Currently the reduction of the levelised cost of electricity (LCOE) is the main goal of concentrating solar power (CSP) research. Central to a cost reduction strategy proposed by the American Department of Energy is the use of advanced power cycles like supercritical steam Rankine cycles to increase the efficiency of the CSP plant. A supercritical steam cycle requires source temperatures in excess of 620°C, which is above the maximum storage temperature of the current two-tank molten nitrate salt storage, which stores thermalenergy at 565°C. Metallicphasechangematerials (PCM) can store thermalenergy at higher temperatures, and do not have the drawbacks of salt based PCMs. A thermalenergystorage (TES) concept is developed that uses both metallic PCMs and liquid metal heat transfer fluids (HTF). The concept was proposed in two iterations, one where steam is generated directly from the PCM – direct steam generation (DSG), and another where a separate liquid metal/water heat exchanger is used – indirect steam generation, (ISG). Eutectic aluminium-silicon alloy (AlSi12) was selected as the ideal metallic PCM for research, and eutectic sodium-potassium alloy (NaK) as the most suitable heat transfer fluid.
Abstract: Battery-powered electric buses currently face the challenges of high cost and limited range, especially in winter conditions, where interior heating is required. To face both challenges, the use of thermalenergystorage based on metallicphasechangematerials for interior heating, also called thermal high-performance storage, is considered. By replacing the battery capacity through such an energystorage system, which is potentially lighter, smaller, and cheaper than the batteries used in buses, an overall reduction in cost and an increase of range in winter conditions could be reached. Since the use of thermal high-performance storage as a heating system in a battery-powered electric bus is a new approach, the requirements for such a system first need to be known to be able to proceed with further steps. To find these requirements, a review of the relevant state of the art of battery-powered electric buses, with a focus on heating systems, was done. Other relevant aspects were vehicle types, electric architecture, battery systems, and charging strategies. With the help of this review, requirements for thermal high-performance storage as a heating system for a battery-powered electric bus were produced. Categories for these requirements were the thermal capacity and performance, long-term stability, mass and volume, cost, electric connection, thermal connection, efficiency, maintenance, safety, adjustment, and ecology.
same quantity of cold water at 32 ˚C is fed into TES tank in each batch. The average temperature of the collected discharge water in the bucket is measured using a digital thermometer. The time difference between the conse- quent discharges is 20 min. The batch wise withdrawing of hot water is continued till the temperature of the outlet water reaches 32 ˚C. A comparative study is also made between the conventional SHS system and com- bined storage system (SHS + LHS).
The discharging process was started with the flow rate of 0.5 and 1lit/hr. The inlet temperature of cold water kept at the atmospheric temperature that is 32°C or lower than the PCM melting Temperature. During the discharging process the cold water is circulated through over the copper tube.Now the heat energy stored in PCM is transferred to the cold water so the cold water temperature is increased .temperature of the PCM and HTF are recorded at intervals of 5 min. The discharging process is continued until the PCM temperature reduces to atmospheric temperature. The temperature of HTF at inlet and outlet are recorded .Also the temperature of the PCM at two location are recorded. Like that the flow rate changed to 1 lit/min and the PCM and HTF temperature are recorded. The heat transfer fluid exit temperature is time dependent because the rate of solidification of the PCM varies with the time. This mode terminates with the solidification of the PCM
The literature is scarce regarding TES concepts associated to wood stoves. A CFD-based methodology was developed by Benesch et al.  to analyse and optimize wood log stoves using sensible heat storage. Various heat storagematerials in solid state were then tested. Thereafter, the research group developed guidelines for heat storage solutions using PCMs applied to wood log stoves . A key conclusion indicated that, to allow effective heat storage at partial combustion load, the PCM melting temperature should not be too high. The following criteria were listed as both essential and challenging for LHS systems applied to wood log stoves: low flammability, low thermal degradation, high heat capacity, high density, suitable melting temperature, affordability, low corrosivity and low toxicity. The guidelines strongly advised a full integration of the LHS unit by the side(s) of the stove, allowing the circulation of exhaust gas through the PCM, while discharging latent heat using air channels and free convection.
