LARRAÑETA , Miguel

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The utilization of solar energy based technologies has attracted increased interest in recent times in order to satisfy the energy demands in buildings. This research work presents a comparative analysis of the energy production and costs of factory made solar heating systems, Thermosiphon Solar Water Heaters Systems (TSWHS) and...

It is very unusual to have global irradiance data for a tilted surface and even more for a surface with a perfect sun tracking. The most common available data is the global horizontal irradiance, thus it is necessary to convert the available data into the desirable inclination. The purpose of this paper is to analyse the different response of...

The freeze protection is essential in the majority of solar thermal installations to prevent breakage of solar thermal collectors. Therefore, there are different methods of protection against freezing of flat plate solar thermal collectors, all of them with certain limitations. This paper shows a novel freeze protection mechanism in the solar...

This Brief Note presents a general and efficient clustered-based methodology for the generation of high-frequency coupled global horizontal irradiance (GHI) and direct normal irradiance (DNI) series, based on the envelope clear sky and Dynamic Paths concepts. The procedure for generating 1-min synthetic irradiance data assumes that the effect...

In building integrated photovoltaic (PV) systems, the reflection of the solar radiation by the walls of the buildings may cause a non-uniform distribution of the incident radiation on the different PV modules. However, by using micro-inverters at strings levels, electricity production may increase instead of provoking losses by mismatching. For...

Photovoltaic (PV) plant failures have a significant influence on PV plant security, reliability, and energy balance. Energy losses produced by a PV plant are due to two large causes: failures and inefficiencies. Knowing the relative influence of energy losses due to failures and energy losses due to inefficiencies on the PV plant energy balance...

This article presents and evaluates the performance of a simplified model to generate 10-min global horizontal synthetic solar radiation data that would correspond to the measurements of a calibrated photovoltaic monocrystalline cell. The model, which only requires global horizontal solar radiation data measured with a thermopile pyranometer as...

In this paper we evaluate the cloud transients by analyzing the dynamics of the direct fraction index kb for one year of solar radiation data in different time steps. We use instant 5-sec data integrated data and compare the number and percentage of occurrences of the different defined sky conditions. We find that the most common situation is...

Laser Ceilometers make use of the elastic LIDAR by emitting signals vertically in the atmosphere and analyzing the profile of the backscattered signal to detect clouds and calculate cloud-base height [1]. Due to the high temporal and vertical resolution, the data provided by the ceilometer is rather useful for solar radiation forecasting or...

The Variability Index (VI) is widely used to quantify the intra-day solar radiation variability. It compares the length of the global horizontal irradiance (GHI) or direct normal irradiance (DNI) profiles with the length of the corresponding clear sky GHI/DNI profiles. The VI is not a normalized index, it shows dependency on the day of the...

The operation and the electricity yield of CSP plants in two days with the same daily-accumulated DNI, even with the same Aperture Normal Irradiance (ANI) can be very different depending on other parameters such as the variability and distribution of the solar radiation. In this paper, we intend to quantify the impact of the intra-daily...

In this paper, we present a description of how to use a web based tool employing the ND model by Larrañeta et al. [1]. The tool is suited for downscaling DNI, GHI or coupled DNI and GHI from 1-h to 1-min. It requires only an annual solar radiation dataset in the hourly resolution as input and provides 1-min data in any location without local...

Several studies have confirmed the relevant impact of the resolution and frequency distribution of solar radiation data on the results of detailed production models. Many of the available direct normal irradiance (DNI) databases generated from the satellite images have an hourly resolution. In the present work, we have proposed improvements to...

When modeling the effect of the cloud transients in the Direct Normal Insolation (DNI), it is particularly relevant to identify those moments in which there are no clouds between the observer and the sun. In this paper, we present a simple algorithm for offline detection of situations where the sun path to the observer is not obstructed by any...

CSP feasibility analysis, bankability assessment and plant design are generally based in one-year meteorological series representative of "typical" o extreme conditions. There is a growing interest in accounting on the inherent variability of the performance of solar plants on their input variables in the plant model. In particular, for...

Many of the available solar radiation databases only provide global horizontal irradiance (GHI) while there is a growing need of extensive databases of direct normal radiation (DNI) mainly for the development of concentrated solar power and concentrated photovoltaic technologies. In the present work, we propose a methodology for the generation...

Bottom-up energy system models are often based on hourly time steps due to limited computational tractability or data availability. However, in order to properly assess the rentability and reliability of energy systems by accounting for the intermittent nature of renewable energy sources, a higher level of detail is necessary. This study...