Design aspects of a reversible heat pump - Organic rankine cycle pilot plant for energy storage

Steger, Daniel; Regensburger, Christoph; Eppinger, Bernd; Will, Stefan; Karl, Jürgen; Schlücker, Eberhard

doi:10.1016/j.energy.2020.118216

Cited by 42 publications

(14 citation statements)

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“…Such heat exchanger technology is especially suited for very small systems (1-10 kW el ), due to the reasonable cost and compactness, but can also be used in much larger applications (hundreds of kW el ), due to their modular nature, as investigated in [44] for VCHPs. For larger applications, in the order of 1000 kW el or higher, shell and tube heat exchangers should be used, as recommended by [45] for ORCs.…”

Section: Overview and Component Selectionmentioning

confidence: 99%

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Rankine Carnot Batteries with the Integration of Thermal Energy Sources: A Review

2020

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This paper provides an overview of a novel electric energy storage technology. The Thermally Integrated Pumped Thermal Electricity Storage (TI-PTES) stores electric energy as thermal exergy. Compared to standard PTES, TI-PTES takes advantage of both electric and low-temperature heat inputs. Therefore, TI-PTES is a hybrid technology between storage and electric production from low-temperature heat. TI-PTES belongs to a technology group informally referred to as Carnot Batteries (CBs). As the TI-PTES grows in popularity, several configurations have been proposed, with different claimed performances, but no standard has emerged to date. The study provides an overview of the component and operating fluid selection, and it describes the configurations proposed in the literature. Some issues regarding the performance, the ratio between thermal and electrical inputs, and the actual TI-PTES utilisation in realistic scenarios are discussed. As a result, some guidelines are defined. The configurations that utilise high-temperature thermal reservoirs are more extensively studied, due to their superior thermodynamic performance. However, low-temperature TI-PTES may achieve similar performance and have easier access to latent heat storage in the form of water ice. Finally, to achieve satisfactory performance, TI-PTES must absorb a thermal input several times larger than the electric one. This limits TI-PTES to small-scale applications.

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Section: Overview and Component Selectionmentioning

confidence: 99%

“…In small-scale ORCs, the fluid density influences the volumetric expander sizes. Similarly, in larger systems, the isentropic enthalpy difference and the volumetric flow rate determine the turbine diameter and stage number, and thus the machine cost [45].…”

Section: Ti-ptes Configurations Proposed In the Literaturementioning

confidence: 99%

Rankine Carnot Batteries with the Integration of Thermal Energy Sources: A Review

2020

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“…Different temperature and pressure levels in HP and ORC mode affect the density of the working fluid and thus its total mass in the fixed volume of piping and instrumentation changes. While the global discrepancies can be countered with a collector vessel (described in [3][4][5]), there are still local differences in the apparatuses' filling. The following procedure shows an analytical method of determining the filling of the heat exchanger, which operates as an HP-condenser and ORC-evaporator.…”

Section: Analytical Model To Calculate the Filling Of A Heat Exchangermentioning

confidence: 99%

“…The system has a thermal power of up to 100 kW and uses brazed plate heat exchangers. The working fluid is R1233zd(E) as it is advantageous in terms of safety and performance [4]. An overview of the pilot plant is shown in [11] and therefore it is not presented here in detail.…”

Section: Experimental Set-upmentioning

confidence: 99%

Heat Exchangers in Carnot Batteries: Condensation and Evaporation in a Reversible Device

et al. 2021

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The combined heat pump–organic Rankine cycle is a thermal–electrical storage concept which allows the reversible use of components in both operation modes (loading and unloading the storage). This saves in terms of investment costs but also creates challenges during design and operation. A heat exchanger is an expensive component destined to be used for the reversible purposes of a heat pump condenser and an organic Rankine cycle evaporator. In this study, the operation of such an apparatus was evaluated based on an analytical model, experimental data and thermal imaging. This study shows that the model can predict the filling of the apparatus distinguished by liquid, vapour and the two-phase region. The thermal imaging supports the model and gives the location of the regions. Connecting both methods, a valid statement about the current condition of the heat exchanger is possible. Due to very small pinch points, the apparatus is not efficiently used in the investigated modes. Extending the pinch to 2 K can already save up to 46.1% of the heat exchange area. The quality of the heat transfer in the evaporator (q˙ORC = 10.9 kW/m2) is clearly higher than in the condenser (q˙HP = 6.1 kW/m2).

