Renewable Energy Devices

Windfarm

The project comprises 2 fixed wind turbines to be located on top of the platform and a variable number of floating wind turbines which are located surrounding the platform, forming an array. The best configuration of the array has been calculated taking into account the turbulence that can be generated by turbines, as well as the least possible inter-array cable length, among other factors. The recommended distance between turbines is from 720 to 1600 meters in order to avoid turbulence. Regarding the mooring systems, each floating wind turbine have 3 mooring lines forming a radius of 600 to 1200 meters (Figure 1). Table 1 includes the basic characteristics of the specific wind turbine (Figure 2).

Figure 1. Windfarm arrangement (not in scale)

Wind Turbines – Siemens 6.0-154

Table 1. Siemens 6 MW [1]

Figure 2. Siemens 6 MW [1]

Considering the floating wind turbines, the floating substructure selected is spar-buoy, which is the same model as Statoil is planning to use for the Hywind Pilot Park, which will become the world’s first floating wind farm installed. The parts and dimensions of the floating unit are demonstrated in Figure 3.

Figure 3. Floating Wind Unit [2]

Wave Energy Converter

For the wave energy extraction the L-shaped Oscillating Water Column converters are used (Figure 4), embedded within the PSP Platform. The capacity of the wave energy system is 28.8 MW. As the platform is divided into modules, the capacity can be increased or decreased by increasing or decreasing the size of the platform. The integrated wave energy converters are based on the Float Incorporated design. They benefit from a predicted capacity coefficient of 41% and have no moving parts under the water.

Figure 4. Wave Energy Converter [3]

Wind Energy Production

Firstly, it must be taken into account that the area selected for the location of the project is considered an unexplored area, there are no references of other renewable energy related projects to have ever been developed on this site. For this reason, it is currently effectively impossible to obtain accurate and detailed data (i.e daily/hourly data) regarding wind speed (and other parameters). Hence, the calculations are made making several assumptions.

Site Data

Based on the data provided by the Crown Estate in form of maps, it can be concluded that the average wind speed of the site is 9.6-11.3 m/s [4].

In order to provide the calculations with some variation regarding the energy produced by turbine through each year, the wind speed range is weighted using the average UK monthly wind speed [5].

Siemens 6 MW Turbine [6]

Calculations

Power (W) = 0.5 * ρair * swept area * (rated speed)3 * Cp,

Where Cp is the capacity coefficient of the wind turbine.

Power (W) = 0.5 * 1.21 (kg/m3) * 18,600 m² * 13³ * Cp = 6 * 10⁶ W,

Therefore, C_p = 0.25 (It is assumed to be constant – while clearly this is a simplification it is a reasonable approach as this is predominantly to calculate an input for the cost assessment).

Therefore, the energy produced by turbine is 27,765 MWh/year and the Capacity coefficient = 27,765 / 6*8,760 = 53%. This value is before downtime, transmission and aerodynamic array losses. Including those, the final CC is 44%.

Wave Energy Production

The output for the wave energy device was estimated using information provided by Float Incorporated. In the prevailing wave climate of 30 to 40 kW/m of incident wave power, the device is rated at 4 MW/100m of frontal platform length. In the proposed configuration the platform is 720 m across and therefore the rated power is 28.8 MW.

In similar sea climates the averaged energy output over the year (capacity factor) is estimated to be 41% as the device uses three chambers, each tuned to a separate part of the wave spectrum.

The annual wave energy output is estimated to be 103,438 MWh/year, not accounting for availability losses which are estimated to be 90% due to the immaturity of the technology.