Another approach would be to have a longer length of piping. The rate at which the soil temperature drops when you extract heat, and then 'recharges' naturally,

Another approach would be to have a longer length of piping. The rate at which the soil temperature drops when you extract heat, and then 'recharges' naturally, will vary greatly if you have 100m vs 1000m of piping. This is why ground source heat pumps use pipes laid out in coils, as it greatly increases the surface area.