Francesco Papi

• Doctor of Engineering
• Post-Doc Researcher at University of Florence

This study investigates the aerodynamic and wake dynamics of floating wind turbines under the combined influence of platform motion and dynamic blade pitch control. Specifically, it focuses on the dynamic induction control strategy employed to mitigate wake losses in wind farms. A series of wind tunnel experiments were conducted using a scaled mode...

Research is flourishing on how to model, mitigate, or even try to exploit the complex motions floating offshore wind turbines (FOWTs) are subjected to due to the combined loading from wind, waves, currents, and buoyancy effects. While preliminary studies made use of simplified inflows to focus attention on blade-flow interaction, recent evidence su...

Floating offshore wind turbines represent a promising new technology in offshore renewables, but they are still in their early stages with few prototypes and limited performance data. As part of the NETTUNO research project, this study examines how platform movement affects the aerodynamics of a floating wind turbine rotor and connects its load res...

To ensure that stall control performs correctly in wind turbines making use of this logic, having accurate airfoil data near and post the stall limit is crucial. Due to the scarcity of experimental data, Computational Fluid Dynamics (CFD) simulations are increasingly used to this end, although modelling stall is critical due to the impact of turbul...

A correct estimation of fatigue and ultimate loads on the structure is key for wind turbine design and certification. In a greater perspective, wind turbines are large structures placed in the natural environment and are thus subject to environmental loads that are stochastic in nature. In the case of offshore turbines, the design space is even vas...

Accurate estimation of the oncoming wind is key to ensure an accurate control of any wind turbine. The wind speed is commonly measured with an anemometer located on the nacelle; hence, the measurement is influenced by the rotor and the nacelle itself and needs to be corrected so as not to incur inaccurate energy yield assessments. This study introd...

Stall regulation turbines still represent the preferred solution for small wind turbines. In stall-controlled rotors the controller plays a key role but, differently from pitch-based ones, no open-source controller was available to date. The study presents the UNICO (UNIfi research COntroller) controller, which has been specifically developed for v...

Blade element momentum (BEM) theory is the backbone of many industry-standard wind turbine aerodynamic models. To be applied to a broader set of engineering problems, BEM models have been extended since their inception and now include several empirical corrections. These models have benefitted from decades of development and refinement and have bee...

Floating offshore wind is widely considered to be a promising technology to harvest renewable energy in deep ocean waters and increase clean energy generation offshore. While evolving quickly from a technological point of view, floating offshore wind turbines (FOWTs) are challenging, as their performance and loads are governed by complex dynamics t...

To ensure a higher penetration of wind energy in local and national energy mixes, power variability induced by wind fluctuations needs to be limited. In this study, three power smoothing approaches are proposed and compared to the conventional unconstrained behavior. The first method makes use only of a state-of-the-art Li-Ion battery (BESS), while...

To realize the projected increase in worldwide demand for floating offshore wind, numerical simulation tools must capture the relevant physics with a high level of detail while being numerically efficient. This allows engineers to have better designs based on more accurate predictions of the design driving loads, potentially enabling an economic br...

Aeroelasticity is recognized as the key enabler that allowed for the massive upscaling of wind turbines in the last decade, leading to long, slender, and flexible blades that equip rotors with lower specific power and unprecedented energy conversion capabilities. In this study, a selection of case studies with increasing size, specifically the NREL...

This study reports the results of the second round of analyses of the Offshore Code Comparison, Collaboration, Continued, with Correlation and unCertainty (OC6) project Phase III. While the first round investigated rotor aerodynamic loading, here, focus is given to the wake behavior of a floating wind turbine under large motion. Wind tunnel experim...

In the case of floating wind turbines (FOWTs), international design standards currently leave a larger degree of freedom to engineers in the specification of the boundary conditions for turbine simulation and certification. This is due to fact that FOWTs are still a young technology, and standards are still evolving. To analyze offshore wind turbin...

As research and industrial interests around FOWTs has grown, an aspect that has recently emerged is the fact that, because a floating foundation is inherently more compliant than a fixed one, in many instances tower resonance frequencies are effectively shifted upwards. While onshore wind turbine towers are typically designed with a soft-stiff appr...

