## 4 Case Study
### Results and Analysis
#### 4.2.2 Economic Analysis in Different Energy Storage Modes  
In order to compare and analyze the economics of the RIES under different energy storage modes, this paper divides the energy storage mode into the following three types:  
Type 1: Single energy storage mode (EES, TES, GES);  
Type 2: Dual energy storage mode (EES-TES, EES-GES, TES-GES);  
Type 3: Integrated energy storage mode (EES-TES-GES). The costs of the RIES in different types under the grid-connected mode are shown in Table 6.  
Figure 4: (**a**) Electrical output of equipment in off-grid mode; (**b**) Electrical output of equipment in grid-connected mode; (**c**) Heat output of equipment in off-grid mode; (**d**) Heat output of equipment in grid-connected mode;(**e**) Gas output of equipment in off-grid mode; (**f**) Gas output of equipment in off-grid mode. As shown in Table 6, for the single energy storage mode, although configuration cost was higher for the EES mode, the system operating cost was the lowest at this time, and the interaction profit with the grid was the largest, so the total cost was the lowest compared with the TES and the GES mode. It shows that the electric energy is stored directly in the power storage system and is transferred to the peak of power consumption, which has better economics than converting into heat and gas energy. The total costs of configuring the dual energy storage were lower than the single energy storage mode. Furthermore, the configuration of EES-TES was the most economical solution. The configuration scheme that the system adopts, the EES-TES-GES integrated energy storage, has the optimal economy compared with the other two types of schemes. However, the energy storage configuration cost increased, and the operating cost was the lowest, and the interaction benefit with the grid was the highest. To further illustrate, the output of each energy storage device in the EES-TES-GES integrated energy storage mode is shown in Figure 5.  
It can be seen from Figure 5, when the wind power was high, the system preferentially sells electricity to the grid, and the remaining electric energy was stored by the electric energy storage. The EES can release the electric energy stored to reduce the power generation costs and gas purchase costs of the MT during the peak of the electric load consumption. The EES plays a role in peak shaving. At 19-24 h and 1-5 h, the TES output increased due to the high heat load. During the daytime, the heat load is relatively stable and the electric load demand increases, the TES can store the heat energy produced by MT and other equipment. The GES mainly supplies/stores gas according to the value of the gas load. During the 1-5 h abandonment period, P2G consumed electric energy to generate natural gas. At this time, the gas load is small, the GES can store natural gas, so the purchased natural gas is reduced. GES supply gas during the peak of gas consumption in the daytime. In summary, under the integrated energy storage mode, each storage energy worked mostly in the peak period of \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Type** & \(\mathbf{C_{\text{inv}}}\)**/**yuan** & \begin{tabular}{c} **Gas** \\ **Costs\({}^{1}\)/yuan** \\ \end{tabular} & \
\begin{tabular}{c} **Power** \\ **Costs\({}^{2}\)/yuan** \\ \end{tabular} & \(\mathbf{C_{\text{op}}}\)/**yuan** &
\begin{tabular}{c} **Total** \\ **Costs/yuan** \\ \end{tabular} \\ \hline EES & 35.48 & 2428.6 & \(-\)501 & 2195.06 & 2230.5 \\ TES & 4.44 & 2449.2 & \(-\)490.2 & 2254.10 & 2258.5 \\ GES & 3.15 & 2428.1 & \(-\)468 & 2310.54 & 2313.6 \\ EES-TES & 37.25 & 2428.0 & \(-\)510.4 & 2150.03 & 2187.2 \\ EES-GES & 31.2 & 2428.9 & \(-\)503 & 2185.42 & 2216.6 \\ TES-GES & 7.45 & 2428.3 & \(-\)485 & 2236.21 & 2243.6 \\ EES-TES-GES & 41.29 & 2427.7 & \(-\)516.6 & 2129.42 & 2170.71 \\ \hline \hline \end{tabular}  
* Interaction costs with the gas network; \({}^{2}\) Interaction costs with the grid.  
\end{table} 
Table 6: The costs of the RIES in different types under the grid-connected mode.