Energy storage charging piles are heating up in winter

Does pile length underestimate the rate of heat exchange?

As shown in Fig. 5 (a), for the case in unfavourable ground conditions, the computed results corresponding to the actual pile length of 30 m underestimated the daily-averaged rate of heat exchange by about 25% for both the modes of heat extraction and injection. To improve the situation, an equivalent pile length was calibrated.

What is an energy pile?

The energy pile represents an embedment of heat exchange pipes into the pile body. In this way, it can serve as a vertical heat exchanger in addition to its primary function of supporting the building. The additional land use and construction costs related to the conventional vertical boreholes of the GSHP system can thus be saved.

What is the temperature range of the energy pile?

In this study, temperature changes of the energy pile were constrained to be within a range of 5–40 °C. This range serves as an input into the thermo-mechanical analysis of the energy pile foundation, resulting in a one-way coupling between the thermal analysis of the whole system and the thermo-mechanical analysis of the energy pile foundation.

How are energy piles distributed?

The energy piles were uniformly distributed with the centre-to-centre pile spacing of 1.8 m, three times the pile diameter. All of them were assumed to be active in this study. For other details of the single energy pile and the ground conditions, please refer to the section 3.3 before.

What is the thermal conductivity of the energy pile?

The thermal conductivity of the concrete of the tested energy pile was about 1.5 W/m/°C, slightly less than the adopted value of 1.6 W/m/°C in this study. On consideration of these differences, the calculated value of 0.035 (m °C)/W for the energy pile under study was justified to be reasonable.

Does a 30 m pile increase heat exchange rate?

Computed results for the case in favourable ground conditions using an equivalent pile length did not show a uniform improvement on that using the original pile length of 30 m. In addition, this slight underestimation of the heat exchange rate will put the system design on the conservative side.