Abstract Water heating represents a large fraction of energy consumption in the residential sector, and it has significant health, economic, and environmental implications. However, it is well known that temperatures between 20 °C and 42 °C promote the multiplication of Legionella species, which are the causative agent of the Legionnaires' disease, a life-threatening form of pneumonia. Conventional tank water heating systems could be reservoirs of Legionella species, and that is why the replacement of these systems with tankless point-of-use water heating (POUWH) systems may keep a low-risk concentration of Legionella pneumophila in the water delivery and reduce energy consumption. This strategy may attain its maximum effectiveness in continental climate regions like Kazakhstan, where water mains-supply does not exceed 20 °C all year-round. Nevertheless, as POUWH systems depend on electricity, greenhouse gas (GHG) emissions may change compared to storage-based or even in-line water heating systems, depending on the energy source of grid electricity and the base-case heating system. This study assesses the use of POUWH systems in Nur-Sultan city, the capital of Kazakhstan, and compares it with commonly used electric and natural gas storage-type water heating systems. The power grid in the country heavily depends on coal (~70%), and the present analysis demonstrates that POUWH is economically competitive and reduces the greenhouse gas (GHG) emissions when compared with electric storage-type water heating (ESWH). However, the opposite happens when POUWH is compared with natural gas storage-type water heating (NGWH). The financial analysis revealed the fuel cost as the most influential factor in economic viability. Despite its debatable economic advantage, POUWH is favored by its intrinsic lower risk of Legionella sp. concentration in delivered hot water, a crucial element that should be considered in a final decision.

中文翻译：

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大陆性气候家庭使用点热水的经济、环境和致病影响

摘要 水加热是住宅部门能源消耗的很大一部分，它具有重大的健康、经济和环境影响。然而，众所周知，20 °C 到 42 °C 之间的温度会促进军团菌的繁殖，军团菌是军团病（一种危及生命的肺炎）的病原体。传统的水箱水加热系统可能是军团菌的蓄水池，这就是为什么用无水箱使用点水加热 (POUWH) 系统替换这些系统可以保持水输送中嗜肺军团菌的低风险浓度并减少能源消耗。该策略可能会在像哈萨克斯坦这样的大陆性气候地区发挥最大效力，那里的水管供应全年不超过 20°C。尽管如此，由于 POUWH 系统依赖于电力，因此与基于存储甚至在线热水系统相比，温室气体 (GHG) 排放可能会发生变化，具体取决于电网电力的能源和基本情况加热系统。本研究评估了 POUWH 系统在哈萨克斯坦首都努尔苏丹市的使用情况，并将其与常用的电力和天然气储存式热水系统进行了比较。该国的电网严重依赖煤炭（约 70%），目前的分析表明，与蓄电式热水器 (ESWH) 相比，POUWH 具有经济竞争力并减少了温室气体 (GHG) 排放。但是，将 POUWH 与天然气储水式热水 (NGWH) 进行比较时，情况正好相反。财务分析显示，燃料成本是影响经济可行性的最重要因素。尽管其经济优势值得商榷，但 POUWH 因其内在的军团菌风险较低而受到青睐。输送热水的浓度，这是最终决定中应考虑的关键因素。