Low-grade Heat Recovery for Sustainable Automotive Manufacturing

Abstract

In response to the need for UK manufacturing to decarbonise its production processes and become more sustainable, an increasing interest has been given to low-grade heat recovery technologies able to energy-efficiently control the temperature and humidity of the air supplied for product-specific applications. This study aims to investigate the novel use of liquid desiccant technology in automotive painting. The work includes a literature review on automotive manufacturing and painting to analyse processes, energy consumption, waste heat sources and the importance of temperature and humidity control, identifying how the liquid desiccant technology could match these conditions. Based on the knowledge of the main operating factors of the liquid desiccant technology, a framework for the techno-economic feasibility analysis of different heat recovery scenarios was developed. The techno economic analysis proposed new correlations for the analysis of the heat and mass transfer in the dehumidifier and regenerator of the liquid desiccant system able to predict the performance of the system under different conditions. Novel configurations for the use of liquid desiccant technology in the field of low-grade heat recovery and painting processes were designed and case studies were carried out to estimate the energy and economic performance of the designed novel configurations. Also, the performance of the technology in different outdoor air conditions, such as hot and humid climates, was estimated and compared with the UK. The case studies showed that the potential for heat recovery from transformers, compressors and thermal oxidisers and its use for air-conditioning, painting operation and air dehydration are high enough to achieve significant energy savings in terms of natural gas and electricity. Also, significant energy savings for cooling and dehumidification are achievable by employing the technology in hot and humid climates. Potential innovative solutions to increase the energy and economic performance of the liquid desiccant technology for automotive painting were also recommended. It was concluded that energy-efficient use of low-grade heat sources to drive the liquid desiccant technology could help the automotive industry to reduce its energy consumption and increase the sustainability of its production process.