This course is dedicated to students with a thorough knowledge of energy issues, and it aims at explaining the various technologies available for the production of electricity from renewable sources. The course deals with a topic of great interest and relevance, from the technical and engineering point of view: producing electricity from renewable sources is becoming increasingly important in a short-medium term scenario, characterized by the need to drastically reduce greenhouse gases and dependence on fossil fuels. The approach to topics is primarily theoretical, in order to understand the physical principles that are at the basis of operation of the different technologies. It also discusses some technological aspects more closely linked to the industrial manufacturing processes, together with the associated economic, managerial, strategic, as well as those related to the environmental impact. The course will provide the students with the technical skills to operate in the field of power plants fed by renewable sources: from decision-making skills required in the design phase, to the technical knowledge related to the operation and maintenance of plants.

Description of topics

Introduction and perspectives. The potential of renewable energy. Classification of sources and typical problems related to their exploitation for the production of electricity on an industrial scale. Incentive schemes adopted. Current situation and forecast scenarios.

Wind energy. Betz theory and laws of operation, types of machines, applications. Sizing criteria, plant regulation and characteristic curves. Coupling with the generator, power electronics for rotor speed control. Characterization of the wind resource of a site, analysis and profitability of a wind farm. Environmental impact of wind power installations. Off-shore wind farms. Mini-wind.

Geothermal energy. Classification of geothermal sources: liquid and vapor-dominated hydrothermal source, hot dry rocks. Exploration techniques and drilling. Adoptable power plants: direct steam cycle, plant with flash and separation of steam, binary ORC cycles. Cogeneration plants. Design aspects, issues related to geothermal fluids and environmental impact.

Energy from biomass. Classification of biomass and future potential. Conversion systems with grate boilers: water steam cycles and ORC. Flue gas treatment systems. Anaerobic digestion for biogas production. LCA analysis applied to the cycle of biomass.

Solar energy. Solar radiation: characteristic angles and the solar spectrum. Instruments for measuring radiation.

Photovoltaic solar energy : the photoelectric effect, processes for silicon production and photovoltaic cell manufacturing, electrical characteristic of the cell and circuit connection, inverter and power conditioning systems. Design criteria for off-grid and grid-connected plants. Thin-film and multi-junction cells, recent technological developments. Concentrating photovoltaic.

Concentrating solar power: classification of concentrating systems. Parabolic-trough collectors, parabolic dish systems, Fresnel collectors, central receiver systems. Thermal performance of a collector, selective coatings. Heat transfer fluids and thermal storage tanks. Sizing of a solar power plant. Operating strategy of a plant and estimation of the yearly production.

Energy from small-hydro plants. Classification of plants and hydraulic machines. Future potential of the resource. Design criteria of a run-off-river hydroelectric plant, regulation. Environmental impact.

Energy from the sea. Introduction to the classification of available technologies or pre-commercial devices: energy from currents, wave, tidal, systems based on the thermal gradient of oceans (OTEC). Integration with desalination plants.

The course is organized in lectures and tutorials. Design of plants are also proposed on different technologies. The exercises are functional to the production of an optional elaborate, to be made through team work, consisting of reports on the proposed themes.

The exam consists of two tests: a written test that is a practical test based on numerical problems and a theoretical written test.

There is the opportunity (optional) to carry out specific projects on selected topics which will be evaluated and will contribute to the final grade.