Citation: Gomaa, M.R.; Murtadha, T.K.; Abu-jrai, A.; Rezk, H.; Altarawneh, M.A.; Marashli, A. Experimental Investigation on Waste Heat Recovery from a Cement Factory to Enhance Thermoelectric Generation. Sustainability 2022, 14, 10146. https://doi.org/10.3390/ su141610146 Academic Editor: Enrique Rosales-Asensio Received: 26 May 2022 Accepted: 11 August 2022 Published: 16 August 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). sustainability Article Experimental Investigation on Waste Heat Recovery from a Cement Factory to Enhance Thermoelectric Generation Mohamed R. Gomaa 1,2, * , Talib K. Murtadha 3 , Ahmad Abu-jrai 4 , Hegazy Rezk 5 , Moath A. Altarawneh 6 and Abdullah Marashli 1 1 Mechanical Engineering Department, Faculty of Engineering, Al-Hussein Bin Talal University, Ma’an 71111, Jordan 2 Mechanical Engineering Department, Benha Faculty of Engineering, Benha University, Benha 13518, Egypt 3 Mechanical Engineering Department, Faculty of Engineering, Mutah University, Al-Karak 61710, Jordan 4 Environmental Engineering Department, Faculty of Engineering, Al-Hussein Bin Talal University, Ma’an 71111, Jordan 5 Department of Electrical Engineering, College of Engineering in Wadi Alddawasir, Prince Sattam bin Abdulaziz University, Wadi Alddawasir 11991, Saudi Arabia 6 Lafarge Jordan Cement, Rashadiya 25111, Jordan * Correspondence: behiri@ahu.edu.jo or behiri@bhit.bu.edu.eg Abstract: This work investigated the potential for waste heat recovery from a cement factory using thermoelectric generation (TEG) technology. Several TEGs were placed on a secondary coaxial shell separated from the kiln shell by an air gap. The performance of the system was tested and evaluated experimentally. Two cooling methods, active water and forced air, were considered. A forced closed- loop water cooling system with a heat exchanger was considered for the active-water cooling method. A heat exchanger was inserted before the water tank to improve cooling efficiency by reducing the inlet temperature of the cooling water tank, in contrast to forced-air cooling, in which a heatsink was used. The obtained results indicated that the closed-loop water-cooled system equipped with a radiator, i.e., active water, has the highest conversion efficiency. The maximum absorbed heat for the forced-air and active-water cooling systems were 265.03 and 262.95 W, respectively. The active-water cooling method improves the power of TEG by 4.4% in comparison with forced-air cooling, while the payback periods for the proposed active-water and forced-air cooling systems are approximately 16 and 9 months, respectively. Keywords: thermoelectric generation; waste heat recovery; energy efficiency; active-water cooling system; forced-air cooling system 1. Introduction Global warming and resource scarcity are still the main issues addressed today in both economic and scientific conferences and meetings [1–3]. Waste heat refers to the heat generated in a system as a byproduct or that leaves the system without adding valuable work [4,5]. Moreover, when this surplus heat goes into the system and mixes with the surrounding atmosphere or groundwater, it becomes unreachable and hard to recover [6]. In this regard, the waste heat recovery system needs to be appropriately evaluated and designed. Moreover, several factors play a crucial role in the selection and efficiency of waste heat recovery systems, for example, the quality and quantity of such waste heat. In fact, the cement production process uses 3 to 4 GJ of energy per ton of cement, and around 40% of the energy is wasted [7]. This makes cement production a perfect target for waste heat recover, not only to minimize and save production costs, but also to save the world and atmosphere from the enormous amount of CO 2 generated by the cement sector. TEG converts heat directly to electricity. It mainly consists of a thermocouple element (n-type and p-type) covered with an aluminum oxide plate. These thermocouples are Sustainability 2022, 14, 10146. https://doi.org/10.3390/su141610146 https://www.mdpi.com/journal/sustainability