Regeneration of shallow borehole heat exchanger fields: A literature review
Xenia Kirschstein, Max Ohagen, Joscha Reber, Philip J. Vardon, Nadja Bishara
Abstract
Ground source heat pumps (GSHP) coupled to shallow borehole heat exchangers (BHE) represent a low emission technology to provide space heating and cooling. However, ongoing long-term heating or cooling of the ground caused by unbalanced loads leads to a performance decline and in the worst case to a system shutdown. Enhanced regeneration can increase the system efficiency, reduce the necessary borehole length or compensate unbalanced loads. In this study, a literature review about the regeneration of shallow BHE fields to counteract ground thermal imbalance is conducted to give an overview about the state-of-the-art and identify research gaps. The most common heat sources for artificial regeneration in heating-dominated applications are space cooling and solar thermal flat-plate collectors, while the most common heat sinks in cooling-dominated applications are space heating and cooling towers. In heating-dominated applications, mostly single buildings are studied. There is a lack of studies on district heating and cooling applications, which are especially needed as the benefit of regeneration increases with system size. There is also a lack of long-term, large system size experimental work to validate theoretical studies. • Regeneration is necessary for a sustainable operation of large borehole heat exchanger fields. • Regeneration methods can be divided into artificial and enhanced natural regeneration. • In heating-dominated applications, typical heat sources are space cooling and solar thermal heat. • In cooling-dominated applications, typical heat sinks are space heating and cooling towers. • There is a lack of long-term experiments on regenerating large borehole heat exchanger fields.