Solar UV irradiances modulate effects of ocean acidification on the Coccolithophorid Emiliania huxleyi

Emiliania huxleyi, the most abundant coccolithophorid in the oceans, is naturally exposed to solar UV radiation (UVR, 280-400 nm) in addition to photosynthetically active radiation (PAR). We investigated the physiological responses of E. huxleyi to the present day and elevated CO2 (390 vs 1000 µatm; with pH(NBS) 8.20 vs 7.86) under indoor constant PAR and fluctuating solar radiation with or without UVR. Enrichment of CO2 stimulated the production rate of particulate organic carbon (POC) under constant PAR, but led to unchanged POC production under incident fluctuating solar radiation. The production rates of particulate inorganic carbon (PIC) as well as PIC/POC ratios were reduced under the elevated CO2, ocean acidification (OA) condition, regardless of PAR levels, and the presence of UVR. However, moderate levels of UVR increased PIC production rates and PIC/POC ratios. OA treatment interacted with UVR to influence the alga's physiological performance, leading to reduced specific growth rate in the presence of UVA (315-400 nm) and decreased quantum yield, along with enhanced nonphotochemical quenching, with addition of UVB (280-315 nm). The results clearly indicate that UV radiation needs to be invoked as a key stressor when considering the impacts of ocean acidification on E. huxleyi.

solaR: geometría, radiación y energía solar en R

The solaR package includes a set of functions to calculate the solar radiation incident on a photovoltaic generator and simulate the performance of several applications of the photovoltaic energy. This package performs the whole calculation procedure from both daily and intradaily global horizontal irradiation to the final productivity of grid connected PV systems and water pumping PV systems. The package stands on a set of S4 classes. The core of each class is a group of slots with yearly, monthly, daily and intradaily multivariate time series (with the zoo package ). The classes share a variety of methods to access the information (for example, as.zooD provides a zoo object with the daily multivariate time series of the corresponding object) and several visualisation methods based on the lattice andlatticeExtra packages.

Assessing the solar irradiation potential for solar photovoltaic applications in buildings at low latitudes ¿ Making the case for Brazil

In Brazil, a low-latitude country characterized by its high availability and uniformity of solar radiation, the use of PV solar energy integrated in buildings is still incipient. However, at the moment there are several initiatives which give some hints that lead to think that there will be a change shortly. In countries where this technology is already a daily reality, such as Germany, Japan or Spain, the recommendations and basic criteria to avoid losses due to orientation and tilt are widespread. Extrapolating those measures used in high latitudes to all regions, without a previous deeper analysis, is standard practice. They do not always correspond to reality, what frequently leads to false assumptions and may become an obstacle in a country which is taking the first step in this area. In this paper, the solar potential yield for different surfaces in Brazilian cities (located at latitudes between 0° and 30°S) are analyzed with the aim of providing the necessary tools to evaluate the suitability of the buildings’ envelopes for photovoltaic use

On-site measurement of limiting subcell in multijunction solar devices

It is well known that the response of any photovoltaic solar cell is dependent on the spectral characteristics of the incident radiation. This dependency is crucial in the output characteristics of a multijunction (MJ) cell where the spectral composition of the radiation determines the overall photocurrent produced, as either the top or the middle subcell will be limiting its response. The current mismatching between top and middle subcell is translated into energy losses, affecting the yield of the system. For research and commercial purposes it is interesting to measure accurately the incident solar radiation on a MJ cell, in terms of its spectral composition. This measurement will allows us to determine the photocurrent generated in each band of the multijunction device. Nowadays, the only way of measuring the photocurrent generated by each subcell is done with isotype cells or with spectroradiometers but there is no device capable of directly measuring each subcell photocurrent. In this paper it is described a device based on a commercial multijunction solar cell that is capable of measuring the direct irradiance for the top and middle bands thus it offers information of the limiting subcell (top or middle) in outdoors conditions.