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“…Commercial applications are currently being developed by different companies; e.g., MAN [20,21] and Energydome [22] have running pilot plants in the MW range. Academics, in recent years, have conducted numerical investigations for their integration into subordinated energy systems/sector coupling [23][24][25]; for the choice of suitable (low-GWP) working fluids and as basis for test rig designs [26,27]; and for the analysis of economic design aspects [28] and part-load behavior [29]. Furthermore, lab-scale experiments have been conducted with 10 kW [30,31] and 840 W max.…”

Section: Introductionmentioning

confidence: 99%

Thermal Operation Maps for Lamm–Honigmann Thermo-Chemical Energy Storage—A Quasi-Stationary Model for Process Analysis

Thiele

Ziegler

2022

Processes

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The Lamm–Honigmann energy storage is a sorption-based storage that can be arbitrarily charged and discharged with both heat and electrical power. The mechanical charging and discharging processes of this storage are characterized by an internal heat transfer between the main components, absorber/desorber and evaporator/condenser, that is driven by the working-fluid mass transferred between those components with the help of an expansion or compression device, respectively. In this paper, thermal operation maps for the mechanical charging and discharging processes are developed from energy balances in order to predict power output and storage efficiency depending on the system state, which, in particular, is defined by the mass flow rate of vapor and the salt mass fraction of the absorbent. The conducted method is applied for the working-fluid pair LiBr/H2O. In a first step, a thermal efficiency is defined to account for second-order losses due to the internal heat transfer; e.g., for discharging from a salt mass fraction of 0.7 to one of 0.5 (kg LiBr)/(kg sol.) at a temperature of 130 ∘C, it is found that the reversible shaft work output is reduced by 1.1–2.9%/(K driving temperature difference). For lower operating temperatures, the reduction is larger; e.g., at 80∘C, the efficiency loss due to heat transfer rises to 3.5%/K for a salt mass fraction of 0.5 (kg LiBr)/(kg sol.). In a second step, a quasi-stationary assumption leads to the thermal operation map from which the discharging characteristics can be found; e.g., at an operating temperature of 130 ∘C for a constant power output of 0.4 kW/m2 heat exchanger area at volumetric and inner machine efficiencies of ηi=ηvol=0.8 and for an overall heat-transfer coefficient of 1500 W/(K m2), the mass flow rate has to rise continuously from 1.5 to 4.2 g/(s m2), while the thermal efficiency is reduced from 97% to 83% due to this rise and due to the dilution of the sorbent. For this discharging scenario, the corresponding discharge time is 4.4 (min·m2)/(kg salt). This results in an exergetic storage density of around 29 Wh/(kg salt mass). For a charge-to-discharge ratio of 2 (charging times equals two times discharging time) and with the same heat-transfer characteristic and machine efficiencies for constant power charging with adiabatic compression, the system is charged at around 0.75 kW/m2, resulting in a round-trip efficiency of around 27%. Besides those predictions for arbitrary charging and discharging scenarios, the derived thermal maps are especially useful for the dimensioning of the storage system and for the development of control strategies. It has to be noted that the operation maps do not illustrate the transient behavior of the system but its quasi-stationary state. However, it is shown, mathematically, that the system tends to return to this state when disturbed.

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Design aspects of a reversible heat pump - Organic rankine cycle pilot plant for energy storage

Cited by 42 publications

References 14 publications

Rankine Carnot Batteries with the Integration of Thermal Energy Sources: A Review

Rankine Carnot Batteries with the Integration of Thermal Energy Sources: A Review

Heat Exchangers in Carnot Batteries: Condensation and Evaporation in a Reversible Device

Thermal Operation Maps for Lamm–Honigmann Thermo-Chemical Energy Storage—A Quasi-Stationary Model for Process Analysis

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