# Techno-Economic Analysis of Waste Heat Recovery in Automotive Manufacturing Plants
## 3 Methodology
### Cost Estimation and Economic Analysis
The NPV measures the overall profitability of an investment by calculating the difference between the present value of cash inflows and outflows over the lifetime of the project; a positive NPV indicates a profitable investment, which can be determined using Equation (11). In this case, \(C_{\text{ncf}}\) refers to the annual economic savings of the system, calculated by subtracting the operational and maintenance costs (\(C_{\text{t}}\)) from the total cost of electricity production (\(C_{\text{pr}}\)). The PBP is the time it takes for the initial investment to be recovered from the project's net cash inflows, providing insight into the risk and financial feasibility of the project. Moreover, the LCOE represents the per-unit cost of electricity generated over the lifetime of the project, accounting for capital, operating, and maintenance costs, and it serves as a standard metric for comparing the cost-effectiveness of different energy generation technologies. The LCOE can be determined using Equation (12). In this study, several assumptions are made. The installed system is expected to have a lifespan (\(y\)) of 20 years, with an annual discount rate (\(d\)) of 6.00% and an inflation rate of 2.00%. Also, the rate of operation and maintenance costs (\(C_{\text{t}}\)) are set at 0.01 EUR per kWh. The business electricity price in Indonesia was assumed 0.065 EUR per kWh. Additionally, the return on \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Components**} & **Unit for the Capacity** & **The Range of the Capacity** & **Currency and Year** & \multicolumn{3}{c}{**Estimated Cost Function or Value**} \\ \cline{2-7}  & **K\(W\)** & 80–10,000 & USD, 2013 & 4.1055 & 0.0570 & 0.0797 \\ ORC pump [20] & kW & 1–100 & USD, 2001 & 3.4771 & 0.1350 & 0.1438 \\ ORC expander [35] & kW & 100–20,000 & USD, 2010 & \(C_{\text{p,EXP}}^{0}=-14\times 10^{3}+1.9\times 10^{3}(P_{\text{EXP}})^{0.75}\) \\ Air-cooled heat exchanger & m\({}^{2}\) & 200–2000 & USD, 2001 & 4.0336 & 0.0234 & 0.0497 \\ for condenser [20] & m\({}^{2}\) & 80–4000 & USD, 2000 & \(C_{\text{p,PVA}}^{0}=328000\left(\frac{\delta_{\text{PVV}}}{80}\right)^{0.68}\) \\ Heat exchanger for & & & & & & \\ preheater and & m\({}^{2}\) & 10–1000 & USD, 2001 & 4.6656 & \(-0.1557\) & 0.1547 \\ recupter [20] & & & & & & \\ PV [37] & kW & - & USD, 2023 & \(758\text{P}_{\text{PV}}\) & \\ Mounting rack [38] & - & - & USD, 2023 & \(10\%\) of PV cost & \\ Inverter cost [38] & kW & - & USD, 2021 & \(300\text{P}_{\text{PV}}\) & \\ Battery bank [38] & kWh & - & USD, 2021 & \(160\text{E}_{\text{BB}}\) & \\ A 100 kW heat pump [39] & - & - & EUR, 2023 & \(\sim\)18,000 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The estimated cost functions for the components. investment (ROI) was determined using Equation (13) to provide insight into how well the investment generates returns relative to the resources invested. \[SIC=\frac{C_{\text{TM}}}{P_{\text{net}}} \tag{10}\]  
\[NPV=-C_{\text{TM}}+\sum_{i=1}^{y}\frac{C_{\text{ncf}}}{(1+d)^{i}} \tag{11}\]  
\[LCOE=\frac{C_{\text{TM}}+\sum_{i=1}^{y}\frac{C_{\text{t}}}{(1+d)^{i}}}{\sum_{i= 1}^{y}\frac{P_{\text{net}}}{(1+d)^{i}}} \tag{12}\]  
\[ROI=\left(\frac{-C_{\text{TM}}+\sum_{i=1}^{y}C_{\text{ncf,i}}}{C_{\text{TM}}} \right)100\% \tag{13}\]