Parametric Study of a Long-Duration Energy Storage Using Pumped-Hydro and Carbon Dioxide Transcritical Cycles

Abstract

The urgent energy transition needs a better penetration of renewable energy in the world’s energy mix. The intermittency of renewables requires the use of longer-term storage. The present system uses water displacement, in a lined rock cavern or in an aerial pressurised vessel, as the virtual piston of compressor and expander functions in a carbon dioxide heat pump cycle (HPC) and in an organic transcritical cycle (OTC). Within an impermeable membrane, carbon dioxide is compressed and expanded by filling and emptying pumped-hydro water. Carbon dioxide exchanges heat with two atmospheric thermal storage pits. The hot fluid and ice pits are charged by the HPC when renewable energy becomes available and discharged by the OTC when electricity is needed. A numerical model was built to replicate the system’s losses and to calculate its round-trip efficiency (RTE). A subsequent parametric study highlights key parameters for sizing and optimisation. With an expected RTE of around 70%, this CO2 PHES (pumped-hydro electricity storage) coupled with PTES (pumped thermal energy storage) could become a game-changer by allowing the efficient storage of intermittent renewable energy and by integrating with district heating and cooling networks, as required by cities and industry in the future.

Storage Futures Study: The Challenge of Defining Long-Duration Energy Storage

“…For example, Figure 5 shows a scenario in which the combination of VRE and storage produces net load peaks of about 10 hours. 7 As discussed previously, this could be provided by a 10-hour duration device, or a 6-hour duration device derated to 60% power capacity. In these cases, the derate means that the power component of the shorter-duration storage system is potentially oversized (more costly) relative to the longerduration system.…”

Heat Recovery Potential in a Semi-Closed Greenhouse for Tomato Cultivation

“…Depending on the storage duration, different storage systems can be employed. A previous study reviewed the storage systems available depending on the storage time [23]. Table 2 summarizes the results of this literature review.…”

Research Summary and Literature Review on Modelling and Simulation of Heat Pumps for Simultaneous Heating and Cooling for Buildings

“…Due to its low temperature at the critical point, large pressure differences are observed over the cycle and therefore a high mechanical work can be obtained on expansion. A parametric study was carried out by our research group on a long-duration energy storage using pumped-hydro and carbon dioxide transcritical cycles as a heat pump [121]. This application affects more the industrial sector in which buildings also demand high amounts of heating and cooling energies.…”