Inequality between energy required and energy supply affects different types of energy technologies. Typical examples of such problems are thermal powergeneration plant, solar systems, cooling and heating systems etc. This gap between available and needed energy can be meet with help of thermalenergystorage systems. Sensible heat storage and latent heat storage are the common methods of thermalenergystorage. Latent heat storage is most proficient rather than sensible heat storage because of their wide energystorage density and also latent heat generated during phasechange at almost constant temperature. Generally Phasechangematerials (PCMs) are used to store the thermalenergy. The energy exchange between PCM and working fluid when it passes through melting and solidification processes. During melting process heat is transfer from hot fluid to PCM and in case of solidification process PCM rejects heat to the cold fluid. Energystorage systems not only deliver constant supply but also save the energy by improving the stability and performance of the system.
the addition of different high thermal conductivity materials. Mettawee and Assassa (2007) placed aluminium powder in the PCM for a compact PCM solar collector and tested its performance during the processes of charging and discharging. The results showed that significant improvement can be achieved. Some investigators studied the graphite matrix embedded within paraffin, and significant improvement in thermal conductivity was achieved (Mettawee and Assassa 2007, Nayak et al. 2006, Py et al. 2001, Nakaso et al. 2008). One intrinsic problem of a graphite matrix is its anisotropy in that the thermal conductivity depends on the direction. To solve this problem, some metal materials with high thermal conductivities could be used to enhance the heat transfer performance of the PCMs. The effectiveness of metal matrix and finned surface as thermal conductivity enhancers was numerically studied by Nayak et al. (2006). Ellinger and Beckermann (1991) experimentally investigated the heat transfer enhancement in a rectangular domain partially occupied by a porous layer of aluminum beads. They found that the introduction of a porous layer caused the solid/liquid interface to move faster initially during the conduction-dominated regime. However, the overall melting and heat transfer rates were found to be lower with the presence of porous layer due to the low porosity and permeability which severely constrains the mixing heat transfer caused by the convection.
To enhance the effective thermal conductivity of the system, the copper tube is formed in coil form. 10 number of coil are used with the distance of 5 cm between the coils. 2 mm thick circular fin has been fitted with spiral coil. The inner tube is made of copper. The outer tube is made of mild steel. The outside of the outer pipe was insulated with 3 mm thick asbestos rope to reduce the heat loss during charging and discharging process of the PCM. The outer tube inner side was filled with 1.374 kg commercial grade paraffin wax being used as latent heat storage media. Type T-copper constantan thermocouples were used for measuring the inlet and outlet temperature of heat transfer fluid (HTF) and the PCM temperature at two locations in the PCM tank. A two tank system are used form maintaining a constant pressure head for inlet water to maintain nearly constant flow rate. Heaters with thermocouple were also provided in the water tanks for constant inlet water temperature during charging mode. Flowing hot water through inner tube started the energy charging test, and the stored energy was extracted by
One of the most reliable phasechangematerials which are being extensively used nowadays as heat storage material in most of the thermalstorage units is paraffin. Paraffin is popularly used because of its properties such as large latent heat and thermal characteristics. The thermal characteristics of paraffin are varied phasechange temperature, low vapor pressure in the molten state, negligible super cooling, appreciable thermal and chemical stability and also self nucleating behavior. A long freeze melt cycle is experienced by the systems which use paraffin as the phasechange material in their thermalenergystorage unit. Paraffin is made of a mixture of long chain of n-alkanes [CH 3 -(CH 2 )-CH 3 ]. Properties such as latent heat of fusion and melting point increases as the
