RENEWABLE ENERGY EDUCATION IN THE ...

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Abstract – The Renewable Energy Laboratory at the University of Valladolid (Spain), ... solar energy laboratory suitable for educational and research purposes.
RENEWABLE ENERGY EDUCATION IN THE DEPARTMENT OF APPLIED PHYSICS AT THE UNIVERSITY OF VALLADOLID (SPAIN) Julia Bilbao , Argimiro de Miguel and Arturo Ayuso Department of Applied Physics, University of Valladolid, Sciences Faculty. Prado de la Magdalena s/n, Valladolid, 47005, Spain 983.42.31.33, [email protected] Abstract – The Renewable Energy Laboratory at the University of Valladolid (Spain), has developed a solar energy laboratory suitable for educational and research purposes. Fundamental studies concerning the solar radiation characteristics, simulation and performance of solar systems and different courses for undergraduate and postgraduate students are being carried out. The laboratory consists of the solar and meteorological radiation station with sensors at different tilts and orientations, an appropriate data acquisition system, a photovoltaic grid connected station and a solar house with Trombe walls. The paper shows the activities in relation to educational courses and projects, conferences, doctoral courses and the experience in setting up the laboratory.

1. INTRODUCTION One of the objectives of the International Community is to increase the development and use of Renewable Energies and recommend the efficient energy utilisation as an important option for reducing greenhouse effect, acid rain, urban pollution, global warming and climatic change. But, the development and use of Renewable Energies require the information, education and training of students and people in general. Renewable Energy Education has not yet reached the general standards of public education, but it is taking place at different social levels. Adequate educational actions and teaching materials as well as an appropriate infrastructure for dissemination and promotion of renewable energies are needed to bridge the gap between international experts and the potential technician and customers. Materials for learning about renewable energy or solar energy are available by different authors, (Duffi and Beckman, 1991, Kumar and Attalage, 2002, Iqbal, 1983). The status of renewable energy education at different levels is available from (Blum et al., 1996, Iskander, et al., 2000) In Spain, the Autonomous Governments, following the European Community guidelines, provide funds for educational courses and research projects in renewable energy but till now, few of them have been established with regularity. The Laboratory of Renewable Energies (LER) of the Sciences Faculty at Valladolid University (Spain) has been working for several years in Renewable Energy education. The laboratory has collaborated in different regional, national and international research projects and has a great experience in renewable education. A big quantity of Renewable Energy educational activities are carried out by the laboratory, some of them are the following: - Undergraduate and Postgraduate courses -Training courses in collaboration with regional Institutions. - Lectures in Summer University courses - Projects for education quality improvement

- Educational material -Field experiments - Software and Simulations - Internet information The objective of this paper is to show the education activities, like lectures, courses in collaboration, organisation and postgraduate courses of third cycle, educational projects and teaching material, at undergraduate and postgraduate levels that have been developed by the Renewable Energy Laboratory at the University Valladolid (Spain) in the last years. The didactic contents and tools of the training sessions, according to the target groups will be shown. Monitoring, data analysis, design and simulations of solar systems will be included. The novelty of the paper is that it is the first time that pedagogic contents, monitoring analysis, solar system simulations or similar actions taken in Castile and Leon region (Spain) are shown 2. RENEWABLE ENERGY EDUCATIONAL ACTIVITIES The activities developed have been the following: 2.1 Graduate and Post-Graduate Courses The paper shows the didactic material and tools of training sessions on solar energy and wind technologies that have been elaborated to different target groups. To this end several independent modules and contents of each session have been developed according to the target groups. We have also built a wide purpose technical training tool that will be easily adapted to the different circumstances and, thus, will be susceptible of easy application in other areas or countries. The courses have made use of conventional learning tools in conjunction with data analysis and solar system simulation. These include some software in order to implement models, implement and new routines and a set-up tutorial procedure to guide the trainees through the design and simulation of solar systems.

