In a Renewable Energy Sources (RES) driven energy scenario, where more and more bulky quantities of RES should be introduced on the grid, the role of energy storages is crucial.Further to already available electric storage technologies (mostly based on batteries), it will be mandatory to have grid flexible large scale energy storages able to operate ramp-up/down with large capacity, whose behaviour/management should be as much similar as possible to traditional power plants (also to guarantee specific grid services like grid frequency regulation via rotating inertia etc.) which are currently used to instantaneously regulate the grid.At this purpose Pumped Thermal Energy Storage (PTES) offers GWh scale storage without geographical constraints, at reasonable costs, and implementing power and heat pump cycles integrated with thermal energy storage (TES) solutions.A PTES system indeed stores heat in two high temperature and low temperature TES units in charging phase using heat pump (HP) that operates on electricity provided by renewable energy sources (solar, wind etc.).The stored heat is used to drive a power cycle at required times.The choice of the working fluid for power cycle as well as heat pump cycles have a significant importance based on the range of storage temperature.Working fluid in PTES has direct effect on the performance, capital cost and efficiency of the whole operation.sCO2 as a working fluid has certain aspects that makes it the ideal candidate for large scale PTES applications.sCO2 cycles are indeed fully compatible with the temperature range of TES hot storage sources and sCO2 has already been used in commercial HP solutions (even targeting high temperature HPs).In addition, sCO2 allows energy storages to embody a compact design as well, making the whole PTES footprint smaller compared to technologies based on other working fluids.Nevertheless, sCO2 based PTES solutions cannot achieve significant Round Trip Efficiency (RTE): in this sense valorise freely available heat sources (like thermal RES or waste heat) could increase COP of the charging cycle and, at the end, RTE in what usually called Thermally Integrated Pumped Thermal Energy Storage (TI-PTES) as showed by authors in previous scientific papers [Maccarini et al., 2023], [Mehdi et al., 2023], with a sCO2 PTES cycle integrated with a single TES solution able to store electricity with good Round Trip Efficiency values.Nevertheless, this thermal input could be valorised not only in the charging cycle, but also in the discharging cycle: different layouts of the proposed TI-PTES will be compared from a techno-economic point of view, assessing different KPIs also looking at how much WH is valorised both in charging and discharging cycles.
COMPARISON OF DIFFERENT LAYOUTS OF A SCO2-BASED THERMALLY INTEGRATED-PUMPED THERMAL ENERGY STORAGE (TI-PTES)
Barberis S.;Shamsi S. S. M.;Maccarini S.;Traverso A.
2024-01-01
Abstract
In a Renewable Energy Sources (RES) driven energy scenario, where more and more bulky quantities of RES should be introduced on the grid, the role of energy storages is crucial.Further to already available electric storage technologies (mostly based on batteries), it will be mandatory to have grid flexible large scale energy storages able to operate ramp-up/down with large capacity, whose behaviour/management should be as much similar as possible to traditional power plants (also to guarantee specific grid services like grid frequency regulation via rotating inertia etc.) which are currently used to instantaneously regulate the grid.At this purpose Pumped Thermal Energy Storage (PTES) offers GWh scale storage without geographical constraints, at reasonable costs, and implementing power and heat pump cycles integrated with thermal energy storage (TES) solutions.A PTES system indeed stores heat in two high temperature and low temperature TES units in charging phase using heat pump (HP) that operates on electricity provided by renewable energy sources (solar, wind etc.).The stored heat is used to drive a power cycle at required times.The choice of the working fluid for power cycle as well as heat pump cycles have a significant importance based on the range of storage temperature.Working fluid in PTES has direct effect on the performance, capital cost and efficiency of the whole operation.sCO2 as a working fluid has certain aspects that makes it the ideal candidate for large scale PTES applications.sCO2 cycles are indeed fully compatible with the temperature range of TES hot storage sources and sCO2 has already been used in commercial HP solutions (even targeting high temperature HPs).In addition, sCO2 allows energy storages to embody a compact design as well, making the whole PTES footprint smaller compared to technologies based on other working fluids.Nevertheless, sCO2 based PTES solutions cannot achieve significant Round Trip Efficiency (RTE): in this sense valorise freely available heat sources (like thermal RES or waste heat) could increase COP of the charging cycle and, at the end, RTE in what usually called Thermally Integrated Pumped Thermal Energy Storage (TI-PTES) as showed by authors in previous scientific papers [Maccarini et al., 2023], [Mehdi et al., 2023], with a sCO2 PTES cycle integrated with a single TES solution able to store electricity with good Round Trip Efficiency values.Nevertheless, this thermal input could be valorised not only in the charging cycle, but also in the discharging cycle: different layouts of the proposed TI-PTES will be compared from a techno-economic point of view, assessing different KPIs also looking at how much WH is valorised both in charging and discharging cycles.
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