. Naturally, the more thermal energy that
is injected into a geothermal resource, the more geothermal energy
should be available to be sustainably extracted. Table 5 demonstrates
that higher rates of heat injection during the summer
phases correspond to significantly improved heat extraction during
the winter phases. Moreover, it can be seen in Table 5 that the increase
in total heat provided begins to taper off above 1200 W of
solar thermal injection. By storing solar energy during summer
periods, the operational savings associated with the substitution of
natural gas/electricity has increased by $181.69/$2063.88 over a 15
year period, which is equivalent to a savings increase of 20.9% for
natural gas and 21.0% for electricity. Note that this is for a single
borehole system, and the savings for a network of vertical bores will
be considerable. This shows that storing solar heat into the ground
will provide the opportunity to increase the capacity of a
geothermal bore without increasing its depth, resulting in
increased savings.