We have identified two main target groups: - Local/regional authorities, technical officers, energy agencies, energy planners, and local utilities: information, further education, and ad-hoc sessions; - Undergraduate and postgraduate students: seminars and specialization courses. The first group is clearly concerned with decision making process and needed mainly a general survey on the energy technology options, on the solar energy potentialities and applications, on the involved economic issues and a little technical information to deal successfully with project management. Technical officers will needed a training more focused on technical issues. The flexibility was possible because of the modular structure of the tutorials. The second group (students) required a general overview like the previous group, but the core of the tutorial was constituted by theoretical and engineering issues. The contents of the courses were a collection of manuscripts of the lectures and exercises, laboratory practices, simulation tools and experimental material descriptions for out-door experiments to complete a comprehensive educational demonstration course on the mentioned topics and they were as tools to start working efficiently in a training programme. The curricula consisted of theoretical and laboratory lessons. The methodology has integrated the theoretical and experimental efforts introducing to the subject in lecture and having laboratory sessions to investigate the physical principles of components of small-scale supply systems. In the field experiments students performed open-air experiments to study the dynamic behaviour of PV grid connected system, solar house, and solar radiation and meteorological station. In lectures the following items have been studied: The main objective of the lessons is to write down about the present energetic system and the introduction explains the differences between traditional and renewable energies. The relevant astronomical relationship and trigonometric equations relating the position of the sun to a horizontal and inclined surface is presented. Shading can cause high losses in the performance systems. Operating results from some experimental programmes have shown that some generators examined were partially shaded and that annual losses were important. So, a study of shading theory was proposed. Then, details about the nature of the radiant energy emanating from the sun, spectral distribution and the total quantity of this energy arriving to the earth are shown. The beam radiation is attenuated by the presence of clouds in its path, as well as by the various elements (ozone, turbidity, precipitable water vapour). Studies about the solar radiation on earth’s surface, on inclined surfaces and the simulation of solar radiation taking the attenuation into account have been presented. The statistical distribution of solar radiation is established because it is very useful for planning the use of solar energy systems.

For evaluating the yield of a power solar plant, mean values of irradiation are not sufficient to estimate the output of electrical energy because the dependence of the technical device on the meteorological data is non-linear. There is a threshold between the irradiation and the output of solar power systems. At least a complete statistical distribution is needed. The silicon solar cell was described, its construction, how it works and its main performance characteristics. The various sources of energy loss in the device are studied and we consider what can be done to improve performance. The latest advances in cell design, including bifacial cell are described. The processes of manufacture alternative crystal and fabrication processes and methods to bring costs down are shown. A PV module is the basic building block of a photovoltaic solar array. It consists of one o more solar cells, interconnected to produce the required power and voltage. The cells are encapsulated behind a transparent window to protect and insulate them from the weather and accidental damage. The power output under standard conditions, the fail effects and the tests carried out for module control are shown. A common denominator for all stand-alone PV systems is that they rely on a battery bank to supply continuous power at night and during hours of limited sunshine. Two basic types: lead acid and nickel cadmium are generally found in PV installations. The type of the battery used affects other design considerations in the system. The charge/discharge process, battery design and the battery characteristics are shown. Description of the main components of the PV systems excluding the array, DC/CD converters and MPPT (maximum power point tracker), DC/AC inverters, battery controllers (regulators) and blocking diodes were studied. A photovoltaic system is an integrated assembly of modules and other components designed to convert solar energy into electricity to provide a particular service, either alone or in conjunction with a back-up supply. It can vary greatly in size and complexity from a few watts to a multimegawatt power station delivering electricity to a grid, and between them, there is a wide range of small and medium power applications. The different PV system from standalone to grid interactive systems will be shown. The design and dimensioning methods with solar radiation data of the place have been evaluated. The program of the subjects is developed with the following characteristics: 1-Fundaments in atmosphere and solar radiation. -Introduction: art state of renewable energies. -Use of solar energy. -Sun as origin of radiation: solar geometry. -Meteorology and climate. -Solar constant. Extraterrestrial solar radiation. -Solar radiation under cloudy sky. -Solar radiation over tilted surfaces. -Meteorological and solar radiation sensors: measurements and calibration.

