## 5 Discussion
### The Effects of CSP and EH in Reserve Services  
#### 5.2.1 Comparison Among Different Reserve Planning Decisions  
In this section, 6 different spinning reserve strategies are formulated to discuss the advantages of the chance-constrained reserve planning model and the effects of the CSP and EH on the system costs. Different reserve strategies are depicted in Table 5. Table 6 shows the simulation results of the system costs based on different reserve strategy. In Tables 5 and 6, Strategy 1, Strategy 2 and Strategy 3 are the practical reserve planning methods with different system configurations while Strategy 4, Strategy 5 and Strategy 6 are the chance-constrained reserve planning with different system structures. In the comparative experiments of the conventional strategy and the proposed method, we could find that in the proposed chance-constrained manner, although the fuel costs, the start-up costs and the penalty costs for renewables spillage would increase, load shedding as the important criteria of system reliability would decrease significantly. Besides, the chance-constrained strategy effectively avoids consideration of extreme renewables fluctuation with low probability which reduces the costs for reserve scheduling and reserve deploying. Therefore, in the same system configuration, the system costs for chance-constrained programming are much lower than the traditional method. To investigate the impacts of reserves from the CSP and EH on the system performance, different reserve settings are considered in the comparative experiments. In Strategy 2 and Strategy 4, CSP \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Strategy** & **Fuel Costs and Start-Up** & **Penalty Costs for Load** & **Penalty Costs for** \\  & **Costs (S)** & **Shedding (S)** & **Renewables Spillage (S)** \\ \hline Strategy 1 & 607,959.73 & 2005.3 & 5129.12 \\ Strategy 2 & 609,017.21 & 1705.31 & 2153.51 \\ Strategy 3 & 610,477.49 & 179.29 & 1274.90 \\ Strategy 4 & 610,624.39 & 197.55 & 6006.07 \\ Strategy 5 & 611,379.23 & 161.18 & 2715.00 \\ Strategy 6 & 611,907.54 & 0.00 & 1432.59 \\ \hline \hline
**Strategy** & **Costs for Reserve Scheduling (S)** & **Costs for Reserve Deploying (S)** & **System Costs (S)** \\ \hline Strategy 1 & 39,615.54 & 6572.71 & 704,195.06 \\ Strategy 2 & 16,363.14 & 5575.36 & 660,028.64 \\ Strategy 3 & 14,402.79 & 2177.49 & 645,092.24 \\ Strategy 4 & 24,599.49 & 5846.88 & 674,393.30 \\ Strategy 5 & 15,963.14 & 4721.84 & 658,952.82 \\ Strategy 6 & 13,756.84 & 1717.01 & 644,287.84 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Simulation results of system costs based on different reserve strategy. \begin{table}
\begin{tabular}{c c} \hline \hline
**Strategy** & **Description** \\ \hline Strategy 1 & Reserve adopts 10\% of load forecast + additional 5\% of wind forecast \\  & No CSP reserve, and no EH \\ Strategy 2 & Reserve adopts 10\% of load forecast + additional 5\% of wind forecast \\ Strategy 3 & Reserve adopts 10\% of load forecast + additional 5\% of wind forecast \\ Strategy 4 & With CSP reserve, and with EH \\ Strategy 4 & Reserve adopts chance-constrained programming \\  & No CSP reserve, and no EH \\ Strategy 5 & Reserve adopts chance-constrained programming \\  & With CSP reserve, but no EH \\ Strategy 6 & With CSP reserve, and with EH \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Different reserve strategies. reserves are scheduled to replace part of the costly thermal unit reserves, and in Strategy 3 and Strategy 6, the EH is installed in the power system. The consideration of CSP reserves would slightly raise the fuel costs of thermal units, because the CSP energy to be released to the power system is now stored in TES to provide reserve services. The operation of the EH to absorb electricity from grid would further increase the fuel costs. Whereas, the increase fuel costs are compensated by the decline on reserve costs.