Design of a solar incubator. Part 1: Monitoring temperature and enthalpy gradients under commercial production

The real increase in energy prices and the intention of reducing pollutant emissions in developed countries makes interesting to use solar energy in all the processes where its application is possible. As it is demonstrated in countries sited at latitudes with optimal conditions of solar radiation and temperature, it is possible to use solar energy as heat source for small-scale hatchery [1,2], but beyond, making a design for proper installation; it is possible to use solar energy as main or support energy source in medium and large size incubators . Monitoring of a normal actual process using temperature and relative humidity sensors is necessary to know the actual operating conditions that the solar heating system must be designed and sized for. Moreover, the identification and analysis of temperature and enthalpy gradients inside the incubator is of major importance.

On the complexity of radiation models for PV energy production calculation

Several authors have analysed the changes of the probability density function of the solar radiation with different time resolutions. Some others have approached to study the significance of these changes when produced energy calculations are attempted. We have undertaken different transformations to four Spanish databases in order to clarify the interrelationship between radiation models and produced energy estimations. Our contribution is straightforward: the complexity of a solar radiation model needed for yearly energy calculations, is very low. Twelve values of monthly mean of solar radiation are enough to estimate energy with errors below 3%. Time resolutions better than hourly samples do not improve significantly the result of energy estimations.

Dry cooling with night cool storage to enhance solar power plants performance in extreme conditions areas

Solar thermal power plants are usually installed in locations with high yearly average solar radiation, often deserts. In such conditions, cooling water required for thermodynamic cycles is rarely available. Moreover, when solar radiation is high, ambient temperature is very high as well; this leads to excessive condensation temperature, especially when air-condensers are used, and decreases the plant efficiency. However, temperature variation in deserts is often very high, which drives to relatively low temperatures during the night. This fact can be exploited with the use of a closed cooling system, so that the coolant (water) is chilled during the night and store. Chilled water is then used during peak temperature hours to cool the condenser (dry cooling), thus enhancing power output and efficiency. The present work analyzes the performance improvement achieved by night thermal cool storage, compared to its equivalent air cooled power plant. Dry cooling is proved to be energy-effective for moderately high day–night temperature differences (20 °C), often found in desert locations. The storage volume requirement for different power plant efficiencies has also been studied, resulting on an asymptotic tendency.

Towards downscaling of aerosol gridded dataset for improving solar resource assessment, an application to Spain

Solar radiation estimates with clear sky models require estimations of aerosol data. The low spatial resolution of current aerosol datasets, with their remarkable drift from measured data, poses a problem in solar resource estimation. This paper proposes a new downscaling methodology by combining support vector machines for regression (SVR) and kriging with external drift, with data from the MACC reanalysis datasets and temperature and rainfall measurements from 213 meteorological stations in continental Spain. The SVR technique was proven efficient in aerosol variable modeling. The Linke turbidity factor (TL) and the aerosol optical depth at 550 nm (AOD 550) estimated with SVR generated significantly lower errors in AERONET positions than MACC reanalysis estimates. The TL was estimated with relative mean absolute error (rMAE) of 10.2% (compared with AERONET), against the MACC rMAE of 18.5%. A similar behavior was seen with AOD 550, estimated with rMAE of 8.6% (compared with AERONET), against the MACC rMAE of 65.6%. Kriging using MACC data as an external drift was found useful in generating high resolution maps (0.05° × 0.05°) of both aerosol variables. We created high resolution maps of aerosol variables in continental Spain for the year 2008. The proposed methodology was proven to be a valuable tool to create high resolution maps of aerosol variables (TL and AOD 550). This methodology shows meaningful improvements when compared with estimated available databases and therefore, leads to more accurate solar resource estimations. This methodology could also be applied to the prediction of other atmospheric variables, whose datasets are of low resolution.