2- Thermal solar radiation conversion. -Fundaments of thermal conversion. -Fotothermal captures and thermal accumulation. 3- Solar passive Systems. -Introduction: general concepts. -Heat transmission fundaments. -Passive caption systems: direct and indirect gain . -Evaluations methods: Day-degree and F-Chart. -Monitoring solar house. 4- Photovoltaic conversion. -Introduction: state of art. -Basic electronic: cells. -PV modules, batteries. -Dimension and design: methodologies. -Applications: electrification, grid systems. 5- Wind energy. -Introduction. -Wind resources. -Technical aspect. -Design and simulation. Different books and web pages were given as a reference. 2.2 Training courses in collaboration with regional Institutions From 1991 the group has collaborated in different courses at regional level and in courses organized by the National Institute of Unemployment (INEM); Enterprises Confederation of Castile and Leon (CECALE); Autonomous Government of Castile and Leon (JCYL) and General Foundation of the University. In the year 2003, the Industry Department of the Autonomous Government and the Valladolid University set up the I University Specialist Course in Renewable Energy at the ETSII (Industrial Engineering Superior School), developed in 250 hours, which the laboratory has collaborated in the tasks of solar and wind resources: description, evaluation, sensors and calibration. 2.3 Summer University courses The teachers of the Renewable Energy Laboratory have collaborated, along the years, in different summer courses in Spain: -VII University Summer Course of Santa Catalina University, Burgo de Osma (Soria, Spain). -University Casado de Alisal (Palencia, Spain). -Conferences at the Summer Course of Best Group Engineering Students (Valladolid, Spain) In these courses, lectures and field experiments in relation to Energy and Environment were given. 2.4 Postgraduate Doctorate Courses At the University of Valladolid Physics Doctoral Programme, the LER has a subject called Solar Energy and Environment where the main topics of the teaching subjects are: -Meteorology and solar radiation o Atmosphere Physics

§ Atmosphere composition § Stability in the atmosphere § Dynamic of the atmosphere o Solar geometry o Solar thermal radiation: solar spectrum o Extraterrestrial solar irradiation -Physical principles of thermal conversion -Physical principles of energy conversion PV into cells -Wind resources o Atmospheric pressure and winds o Dynamic equations o Atmospheric boundary layer After a first year, students do a tutorial research work. The last tutorial works presented have been the following: -Climatic variables for installation design and efficient use of the energy. -Perez’ solar radiation model: evaluation of coefficients from experimental values -Alternating –alternating direct conversion matrix development for Aeolian applications -Thermal collector evaluations Some doctoral thesis have been presented in the last years: -Measurements and modelling of solar diffuse irradiation on tilted surfaces. -Comparison of methodologies for generating typical meteorological years and their application to solar thermal, passive and photovoltaic simulations. -Solar global irradiation on tilted and oriented surfaces and application to passive systems. (in course). 3. EDUCATIONAL PROJECTS In the last years, the Renewable Energy Laboratory at the University of Valladolid, (Spain) has achieved the following educational research projects financed by the Department of Education and Culture at the Autonomous Government of Castile and Leon region (Spain): -Electricity practices with PV technology The material of the project is composed of a manuscript with the PV technology basic lectures and 20 outlined descriptions of experimental practices for PV applications, such as solar radiation intensity, characteristics of current-tension, solar cells association, I-V curves of solar cells, solar cells and shadow and simulation of solar batteries. -Learning course for thermal solar applications (in course) The project describes the material for a learning course for students at postgraduate level. It will be developed by means of lecture notes, transparencies, exercises, experiments and system simulation software. 4. EDUCATIONAL MATERIAL

4.1 Manuscripts Some manuscripts in relation to the different courses have been performed. The curricula consist of the following subjects: -Fundaments of solar geometry, solar radiation and meteorological variables. -Thermal conversion of solar energy. -Passive use of solar energy. -Photovoltaic conversion and application. -Wind energy systems. At the different courses the writing material is given to students as a reference. Practical introduction in the solar geometry, some practices about sun position, movements of the sun and calculation of solar extraterrestrial irradiation have been prepared. Scientific principles of the solar radiation sensors and the evaluation of shadowing effects on solar modules have been gathered, as well as sensor calibration and recording data. Solar spectra practice: the influence of the solar spectral radiation on the solar systems is evaluated by different spectral models, which are necessary for, studying the different performance of the PV materials. The list of practices is the following: -Solar geometry and air mass -Extraterrestrial solar irradiation: variation with latitude -Meteorological variables: analysis of a measurement campaign. -Soil temperature and heat transfer -Solar global, diffuse and direct irradiation: solar fraction, clearness index -Radiation balance near surface: radiative fluxes in the lower atmosphere. 4.1 Experimental material Some practical experiments of laboratory have been prepared, concerning the characteristics of PV solar cells. The current-voltage characteristics of a solar cell may be measured either in natural sunlight or with a solar simulator. The test instrumentation is composed of a reference solar cell, a temperature sensor, variable load, current and voltage measurement equipment, and a temperature monitor. The variable load should be an electronic circuit that sweeps the load from short-circuit to open-circuit slowly enough so that the characteristics can be measured either digitally or with an x-y plotter. The irradiance can be measured with a reference cell, ETC (equivalent technology cells). To know the modules performance, it is necessary to calculate the temperature coefficients (the variation of current and voltage with the temperature) and this experiment is being prepared. The calculation of the shading effects on PV modules will be carried out and shown over Visual-Basic software; experiments of charge/discharge cycles would be installed and the evaluation of the efficiency of electrical device is being developed. 4.1.1Field Experiments

