## 4 Simulation Results
### Control Strategy about Micro-CHP  
The previous analysis is based on the same hot water supply temperature between CHP and other configurations. The following studies the optimal economic strategy of micro-CHP, with aim of finding the best threshold by CHP operating at different hot water supply temperatures. When the TES's water temperature is lower than minimum temperature (\(T_{min}\)), the CHP unit starts to work automatically under the control of the EMS system, and when the water temperature is higher than maximum temperature (\(T_{max}\)), the CHP unit stops working. It is different from electric-lead strategy [27]. Heat-lead strategy adopts a greedy control strategy in this paper. It means that users can be merely energy consumers. Each user just participates in the use of heat energy, rather than the scheduling of heat energy. Meanwhile, the traditional real-time scheduling control strategy is usually used to optimize the system. The number of feasible decision sequences increases exponentially with the increase of state variables, decision variables, and length of time, which leads to more complex calculation [28]. The advantage of the greedy control strategy is that it is simple to implement and does not require real-time scheduling like electric-lead does. The simulation is still based on the AHUE for 31.28%. The economic efficiency of the three strategies (\(S_{chp,1}\), \(S_{chp,2}\), and \(S_{chp,d}\)) is compared with an internal combustion-based CHP system with generating power of 25.3 kW and heating power of 38.5 kW, a TES for heat storage, an EMS system, and plate water-heat exchanger, etc. Considering the different electricity prices at each period, the three strategies correspond with different temperature range and configuration, as shown in Table 4. \(S_{chp,d}\) is similar to \(S_{chp,2}\), but the difference for both is that during the period of flat electricity prices, the \(S_{chp,d}\) system uses electric heating tubes to convert all the electrical energy generated by CHP into heat to reduce the work of CHP. Therefore, the thresholds for starting and stopping the equipment are in different electricity price periods, including off-peak electricity price, flat electricity price, and peak electricity price, which are divided into three intervals. For mode, it is suggested that the start-up temperature should be higher during the high electricity prices. Similarly, it is suggested to reduce the start-up temperature to avoid the operation of CHP units when the electricity prices is low. The above operational logic has been implemented in a home-made numerical code, written in Matlab, which has been realized to establish for each strategy the optimal operation schedule that maximizes the revenues for the CHP concerning the separate generation. Table 5 shows the comparison of annual operating energy consumption, annual revenue, capital saving rate and payback. The NPV of micro-CHP system shows similar results of literature [13]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Period** & \(\mathcal{S}_{chp,1}\) & \(\mathcal{S}_{chp,2}\) & \(\mathcal{S}_{chp,d}\) \\ \hline
08:00–12:00 and 17:00–21:00 & 39–45 \({}^{\circ}\)C & 39–50 \({}^{\circ}\)C & 39–50 \({}^{\circ}\)C \\
12:00–17:00 and 21:00–24:00 & 39–45 \({}^{\circ}\)C & 39–45 \({}^{\circ}\)C & 39–45 \({}^{\circ}\)C \\
00:00–08:00 & 39–45 \({}^{\circ}\)C & 35–39 \({}^{\circ}\)C & 35–39 \({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The operation temperature range of three control strategies each period.