By: Carlos Armenta-Déu
Professor, Department of Matter Structure, Thermal Physics and Electronics, Faculty of Physical Sciences, Complutense University of Madrid, 28040 Madrid, Spain
This paper proposes a new method to store thermal energy for electricity generation in power plants.
The system is based on heat exchange between the hot geological substrate and inorganic salt solution
to store thermal energy under molten salt form. To this goal, we design an underground pipeline system
that transports heat fluid carrier in solid form until reaching the geological substrate at the appropriate
temperature for the phase change where heat transfer from the substrate to the fluid melts the salt
solution. The proposed design saves space, investment and maintenance costs, and is compatible with
modern geotechnical engineering techniques. The system is also compatible with low and high
geothermal gradients. Operating temperatures are within the current range for depths between 1.6 km
and 2.6 km, which are accessible using conventional drilling techniques. The selected geological
substrate maintains molten salt in liquid phase for as long as necessary due to the geological
environment, preserving the enthalpy level. A simulation runs for current heat storage system
temperature for solar thermal power plants, proving the feasibility of the new design and the capacity
of the geological substrate to thermally recharge the heat storage system within time limits. The system
reveals as a practical solution to preserve thermal energy long enough to use when heat generation
from conventional or renewable energy sources decays or lacks. The proposed methodology is feasible
and reliable if we deal with massive energy storage where heat power generation compensates for
investment in geological engineering. The system is modular and adaptive to variable working
conditions. Besides, it becomes practical for intermittent thermal power generation and fluctuating
energy demand.
Citation:
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