The experimental measurement campaigns of the Renewable Energy Laboratory take place at the rural University Laboratory, C.I.B.A. (Low Atmosphere Research Centre), located 35 km from the city of Valladolid and whose geographical characteristics are 42º 49’ N, 4º 56’ W and 840 m above sea level. The laboratory is located over a parcel of 5000 m2 , perfectly flat place which allows the laboratory to be positioned away from shadows. The microclimate is continental with cold winters and warm summers. The coldest month is January, when the mean temperature is 3ºC . In June and July average temperature is 20 ºC. The prevailing winds in the region are from northwest, of 3.5 to 6.0 ms -1 . At C.I.B.A. site there are modern experimental devices for the study of several fields of renewable energy, meteorology and other Atmospheric Physics subjects. The following solar field experiments are established: a solar house, a photovoltaic plant and a meteorological and solar radiation station and a 100 m tower equipped with wind velocity and direction sensors. The C.I.B.A. solar house was built incorporating available solar and energy-efficient technologies to serve three primary purposes: -To demonstrate how solar and energy-efficient technologies can be incorporated into a solar house of traditional design, typical of Castile and Leon. -To be used as an educational resource and laboratory for students, professional organisations, and the general public. -To serve as a research laboratory for graduate students in engineering, architecture, interior design, and other related disciplines. Figure 1 shows the meteorological and solar radiation station, at the C.I.B.A laboratory. Different solar sensors were installed in order to record different portions of thermal radiation electromagnetic spectrum, from ultraviolet to far infrared (UV-far IR). The following sensors are being used: Total Ultraviolet Radiation Pyranometer (Model-Eppley TUVR), UVB-1 Ultraviolet Pyranometer (Model-Yankee), LI-190SA Quantum Sensor (Model-Licor), six LI -210 Photometric Sensor (Model-Licor), two Pyrgeometer (Model-Eppley PIR), four CM -6B piranometers (Model-Kipp & Zonen), four CM-11 pyranometers (Model Kipp & Zonen) and a Pyrheliometer (Model-Eppley NIP), for the measuring of the following variables respectively, total ultraviolet radiation, UVB radiation, photosynthetically active radiation, illumination, infrared radiation (upwards and downwards), vertical global radiation, horizontal and 42º tilted global and diffuse radiation and direct radiation, respectively. In addition, several sensors are being used for measuring other meteorological variables. An HMP35AC Temperature and Relative Humidity Probe (Model-Campbell), an ARG100 Rain Gauge (ModelCampbell), A100R anemometer (Model-Vector Instruments) and a W200P Potentiometer Wind Vane (Model-Vector Instruments) are used for recording temperature, relative humidity, rain, wind speed and wind

direction, respectively. The data acquisition system consists of two programmable dataloggers (CampbellCR23X) with transfer of data via an RS232 connection to a computer. Instantaneous readings are made every thirty seconds and averaged to provide readings every 10minutes and every hour, which are recorded by the datalogger. From the recorded data, the following applications have been made: evaluation of the diffuse solar radiation characteristic parameters of the Perez’ model on tilted surfaces, by means of the data from vertical and horizontal pyranometers; studies of parameterisation of the ultraviolet (TUVR pyranometer) and PAR (quantum sensor) solar radiation with global and diffuse solar radiation on horizontal surface; calculation of ultraviolet indices (UVB pyranometers) for the prevention of the effects that this radiation causes on human health; modelling of the infrared radiation for cloudless and cloudy skies from the global solar radiation, design of isoline maps of Castile and Leon data, (Spain), including solar radiation measured data from C.I.B.A. and other meteorological stations.

