在干旱地区（如亚利桑那州），开环太阳能热式家用热水器系统很常见，因为它们简单、廉价，而且不需要换热器，因此可以轻松改造传统系统。由于可靠性、简单性和经济性，从储水箱通过收集器循环热水以防止冻结的技术在干旱地区也很常见。开环系统可以很容易地由光伏（PV）模块供电，因此该系统完全独立于公用电。与传统系统一样，光伏系统可以实现再循环防冻保护。本文的主要目的是描述一种为光伏发电系统提供再循环冷冻保护的简单技术，并给出运行结果。 假定读者熟悉带再循环防冻保护的传统110 Vac供电系统。值得注意的是，本文提出的技术可以很容易地应用于闭环、排水、回排和空气太阳能家用热水器系统。引文:俄亥俄州辛辛那提ASHRAE学报第87卷第2部分研讨会

Open loop solar thermal domestic hot water heater systems are common in arid regions (e.g., Arizona) because they are simple, inexpensive and permit easy retrofit of conventional systems since a heat exchanger is not required. The technique of circulating hot water from the storage tank through the collectors to prevent freezing is also common in arid regions because of reliability, simplicity and economy.The open loop system can easily be powered by a photovoltaic (PV) module such that the system is completely independent of utility power. As with the conventional system, recirculation freeze protection can be obtained with the PV system.The primary purpose of this paper is to describe a simple technique developed to provide recirculation freeze protection for the PV powered system, and to present operating results. It is assumed that the reader is familiar with the conventional 110 Vac powered system with recirculation freeze protection. It should be noted that the techniques presented in this paper may be easily applied to closed loop, drain down, drain back, and air solar domestic water heater systems.