Analysis of high concentrator photovoltaic modules in outdoor conditions: Influence of direct normal irradiance, air temperature, and air mass

The study of high concentrator photovoltaic (HCPV) technology under real conditions is essential to understand its real behavior. The influence of direct normal irradiance (DNI), air temperature (Tair), and air mass (AM) on the maximum power of two HCPV modules was studied for more than three years. Results found are presented in this paper. As expected, the main influence on the maximum power is DNI. Also, Tair has been found to have small influence on the maximum power. Regarding AM, two different behaviors have been found. The maximum power could be considered independent of AM for AM 2, while it decreases with an approximate linear behavior for AM > 2. Also, the maximum power of a HCPV module could be estimated with a linear mathematical fitting based on DNI, Tair, and AMThis work is a part of the project “SIGMPLANTAS: La innovacion en las plantas y modelos de sistemas de Concentracion Fotovoltaica en España,” IPT-2011-1468-920000 supported by the Spanish Science and Innovation Ministry and by the European Regional Development Fund/Fondo Europeo de Desarrollo Regional (ERDF/FEDER)S

Analytical modelling of high concentrator photovoltaic modules based on atmospheric parameters

PublishedJournal Article© 2015 Eduardo F. Fernández et al. The goal of this paper is to introduce a model to predict the maximum power of a high concentrator photovoltaic module. The model is based on simple mathematical expressions and atmospheric parameters. The maximum power of a HCPV module is estimated as a function of direct normal irradiance, cell temperature, and two spectral corrections based on air mass and aerosol optical depth. In order to check the quality of the model, a HCPV module was measured during one year at a wide range of operating conditions. The new proposed model shows an adequate match between actual and estimated data with a root mean square error (RMSE) of 2.67%, a mean absolute error (MAE) of 4.23 W, a mean bias error (MBE) of around 0%, and a determination coefficient (R 2) of 0.99.Partial funding for this study was provided through EPSRC funded BioCPV (EP/J000345/1) project. Also, this work is part of the project “Desenvolvemento de novos conceptos baseados en tecnoloxía de concentración fotovoltaica para a produción de enerxía eléctrica adaptados a distintas zonas climáticas,” through the program “Formación Posdoutoral do Plan Galego de Investigación, Innovación e Crecemento 2011–2015 (Plan I2C)” funded by the Xunta de Galicia and by the European Social Fund

Vertical-Tunnel-Junction (VTJ) Solar Cell for Ultra-High Light Concentrations (>2000 Suns)

A novel architecture of cell structure tailored to ultra-high (>2000 suns) concentration ratios is proposed. The basic solar cell consists of two p-n junctions connected in series by a highly doped tunnel diode with the metallic contacts located laterally. The tunneling connection allows using direct band-gap semiconductor compounds aiming to optimize the absorption of the spectrum. The performance of the novel architecture is investigated up to ultra-high concentration using TCAD software. Simulations show its viability for developing a new generation of solar cells to increase the potential in terms of efficiency and cost reduction of ultra-high concentrator systems. The solar cell does not show any degradation with concentration and efficiency as high as 28.4% at 15000 suns has been obtained for a preliminary designThe work of E. F. Fernández and F. Almonacid was supported by the Spanish Economy Ministry and FEDER funds under Project ENE2016-78251-R. The work of N. Seoane and A. J. García-Loureiro was supported in part by the Spanish Ministry of Economy and Competitiveness and FEDER funds under Grants TEC2014-59402-JIN and TIN2016-76373-P and in part by the Xunta de Galicia and FEDER funds under Grant GRC 2014/008S

Characterisation and impact of non-uniformity on multi-junction solar cells (MJSC) caused by concentrator optics

In this work, it has been developed a method to generate non-homogeneous light patterns on multi-junction solar cells. These patterns have been generated modifying the distance between the CPV receiver and the primary optics, which is based on a Fresnel lens. In order to diminish the impact of other variables, the incident spectrum, laboratory temperature and effective concentration have been kept constant: SMRtop-mid = 1 ± 0.02, 25 ± 0.5ºC and 380 ± 3 suns, respectively. The light patterns on the top and middle subcells are measured using a CCD camera and band-pass filters. Results show that the electrical performance of the solar cells depends on the spatial and spectral profiles. The present work introduces a procedure to characterise and evaluate the impact of non-uniformities on the output of multi-junction solar cells. Nevertheless, this work is not intended to predict the actual output of the cell as a function of the light profiles, but to provide indications for possible underlying mechanisms.This work is partially funded by European Regional Development Fund (ERDF) and Spanish Economy Ministry, grant number ENE2016-78251-

