; and comparing linear and exponential parameterization the last one shows higher correlation coefficients.