After passing the exam, the students will acquire the following knowledge: - the main technologies to directly convert solar energy into electricity by photovoltaic generators (from the solar cells to the PV arrays with the proper protections); - the main technologies to convert DC power into AC power with optimal efficiency (including general aspects of power electronics) to obtain grid-connected PV systems; - the main technologies about the wind energy generators and plants; - the state of the art and perspective in the market of wind energy plants. Then, the students will acquire the following skills and abilities: - the calculation of the evolution of the electrical parameters and the energy production, according to the variations of solar irradiance and cell temperature; - the assessment of the reverse voltages and reverse currents in the case of current-voltage mismatch in a PV array; - the correct choice of the main components (PV generator and inverter) for the system design; - the setup of the experimental test for verifying the actual performance of PV generators and inverters; - the calculation of productivity, efficiency and the main techno-economic indexes of wind power systems; - the correct design and sizing of the main components in the plants, given their specific requirements.

Basic knowledge about electric circuit theory (electrical circuit analysis) and applied mechanics.

Lectures (about 51 h) Summary of electric circuit theory. State of the art in Photovoltaic (PV) technologies: general advantages and drawbacks; manufacturing process of crystalline silicon solar cells; thin film technologies and high-efficiency technologies; configurations and tasks of power conditioning units (inverters). Structure of the semiconductors: energy bands; doping with electron/hole; p-n junction, diffusion and electric field; losses in the energy conversion; spectral response and efficiency of the main technologies. The current-voltage characteristic curve (I-V curve) and the equivalent circuit of the solar cell; dependence on irradiance and temperature; profiles of meteorological and electrical quantities under clear sky conditions. Focus on an application problem: series/parallel connection of real cells; mismatch of their I-V curves due to production tolerance, defects and shading effect; hot spots and breakdown; bypass and blocking diodes. Structure of a PV module; datasheets of the commercial PV modules; qualification tests to simulate accelerated ageing; detection of faults by thermography and electroluminescence imaging. Unconventional aspects of PV generators with respect to the voltage sources; use of fuses in large PV plants; use of blocking diode in case of reverse current in a shaded string; the designer issue in case of partial shading of strings (concentrated and equally distributed shadings). The usage of transistors in DC-AC converters; PWM modulation and H-bridge voltage source inverter; paths of current with positive, negative and zero output voltage; active/reactive power control for grid connection; Maximum Power Point Tracking (MPPT); technical specifications of commercial inverters. Conventional calculation of energy production: evaluation of solar radiation, loss sources in the productivity. An innovative procedure to assess the energy production: automatic data acquisition systems, experimental tests and results on operating PV plants; economic analysis by the Net Present Value (NPV) method. Cost of energy production. Summary about the stand-alone and grid-connected PV plants equipped with electrochemical batteries. Wind resource characterization, global and local availability. Wind generation, measurement of speed, space and time distribution, gusts. Evaluation of wind potential, Betz theory. Wind turbine: historical evolution, horizontal axis and vertical axis layouts. Bladeless wind energy systems. Turbine main components and subsystems. Blades and turbine aerodynamics characterization, coefficients of lift/drag and coefficient of thrust, stall conditions, basics of aeroelasticity, flutter. Mechanical limitations, static and fatigue loads. Mathematical modeling and experiments. Generator control, tip speed ratio control, speed and torque limitation, power shedding. Turbine wake, Wind farm layout. Electrical systems: structure and operation of synchronous and induction (asynchronous) machines, equivalent circuit and integration in the variable speed drives by power electronics, a solution for variable speed wind turbines: the doubly-fed induction generator. Ideal calculation of energy production for a single wind turbine by the manufacturer power curve, issues affecting the real energy production: wake and park effects, failure rate and reliability, deviations from the manufacturer power curve, power losses consequent to grid connection and curtailment in case of power frequency issues.

The course is organized with 51 h of lectures (above described) and 29 h of classroom exercises, laboratories and guided tours. Classroom exercises for a total of about 20 h, starting from a summary of electric circuits. 1) Usage of PVGIS software for solar radiation and PV energy estimation. 2) Calculation of the electrical parameters of the PV modules in conditions different from the rated STC by datasheet of the manufacturers. 3) Calculation of reverse voltage across the terminals of a shaded cell in a string subject to mismatch and calculation of reverse current in a shaded string supplied by irradiated strings. 4) Optimal coupling between PV array and inverter: constraints of power/voltage/current from MPPT. 5) Calculation of the energy production in a PV system from SO-DA database. 6) Simulation of integration of electrochemical storage to increase the self-sufficiency of active users. 7) Elaboration of wind data from free databases, evaluation of resource potential, extreme events. 8) Simulation of a wind turbine and farm, assessment of energy production and farm layout. 9) Usage of equivalent circuits for synchronous and induction machines to calculate powers and efficiencies. 10) Calculation of power losses inside distribution transformers and lines. Laboratories and guided tours for a total of about 9 h: 1) Measurement of the I-V curve of a diode by digital multimeters. 2) Familiarization with oscilloscope and function generator. 3) Measurement of the I-V curve of a PV module by digital storage oscilloscope. 4) Measurement of the output characteristics by digital multimeters for a transistor operating as a switch . 5) Measurement of efficiency and power quality for single-phase inverter by automatic data acquisition system. 6) Guided tour to the PV plants operating inside the Politecnico di Torino headquarter.

Teaching documents (handouts on photovoltaic power systems and slides on the lectures) on the POLITO portal of the teacher. For deepening, it is suggested to read the books: - T. Markvart, Solar Electricity, 2nd Edition, 2000, J. Wiley and Sons Ltd., USA; - J. F. Manwell, J. G. McGowan, A. L. Rogers, Wind Energy Explained: Theory, Design and Application, 2nd Edition, 2010, J. Wiley and Sons Ltd., USA; - M. Patel, Wind and Solar Power Systems, 2006, CRC Press, USA.

Exam: Written test;

The written test lasts 1 h and consists of two theoretical questions regarding the knowledge of multiple topics (each one with 10 points) and one exercise regarding the skills and abilities of the "Expected Learning Outcomes" (10 points), like the sample written tests on the portal. The theoretical questions for a total of 20 points require short discussions, drawings and formulas, while the numerical exercise regards the skills and abilities acquired during the classroom exercises for a total of 10 points. The exam is passed if the students reach 18 points as a summation of the scores in the two theoretical questions and in the exercise, without any constraint regarding a minimum score in each of the three parts accounting for 10 points. The "30/30 cum laude" grade can be obtained only if the exam commission, with mark of 30/30, decides to ask a specific oral question about the content of the written test and the student responds in an effective way to that oral question. It is possible to use a pocket electronic calculator, but it is not permitted to use handouts or notes regarding the program of the course. NO oral test is possible to improve the grade, the mark is automatically registered. The space at disposal for the answers, on the single sheet of the written exam (front and back sides), is limited to test the ability of the student to summarize the concepts.

In addition to the message sent by the online system, students with disabilities or Specific Learning Disorders (SLD) are invited to directly inform the professor in charge of the course about the special arrangements for the exam that have been agreed with the Special Needs Unit. The professor has to be informed at least one week before the beginning of the examination session in order to provide students with the most suitable arrangements for each specific type of exam.