Experimental Investigation on a Latent Heat Thermal Storage Unit for Solar Cooling Application

Green ◽  
2011 ◽  
Vol 1 (2) ◽  
Author(s):  
L. Chidambaram ◽  
A. S. Ramana ◽  
G. Kamaraj ◽  
R. Velraj
Keyword(s):  
Solar Energy ◽  
Latent Heat ◽  
Solar Collector ◽  
Heat Storage ◽  
Storage System ◽  
Thermal Storage ◽  
Environmental Crisis ◽  
Storage Unit ◽  
Latent Heat Storage ◽  
Solar Cooling

AbstractConventional cooling technologies that utilize harmful refrigerants consume more energy and cause peak loads leading to negative environmental impacts. As the world grapples with the energy and environmental crisis, there is an urgent need to develop and promote environmentally benign sustainable cooling technologies. Solar cooling is one such promising technology, given the fact that solar energy is the cheapest and most widely available renewable energy that matches the cooling load requirements. However thermal storage systems are essential to overcome the disadvantage of the intermittent nature of solar energy and variations in the cooling demand. The enhanced utilization of solar energy and other consequences of thermal storage integrated systems have gained the attention of researchers in recent years. The concept of combined sensible and latent heat storage system is successfully introduced in several applications and it has many advantages. This paper presents the performance of the solar collector system and the charging characteristics of a PCM based latent heat thermal storage unit, which is designed to provide continuous supply of heat for the operation of 1 kW vapor absorption refrigeration unit. Investigations on PCM integrated thermal storage system have revealed improvement in heat storage capacity, lower heat loss and an increased solar collector efficiency due to better thermal stratification.

scholarly journals Effective Separation of a Water in Oil Emulsion from a Direct Contact Latent Heat Storage System

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2264 ◽  
Author(s):  
Sebastian Ammann ◽  
Andreas Ammann ◽  
Rebecca Ravotti ◽  
Ludger Fischer ◽  
Anastasia Stamatiou ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Latent Heat ◽  
Direct Contact ◽  
Heat Storage ◽  
Storage System ◽  
Heat Transfer Fluid ◽  
Storage Unit ◽  
Latent Heat Storage ◽  
Oil Emulsion ◽  
Water In Oil Emulsion

The problem of emulsification between Phase Change Material (PCM) and Heat Transfer Fluid (HTF) in direct contact latent heat storage systems has been reported in various studies. This issue causes the PCM to flow out of the storage tank and crystallize at unwanted locations and thus presents a major limitation for the proper operation of such systems. These anomalies become more pronounced when high HTF flow rates are employed with the aim to achieve fast heat transfer rates. The goal of this paper is to find a method which will enable the fast separation of the formed emulsion and thus the uninterrupted operation of the storage unit. In this study, three separation methods were examined and the use of superhydrophobic filters was chosen as the best candidate for the demulsification of the PCM and HTF mixtures. The filter was produced by processing of a melamine sponge with different superhydrophobic adhesives and was tested with emulsions closely resembling the ones formed in a real direct contact setup. The superhydrophobic filter obtained, was able to separate the emulsions effectively while presenting a very high permeability (up to 1,194,980 kg h−1 m−2 bar−1). This is the first time the use of a superhydrophobic sponge has been investigated in the context of demulsification in direct contact latent heat storage.

scholarly journals A Domestic Solar/Heat Pump Heating System Incorporating Latent and Stratified Thermal Storage

2008 ◽  
Author(s):  
Christoph Trinkl ◽  
Wilfried Zo¨rner ◽  
Vic Hanby
Keyword(s):  
Latent Heat ◽  
Heat Pump ◽  
Solar Collector ◽  
Energy Demand ◽  
Heat Storage ◽  
Thermal Storage ◽  
Heating System ◽  
System Control ◽  
Latent Heat Storage ◽  
Solar Heat