Towards cost reduction in concentrating solar power: innovative design for an efficient fresnel based solar field

Energía termosolar (de concentración) es uno de los nombres que hacen referencia en español al término inglés “concentrating solar power”. Se trata de una tecnología basada en la captura de la potencia térmica de la radiación solar, de forma que permita alcanzar temperaturas capaces de alimentar un ciclo termodinámico convencional (o avanzado); el futuro de esta tecnología depende principalmente de su capacidad para concentrar la radiación solar de manera eficiente y económica. La presente tesis está orientada hacia la resolución de ciertos problemas importantes relacionados con este objetivo. La mencionada necesidad de reducir costes en la concentración de radiación solar directa, asegurando el objetivo termodinámico de calentar un fluido hasta una determinada temperatura, es de vital importancia. Los colectores lineales Fresnel han sido identificados en la literatura científica como una tecnología con gran potencial para alcanzar esta reducción de costes. Dicha tecnología ha sido seleccionada por numerosas razones, entre las que destacan su gran libertad de diseño y su actual estado inmaduro. Con el objetivo de responder a este desafío se desarrollado un detallado estudio de las propiedades ópticas de los colectores lineales Fresnel, para lo cual se han utilizado métodos analíticos y numéricos de manera combinada. En primer lugar, se han usado unos modelos para la predicción de la localización y la irradiación normal directa del sol junto a unas relaciones analíticas desarrolladas para estudiar el efecto de múltiples variables de diseño en la energía incidente sobre los espejos. Del mismo modo, se han obtenido analíticamente los errores debidos al llamado “off-axis aberration”, a la apertura de los rayos reflejados en los espejos y a las sombras y bloqueos entre espejos. Esto ha permitido la comparación de diferentes formas de espejo –planos, circulares o parabólicos–, así como el diseño preliminar de la localización y anchura de los espejos y receptor sin necesidad de costosos métodos numéricos. En segundo lugar, se ha desarrollado un modelo de trazado de rayos de Monte Carlo con el objetivo de comprobar la validez del estudio analítico, pero sobre todo porque este no es preciso en el estudio de la reflexión en espejos. El código desarrollado está específicamente ideado para colectores lineales Fresnel, lo que ha permitido la reducción del tiempo de cálculo en varios órdenes de magnitud en comparación con un programa comercial más general. Esto justifica el desarrollo de un nuevo código en lugar de la compra de una licencia de otro programa. El modelo ha sido usado primeramente para comparar la intensidad de flujo térmico y rendimiento de colectores Fresnel, con y sin reflector secundario, con los colectores cilíndrico parabólicos. Finalmente, la conjunción de los resultados obtenidos en el estudio analítico con el programa numérico ha sido usada para optimizar el campo solar para diferentes orientaciones –Norte-Sur y Este-Oeste–, diferentes localizaciones –Almería y Aswan–, diferentes inclinaciones hacia el Trópico –desde 0 deg hasta 32 deg– y diferentes mínimos de intensidad del flujo en el centro del receptor –10 kW/m2 y 25 kW/m2–. La presente tesis ha conducido a importantes descubrimientos que deben ser considerados a la hora de diseñar un campo solar Fresnel. En primer lugar, los espejos utilizados no deben ser plano, sino cilíndricos o parabólicos, ya que los espejos curvos implican mayores concentraciones y rendimiento. Por otro lado, se ha llegado a la conclusión de que la orientación Este-Oeste es más propicia para localizaciones con altas latitudes, como Almería, mientras que en zonas más cercanas a los trópicos como Aswan los campos Norte-Sur conducen a mayores rendimientos. Es de destacar que la orientación Este-Oeste requiere aproximadamente la mitad de espejos que los campos Norte-Sur, puediendo estar inclinados hacia los Trópicos para mejorar el rendimiento, y que alcanzan parecidos valores de intensidad térmica en el receptor todos los días a mediodía. Sin embargo, los campos con orientación Norte-Sur permiten un flujo más constante a lo largo de un día. Por último, ha sido demostrado que el uso de diseños pre-optimizados analíticamente, con anchura de espejos y espaciado entre espejos variables a lo ancho del campo, pueden implicar aumentos de la energía generada por metro cuadrado de espejos de hasta el 6%. El rendimiento óptico anual de los colectores cilíndrico parabólicos es 23 % mayor que el rendimiento de los campos Fresnel en Almería, mientras que la diferencia es de solo 9 % en Aswan. Ello implica que, para alcanzar el mismo precio de electricidad que la tecnología de referencia, la reducción de costes de instalación por metro cuadrado de espejo debe estar entre el 10 % y el 25 %, y que los colectores lineales Fresnel tienen más posibilidades de ser desarrollados en zonas de bajas latitudes. Como consecuencia de los estudios desarrollados en esta tesis se ha patentado un sistema de almacenamiento que tiene en cuenta