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Operational performance of a novel fast-responsive heat storage/exchanging unit (HSEU) for solar heating systems

Fan, Yi; Zhao, Xudong; Li, Jing; Cheng, Yuanda; Zhou, Jinzhi; Yu, Min; Li, Guiqiang; Badiei, Ali; Du, Zhenyu; Ji, Jie; Zhu, Zishang; Ma, Xiaoli; Bai, Huifeng; Myers, Steve


Yi Fan

Yuanda Cheng

Jinzhi Zhou

Min Yu

Guiqiang Li

Ali Badiei

Zhenyu Du

Jie Ji

Huifeng Bai

Steve Myers


In order for a solar heating system to provide heat immediately after sunrise, a fast response is needed to the heat demand of a serviced space. The majority of existing solar heating systems have a slow response time due to the large volume of water stored in the heat storage/exchanger unit (HSEU). This leads to a slow heat delivery cycle, which results in discomfort for the occupants and thus creates a huge barrier to the wide deployment of solar heating systems. To overcome this critical issue, a novel interactive heat storage/exchanging unit (HSEU) employing a double-tank configuration was developed. Unlike conventional HSEUs, which have a single tank acting as the heat storage and exchanging unit, the new HSEU is comprised of a small tank for heat exchange combined with a large tank for heat storage. The small tank enables fast transfer of solar heat to the heating loop fluid without having to heat up the large volume of water in the entire HSEU tank, whilst the large tank is used to store and exchange heat between itself and the small tank using a temperature-oriented control mechanism. To test the proposed design, the heat transfer between the first (solar loop) and second (heating loop) fluids, the heat and mass transfer between the small and large tank and the associated operational strategy were investigated experimentally and theoretically for comparison. A conventional single tank HSEU requires around 120 minutes to deliver heat to a served space, whilst the new interactive double-tank HSEU can provide heat to the served space in around 20 minutes, thus creating a heating system which can respond significantly faster than traditional systems. The investigation of the heat exchange effect between the solar and heating loop fluids showed that the new HSEU achieved a convective heat transfer coefficient of as high as 391W/m2·K, which is 551% higher than that of a conventional tank. As a result, the solar thermal efficiency of the solar panel-array in the new HSEU based system was increased by 7.5% compared to conventional HSEU based systems.


Fan, Y., Zhao, X., Li, J., Cheng, Y., Zhou, J., Yu, M., …Myers, S. (2020). Operational performance of a novel fast-responsive heat storage/exchanging unit (HSEU) for solar heating systems. Renewable energy, 151, 137-151.

Journal Article Type Article
Acceptance Date Nov 2, 2019
Online Publication Date Nov 7, 2019
Publication Date 2020-05
Deposit Date Nov 7, 2019
Publicly Available Date Nov 8, 2020
Journal Renewable Energy
Print ISSN 0960-1481
Electronic ISSN 1879-0682
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 151
Pages 137-151
Keywords Renewable Energy; Sustainability and the Environment; Fast response; Heat storage/exchanging unit; Response time; Space heating; Solar thermal efficiency; Heat transfer coefficient
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