Detailed numerical investigation of a pumped thermal energy storage with low temperature heat integration

• Published in: Energy (Oxford) 2018-02, Vol.145, p.665-676
• Main Authors: Jockenhöfer, Henning, Steinmann, Wolf-Dieter, Bauer, Dan
• Format: Article
• Language: English
• Subjects: Adiabatic; Adiabatic flow; Alternative energy; Butene; Computer simulation; Design optimization; Electric power; Energy; Energy consumption; Energy conversion; Energy conversion efficiency; Energy storage; Exergy; Heat transfer; Hydraulic design; Integration; Low temperature; Mathematical models; ORC; ORC-CHEST; Power consumption; Power to heat to power; PTES; Pumped thermal energy storage; Pumps; Renewable energy; Storage; Subcritical; Thermal energy; Thermodynamics; Waste heat integration; Working fluids
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2017.12.087

In future energy systems, storage technologies for electrical energy are considered to be a key component for increasing the share of renewable energy use. Pumped thermal energy storage technologies represent a promising approach to complement established storage technologies such as pumped-hydro power storages without their geological restrictions. Assuming an ideal, reversible and adiabatic energy conversion process, the stored electrical energy can be entirely recovered. However, the efficiency of real processes is limited by irreversibilities. These exergy losses can be compensated by the integration of low temperature heat. The exergetic efficiency can be further increased by using thermal energy provided during discharging. In this paper, a fully heat-integrated, subcritical PTES using butene as the working fluid is presented. The results of a detailed numerical simulation of the cycle regarding exergy losses during heat transfer, efficiencies of machinery and parasitic energy consumption are shown. A maximum net electrical power ratio between charging and discharging of 125% is obtained, while the maximum exergetic efficiency is 59%. The conducted numerical simulation includes pressure losses and pinch points, allowing for a more in-depth understanding and for a pre-optimization of the hydraulic design. •A thermally integrated PTES-system based on an Organic Rankine-cycle is presented.•Applications for the ORC-CHEST in superordinated energy systems are presented.•A realistic numerical analysis considering irreversibilities was conducted.•Maximum power-ratio of 1.25 and maximum exergetic efficiency of 0.59 are obtained.