# The Potential for the Use of Hydrogen Storage in Energy Cooperatives
## 4 Results and Discussion  
The above shape of energy cooperatives EC1-EC4 underwent nine types of simulation using:* breakdown by source type (PV, WIND, MIX),
* different variants of the cooperative:
* CASE_0: a conventional cooperative connected to a grid and using a virtual network storage in the discount model,
* CASE_1A: a cooperative with a hydrogen storage with the minimum capacities of generating sources,
* CASE_1B: a cooperative with a hydrogen storage with the minimum storage capacity. Table 3 shows scenarios for the optimal selection of source capacity and storage capacity for each variant of cooperative EC1. A visualization of the data contained in Table 3 can be found in Figure 2 (below the table). The results obtained by simulation and presented in Table 3 can be interpreted as follows: \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**CASE**} & \multirow{2}{*}{**PV**} & \multicolumn{2}{c}{**MIX**} & \multicolumn{2}{c}{**PV**} & \multicolumn{2}{c}{**WIND**} & \multirow{2}{*}{**MSC**} \\  & & **WIND** & **MSC** & **PV** & **WIND** & **MSC** & **PV** & **WIND** & **MSC** \\  & & **kW** & **MWh** & & **kW** & **MWh** & & **kW** & **MWh** \\ \hline
0 & 9.970 & 27.344 & 5.167 & 44.288 & 0 & 11.759 & 0 & 39.412 & 6.013 \\
1A & 11.855 & 35.896 & 12.101 & 69.873 & 0 & 26.770 & 0 & 53.238 & 12.713 \\
1B & 25.33 & 66.235 & 1.326 & 92.016 & 0 & 19.019 & 0 & 81.005 & 2.890 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Scenario-based characteristics of the selection of the type and capacity of generating sources and the storage capacity in EC1. Figure 2: Visualization based on the data of Table 3.  
* CASE_0: When PV modules were the only type of source used, the conventional cooperative had a total installed capacity of 44.288 kW and the maximum accumulated surplus electricity (accumulated in the operator's grid) reached 11.759 MWh. * CASE_1A: When a virtual (grid) storage was replaced with a hydrogen storage, the calculation was based on the power-to-power chain [59] with a final efficiency of 29% and on the assumption that the cooperative seeks to minimize the capacity of the sources while meeting the condition of energy self-sufficiency [60]. Then the total installed PV capacity will be 69.873 kW, and the maximum filling in the hydrogen storage will reach 26.77 MWh. * CASE_1B: Energy independence of a cooperative is achieved while meeting the criterion of minimum hydrogen storage capacity. In this case, the capacity of the installed PV sources is 92.016 kW, and the storage capacity will reach 19.019 MWh. An analysis of the results leads to the following conclusions:
* From the perspective of the cooperative's energy balance, it is possible to achieve energy independence by replacing the virtual energy storage in the distribution network by a hydrogen storage fitted with an electrolyzer. This requires oversizing the capacity of the generating source and the storage. For the scenario analyzed based on PV sources, we need to increase the power capacity (CASE_1A/CASE_0) from 44.288 kW to 69.873 kW (by 58%) and storage capacity from 11.759 MWh to 26.77 MWh (by 128%). The need to oversize the capacity of the sources and the storage capacity was also confirmed through simulation carried out at the level of cooperatives of different sizes and random participants. The relationship of the change of energy storage capacity [%] as a function of mean yearly demand [MWh] for CASE_1A vs. CASE_0 is shown in Figure 3 along with the quantiles shown in Table 4. A single point in Figure 1 is the result of one computing session. Depending on the type of generating source and the size of cooperative, we can observe different levels of concentration and symmetry of results, and the higher the number of members within a single cooperative, the greater the symmetry and level of concentration of results. For instance, for a scenario with PV sources and 40 cooperative members, the criterion specified in CASE_1A is satisfied when storage capacity is increased by around 209% on average.