Energies 2022, 15, 8461. https://doi.org/10.3390/en15228461 www.mdpi.com/journal/energies Review Overview of Natural Gas Boiler Optimization Technologies and Potential Applications on Gas Load Balancing Services Georgios I. Tsoumalis, Zafeirios N. Bampos, Georgios V. Chatzis and Pandelis N. Biskas * School of Electrical and Computer Engineering, Faculty of Engineering, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece * Correspondence: pbiskas@auth.gr; Tel.: +30-6973-841753 Abstract: Natural gas is a fossil fuel that has been widely used for various purposes, including res- idential and industrial applications. The combustion of natural gas, despite being more environ- mentally friendly than other fossil fuels such as petroleum, yields significant amounts of greenhouse gas emissions. Therefore, the optimization of natural gas consumption is a vital process in order to ensure that emission targets are met worldwide. Regarding residential consumption, advancements in terms of boiler technology, such as the usage of condensing boilers, have played a significant role in moving towards this direction. On top of that, the emergence of technologies such as smart homes, Internet of Things, and artificial intelligence provides opportunities for the development of automated optimization solutions, which can utilize data acquired from the boiler and various sen- sors in real-time, implement consumption forecasting methodologies, and accordingly provide con- trol instructions in order to ensure optimal boiler functionality. Apart from energy consumption minimization, manual and automated optimization solutions can be utilized for balancing pur- poses, including natural gas demand response, which has not been sufficiently covered in the exist- ing literature, despite its potential for the gas balancing market. Despite the existence of few re- search works and solutions regarding pure gas DR, the concept of an integrated demand response has been more widely researched, with the existing literature displaying promising results from the co-optimization of natural gas along with other energy sources, such as electricity and heat. Keywords: domestic gas boiler; energy efficiency; consumption minimization; demand response; gas balancing; integrated demand response 1. Introduction Climate change as a result of global warming is gradually becoming an important issue of modern society. Its main cause is greenhouse gas emissions, which constitute the result of mainly anthropogenic activities involving the burning of fossil fuels, which cur- rently supply more than 85% of the worldwide energy consumption, and their use is con- stantly increasing [1], despite the fact that they are finite resources [2]. Such applications include energy generation and energy related activities in domestic and tertiary buildings. Another important problem that our society is facing is energy poverty, which currently remains a problem even for developed countries and is strongly linked to modern living standards, affecting the health and the emotional state of those facing it [3]. In order to address these issues, multiple options are examined towards the sustainability and acces- sibility of energy, including (a) the transition to clean renewable energy sources such as solar, wind, and hydroelectric energy [4], (b) the switch to more environmentally friendly fuels, such as shale gas and natural gas [5,6], even as transitory fuels towards full decar- bonization by the year 2050 [7], and (c) the efficiency improvement of existing energy consumption units [8,9] such as industrial, commercial, residential, and public buildings. For the latter, in the European Green Deal, there are provisions that require Member States Citation: Tsoumalis, G.I.; Bampos, Z.N.; Chatzis, G.V.; Biskas, P.N. Overview of Natural Gas Boiler Optimization Technologies and Potential Applications on Gas Load Balancing Services. Energies 2022, 15, 8461. https://doi.org/10.3390/en15228461 Academic Editors: Yukun Hu, Mirko Morini, Dionysia (Denia) Kolokotsa, Erik Dahlquist and Esko Juuso Received: 9 October 2022 Accepted: 9 November 2022 Published: 12 November 2022 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and institu- tional affiliations. Copyright: © 2022 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https://cre- ativecommons.org/licenses/by/4.0/).