This course deals with 3 renewable technologies for power generation: wind, hydro and geothermal energy. The course is dedicated to students with a thorough knowledge of energy issues, in fact the approach to topics is mainly theoretical, in order to understand the physical principles that are at the basis of operation of the different technologies. It discusses technological aspects related to the regulation and operation of power plants, as well as those related to the environmental impact and the economics. The course will provide the students with the technical skills to operate in the field of wind, hydroelectric and geothermal plants: from decision-making skills required during the design stage, like the preliminary evaluation of the renewable resource, the power plant yield and the business plan drafting, to the technical knowledge related to the operation and maintenance of plants, like regulation strategy, system optimization, dispatchability and forecasting together with strategic aspects.

Knowledge and understanding:

The student is able to understand the physical working principle and main industrial manufacturing processes of wind, hydroelectric and geothermal plants. 

The student is able to assess the potential energy production and costs of a wind (both on-shore and off-shore), hydroelectric and geothermal plant.

The student is able to understand the energy and environmental balance of power plants based on wind, hydro and geothermal energy, taking into account their environmental impact, avoided emissions and energy saving in a LCA perspective.

The student is able to understand the part load regulation of a power 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 wind, hydro and geothermal energy, assessing both its economic feasibility and environmental benefits, in terms of avoided emissions 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 wind, hydroelectric and geothermal plants.

Communication skills:

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

Wind energy. Betz theory and laws of operation, types of machines, applications. Sizing criteria, plant regulation and characteristic curves. Velocity triangles on a blade profile. Types of electric generators. Drivetrain configurations: gearbox based and direct drive solutions. Regulation strategies, generator technologies and power electronics for rotor speed control. Behavior of the machine under dynamic wind load. Anemometry and characterization of the wind resource of a site, analysis and profitability of a wind farm. Environmental impact of wind power installations. Off-shore wind turbines: characteristics, foundations, electric connections, construction of a wind farm, operation and maintenance issues, floating installations. Small and micro-wind: characteristics and main differences compared to multi-MW commercial wind turbines. Off-grid installations.

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, hybrid configurations. ORC cycles for medium and low enthalpy geothermal applications. Plants coupled to other renewable energy sources. Cogeneration plants feeding district heating networks. Thermal applications and geothermal heat pumps. Design aspects, issues related to geothermal fluids and environmental impact. Purification of gaseous pollutants.

Hydroelectric plants. Classification and plant layout: weir integrated plants and headwater diversion channel, run of river and storage plants. Types of hydraulic machines: Pelton, Francis, Kaplan, Turgo, Crossflow, Archimedean screw, Very Low Head Turbine. Intake systems, dams and weirs, sizing of the penstocks and main components of a plant. Typical layout of hydroelectric installations on rivers, channels and water supply systems. Pumped-Storage Hydroelectricity (PSH): strategic importance, design criteria, operating mode and economic assessment. Flow rate measurement, assessment of hydraulic resource and energy potential, technical-economic optimization of the plant. Small-hydro: future potential of the resource. Design criteria of a run-of-river small hydroelectric plant. Advantages of variable speed regulation. Environmental impact of hydroelectric plants. Operation, maintenance and control system.

The knowledge of the system configurations and the operating principles of the main power cycles fed by fossil fuels is fundamental for the Geothermal energy section. 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 exam consists of two parts: an oral test (approximate duration 30 minutes) and the evaluation of a group work (3-4 people) on selected topics that will be proposed through the course. The final mark will result as a weighted average between the oral test (70%) and the group work (30%). The evaluation of group works will consist on a discussion that will take place in two separate dates at the end of the course (will be communicated on time). The oral test can be carried out at most twice within the same Academic Year.

The oral test aims to ascertain the degree of understanding of the fundamental aspects of the course, from the theoretical working principle of the various treated 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. One or more questions of the oral exam may focus on topics covered during the tutorials.