la variación del flujo térmico en el receptor a lo largo del día, especialmente para campos con orientación Este-Oeste. Este invento permitiría el aprovechamiento de la energía incidente durante más parte del año, aumentando de manera apreciable los rendimientos óptico y térmico. Abstract Concentrating solar power is the common name of a technology based on capturing the thermal power of solar radiation, in a suitable way to reach temperatures able to activate a conventional (or advanced) thermodynamic cycle to generate electricity; this quest mainly depends on our ability to concentrate solar radiation in a cheap and efficient way. The present thesis is focused to highlight and help solving some of the important issues related to this problem. The need of reducing costs in concentrating the direct solar radiation, but without jeopardizing the thermodynamic objective of heating a fluid up to the required temperature, is of prime importance. Linear Fresnel collectors have been identified in the scientific literature as a technology with high potential to reach this cost reduction. This technology has been selected because of a number of reasons, particularly the degrees of freedom of this type of concentrating configuration and its current immature state. In order to respond to this challenge, a very detailed exercise has been carried out on the optical properties of linear Fresnel collectors. This has been done combining analytic and numerical methods. First, the effect of the design variables on the ratio of energy impinging onto the reflecting surface has been studied using analytically developed equations, together with models that predict the location and direct normal irradiance of the sun at any moment. Similarly, errors due to off-axis aberration, to the aperture of the reflected energy beam and to shading and blocking effects have been obtained analytically. This has allowed the comparison of different shapes of mirrors –flat, cylindrical or parabolic–, as well as a preliminary optimization of the location and width of mirrors and receiver with no need of time-consuming numerical models. Second, in order to prove the validity of the analytic results, but also due to the fact that the study of the reflection process is not precise enough when using analytic equations, a Monte Carlo Ray Trace model has been developed. The developed code is designed specifically for linear Fresnel collectors, which has reduced the computing time by several orders of magnitude compared to a wider commercial software. This justifies the development of the new code. The model has been first used to compare radiation flux intensities and efficiencies of linear Fresnel collectors, both multitube receiver and secondary reflector receiver technologies, with parabolic trough collectors. Finally, the results obtained in the analytic study together with the numeric model have used in order to optimize the solar field for different orientations –North-South and East-West–, different locations –Almería and Aswan–, different tilts of the field towards the Tropic –from 0 deg to 32 deg– and different flux intensity minimum requirements –10 kW/m2 and 25 kW/m2. This thesis work has led to several important findings that should be considered in the design of Fresnel solar fields. First, flat mirrors should not be used in any case, as cylindrical and parabolic mirrors lead to higher flux intensities and efficiencies. Second, it has been concluded that, in locations relatively far from the Tropics such as Almería, East-West embodiments are more efficient, while in Aswan North- South orientation leads to a higher annual efficiency. It must be noted that East-West oriented solar fields require approximately half the number of mirrors than NS oriented fields, can be tilted towards the Equator in order to increase the efficiency and attain similar values of flux intensity at the receiver every day at midday. On the other hand, in NS embodiments the flux intensity is more even during each single day. Finally, it has been proved that the use of analytic designs with variable shift between mirrors and variable width of mirrors across the field can lead to improvements in the electricity generated per reflecting surface square meter up to 6%. The annual optical efficiency of parabolic troughs has been found to be 23% higher than the efficiency of Fresnel fields in Almería, but it is only around 9% higher in Aswan. This implies that, in order to attain the same levelized cost of electricity than parabolic troughs, the required reduction of installation costs per mirror square meter is in the range of 10-25%. Also, it is concluded that linear Fresnel collectors are more suitable for low latitude areas. As a consequence of the studies carried out in this thesis, an innovative storage system has been patented. This system takes into account the variation of the flux intensity along the day, especially for East-West oriented solar fields. As a result, the invention would allow to exploit the impinging radiation along longer time every day, increasing appreciably the optical and thermal efficiencies.

