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.

Knowledge and understanding:

The student is able to understand the physical working principle and main industrial manufacturing processes of a renewable technology. 

The student is able to assess the potential energy production and costs of a renewable source.

The student is able to understand the energy and environmental balance of power plant plant based on a renewable source, taking into account its environmental impact and avoided emissions and energy saving in a LCA perspective.

The student is able to understand the part load operation of a renewable plant, and to evaluate the main performance indexes related to an annual operation.

Applying knowledge and understanding:

The student is able to make a preliminary design of a power plant based on a renewable source, assessing both its economic feasibility and environmental benefits, in terms of avoided emmissions and energy saving.

The student is able to correctly operate a renewable plant in terms of optimized schedule and forecasting, dispatching electricity and maintenance operations.

Making judgements:

The student is able to autonomously manage the design choices concerning the construction and operation of renewable source plants.

Communication skills:

The student is able to communicate the results of his / her activity in a clear and effective way.

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. Adopted incentive schemes. 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. Small and micro-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-of-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 knowledge of the system configurations and the operating principles of the main power cycles fed by fossil fuels is fundamental. These concepts are provided by the Conversion of energy / Energy conversion (energy students) and Energy Systems LM (mechanical students) courses.

The course is organized in lectures and tutorials. Design of plants are also proposed on different technologies. The exercises are functional to the understanding of topics and to the preparation of the exam (the ability to solve the proposed exercises is a necessary but not sufficient condition for passing the exam).

The exam consists of two tests: a written test (duration 90 minutes) that is a practical test based on two numerical problems and a theoretical written test based on 4 open-ended questions (duration 60 minutes). The final mark will result as a weighted average between the practical (60%) and theoretical part (40%). The two tests can be carried out on two separates dates within the same Academic Year. To proceed to the theoretical exam an evaluation equal/above 16/30 is mandatory.

There is the opportunity (optional) to carry out specific projects on selected topics in the form of work groups which will be evaluated and will contribute to the final grade (max 3 points of increase on the final mark).

The two tests aims to ascertain the degree of understanding of the fundamental aspects of the course, from the theoretical working principle of the various renewable technologies, to the operating strategy of a plant in off-design conditions, the forecast of its annual energy output, the evaluation of the environmental balance and the economic assessment of an investment. In particular the written test will aim at evaluating student's ability in the calculation and preliminary design of renewable power plants, assessing the electricity production, economic feasibility and environmental benefits, in terms of avoided emissions and energy saving. The theoretical test will aim at evaluating the understanding of the physical concepts underlying their design and operation.