Both solar and heat pump heating systems are innovative technologies for sustaining ecological heat generation. They are gaining more and more importance due to the accelerating pace of climate change and the rising cost of limited fossil resources. Against this background, a heating system combining solar thermal collectors, heat pump, stratified thermal storage and water/ice latent heat storage has been investigated. The major advantages of the proposed solar/heat pump heating system are considered to be its flexible application (suitable for new and existing buildings because of acceptable space demand) as well as the improvement of solar fraction (extended solar collector utilisation time, enhanced collector efficiency), i.e. the reduction of electric energy demand for the heat pump. In order to investigate and optimise the heating system, a dynamic system simulation model was developed. On this basis, a fundamental control strategy was derived for the overall coordination of the heating system with particular regard to the performance of the two storage tanks. In a simulation study, a fundamental investigation of the heating system configuration was carried out and optimisation derived for the system control as well as the selection of components and their dimensioning. The influence of different parameters on the system performance was identified, where the collector area and the latent heat storage volume were found to be the predominant parameters for system dimensioning. For a modern one-family house, a solar collector area of 30m2 and a latent heat store volume of 12.5m3 are proposed. In this configuration, the heating system reaches a seasonal performance factor of 4.6, meaning that 78% of the building’s and users’ heat demand are delivered by solar energy. The results show that the solar/heat pump heating system can give an acceptable performance using up-to-date components in a state-of-the-art building.

Numerical and Experimental Analysis of a PCM Thermal Storage System

2014 ◽  
Author(s):  
Adriano Sciacovelli ◽  
Vittorio Verda
Keyword(s):  
Latent Heat ◽  
Phase Change Materials ◽  
Heat Storage ◽  
Storage System ◽  
District Heating ◽  
Thermal Storage ◽  
Working Fluid ◽  
Latent Heat Storage ◽  
Thermal Enhancement ◽  
Charging And Discharging Processes

Phase-change materials (PCM) are particularly promising for thermal storage in energy systems where the working fluid is either characterized by small specific heat or small temperature difference. In these cases, sensible heat storage would involve small energy densities (i.e. energy per unit volume). Latent heat storage would allow one to reduce the volume of storage tanks, but also reduce problems related with thermal stratification. On the other hand, heat transfer in PCMs needs to be enhanced in order to complete the charging and discharging processes in reasonable time. This paper reports the numerical and experimental activity performed by the authors related with the design of latent heat storage systems for district heating applications. Among the various enhancement methods, fins present some technical advantages related with manufacturing and management, which make them suitable for the application in district heating systems. The following aspects are considered in this paper: 1) melting and solidification; 2) modeling approaches and validation; 3) thermal enhancement with circular, radial or Y-shaped fins.

scholarly journals Numerical study of an Evacuated Tube Solar Collector incorporating a Nano-PCM as a latent heat storage system

2021 ◽  
Vol 24 ◽  
pp. 100859
Author(s):  
Raja Elarem ◽  
Talal Alqahtani ◽  
Sofiene Mellouli ◽  
Walid Aich ◽  
Nidhal Ben Khedher ◽  
...  
Keyword(s):  
Latent Heat ◽  
Solar Collector ◽  
Heat Storage ◽  
Numerical Study ◽  
Storage System ◽  
Latent Heat Storage ◽  
Evacuated Tube Solar Collector ◽  
Evacuated Tube

Numerical and Experimental Investigation on a Combined Sensible and Latent Heat Storage Unit Integrated With Solar Water Heating System

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
N. Nallusamy ◽  
R. Velraj
Keyword(s):  
Numerical Model ◽  
Latent Heat ◽  
Solar Collector ◽  
Storage Tank ◽  
Heat Storage ◽  
Heating System ◽  
Storage Unit ◽  
Latent Heat Storage ◽  
Solar Water Heating ◽  
Solar Water Heating System

The present work investigates, theoretically and experimentally, the thermal performance of a packed bed combined sensible and latent heat storage unit, integrated with the solar water heating system. A one-dimensional porous medium approach with the finite difference technique is used to develop the numerical model to obtain the temperature profiles of both the phase change material (PCM) and heat transfer fluid (HTF), and the molten mass fraction of the PCM at any axial location of the cylindrical storage tank during the charging process. The model also incorporates the effect of the varying fluid inlet temperature to accommodate the actual conditions that prevails in the solar collector. Experimental apparatus utilizing paraffin as PCM, which is filled in high-density polyethylene spherical capsules, is constructed and integrated with a solar flat plate collector to conduct the experiments. The water used as HTF to transfer heat from the solar collector to the storage tank also acts as a sensible heat storage (SHS) material. The results of the numerical model are compared into the experimental results of the temperature profile for various porosities and HTF flow rates. It is found that the results of the numerical model are in good agreement with the experimental results. The performance parameters, such as instantaneous heat stored, cumulative heat stored, and charging rate are also studied in detail.