Determinación y caracterización de los indicadores que intervienen en un sistema integral de iluminación natural y protección solar : aplicado a la incorporación de bandejas en los huecos de fachadas existentes

En esta tesis se estudia cómo lograr el equilibrio entre dos fenómenos naturales que afectan a los huecos de fachadas: la iluminación natural y la ganancia solar. Es decir, el cómo, conseguir la optimización de la iluminación natural que se introduce a través de las ventanas existentes, sin realizar una laboriosa intervención de sustitución de las mismas y el cómo, conseguir la protección de la radiación solar directa de la zona acristalada, para evitar tanto las ganancias térmicas innecesarias como el deslumbramiento que afecta a la calidad lumínica de los recintos. Para el desarrollo esta investigación se ha propuesto una metodología de estudio dividida en dos fases: La primera, de Análisis y Diagnóstico, en la que se han de definir los estándares a cumplir y las variables con las que se evaluarán las bandejas. Y, la segunda, de Evaluación y Comprobación en la que se han de establecer los criterios de valoración y ponderación de cada variable. En la primera fase, se definirán las variables físico-ambientales, para lo que se seleccionarán algunas ciudades a estudiar, a las cuales se les estudiará las necesidades de confort térmico, se determinarán las dimensiones que deben tener las protecciones solares en esas ciudades, además se determinarán las actuaciones a realizar en los huecos de fachada según sea su posición en el plano vertical de la misma. Así mismo, se plantea hacer un análisis de casos reales, para lo que se caracterizarán desde el punto de vista lumínico algunas viviendas, realizando medidas “in situ” y comparando resultados con los que se obtienen de los programas de simulación, para seleccionar las viviendas en las que la realidad y la simulación se aproximen más, una de estas viviendas servirá de modelo en las simulaciones que se realizará en la segunda fase. También, en esta primera fase, mediante un modelo neutro, se estudiará el comportamiento térmico y lumínico del tamaño del hueco en el que se insertará la bandeja posteriormente, para luego estudiar la posición de la bandeja en el plano vertical de la ventana, desde el punto de vista ergonómico. Y finalmente se estudiará, el comportamiento térmico y lumínico del modelo con la bandeja ubicada a 40, 50 y 60cm del techo. En la segunda fase, se establecerá la valoración y ponderación de las variables con las que seleccionar la bandeja que mejor equilibre los aspectos térmicos y lumínicos, teniendo en cuenta estrategias pasivas de acondicionamiento ambiental, como favorecer las ganancias solares en invierno en horas diurnas y evitar las pérdidas de calor en horas nocturnas; y en verano implementar sistemas de sombreamiento en la zona acristalada para evitar las ganancias de calor; y, tanto en verano como en invierno, aprovechar la iluminación natural, para favorecer la iluminancia útil y evitar el deslumbramiento. Una vez definidos los criterios de valoración y ponderación se aplicará a la evaluación térmica y lumínica del modelo neutro con la bandeja, consiguiendo seleccionar la bandeja con mejor comportamiento. Posteriormente se comprobará la metodología de estudio desarrollada en el modelo seleccionado, se evaluará el comportamiento térmico y lumínico, con la incorporación de algunas alternativas de bandeja. Con esta investigación se quiere demostrar que mediante la aplicación de esta metodología de estudio, es posible evaluar y seleccionar bandejas que respondan a las necesidades requeridas en distintos casos de estudio, por lo que se considera que, la bandeja puede ser un elemento arquitectónico aplicable tanto en rehabilitación como en nueva construcción, de espacios en los que sea necesario mejorar sus condiciones lumínicas y térmicas simultáneamente. ABSTRACT This thesis studies how to balance two natural events that affect the window opening of facades: daylighting and solar gain. That is to say, how to achieve optimization of natural light that gets in through the existing windows, without making a laborious intervention of replacing them and how to get protection from direct solar radiation from the glass area, to avoid unnecessary heat gain and glare affecting the light quality of the enclosures. To develop this research, it has been proposed a methodology of study divided into two phases: First phase, Analysis and Diagnostics, in which the variables with which the light shelf are evaluated will be defined along with the standards the light shelves will meet. The second phase, Assessment and Verification, in which the assessment criteria and weighting of each variable will be established. In the first phase, the physical and environmental variables shall be defined, various cities will be selected to be studied, and in each the needs of thermal comfort will be determined along with the dimensions of shading devices in the cities. In addition the actions to be taken in the window opening of the façade will be determined, depending on their position in the vertical plane. An analysis of real cases will be undertaken, which will be characterized from the luminous point of view, performing "in situ" measurements and comparing results with those obtained from simulation programs, to select places/dwellings where reality and simulation are closer, one of these places/dwellings will be a model, in the simulations to perform at the second phase. Also, in this first phase, by a neutral model, the thermal and light behavior of the size of the window opening will be studied, in which the light shelf is inserted later, the position of the light shelf in the vertical plane of the window is studied, from an ergonomic point of view. And finally to study the thermal and light behavior of the model with the light shelf located at 40, 50 and 60cm from the ceiling. In the second phase, the evaluation and weighting of the variables will be established selecting the light shelf that best balances the thermal and daylighting aspects, taking into account passive environmental conditioning strategies; such as getting solar gains in winter during daylight hours, and preventing heat loss during the night hours; and in summer implementing shading systems in the glazing area to avoid heat gains. And in both summer and winter, taking advantage of natural lighting, to improve useful illuminance and avoid glare. Once defined, the evaluation criteria and weighting will be applied to thermal and daylighting evaluation to the neutral model with the light shelf, the best performing light shelf will be selected. The study methodology developed in the selected model will be verified the thermal and daylighting performance with the addition of some light shelf alternative will also be studied. With this research, we want to show that by applying this study methodology it is possible to evaluate and select the light shelf that meets the needs required in different case studies, so it is considered that the light shelf may be an applicable architectural element in both refurbishment and new construction of spaces where necessary to improve their daylighting and thermal conditions simultaneously.

