Abstract:
Multi-megawatt thermo-electric energy storage based on
thermodynamic cycles is a promising alternative to PSH
(Pumped-Storage Hydroelectricity) and CAES (Compressed Air
Energy Storage) systems. The size and cost of the heat storage
are the main drawbacks of this technology but using the ground
as a heat reservoir could be an interesting and cheap solution. In
that context, the aim of this work is i) to assess the performance
of a massive electricity storage concept based on CO2
transcritical cycles and ground heat exchangers, and ii) to carry
out the preliminary design of the whole system. This later
includes a heat pump transcritical cycle as the charging process
and a transcritical Rankine cycle of 1 – 10 MWe as the
discharging process.
A steady-state thermodynamic model is realized and several
options, including regenerative or multi-stage cycles, are
investigated. In addition, a one-dimensional design model of the
geothermal heat exchanger network is used to optimize the
number of wells for the ground heat storage.
The results show the strong dependency between the
charging and discharging cycles, and how the use of regenerative
heat exchangers and a two-phase expander (in the charging
cycle) could increase the system efficiency and lower the
investment cost.
Description:
Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016.
