Analysis of a novel solar electricity generation system using cascade Rankine cycle and steam screw expander

Li, Jing; Li, Pengcheng; Pei, Gang; Alvi, Jahan Zeb; Ji, Jie

doi:10.1016/j.apenergy.2015.12.087

Cited by 72 publications

(45 citation statements)

References 35 publications

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“…Moreover, in Figure , similar decreases in the SE overall efficiency η SE (off‐design working conditions) are also manifest when r p < r p,b , namely, in underexpansion operating conditions. In fact, in this other case (when exhaust pressures p 4 increase and evaporation temperatures T 3 drop), the resultant working expansion ratios become progressively lower than the fixed built‐in expansion ratio, thereby causing blowdown operating conditions …”

Section: Resultsmentioning

confidence: 99%

“…The solar power collector efficiency η PTC of a PTC (sole module) is evaluated by Equation , where T a (K) is ambient temperature, T (K) is temperature at the PTC inlet, and G b (W/m 2 ) is beam solar radiation:

η_{PTC} ((), T) = 0.762 - 0.212 \cdot \frac{T - T_{a}}{G_{normalb}} - 0.001672 \cdot \frac{{((), T - T_{a})}^{2}}{G_{normalb}} .

…”

Section: Numerical Modelsmentioning

confidence: 99%

“…In Equation , the SE overall isentropic efficiency η SE contemplates all the efficiencies listed above. In the same equation, η D = η L ·η ti represents the diagram efficiency:

η_{SE} = η_{Th} \cdot η_{L} \cdot η_{ti} \cdot η_{m} = η_{Th} \cdot η_{D} \cdot η_{m} .

…”

Section: Numerical Modelsmentioning

confidence: 99%

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Energy performance and numerical optimization of a screw expander–based solar thermal electricity system in a wide range of fluctuating operating conditions

2019

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Summary This paper provides fundamental principles to study the thermodynamic performance of a new screw expander–based solar thermal electricity plant. While steam turbines are generally used in direct steam generation solar systems without admitting fluid in two‐phase conditions, steam screw expanders, as volumetric machines, can convert thermal to mechanical energy also by expanding liquid‐steam mixtures without a decline in efficiency. In effect, steam turbines are not as competitive as screw expanders when the net power is smaller than 2 MW and for low‐grade heat sources. The solar electricity generation system proposed in this paper is based on the steam Rankine cycle: Water is used as both working fluid and storage, parabolic trough collectors are used as a thermal source, and screw expanders are used as power machines. Since screw expanders can operate at off‐design working conditions in several situations when installed in direct steam generation solar plants, studying expander performance under fluctuating working situations is a crucial issue. The main aim of the present paper is to establish a thermodynamic model to study the energetic benefits of the proposed power system when off‐design operating conditions and variable solar radiation occur. This entails, first and foremost, developing overexpansion and underexpansion numerical models to describe the polytropic expansion phase, which considers all the losses affecting performance of the screw expander under real operating conditions. To assess the best operating conditions and maximum efficiency of the whole power system at part‐load working conditions under fluctuating solar radiations, parametric optimization is then improved in a wide range of variable working conditions, assuming condensation pressures of water increasing from 0.1 to 1 bar, under an evaporation temperature rising from 170°C to 300°C.

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Section: Resultsmentioning

confidence: 99%

η_{PTC} ((), T) = 0.762 - 0.212 \cdot \frac{T - T_{a}}{G_{normalb}} - 0.001672 \cdot \frac{{((), T - T_{a})}^{2}}{G_{normalb}} .

