**5. Calculations**

To know the power generated by the turbines, we need to know the wind and the current speed, the surface area of the blades, the fluid density and the power coefficient, which varies with wind and current speed.

The equation that allows us to obtain the power has already been mentioned previously (3). For our wind speed values, results are presented on Table 3.


**Table 3.** Values of *Cp* according to chosen wind speeds.

The blade's surface area is given by *πr*2, 21,124 m2, where the radius of the surface is 82 m. The normally considered value of air density will be used in these calculations; 1.2225 Kg/m3. The power estimated for different wind speeds is presented on Table 4.

**Table 4.** Values of Power according to wind speed.


Calculating the energy produced during a year, a maintenance period of 15 days was considered when the turbines are not working. At rated power (8 MW), the energy produced would be 16,800 MWh a year. At average power (3.232 MW), the energy produced would be 11,946 MWh a year.

To know the power generated by the tidal turbines we use the same equation but with different data.

The power coefficient for the chosen tidal turbine is not known. Through a study of some different tidal turbines, it was estimated that the power coefficient would be approximately 0.4, and that is the value used in the calculations.

Tidal turbines are also significantly smaller than wind turbines, and because of that, the blade's surface area is also smaller, with a radius of 9 m and a surface area of 254,469 m2

For tidal turbines, the fluid considered is water, and the fluid density is 999 kg/m3. The power estimated for different wind speeds is on Table 5.


Calculating the energy produced during a year, a maintenance period of 15 days was considered when the turbines are not working. At rated power (1.5 MW), the energy produced would be 5040 MWh a year. At average power (175.746 kW), the energy produced would be 591 MWh a year.

#### *5.1. Simulations*

To simulate the proposed structure, where tidal and wind turbines will be installed, as well as piezoelectric materials, it is necessary to simulate some conditions such as wind flow and pressure around the structure.

A 3D model of the structure was constructed using Geometry tool provided by the software.

To make the process easier, the structure was built in parts, and then all the parts were joined as presented on Figure 3. The wind blade has been modeled in 3D and is only a geometric approximation of a real blade due to 3D design software limitations. The blade is 82 m long (actual length of the model Vestas V164-8.0). The tidal turbine was designed using the same base as the wind turbine blade. The tidal turbine is significantly shorter, with each blade just 9 m long, but it is wider and stronger. The floating platform used in the WindFloat project was also designed. Each pole is 30 m high, being 50 m apart. The main tower is 190 m high and joins all of the designed components.

**Figure 3.** Structure drawn using the software.

In order to proceed with the simulations, it is necessary to attribute materials to the designed structures. The structure is made of different materials, including being coated by anti-corrosion materials due to the corrosive effect of water and rain, but it is mainly composed of iron, so the material chosen for all of the structure was iron.