It is a single-phase photovoltaic solar installation which is connected to the grid. This type of installation is characterized by its connection in parallel to a point of the mains of low voltage and it works according to the circumstances like load or generator. The solar energy, when available, is transformed directly into electricity, which is provided to the grid, not existing any accumulation of energy. When the solar irradiation does not find threshold value, at night, the system is disconnected from the grid and is kept in waiting state. The data acquisition system was designed to operate automatically. Meteorological, input-output inverter and array parameters are monitored, at one minute sampling intervals. Average values are computed every ten minutes and every hour. In addition to data acquisition, the monitoring system entails independent measuring to record data of solar irradiance on array surface, of the DC power in each array field and of the 220 AC energy output.

Figure 2. - 4.3 kW grid-connected photovoltaic plant. The C.I.B.A. PV plant, is one of the first grid-connected systems in Castile and Leon region (Spain). Figure 3 shows the C.I.B.A. solar house whose characteristics are the following: Figure 1.-Meteorological and solar radiation station. From the recording data, different studies have been performed in order to train students in the task of solar resources evaluation. Figure 2 shows the grid-connected photovoltaic plant located at C.I.B.A. laboratory. The location has ideal characteristics for this type of solar systems, including low pollution as a result of being away from any urban area, and of having a large celestial surface and a high solar irradiation level. The photovoltaic plant consists of two arrays of 120 W monocrystalline silicon modules, ATERSA type, each one is connected to one inverter. The arrays are made up of 18 photovoltaic modules assembled in six parallel combinations, each of them contains three modules connected in series. The solar panels were installed with a tilt angle that can be varied. Two TAURO PRM 2000/3 inverters provide DC/AC power conversion.

Figure 3.-C.I.B.A. solar house

A 300 m2 building was designed taking into account bioclimatic principles and the needs of the laboratory. The laboratory intends to use passive solar and other energy saving techniques to provide thermal comfort and good daylighting. It is arranged along the east-west axis. The building is well insulated. Five bases of pebble bed, each of one fed by a Trombe wall (5.4 m2 and 20 cm thickness) and two windows (6.6 m2 ) have been used for the floor and walls. Trombe walls technology used is composed of a frontal wall of black chrome with double glazing of 4mm separated 6 mm. Trombe walls occupy 26,5 m2 (25%) of the south side of the house and the air can circulate by convection and in some cases, using electric fans. The surface with glass, 76.5 m2 , is distributed by the Trombe walls, windows and skylights. To prevent overheating, the window area and the Trombe walls have been protected with electric blinds. The house is monitored by temperature, humidity and heat flux sensors. The energy balance of the building can be evaluated from values of air temperature, degrees-day, day length and the information of the indoors sensors.. 5. SOFTWARE Software has been prepared in order to gain a detailed insight into the main important parameters of a solar system. The software has been used for training purposes as well, but the trainees will be well aware of the layout and the basis of the solar system. The software required: a) to implement a wider choice of models; b) to gather information to explain the design steps, the simulation procedures and the results interpretation: c) to implement new routines; d) to set-up tutorial procedures to guide the trainees through the design and simulation process. Software simulation about solar geometry, photovoltaic systems (panel power and I-V curves simulation software) and solar radiation on tilted surfaces have been performed. The software language was Visual basic 6,.and from the results students can plot the evaluation of the system and obtain results and conclusions from different variables by means of EXCELL, GRAPHER or MATLAB programmes. For more important computational requirements C language was used. In this work, the following software have been developed:

Figure 4. SOLPOSI software screen Figure 4 shows a screen of the SOLPOSI software where the characteristics of a place (Valladolid) can be seen: longitude, latitude, month, day and time. It can continue with the selection of options different, (day angle, declination, irradiance, irradiation, time, etc). 5.2 SOLCYL software Figure 5 shows the Castile and Leon map. It is the opening screen of the SOLCYL software which simulates daily solar global irradiation on tilted surfaces facing south in the region. It is carried out from hourly and daily global and diffuse horizontal solar irradiation values measured at different meteorological stations distributed over the region. Longitude, latitude, tilt angle and month may be introduced. From the data obtained, the evolution of solar radiation can be evaluated.

