# Potential of Onshore Wind Turbine Inertia in Decarbonising the Future Irish Energy System
## 5 Conclusions  
Increasing installed capacities of grid frequency converter connected generation units like WTs and PVs decreases synchronous inertia in energy systems. System inertia is an essential part of grid frequency stability. It limits the instantaneous ROCOF and limits the grid frequency nadir. The trend of decreasing system inertia is not reflected adequately in current unit commitment and economic dispatch models. If inertia in such models is considered at all, only synchronous inertia from fossil power plants is represented. This leads to increased CO\({}_{2}\) emissions, RES curtailment and system costs, since power systems require a minimum system inertia to maintain controllability of the grid frequency. While WTs are a key technology to decarbonise energy systems and a source for an synthetic inertial response, SI is not incorporated into energy system models. This work closes this research gap. The influence and potential of SI provision by WT on system indicators like CO\({}_{2}\) emissions, variable RES curtailment and system costs is \begin{table}
\begin{tabular}{l c c c c} \hline \hline
**Scenario** & **CO\({}_{2}\) Emissions** & **Reductiona** & **Curtailment** & **Reductiona** \\  & **[t]** & **[\%]** & **[MWh]** & **[\%]** \\ \hline Base & 4,789,225 & 0.00 & 2,613,969 & 0.00 \\ ROCOF = 1 Hz/s, \(H_{dem}\) = 3.5 s & 4,085,047 & 14.70 & 2,341,290 & 10.43 \\ ROCOF = 1 Hz/s, \(H_{dem}\) = 5 s & 4,066,117 & 15.10 & 2,341,290 & 10.43 \\ ROCOF = 2 Hz/s, \(H_{dem}\) = 3.5 s & 3,474,372 & 27.45 & 1,575,412 & 39.73 \\ ROCOF = 2 Hz/s, \(H_{dem}\) = 5 s & 3,305,005 & 30.99 & 1,570,872 & 39.90 \\ \hline \hline \end{tabular}  
* with respect to the base scenario.  
\end{table} 
Table 4: CO\({}_{2}\) emissions and curtailment results of the analysed scenarios. \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Scenario** & **System Costs** & **Reductiona** & **Cost Savingsa** & **for Provided SI** \\  & **[EURO]** & **[\%]** & **[EURO/kg\(\cdot\)m\({}^{2}\)]** \\ \hline Base & 737,265,818 & 0.00 & 0.00 \\ ROCOF = 1 Hz/s, \(H_{dem}\) = 3.5 s & 625,765,315 & 15.12 & 0.09 \\ ROCOF = 1 Hz/s, \(H_{dem}\) = 5 s & 622,733,455 & 15.53 & 0.06 \\ ROCOF = 2 Hz/s, \(H_{dem}\) = 3.5 s & 525,560,884 & 28.71 & 0.17 \\ ROCOF = 2 Hz/s, \(H_{dem}\) = 5 s & 496,034,635 & 32.72 & 0.14 \\ \hline \hline \end{tabular}  
* with respect to the base scenario.  
\end{table} 
Table 5: Overall system costs and cost savings with respect to the provided SI of the analysed scenarios. analysed. Therefore, a methodology to depict SI provision in dispatch optimisation problems is presented. The methodology is incorporated into an open source unit commitment and economic inertia dispatch modelling tool and applied to the all-Island Irish power system. Ireland today is already a power system, in which wind feed-in is curtailed due to low power system inertia and the grid operator has to react by defining an operational level for power system inertia. The model framework OpInMod creates minimum inertia constraints which have to be met by synchronous inertia sources and SI provided by WT. Data and the scenario researched are based on the 2020 DYNDP. Two parameters, the ROCOF threshold determining the needed minimum synchronous system inertia and the demanded inertia constant which determines the provided wind inertia are varied for analysis purpose. The result analysis shows that the introduction of SI provided by WTs results in the disconnection of fossil fuel fired power plants. The thereof missing inertia is replaced by the provided SI by WTs. Thus, less CO2 is emitted and costs decrease since WTs are a zero marginal cost source. Based on the analysed parameter combinations, up to 30.99% of the CO2 emissions can be saved due to the provision of SI by WTs. Curtailment reduction for the parameter combinations show similar results.