Simulation of the Part Load Behavior of Combined Heat Pump-Organic Rankine Cycle Systems

Eppinger, Bernd; Muradi, Mustafa; Scharrer, Daniel; Zigan, Lars; Bazan, Peter; German, Reinhard; Will, Stefan

doi:10.3390/en14133870

Cited by 10 publications

(13 citation statements)

References 29 publications

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“…The thermo-fluid-dynamics analysis of the exchange between the water and the PCM of the storages has not been performed, but, simply, the constant temperature at which the phase change must take place has been considered in the model. For further details about the thermo-fluid-dynamics of PCM, refer for instance to [29,30].…”

Section: Methodsmentioning

confidence: 99%

“…1 HP fi HP second stage. Four temperature differences between the highest and the lowest cycle tem have been considered for the HP and the ORC to investigate the fluids' perform ble 3), keeping the lowest temperature at a minimum of 15 °C (near the cons ground temperature of 12 °C) and the highest temperature at a maximum of 16 An almost ideal component behavior has been used to perform this investigation, since no pressure drops have been taken into consideration [30], and only a few machine efficiencies not equal to unity have been used, as described in Table 2. Four temperature differences between the highest and the lowest cycle temperatures have been considered for the HP and the ORC to investigate the fluids' performances (Table 3), keeping the lowest temperature at a minimum of 15 • C (near the constant CStor ground temperature of 12 • C) and the highest temperature at a maximum of 160 • C.…”

Section: Preliminary Fluids Selectionmentioning

confidence: 99%

“…HP compressors and the ORC expander are considered to be screw machines, and no pressure drops have been taken into account for them, nor for heat exchangers and the ORC pump, as done by Eppinger et al [30].…”

Section: Design Modelsmentioning

confidence: 99%

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Part-Load Energy Performance Assessment of a Pumped Thermal Energy Storage System for an Energy Community

Nadalon,

De Souza,

Casisi

et al. 2023

Energies

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Research on pumped thermal energy storage (PTES) has gained considerable attention from the scientific community. Its better suitability for specific applications and the increasing need for the development of innovative energy storage technologies are among the main reasons for that interest. The name Carnot Battery (CB) has been used in the literature to refer to PTES systems. The present paper aims to develop an energy analysis of a CB comprising a high-temperature two-stage heat pump (2sHP), an intermediate thermal storage (latent heat), and an organic Rankine cycle (ORC). From a broad perspective, the CB is modeled considering two types of heat inputs for the HP: a cold reservoir in the ground (at a constant temperature of 12 °C throughout the entire year) and a heat storage at 80 °C (thermally-integrated PTES—TI-PTES). The first part defines simple models for the HP and ORC, where only the cycles’ efficiencies are considered. On this basis, the storage temperature and the kind of fluids are identified. Then, the expected power-to-power (round-trip) efficiency is calculated, considering a more realistic model, the constant size of the heat exchangers, and the off-design operation of expanders and compressors. The model is simulated using Engineering Equation Solver (EES) software (Academic Professional V10.998-3D) for several working fluids and different temperature levels for the intermediate CB heat storage. The results demonstrate that the scenario based on TI-PTES operation mode (toluene as the HP working fluid) achieved the highest round-trip efficiency of 80.2% at full load and 50.6% round-trip efficiency with the CB operating at part-load (25% of its full load). Furthermore, when the HP working fluid was changed (under the same scenario) to R1336mzz(Z), the round-trip full-load and part-load efficiencies dropped to 72.4% and 46.2%, respectively. The findings of this study provide the HP and ORC characteristic curves that could be linearized and used in a thermo-economic optimization model based on a Mixed-Integer Linear Programming (MILP) algorithm.

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Section: Methodsmentioning

confidence: 99%

Section: Preliminary Fluids Selectionmentioning

confidence: 99%

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Part-Load Energy Performance Assessment of a Pumped Thermal Energy Storage System for an Energy Community

Nadalon,

De Souza,

Casisi

et al. 2023

Energies

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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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“…Many research centers have been interested in the study of CHP plants [10][11][12][13]. Some studies addressed the development of calculation algorithms for the optimal configuration and operation of the plants [14][15][16][17][18][19][20]. In the 1990s, many experimental investigations concerning micro-CHP systems were carried out at the University of Naples Federico II [21,22].…”

Section: Introductionmentioning

confidence: 99%

Development of a 1 kW Micro-Polygeneration System Fueled by Natural Gas for Single-Family Users

Gimelli

Muccillo

2021

Energies

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The use of primary energy saving techniques and renewable energy systems has become mandatory to tackle the effects of global temperature rise. As a result, a transition is taking place from centralized energy generation to distributed energy generation. Starting from the experience concerning a 15 kW micro-CHP plant previously designed at DII, this paper addresses the development of a 1 kW micro-CHP system fueled by natural gas for single-family users. Specifically, the paper presents a wide experimental investigation aimed at optimizing performance and emissions of a small scale two-stroke spark ignition gasoline engine properly modified to be fueled with natural gas to make the engine more suitable for cogeneration purposes. The described activity was carried out at the DII of the University of Naples Federico II. Rigorous laboratory tests were conducted with the engine in order to characterize both gasoline and CNG operation in terms of brake mechanical power, overall efficiency and exhaust gas emissions in different operating regimes. Furthermore, several physical quantities associated with the engine operation were measured through several sensors in order to optimize performance and emissions achieved when the engine is fueled with CNG. In particular, dynamic pressure variations inside the cylinder were measured and analyzed to evaluate the effect of the adopted fuel on the optimum ignition-timing angle and cyclic dispersion.

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Simulation of the Part Load Behavior of Combined Heat Pump-Organic Rankine Cycle Systems

Cited by 10 publications

References 29 publications

Part-Load Energy Performance Assessment of a Pumped Thermal Energy Storage System for an Energy Community

Part-Load Energy Performance Assessment of a Pumped Thermal Energy Storage System for an Energy Community

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

Development of a 1 kW Micro-Polygeneration System Fueled by Natural Gas for Single-Family Users

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