1. SOLPOSI 2. SOLCYL 3. LERPV 4. TRYPV 5. SOLTHERM 5.2 SOLPOSI software The software evaluates the solar angles, the time equation, local apparent time and the extraterrestrial solar irradiation being previously given the geographical and time characteristics of the place.

Figure 5.-Opening screen of SOLCYL program. 5.3 LERPV software Figure 6 is the opening screen of LERPV software, which simulates photovoltaic panel I-V curves in references conditions and any other. To use it, students

may introduce original panel specifications and the operation conditions to get IV curves. This program also simulates battery I-V curves in reference conditions or any other. PV panels model, (Lorenzo, 1994), has been used for simulation.

Figure 6. Opening screen of LERPV program. 5.4 TRYPV software Figure 7 shows the main screen of TRYPV software, which simulates PV panel output characteristics, in a certain place, from test reference year data. The output variables are current intensity, voltage and panel power. The inputs are: number of PV panels, maximum power, number of panels connected series, panel tilt, temperature coefficient, reference irradiance, reference temperature, number and azimuth of panels, station geographical characteristics.

out by this research group. The main page can be seen in Figure 8. This web page shows a Spanish version and an English version.

Figure 8. Main screen of the Renewable Energy Laboratory web page at Valladolid University (Spain) A section of this page is specially dedicated to the students, and the main educational activities of this group are shown, as well as information about different subjects related to the renewable energies. In addition other pages connections concerning the solar energy are offered. The different sections of the web page are: -Laboratory components; curricula of different subjects given by the teacher group; -Teaching group in graduate and postgraduate courses. -Description of the PV plant, located at C.I.B.A. site. -Developed Research Projects. -Doctoral thesis. -Publication at national and international level. -Congress attendance and papers presented in pdf format, technical reports and different links. 7. CONCLUSIONS

Figure 7 Opening screen of. TRYPV software 6. INTERNET The Renewable Energy Laboratory has a web page, http:/www.uva.es/renova to show the activities carried

In this paper the didactic contents and tools of training courses on Renewable Energies Technology, developed by the Laboratory of Renewable Energies at the University of Valladolid, have been assembled, explained and shown. In the last years, didactic models contents were analysed and prepared to be accessible for each target group. Experimental materials were performed in open-air experiments to study the PV system and meteorological and radiometric station with data logger was established. Experimental measurement results are published through Internet and web system. We are trying to show the results in real time by telemonitoring processes.

The authors collaborate at the I course of University Specialist at Renewable Energies, given at the Industrial Engineering Superior School of Valladolid University. It is offered to postgraduate students with a duration of 250 hours in a year. The course started at the beginning of 2003 and has been designed for engineers and scientist who have completed at least four years of academic education or for people with professional experience in the field of energy. The course will be offered in different modules of Renewable Energy specialities next year. At the sight of the established activities, it seems that the programmes for education in renewable energy (solar) are a good idea and produce a positive impact on environment. New projects for education at secondary school level will be performed Acknowledgements This work was supported by a grant Project number UV06/03 from the Department of Education and Culture, Autonomous Government of Castile and Leon region, (Spain) REFERENCES Blum K., Broman, L. and Gertzen J. (1996) Progress in Solar energy education. Proceedings of the 4 th International Symposium on Renewable energy education, December , Bangkok, Thailand, Volume 5.

Duffie J.A. and Beckman W.A. (1991) Solar Engineering of Thermal Processes, 2nd edn. pp. 54-59. Wiley Interscience, New York. Iqbal, M. (1983) An introduction to solar radiation. Academic Press. New York. Iskandr, Scerri, E. and Miles, J. (2000) Integrating renewable Energy Studies in under graduate curriculum: the IET/SAT experience. World Renewable Energy Congress VI (WREC2000),1-7 July. A.A.M. Sayigh (Eds), pp 2454-pergamen Press, New York.2457 Kumar, S. and Attalage, R.A. (2001). A Web based course for learning solar thermal processes. Energy program,. Asian Institute of Technology. Klong Luang. Thailandia. Lorenzo, E. (1994) Electridad solar. Ingeniería de los sistemas fotovoltaicos. Progensa, Sevilla,(Spain).