Energy storage charging piles at high temperatures outdoors

Can energy piles store solar thermal energy underground?

Ma and Wang proposed using energy piles to store solar thermal energy underground in summer, which can be retrieved later to meet the heat demands in winter, as schematically illustrated in Fig. 1. A mathematical model of the coupled energy pile-solar collector system was developed, and a parametric study was carried out.

What is the maximum temperature of a solar energy pile?

It indicates that both the inlet and outlet temperature of the energy pile undergo a rapid increase during the first hour. Then they increase quite slowly as the underground storage of solar thermal energy continues. The maximum inlet temperature is about 60 °C.

How much energy is stored per unit pile?

Quantitatively, the daily average rate of energy storage per unit pile length reaches about 200 W/m for the case in saturated soil with turbulent flowrate and high-level radiation. This is almost 4 times that in the dry soil. Under low-level radiation, it is about 60 W/m.

How big is an energy pile?

To facilitate a comparison with the model-scale experimental results, the whole model was scaled up geometrically so that the energy pile in prototype has dimensions of 1 m in diameter × 10 m in length. This was determined to avoid oversizing the pile diameter.

How big should a thermal loop be in an energy pile?

This was determined to avoid oversizing the pile diameter. It should be noted that a realistic diameter of 20 mm was adopted for the thermal loop embedded inside the energy pile.

Can solar thermal energy be stored underground?

Energy piles, which embed thermal loops into the pile body, have been used as heat exchangers in ground source heat pump systems to replace traditional boreholes. Therefore, it is proposed to store solar thermal energy underground via energy piles.