Modelagem de um secador solar de produtos agrícolas com sistema de armazenagem de energia térmica

Nos países em desenvolvimento, como o Brasil, a secagem de produtos agrícolas com uso de secador solar representa uma alternativa promissora de baixo custo, reduzindo perdas e agregando valor aos produtos. Porém, devido à natureza periódica da radiação solar e das condições do tempo, nem sempre é viável sua utilização. Dessa forma, o objetivo do trabalho foi a modelagem de um sistema auxiliar de armazenagem de energia térmica (SAET) em um secador solar, cuja finalidade é armazenar energia durante o dia para ser utilizada conforme necessário. Com base em registros de temperatura e umidade relativa, ambas do ar, de um secador solar, foi feito um estudo da termodinâmica dos processos envolvidos, a fim de propor meios para o dimensionamento do SAET. Foram explorados a estimativa do fluxo de massa de ar no secador, a modelagem da temperatura em função da radiação, e o dimensionamento para diferentes modos de operação do SAET, considerando o sistema ideal. Este dimensionamento tratou tanto do caso de fornecimento contínuo de fluxo de água preaquecida, como de uso de automação para controlar o fluxo. A estimativa de fluxo de ar no secador se aproximou de valores típicos encontrados na literatura. O dimensionamento do sistema, embora considerado ideal, mostra que a utilização do SAET melhora o desempenho do secador, servindo como parâmetro para melhor compreender o comportamento das variáveis durante seu funcionamento.

Earth-atmosphere radiation budget analyses derived from NOAA satellite data, June 1974-February 1978 /

Mode of access: Internet.

Solar radio emission; spectral observations in the decameter range, 24 July 1959-28 February 1961.

Cover title.

TIROS III radiation data users' manual.

Bibliography: p. 10.