Simulation study on a Domestic Solar/Heat Pump Heating System Incorporating Latent and Stratified Thermal Storage

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Christoph Trinkl ◽  
Wilfried Zörner ◽  
Vic Hanby
Keyword(s):  
Latent Heat ◽  
Heat Pump ◽  
Simulation Study ◽  
Solar Collector ◽  
Heat Storage ◽  
Thermal Storage ◽  
Heating System ◽  
Latent Heat Storage ◽  
Solar Heat ◽  
Heat Demand

Both solar and heat pump heating systems are innovative technologies for sustaining ecological heat generation. They are gaining more and more importance due to the accelerating pace of climate change and the rising cost of limited fossil resources. Against this background, a heating system combining solar thermal collectors, heat pump, stratified thermal storage, and water/ice latent heat storage has been investigated. The major advantages of the proposed solar/heat pump heating system are considered to be its flexible application (suitable for new and existing buildings because of acceptable space demand), as well as the improvement of solar fraction (extended solar collector utilization time, enhanced collector efficiency), i.e., the reduction of electric energy demand for the heat pump by management of the source and sink temperatures. In order to investigate and optimize the heating system, a dynamic system simulation model was developed. On this basis, a fundamental control strategy was derived for the overall co-ordination of the heating system with particular regard to the performance of the two storage tanks. In a simulation study, a fundamental investigation of the heating system configuration was carried out and an optimization was derived for the system control, as well as the selection of components and their dimensioning. The influence of different parameters on the system performance was identified, where the collector area and the latent heat storage volume were found to be the predominant parameters for system dimensioning. For a modern one-family house of 120 m2 living area with a specific annual heat demand of 60 kWh/(m2 a) for both heating and domestic hot water, a solar collector area of 30 m2, and a latent heat store volume of 12.5 m3 are proposed for the location of Wuerzburg (Germany). In this configuration, the heating system reaches a seasonal performance factor of 4.6, meaning that 78% of the building’s and users’ heat demand are delivered by solar energy. The results show that the solar/heat pump heating system can give an acceptable performance using up-to-date components in a state-of-the-art building.

Thermo-Mechanical Storage of Electricity at Power Plant Scale

2013 ◽  
Author(s):  
Wolf-Dieter Steinmann
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Latent Heat ◽  
Heat Storage ◽  
Storage Systems ◽  
Storage System ◽  
Thermal Storage ◽  
Maximum Temperature ◽  
Latent Heat Storage ◽  
Temperature Heat

The availability of cost effective storage capacity is considered essential for increasing the share of renewables in electricity generation. With the development of solar thermal power plants large thermal storage systems have become commercial in recent years. Various storage concepts are applied, systems using solid storage media are operated at a maximum temperature of 680 °C, other systems using molten salt as storage medium show thermal capacities in the GWh range. Heating these storage systems directly by surplus electricity and using the heat later during the discharge process to operate turbines is not very attractive, since the process is limited by the Carnot efficiency. Alternatively, surplus electricity can be used to transform low temperature heat into high temperature heat which is stored in a thermal storage system during the charging process. During discharge, this heat is used to drive a turbine generating electric energy. Theoretically, this concept allows a roundtrip efficiency of 100%. Various options for the implementation of this storage concept have been suggested, using air or CO2 as working fluids. Recently, DLR has demonstrated the operability of a latent heat storage system connected to a steam circuit at 100 bar. The availability of this latent heat storage technology allows new implementations of the storage concept based on heat transformation. Using a left-running Rankine cycle during the charging process, heat from the environment is used to evaporate steam, which is compressed using the surplus electricity. Superheated steam exiting the compressor flows through the thermal storage system composed of latent heat storage sections and sensible heat storage sections. After throttling, the water enters the evaporator again. During discharging, heat from the storage system is used to evaporate and superheat steam, which drives the turbine. A cascaded implementation of this concept, using ammonia for the low temperature part of the process, while water is used for the high temperature part, reaches a storage efficiency of 70%. The integration of low temperature waste heat sources allows the compensation of losses.

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