Energies 2021, 14, 2413. https://doi.org/10.3390/en14092413 www.mdpi.com/journal/energies Article Maximizing Thermal Energy Recovery from Drinking Water for Cooling Purpose Jawairia Imtiaz Ahmad 1,2, *, Sara Giorgi 3 , Ljiljana Zlatanovic 1,4,5 , Gang Liu 1,6 and Jan Peter van der Hoek 1,3,5 1 Sanitary Engineering, Department of Water Management, Faculty of Civil Engineering and Geosciences, Delft University of Technology, P.O. Box 5048, 2600 GA Delft, The Netherlands; ljiljana.zlatanovic@pwn.nl (L.Z.); gliu@rcees.ac.cn (G.L.); J.P.vanderHoek@tudelft.nl (J.P.v.d.H.) 2 Institute of Environmental Sciences and Engineering, School of Civil and Environmental Engineering, National University of Science and Technology, H-12 Sector, Islamabad 44000, Pakistan 3 Waternet, Korte Ouderkerkerdijk 7, 1096 AC Amsterdam, The Netherlands; sara.giorgi@waternet.nl 4 Water Supply Company Noord-Holland PWN, Rijksweg 501, 1991 AS Velserbroek, The Netherlands 5 Amsterdam Institute for Advanced Metropolitan Solutions, Kattenburgerstraat 5, 1018 JA Amsterdam, The Netherlands 6 Key Laboratory of Drinking Water Science and Technology, Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China * Correspondence: j.i.ahmad@tudelft.nl Abstract: Drinking water distribution networks (DWDNs) have a huge potential for cold thermal energy recovery (TED). TED can provide cooling for buildings and spaces with high cooling re- quirements as an alternative for traditional cooling, reduce usage of electricity or fossil fuel, and thus TED helps reduce greenhouse gas (GHG) emissions. There is no research on the environmental assessment of TED systems, and no standards are available for the maximum temperature limit (Tmax) after recovery of cold. During cold recovery, the water temperature increases, and water at the customer’s tap may be warmer as a result. Previous research showed that increasing Tmax up to 30 °C is safe in terms of microbiological risks. The present research was carried out to determine what raising Tmax would entail in terms of energy savings, GHG emission reduction and water tem- perature dynamics during transport. For this purpose, a full-scale TED system in Amsterdam was used as a benchmark, where Tmax is currently set at 15 °C. Tmax was theoretically set at 20, 25 and 30 °C to calculate energy savings and CO2 emission reduction and for water temperature modeling during transport after cold recovery. Results showed that by raising Tmax from the current 15 °C to 20, 25 and 30 °C, the retrievable cooling energy and GHG emission reduction could be increased by 250, 425 and 600%, respectively. The drinking water temperature model predicted that within a distance of 4 km after TED, water temperature resembles that of the surrounding subsurface soil. Hence, a higher Tmax will substantially increase the TED potential of DWDN while keeping the same comfort level at the customer’s tap. Keywords: energy transition; cold recovery; cooling; carbon footprints reduction; drinking water distribution networks; greenhouse gas emissions 1. Introduction Resource recovery from the water cycle is gaining much attention. The focus is much on materials from wastewater, such as nutrients, carbon, energy in the form of biogas and water itself [1–3]. Resource recovery from drinking water has also been described and is applied in practice, e.g., the recovery of calcite from the pellet softening process in drink- ing water treatment [4]. The thermal energy from sewage water and wastewater treatment plant effluent has been pointed at as a valuable resource [5,6]. However, at the same time, Citation: Ahmad, J.I.; Giorgi, S.; Zlatanovic, L.; Liu, G.; van der Hoek, J.P. Maximizing Thermal Energy Recovery from Drinking Water for Cooling Purpose. Energies 2021, 14, 2413. https://doi.org/ 10.3390/en14092413 Academic Editor: Peter Childs Received: 25 March 2021 Accepted: 20 April 2021 Published: 23 April 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Copyright: © 2021 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 (http://creativecommons.org/licenses /by/4.0/).