To realize the projected increase in world-wide demand for floating offshore wind, numerical simulation tools must capture the relevant physics with a high level of detail while being numerically efficient. This allows engineers to have better designs based on more accurate predictions of the design driving loads, potentially enabling an economic b...

Blade Element Momentum (BEM) theory is the backbone of many industry-standard wind turbine aerodynamic models. To be applied to a broader set of engineering problems, BEM models have been extended since their inception and now include several empirical corrections. These models have benefitted from decades of development and refinement and have bee...

Consensus is arising on considering floating offshore wind as the most promising technologies to increase renewable energy generation offshore. While evolving fast from a technological point of view, Floating Offshore Wind Turbines (FOWTs) are challenging, as their performance and loads are governed by complex dynamics that are a result of the coup...

The deployment of multiple closely-spaced Darrieus turbines has recently gained interest in the academic and industrial sectors due to their potential to increase power output and wake recovery. However, the computational cost of accurate three-dimensional, blade-resolved CFD analyses rapidly becomes unfeasible as long as multiple rotors are added,...

This paper provides a summary of the work done within Phase III of the Offshore Code Comparison Collaboration, Continued, with Correlation and unCertainty (OC6) project, under the International Energy Agency Wind Technology Collaboration Programme Task 30. This phase focused on validating the aerodynamic loading on a wind turbine rotor undergoing l...

This study reports the results of the second round of analyses of the OC6 project Phase III. While the first round investigated rotor aerodynamic loading, here focus is given to the wake behavior of a floating wind turbine under large motion. Wind tunnel experimental data from the UNsteady Aerodynamics for FLOating Wind (UNAFLOW) project are compar...

The present study investigates the feasibility of coupling the intermittent electric power generation from a wind farm with alkaline electrolyzers to produce green hydrogen. A physically accurate model of commercial electrolytic modules has been first developed, accounting for conversion efficiency drop due to modules’ cool down, effects of shutdow...

Offshore wind turbines are subject not only to varying wind conditions during their lifetime, but also sea conditions. Therefore, in addition to wind speed, other sea-related quantities need to be considered to characterize a specific installation site. International standards suggest that, at a minimum, significant wave height, peak spectral perio...

In the study, an extended sensitivity analysis is presented, which was aimed at properly tuning the parameters of an algorithm based on the Discrete Wavelet Transform (DWT) for use in power smoothing of utility-scale wind turbines coupled with batteries. More specifically, a twofold implementation is proposed, so that the proposed algorithm can ope...

Small wind turbines (SWTs) have known alternate fortune but can now play a key role in distributed production to foster energy transition. Among the typical features of small machines, the use of stall regulation is a distinctive one, since the ubiquitous variable speed pitch regulation used in utility-scale rotors is hampered by space constraints...

In work package 2 of the FLOATECH project a detailed validation and verification of the capabilities of QBlade-Ocean is carried out. A detailed description of the models used in the validation is provided in Deliverable 2.1 and results of the validation that was carried out are presented in Deliverable 2.2. Some modifications to the models used in...

While most wind energy comes today from utility-scale machines, small wind turbines SWTs can still play a role in off-grid installations or in the context of distributed production and smart energy systems. Due to cost reasons, SWTs (especially up to 100kW) are usually controlled via progressive stall of the blades. Accurate airfoils polars are the...

This report constitutes deliverable 2.2 of the FLOATECH project, funded under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101007142. For the detailed validation and verification of the capabilities of QBlade-Ocean in work package 2 (WP2) of FLOATECH, a detailed definition of the three considered mod...

This paper provides a summary of the work done within Phase III of the Offshore Code Comparison, Collaboration, Continued, with Correlation and unCertainty project (OC6), under International Energy Agency Wind Task 30. This phase focused on validating the aerodynamic loading on a wind turbine rotor undergoing large motion caused by a floating suppo...

Upscaling is currently seen as one of the most promising techniques to lower the Levelized Cost of Energy of wind farms and is a trend that has been ongoing for many years. Floating wind turbines are still a quite novel technology. In this kind of application, the benefits of upscaling are potentially even greater than those that can be seen in lan...

