# Techno-Economic Analysis of Waste Heat Recovery in Automotive Manufacturing Plants
## 3 Methodology
### Cost Estimation and Economic Analysis  
The economic analysis evaluates the cost-generation process associated with internal operations and final products in energy systems and industrial plants. The analysis provides a comprehensive view of operational efficiency by assessing the costs involved in each energy production stage. It enables a more accurate evaluation of the financial implications of different energy generation methods and technologies. Furthermore, understanding these costs helps to identify opportunities for optimising resource allocation and improving overall performance. This detailed economic insight is essential for making informed investment decisions, cost reductions, and long-term financial sustainability in energy projects. The investment cost is determined by the additional components purchased for the system, including the ORC, heat pump, TES, and PV. The estimated cost (\(C_{p}^{0}\)) of each component can be estimated based on its specific capacity (\(X\)) or relevant parameters. For instance, the cost of rotary components, such as turbines and pumps, can be estimated based on their output power (\(P\)) or volumetric flow rate (\(\dot{V}\)). Similarly, the cost of stationary components, like evaporators, condensers, and TES units, can be estimated using factors such as heat exchanger area (\(A\)), heat transfer rate (\(\dot{Q}\)), or other relevant parameters. Several estimated cost functions used in this study are described and listed in Table 4, and some of them use Equation (7). \[C_{p}^{0}=10^{K_{1}+K_{2}\log_{10}\left(X\right)+K_{3}\left(\log_{10}\left(X \right)\right)^{2}} \tag{7}\]  
Based on a recent market survey, the estimated cost for a 100-kW heat pump is approximately 18,000 EUR. A recent review article [31] highlights that TES can be integrated into ORC systems in multiple configurations, offering flexibility in its application. Given this adaptability, it is reasonable to approximate the cost of TES at a similar level to the estimated cost of the evaporator used in this study. Some component purchase costs were sourced from different years, so these costs need to be adjusted to reflect the base year for this calculation in 2023. All purchase costs were converted from USD to EUR using the annual average exchange rate. Also, the costs were adjusted using the chemical engineering plant cost index (CEPCI) [32]. To estimate the bare module capital cost (\(C_{\text{BM}}\)), the total purchase cost is multiplied by the bare module factor \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Unit** & **Value** \\ \hline System losses & \(\%\) & 14.08 \\ Tilt & \(\circ\) & 35 [30] \\ Azimuth & \(\circ\) & \(-2\) \\ DC-to-AC size ratio & \(-\) & 1.2 \\ Inverter efficiency & \(\%\) & 96\(\%\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Boundary conditions of PV. (\(F_{\text{BM}}\)), which accounts for the development of the existing system [20]. The bare module factor for each component is taken from this study [20]. To account for additional expenses such as contractor fees, auxiliary facilities, system integration, installation, and project costs, the capital cost of the bare module is further multiplied by 1.18 [33] to estimate the total module capital cost (\(C_{\text{TM}}\)). The bare module and total module capital costs are determined using Equations (8) and (9), respectively. \[C_{\text{BM}}=\sum_{i=1}^{n}C_{\text{p,i}}F_{\text{BM}} \tag{8}\]  
\[C_{\text{TM}}=1.18\sum_{i=1}^{n}C_{\text{BM,i}} \tag{9}\]  
Some of the key economic indicators used in this study include specific investment cost (SIC), net present value (NPV), PBP, and levelized cost of electricity (LCOE). The SIC refers to the total capital cost required for the project, expressed per unit of capacity, which helps to compare the cost efficiency of different projects, which is described in Equation (10).