# Techno-Economic Analysis of Waste Heat Recovery in Automotive Manufacturing Plants
## 1 Introduction  
In recent years, growing attention has been given to enhancing energy efficiency across various industries in support of sustainable development goals and net-zero emission targets [1, 2]. One of the key areas of focus is the utilisation of waste heat generated by industrial processes, which often remains untapped despite its substantial energy potential. By capturing and reusing this excess heat, industries can significantly improve energy efficiency, reduce reliance on conventional energy sources, and lower carbon emissions [3]. This approach not only reduces energy demand, but also supports the shift toward net-zero emissions by decreasing the need for fossil fuel-based energy, thereby mitigating greenhouse gas emissions. Several innovative technologies are being developed to harness waste heat more effectively, enabling its repurposing for heating, power generation, and other industrial processes [4]. There are several manufacturing processes--all across the various fields of industries--where energy efficiency could be improved. A representative example from the automotive industry will be presented. This sector has seen significant growth in recent years, particularly with the rise of electric vehicles [5; 6]. Within this industry, the car body paint shop is a critical step in manufacturing, requiring substantial amounts of both electricity and thermal energy [7]. This high demand makes it an ideal candidate for co-generated and recovered energy from other processes, enhancing overall energy efficiency. In the literature, several studies have explored the potential of waste heat recovery in automotive paint shops to improve system efficiency [7; 8]. One innovative approach focuses on recovering waste energy, specifically from the exhaust gases of regenerative thermal oxidisers (RTOs) used in the paint shop [7]. RTOs are critical for air pollution control, but they release large amounts of unused heat. By capturing this waste heat and repurposing it within the paint shop or other parts of the manufacturing processes, the factory can significantly reduce energy consumption, lower operational costs, and contribute to sustainability goals. This study introduces a novel approach and provides a preliminary analysis of power generation by utilising waste heat from automotive paint shops. As waste heat recovery technologies continue to attract attention, this research investigates the potential of integrating a high-temperature heat pump to upgrade waste heat, storing the enhanced thermal energy in a thermal energy storage (TES) system. Moreover, it explores the use of an organic Rankine cycle (ORC) to efficiently convert low-grade waste heat into electricity, thus optimising the utilisation of available waste energy. The ORC is particularly suited for this purpose due to its capability to operate at low to medium temperatures, making it ideal for recovering heat in such industrial settings. The article explores the integration of ORC technology, a heat pump, TES, and photovoltaics (PV) and presents a techno-economic analysis to assess its feasibility in automotive paint shops. The analysis evaluates critical factors such as the amount of recoverable waste heat, the system's efficiency, and the associated economic benefits. Four scenarios are described and examined for economic feasibility. By doing so, this research contributes to advancements in waste heat recovery, offering a thorough evaluation of how ORC technology can improve industrial sustainability. Also, the study provides valuable insights into how industries can optimise their energy consumption by recovering waste heat, thus supporting the transition toward more sustainable and energy-efficient production processes. After the introduction, Section 2 provides a literature review that discusses the current state of the art and positions the contributions of this study within the broader research context.