Abstract
Thermal energy storage (TES) became one of the main research topics in modern power engineering. The design of TES devices and systems depend on their application. Different thermal energy storage materials (e.g., solids, liquids, or phase change materials) can be applied in TES devices. The selection of the thermal energy storage material depends mainly on the thermal power and operating temperature range of the TES device. These devices and systems are applied in different energy conversion systems, including solar power plants or combined heat and power (CHP) stations. The application of TES devices is also considered in the case of other industries, such as metallurgy. The possible application of TES devices is particularly promising in the case of organic Rankine cycle (ORC) systems. These systems are often utilizing floating heat sources such as solar energy, waste heat, etc. TES device can be therefore applied as the evaporator of the ORC system in order to stabilize these fluctuations. In this paper, the possible thermal energy storage materials used in TES devices applied in ORCs are discussed. Moreover, the modelling results are reported related to assessment parameters which can be applied to size the TES device for ORC system utilizing different low-boiling working fluids. The thermal properties of working fluids are taken from CoolProp. The function of heat capacity of different TES materials is also provided and the calculation is computed by employing MATLAB. The result shows that based on the simulation, the gradient of the natural characteristic of TES with working fluids (ζ(Tb)) tends to decrease. The presented result in this paper gives a new point of view which can be used by scientists and engineers during the design and implementation of TES evaporators dedicated to ORC power systems.
Highlights
Intensive research aimed at methods and technologies which can be utilized by the modern power industry for environmental protection and efficiency improvement is currently proceeded
The obtained modelling results related to the variation of the dimensionless storage mass parameter ζ vs. temperature of the working fluid at the outlet of the Thermal energy storage (TES) device (Tb) are summarized in Figure 3 for different working fluids and different solids used as the thermal energy storage materials
This paper has presented the results of the analysis on sizing the TES evaporator for organic Rankine cycle (ORC) systems and its gradient as a function of temperature before the expansion process
Summary
Intensive research aimed at methods and technologies which can be utilized by the modern power industry for environmental protection and efficiency improvement is currently proceeded. In the following part of the paper, the results of modelling of the size of the TES device which is considered to be applied as the main heat source for the ORC system are presented for different low-boiling working fluids, storage materials and operating temperature ranges. Taking into account the thermal properties of the selected fluids we decided to limit the treatment to the subcritical cycles, the modelling is proceeded for the TES device temperature ranging from 373.15 ≤ܶ୳୮୮ୣ୰≤ ܶୡ୰୧୲-20 K (see Table 3) For these conditions of the heat source the heat amount needed to preheat and evaporate the working fluid (per 1 kg of substance) can vary for different working fluids and could be calculated using Equations (1) and (2).
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