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Precise solar radiation measurements are essential for the monitoring and the evaluation of concentrating solar systems. In this paper the quality of irradiance measurements from the low cost systems SPN1 and Rotating Shadowband Irradiometer (RSI) are compared to reference measurements from a Pyrheliometer, a Pyranometer and a Shadow Ring Pyranometer. A graphical and statistical analysis of the measurement differences has been conducted. The investigation is based on data of nearly one year and focuses mainly on deviations regarding the Direct Normal Irradiance (DNI). Furthermore, estimations for the expected errors are given. It is shown, that the mean deviation of DNI measurements from the RSI are rather small. However, large short time variability can lead to considerable measurement inaccuracies. The SPN1 shows a strong non-linear bias that should be corrected. [ABSTRACT FROM AUTHOR]

Two generations of solar spectral irradiance meters (SolarSIMs), D1 and D2, are evaluated against reference instrumentation at the University of Ottawa SUNLAB outdoor test facility since their commissioning on September, 2014 and October, 2015, respectively. The average spectral direct normal irradiance (DNI) of the instruments was found to be well within ±1% at the six measured bands, centred at 420, 500, 610, 780, 880, and 940 nm, and mainly within ±2% for the remaining wavelengths in the 280-4000 nm range as compared to the reference SolarSIMs. The difference in cumulative energy densities as measured by the SolarSIMs and an Eppley model NIP pyrheliometer was found to be less than 0.5%. No degradation was observed during 19 months of operation. [ABSTRACT FROM AUTHOR]

For solar resource assessment of solar power plants and adjustment of satellite data, high accuracy measurement data of irradiance and ancillary meteorological data is needed. For the MENA region (Middle East and Northern Africa), which is of high importance for concentrating solar power applications, so far merely 2 publicly available ground measurement stations existed (BSRN network). This gap has been filled by ten stations in Morocco, Algeria, Tunisia, Egypt and Jordan. In this publication the data quality is analyzed by evaluating data completeness and the cleanliness of irradiance sensors in comparison for all of the stations. The pyrheliometers have an average cleanliness of 99.2% for week-daily cleaning. This is a 5 times higher effort than for Rotating Shadowband Irradiometer (RSI) stations which even have a slightly higher average cleanliness of 99.3% for weekly cleaning. Furthermore, RSI stations show a data completeness of 99.4% compared to 93.6% at the stations equipped with thermal sensors. The results of this analysis are used to derive conclusions concerning instrument choice and are hence also applicable to other solar radiation measurements outside the enerMENA network. It turns out that RSIs are the more reliable and robust choice in cases of high soiling, rare station visits for cleaning and maintenance, as usual in desert sites. Furthermore, annual direct normal and global horizontal irradiation as well as average meteorological parameters are calculated for all of the stations. [ABSTRACT FROM AUTHOR]

Solar process heat holds a large potential for the application of solar collectors. In the process temperature range above 120?C concentrating collectors such as parabolic trough and liner concentrating Fresnel collectors are used. In order to support the further development of process heat systems with concentrating collectors it is necessary to install, operate and monitor more field systems in which these collectors are operated under real conditions in the industry. A cost-efficient but sufficiently exact measurement of the direct solar irradiation is necessary for the energetic evaluation of system performance and a technical assessment of the collectors. In this paper we report on a comparison of three different possibilities for the measurement of the direct solar irradiation. [ABSTRACT FROM AUTHOR]

In the frame of the European project SOPHIA, a spectral network based on component (also called isotypes) cells has been created. Among the members of this project, several spectral sensors based on component cells and collimating tubes, so-called spectroheliometers, were installed in the last years, allowing the collection of minuteresolution spectral data useful for CPV systems characterization across Europe. The use of spectroheliometers has been proved useful to establish the necessary spectral conditions to perform power rating of CPV modules and systems. If enough data in a given period of time is collected, ideally a year, it is possible to characterize spectrally the place where measurements are taken, in the same way that hours of annual irradiation can be estimated using a pyrheliometer. [ABSTRACT FROM AUTHOR]

The SSIM prototype was designed at the University of Ottawa as a cost-effective alternative to a field spectroradiometer. The instrument was installed at the University of Ottawa's CPV testing facility in September, 2013, collecting the environmental and spectral data from October, 2013 to March, 2014. The SSIM's performance was compared against an ASD field spectroradiometer and an Eppley pyrheliometer during a six month study. It was observed that the SSIM can accurately reproduce the solar spectrum and the direct normal irradiance. The mean difference between the SSIM and the Eppley pyrheliometer was within ±1.5% for cloudless periods in October, 2013. However, bandpass filter degradation and moisture ingress limited the long term performance of the device. [ABSTRACT FROM AUTHOR]

Forecast DNI values in hourly resolution for one day ahead are evaluated by a comparison with pyrheliometer ground measurements. Three months of such day ahead forecasts from four different providers for a site close to Questa, NM, USA are analyzed firstly by calculating the RMSE and the mean bias error. Secondly, cumulative distributions of the DNI forecast errors are calculated as they better suit the context of a utility's use of the forecast. [ABSTRACT FROM AUTHOR]