## 6 Economic Evaluation
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Facility** & **Basic Cost (k\$)** & **Basic Scale** & **Unit** & **Scale Factor** & **Source** \\ \hline Cooling tower & 27,355.45 & 1,845,000 & m\({}^{2}\) & 1 & \\ \hline CON & 1715.287 & 18,000 & m\({}^{2}\) & 1 & [47] \\ \hline Stack & 3827.12 & 1,178,352 & m\({}^{3}\)/h & 1 & \\ \hline SH & 45.84 & 500 & m\({}^{2}\) & 0.741 & [48] \\ \hline ECO & 693.00 & 13,149 & m\({}^{2}\) & 0.68 & [49] \\ \hline PAH & 800.00 & 8372 & m\({}^{2}\) & 0.68 & [50] \\ \hline SAH & 800.00 & 8372 & m\({}^{2}\) & 0.68 & \\ \hline \hline \end{tabular}
\end{table} 
Table 18: Primary data of the scale-up method for the cost of several facilities. The total investment of proposed WTE design (\(C_{\text{tot,pw}}\), $) is calculated by Equation (12).  
\[C_{\text{tot,pw}}=C_{\text{tot,ow}}-\sum C_{\text{cc}} \tag{12}\]  
where \(C_{\text{tot,ow}}\) is the total investment of original WTEU, $; \(\sum C_{\text{cc}}\) is the total investment of changed components, $.  
The dynamic payback period (DPP, year) and the net present value (NPV, $) are evaluated to examine the economic benefits of proposed WTE design. DPP is calculated by the project's net cash flow each year after discounting it into the present value at a specific discount rate [51]. The DPP is determined by Formula (13), and a shorter DPP means faster payback. The NPV denotes the present value of net profit in the whole project life cycle, which is defined by Equation (14) [42]. More NPV reveals the more profitable the project is. \[\sum_{\text{a}=1}^{DPP}\frac{C_{\text{in}}-C_{\text{out}}}{(1+r_{\text{dis}}) ^{a}}=0 \tag{13}\]  
\[NPV=\sum_{\text{a}=1}^{n}\frac{(C_{\text{in}}-C_{\text{out}})}{(1+r_{\text{dis }})^{a}} \tag{14}\]  
where \(a\) is a year in the lifetime of a project; \(C_{\text{in}}\) and \(C_{\text{out}}\) represent the cash inflows and outflows in a year, $; \(r_{\text{dis}}\) is the discount rate; n is the project lifetime, year.  
During the construction of suggested WTE project, it is not profitable. In the economic period, the yearly cash inflows depend on the income from electricity sales and waste disposal, which can be expressed as:  
\[C_{\text{in}}=P_{\text{w}}\times t\times c_{\text{e}}+m_{\text{w}}\times 3.6 \times t\times c_{\text{tnds}} \tag{15}\]  
where \(t\) is the operating hours of WTEU in a year, h; \(c_{\text{e}}\) is the on-grid tariff, $/kWh; \(c_{\text{tnds}}\) is the waste disposal subsidy, $/t. In the building period, the investment cost of suggested WTE project is cash outflows. In the payback period, the income tax and the cost of operation and maintenance are the cash outflows. The cash outflow (\(C_{\text{out}}\)) of WTE project is conveyed as:  
\[C_{\text{out}}=C_{\text{it}}+C_{\text{o}\&\text{cm}} \tag{16}\]  
\[C_{\text{it}}=[C_{\text{in}}-C_{\text{o}\&\text{cm}}]\times r_{\text{it}} \tag{17}\] \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**Component**} & \multicolumn{2}{c}{**Initial WTE Design (kS)**} & \multicolumn{2}{c}{**Proposed WTE Design (kS)**} & \multicolumn{2}{c}{**Difference (kS)**} \\ \hline \multirow{8}{*}{Removed} & ST & 4126.61 & - & \(-\)4126.61 \\  & EG & 369.71 & - & \(-\)369.71 \\  & CON & 45.53 & - & \(-\)45.53 \\  & CWP & 211.74 & - & \(-\)211.74 \\  & Cooling tower & 920.06 & - & \(-\)920.06 \\  & CP & 8.90 & - & \(-\)8.90 \\  & RH2 & 18.96 & - & \(-\)18.96 \\  & DEA & 38.51 & - & \(-\)38.51 \\  & Stack & 331.86 & - & \(-\)331.86 \\ \hline \multirow{4}{*}{Transformed} & ECO & 246.58 & 346.08 & +99.50 \\  & SH & 107.78 & 203.60 & +95.82 \\  & PAH & 252.53 & 761.37 & +508.84 \\  & SAH & 109.58 & 257.31 & +147.73 \\ \hline \multirow{2}{*}{Added} & EP & - & 7.09 & +7.09 \\ \cline{2-2}  & AE & - & 62.88 & +62.88 \\ \hline \multirow{2}{*}{Sum} & \multirow{2}{*}{6788.35} & \multirow{2}{*}{1638.33} & \multirow{2}{*}{\(-\)5150.03} \\ \cline{1-1} \cline{3-3}  & & & \\ \end{tabular}
\end{table} 
Table 19: Comparison of the investment cost between initial and proposed WTE designs.