…”

Section: Numerical Modelsmentioning

confidence: 99%

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Energy performance and numerical optimization of a screw expander–based solar thermal electricity system in a wide range of fluctuating operating conditions

2019

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“…Built-in VFR refers to the VFR under nominal working conditions, and the turbine will be manufactured according to this value. A low built-in VFR is desirable since it is advantageous to improve the mass flow rate of working fluid through the turbine, and the leakage loss decreases accordingly [54]. Furthermore, a lower built-in VFR is conducive to reduce the structural complexity and the manufacturing costs of the turbine.…”

Section: Thermodynamic Performance Analysismentioning

confidence: 99%

Thermo-Economic Performance Analysis of a Regenerative Superheating Organic Rankine Cycle for Waste Heat Recovery

Han

et al. 2017

Energies

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Abstract:The Organic Rankine Cycle (ORC) is a promising form of technology for recovering low-grade waste heat. In this study, a regenerative ORC system is established to recover the waste flue gas of 160 • C. Focusing on thermodynamic and economic performance while simultaneously considering the limitations of volume flow ratio (VFR) and the effect of superheat, working fluid selection and parameter optimization have been investigated. The optimization of the evaporation temperature is carried out by analyzing the variation of net power output and specific investment cost (SIC). Then, the net power output, specific net power output, total exergy destruction rate, VFR, total capital cost, and levelized electricity cost (LEC) are selected as criteria, and a fuzzy multi-criteria evaluation method is adopted to select a more suitable working fluid and determine the optimal degree of superheat. In addition, the preheating coefficient, latent heat coefficient, superheating coefficient, and internal heat coefficient were proposed to explore the effect of working fluid critical temperature on thermal efficiency. Research studies demonstrate that there is an optimal evaporation temperature, maximizing net power output and minimizing the SIC. Isohexane and butane have greater specific net power output due to greater latent heat. A suitable degree of superheat is not only conducive to improving the working capacity of working fluids, but also reduces the VFR, total capital cost, SIC, and LEC for different working fluids. Thus, the system's thermodynamic and economic performance-as well as the operational stability-are improved. Among the six working fluids, butane exhibits the best comprehensive performance, and its optimal evaporation temperature and degree of superheat are 100 • C and 5 • C, respectively.

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“…Molten salt has been implemented as the heat transfer fluid (HTF) in the USA Solar‐Two power tower project. Because of the simple structure of these storage systems, they are also recommended for parabolic trough collector power plants . There are already numerous plants readily existing with 7.5 to 15 hours under full load storage conditions.…”

Section: Introductionmentioning

confidence: 99%

Development and analysis of a new integrated solar energy system with thermal storage for fresh water and power production

Demir

Dinçer

2017

Int J Energy Res

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Summary In this study, a new integrated solar‐energy based system for fresh water and electricity production is proposed and thermodynamically analyzed. The proposed system consists of a solar tower with a volumetric solar receiver, a Rankine cycle driven by solar power, molten salt storage subsystem and a multi‐stage flash distillation (MFD) subsystem. In the present system, solar tower charges the molten salt, which flows through a heat exchanger to produce steam for the Rankine cycle. A part of the molten salt directly goes to hot storage tank after they are heated up by the solar tower. In order to keep the generated energy at the same level, molten salt in the hot storage tank compensates the deficient energy when direct normal irradiance (DNI) level is not sufficient. After the sunset, only the molten salt from the storage supplies energy to the cycle. The MFD produces the desired amount of fresh water from seawater. The seawater used for the distillation is heated by the saturated steam‐water mixture coming from the steam turbine. Utilizing the output fluid as a heat source for the MFD also eliminates the external device for condensation. All system components of the integrated system are analyzed in the Engineering Equation Solver (EES). The overall energy and exergy efficiencies are calculated for each system component. The capacity of the power generation and fresh water production of the proposed system is also calculated. Moreover, a parametric study is undertaken to investigate the effects of varying ambient conditions on the system performance.

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Analysis of a novel solar electricity generation system using cascade Rankine cycle and steam screw expander

Cited by 72 publications

References 35 publications

Energy performance and numerical optimization of a screw expander–based solar thermal electricity system in a wide range of fluctuating operating conditions

Energy performance and numerical optimization of a screw expander–based solar thermal electricity system in a wide range of fluctuating operating conditions

Thermo-Economic Performance Analysis of a Regenerative Superheating Organic Rankine Cycle for Waste Heat Recovery

Development and analysis of a new integrated solar energy system with thermal storage for fresh water and power production

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