Optical modeling of four Fresnel-based high-CPV units

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordHigh Concentrator Photovoltaic (HCPV) units are typically based on the use of Fresnel lenses, refractive secondary optical elements (SOE), and triple-junction (TJ) solar cells. In this work, a detailed optical modeling is applied to analyze the performance of four Fresnel-based HCPV units equipped with different refractive SOEs while considering the subcells current density generation. Wavelength-dependent material properties are utilized while simulating the optical performance. The spectral response of a typical TJ solar cell is also included. This modeling allows to establish the subcell current limitation and the spectral matching ratio, SMR, values in each case. The following SOEs have been used for simulating the HCPV units: (i) Dielectric-cross compound-parabolic-concentrator (DCCPC), (ii) (SIngle-Lens-Optical element) SILO-Pyramid, (iii) Refractive truncated pyramid (RTP) and, (iv) Trumpet. Results show that the HCPV units with SOEs RTP and Trumpet, exhibit bottom subcell current limitation and lowest optical polychromatic efficiency, this is partly due to the irradiance absorption in the bottom cell spectral region and longer optical path length of the concentrated rays within the SOE material. In the case of the HCPV unit with the DCCPC SOE, top and bottom subcells limit the current generation alternatively depending on the misalignment angle of the HCPV unit respect to the simulated sunrays. None of the SMR parameters are equal to 1 under normal alignment of the HCPV units. The short-circuit current density distributions for each subcell in each case are studied under normal alignment and under 1° of misalignment angle.European Regional Development Fund (ERDF) and Spanish Economy Ministry (ENE2013-45242-R and ENE2016-78251-R); Universidad de Jaén (UJA) and Caja Rural de Jaén (UJA2015/07/01). Financial support provided by the Universidad de Jaén Doctoral School

Hábitos de sueño y problemas relacionados con el sueño en adolescentes: relación con el rendimiento escolar

ObjetivoConocer la prevalencia de trastornos de sueño en los adolescentes. Describir los hábitos de sueño de los adolescentes y su relación con los trastornos del sueño y los factores asociados. Conocer la relación entre los trastornos del sueño y/o los hábitos de sueño inadecuados con el rendimiento escolar.DiseñoEstudio observacional, descriptivo y transversal.EmplazamientoInstitutos de enseñanza secundaria obligatoria (ESO) de la ciudad de Cuenca.ParticipantesUn total de 1.293 alumnos escolarizados en primero y cuarto cursos de ESO.Mediciones principalesHábitos de sueño en días lectivos y fines de semana y prevalencia de trastornos del sueño medidos mediante un cuestionario estructurado con preguntas abiertas y cerradas, autoadministrado y anónimo. Se determinó el rendimiento escolar de los alumnos y su relación con los hábitos y trastornos de sueño.ResultadosDe los 1.293 alumnos matriculados, completaron la encuesta 1.155 (89,33%), 537 (45,9%) chicos y 618 (54,1%) chicas, con una media de edad de 14 años (rango, 11-18 años). Los días laborables se acuestan en promedio a las 23.17 y se levantan a las 7.46 (tiempo medio, 8 h y 18 min) y los fines de semana se acuestan a la 1.02 y se levantan a las 10.42 (tiempo medio, 9 h y 40 min). El 45,4% declara dormir mal la noche del domingo al lunes. El promedio de asignaturas suspendidas es mayor en los adolescentes con queja de sueño (2,28 frente a 1,91; p = 0,04), los que se levantan cansados (2,17 frente a 1,97; p = 0,048) y los que tienen somnolencia diurnal (2,17 frente a 1,75; p = 0,004).ConclusionesEl horario escolar conlleva deuda de sueño durante la semana que se recupera parcialmente el fin de semana. En los fines de semana se produce una rotura en los hábitos de sueño de los adolescentes. Los adolescentes con problemas relacionados con el sueño muestran peor rendimiento escolar.ObjectiveTo determine the prevalence of sleep disorders in adolescence.To describe sleeping habits of adolescents in relation to sleep disorders and associated factors. To determine the relation between sleep disorders/inappropiate sleeping habits and school performance.DesignObservational, descriptive, crosssectional study.SettingSecondary school of Cuenca (city in Spain).Participants1293 school children of first and fourth curses of secondary education.Main measuresStructured questionnaire with opened and closed questions on sleeping habits during weekdays and at weekends and sleep disorders to be answered by the adolescents anonymously and on their own. Student's school performance with relation with to sleeping habits and sleep disorders were determined.Results1155 students out of 1293 (response rate 89.33%) answered the questionnaire, 537 (45.9%) boys and 618 (54.1%) girls, 14 years old on average (between 11-18 years). On weekdays students went to bed at 23.17 h and got up at 7.46 h (average sleeping time =8 hours and 18 minutes). At weekends they went to bed at 1.02 h and got up at 10.42 h (average sleeping time =9 hours and 40 minutes). 45.4% of students said to sleep badly on Sunday night's.On average the number of subjects failed in class is higher with adolescents who complain about sleep (2.28 vs 1.91; P=.04), who are tired at waking up time (2.17 vs 1.97; P=.048) and who have morning sleepiness (2.17 vs 1.75; P=.004).ConclusionsSchools hours cause deficitsleeping time during weekdays which is partly made up for at weekend. At weekends there is an interruption of the adolescent's sleeping habits. School performance of adolescents with sleep disorders is lower