# Energy Productivity Potential of Offshore Wind in Poland and Cooperation with Onshore Wind Farm
## 3 Results and Discussion  
Using Equation (2) and the ERA5 data, the wind speed for the Baltic Sea offshore area was determined. These results were matched with the hourly energy production achieved for onshore wind in Poland. The values thus obtained for the period 1 January 2022-31 December 2022 are shown in Figure 5.  
In the figure above, a relatively high convergence of values can be seen; the fit coefficient, R\({}^{2}\), is about 0.6. For wind speeds over the Baltic area higher than 12 m/s (rated power), the hourly energy production from the onshore turbine is higher than 1500 MWh in 99% of cases. Additionally, based on Equation (2), the wind speed was determined for Slawno city (Zachodnio Pomorskie vovodeship--Seaside district, 100 m above the ground, geographical coordinates: 54.25\({}^{\circ}\) N, 16.75\({}^{\circ}\) E) and for the Masovian region (central Poland 52.25\({}^{\circ}\) N 21.0\({}^{\circ}\) E). A comparison of wind speeds in the form of a ranked velocity diagram for the offshore Baltic Sea, Slawno and Masovian region is presented in Figure 6.  
For the Masovian region, 57% of the wind speed hours were lower than 6 m/s; for Slawno it was 41%, and for offshore it was 27%. For wind speeds in excess of 12 m/s for the offshore region, it was more than 2000 h, for Slawno it was 600 h and for the Masovian region it was only 250 h. By applying the results to hourly wind-specific yield, a comparison in the format of share of time ST was obtained (Figure 7). Figure 5: Onshore wind energy production as a function of offshore wind speed ws(B), Poland, 2022. Source: own calculation based on [14; 36]. An offshore-specific yield of more than 0.9 MWh/MW would have occurred in 36.0% of the hours, with about 1.2% onshore. In comparison, a productivity of less than 0.1 MWh/MW occurred for 22.1% of the hours in the analyzed period for onshore and 18.8% of the hours for offshore. The hourly productivity for onshore (real value, \(SY(P)\)) and offshore (from simulation, \(SY(B)\)) and the difference (\(dSY\)) between these productivities are depicted in Figure 8.  
The highest hourly productivity for offshore wind would occur in the first months of 2022. A similar situation occurred for onshore wind turbines. Significantly, the smallest differences in hourly productivity would occur in the summer of 2022. The results from Figure 8 aggregated to daily totals (based on Equations (4) and (6)) are depicted in Figure 9.  
In January and February, relatively high productivity was observed from the wind sources; in the following months, only occasionally high productivity was achieved, more often for offshore wind. The fit coefficient R\({}^{2}\) was 0.53. In addition, calculations were made for selected days in 2022. Sample energy production calculations (from onshore and offshore wind, and also photovoltaic) for 5 March 2022 and for 1 August are given in Figure 10.  
Figure 6: Distribution of hours with wind speed data in 2022 for Baltic sea: _ws(B)_, Slawno _ws(S)_ and Masovian Region _ws(M)_.  
Figure 7: Share of time \(ST\) in 2022 with ranges of specific yield from \(SY1\) to \(SY2\). Figure 8: Hourly value of: (**a**) real wind energy productivity for onshore wind _SY(P)_; (**b**) theoretical offshore wind energy productivity, _SY(B)_; (**c**) difference of wind offshore and onshore energy production—specific yield (_dSY_). Figure 9: Wind energy daily specific yield: offshore _SY(B)_ and onshore _SY(P)_, Poland 2022. On 1 August 2022, during the evening, the peak energy consumption (hours 18-22) and potential energy production from offshore wind would increase to complement the decreasing amount of energy production from solar PV (the amount would depend on the issue of scale--installed capacity). During this time, there was also a reduction in available power from onshore wind (from 795 MW to 636 MW). In addition, it was calculated that on that day, by 4 pm, the potential energy production from offshore wind would be zero (offshore wind speed values lower than cut-in speed).