Large, highly flexible wind turbines of the new generation will make designers face un-precedent challenges, mainly connected to their huge dimensions. To tackle these challenges, it is commonly acknowledged that design tools must evolve in the direction of both improving their accuracy and turning into holistic, multiphysics tools. Furthermore, th...

Leading edge erosion of wind turbine blades is still an important challenge for wind energy professionals, both at research and industrial level. While the efficiency and durability of materials and coatings are improving rapidly, it is important to explore innovative solutions at the aerodynamic design level to mitigate the adverse effects of surf...

Reliable predictions of the aero- and hydrodynamic loads of fixed-bottom and floating offshore wind turbines are paramount for assessing fatigue life and designing load and power control systems. However, significant uncertainty affecting aerodynamic predictions still exists. This study presents cross-comparative analyses of the predictions of aero...

The exponential reduction in cost of photovoltaic panels and the forecasts projecting a similar behaviour for battery-based energy storage systems are driving increasing attention on residential energy systems based on photovoltaic (PV) panels and batteries. Such systems, if combined with demand electrification, could help decarbonising the sector...

As wind turbine technology proceeds towards the development of more advanced and complex machines, modelling tools with fidelity higher than the ubiquitous Blade Element Momentum (BEM) method are needed. Among them, the Actuator Line Method (ALM) stands out in terms of accuracy and computational cost. Moving from this background, an advanced ALM me...

Energy Storage Systems (EES) are key to further increase the penetration in energy grids of intermittent renewable energy sources, such as wind, by smoothing out power fluctuations. In order this to be economically feasible; however, the ESS need to be sized correctly and managed efficiently. In the study, the use of discrete wavelet transform (Dau...

While most wind energy comes from large utility-scale machines, small wind turbines (SWTs) can still play a role in off-grid installations or in the context of distributed production and smart energy systems. Over the years, these small machines have not received the same level of aerodynamic refinement of their larger counterparts, resulting in a...

Wind Energy is substantially growing in recent years and is now one of the most competitive renewable energy sources on the market. To further foster the growth of this energy source, increasing effort is put into building accurate numerical models. Most models compute the loads acting on the turbine as a dependence of some sort to the angle of att...

Wind turbine blade erosion has risen to the attention of researchers and industry lately in an effort to keep ageing wind farms productive. Although not new, erosion-related blade damage seems to be more severe in recent, particularly off-shore, installations. With the high blade-tip speeds of modern wind turbines, installation in rainy locations c...

Wind turbines operate in challenging environmental conditions. In hot and dusty climates, blades are constantly exposed to abrasive particles that, according to many field reports, cause significant damages to the leading edge. On the other hand, in cold climates similar effects can be caused by prolonged exposure to hail and rain. Quantifying the...

Wind turbines often operate in challenging environmental conditions. In hot and dusty climates, wind turbine blades are constantly exposed to abrasive particles that, according to many field reports, cause significant damages to the blade’s leading edge. On the other hand, in cold climates similar effects can be caused by prolonged exposure to hail...

Wind turbines operate in all sorts of weather conditions around the globe, exploiting installation sites with high power production potential. These machines operate within the atmospheric boundary layer and are therefore subject to impacts with rain, hail dust particles and insects, often leading to rapid blade deterioration and performance drops....

Wind turbine blade deterioration issues have come to the attention of researchers and manufacturers due to the relevant impact they can have on the actual annual energy production (AEP). Research has shown how after prolonged exposure to hail, rain, insects or other abrasive particles, the outer surface of wind turbine blades deteriorates. This lea...

Load calculations play a key role in determining the design loads of different wind turbine components. To obtain the aerodynamic loads for these calculations, the industry relies heavily on the Blade Element Momentum (BEM) theory. BEM methods use several engineering correction models to capture the aerodynamic phenomena present in Design Load Case...

Load calculations play a key role in determining the design loads of different wind turbine components. State of the art in the industry is to use the Blade Element Momentum (BEM) theory to calculate the aerodynamic loads. Due to their simplifying assumptions of the rotor aerodynamics, BEM methods have to rely on several engineering correction mode...