nanoparticles is considered essential to the technological upheaval, which is attentive with significant materials’ illusion and amended physical, chemical and biological properties. Nanosciences are known as antibacterial agents because of their structure, size, and surface properties. Thus, nanotechnology gives a way to get better the inorganic antibacterial agents activity. Nanoparticles of metal oxide like toMgO, ZnO and CaO were inspected as agents of inorganic antibacterial. MgO is an example of important inorganic material having a wide bandgap. It was used in different applications including catalysis, catalyst supports, refractory materials, adsorbents, etc. In the field of medicine, MgO is used for the heart burn relief and for regeneration of bone. Recently, MgO nanoparticles have shown promise for application in tumor treatment. MgO nanoparticles also have considerable potential as an antibacterial agent. Nanostructured materials promise fruitful development for applications in the aerospace sector due to their low density, high strength and thermal stability [7,8]. Different antimicrobial agents have different effects on different organisms  due to which nanoscience best act as antibacterial agents because of their structure, size, and surface properties. Nanotechnology has attracted the interest of numerous research groups around the world due to its potential for application in various industries . Polymeric materials have unique properties such as low density, light weight, and high flexibility and are widely used in various industrial sectors [11,12]. Polymers are considered a good choice as host materials, because they normally exhibit long-term stability and possess flexible reprocessability and they can be designed to yield a variety of bulk physical properties .
Thermalenergystorage (TES) is becoming a growing concern in modern technology and it has number of applications. Energystorage is essential whenever there is a mismatch between the supply and consumption of energy. Growing energy demands, lack of fossil fuels, and the continuous increase in the level of greenhouse gas emissions are the main driving forces to practice various sources of renewable energy. Due to irregular and unpredictable nature of solar energy; efficient, ermal energystorage devices and methods have to be developed. Among the different possibilities to store energy, systems using PhaseChangeMaterials (PCM) can be preferred for its consistency in latent heat storage. The use of PCM is an effective way of storing thermalenergy and has the advantages of having high storage density and the isothermal nature of the storage process. Due to this, the volume of material is reduces and so the cost of the system. But the vity which leads to poor heat transfer so heat transfer enhancement techniques should be used. This paper summarise the selection of thermalenergy
Global warming has become a serious problem to human being. It is caused by the emission of greenhouse gasses. This phenomenon adversely affects the environment and cause the depletion of energy sources. An appropriate and organized method must be taken to save the energy. Thermalenergystorage (TES) is one of the best alternative and TES using PCM is one of the best technique. Thermalstorage device is able to absorb, store and release energy when needed. PCM is targeted to be applied in the passive cooling system method as it is a promising material that suits this purpose. Compare to other PCMs, paraffin is the most studied materials for thermalenergystorage applications. However, the main problem of paraffin is the liquid leakage of this material during solid to liquid phasechange. This will affect the original quantity of the paraffin used hence reduce its effectiveness. Figure 1.4 illustrates the leakage problem of paraffin when it is use in a building.
Considerable research over the years has focused on the importance of stored latent heat by incorporating PCMs into building materials in order to save energy, enhance heat transfer and increase the thermal mass in buildings. To achieve these aims, some studies have been directed at developing encapsulation methods: at macro, micro and nano levels. But the drawbacks of this method are its cost and complicated processing. Therefore, many studies have employed a cheaper, simpler and less complicated method i.e. the preparation of form-stable composite PCMs. As indicated in the literature review above, researchers studied the thermal properties of PCMs added to the carrier materials, usually measured by DSC, and then analysed their thermal performance. But they did not study all types of carrier materials that could be used to incorporate various PCMs in building materials. Moreover, they did not take into account the flammability of PCMs. Organic PCMs incorporated in building materials are highly flammable, there is thus a fire risk related to PCM-containing PL. Therefore, to meet building fire requirements, the addition of flame retardant to PCM PL is necessary. As a consequence it is important to understand the fire and smoke behavior of phasechangematerials in building applications with and without flame retardants.
more thermalenergy per unit volume . Heat is absorbed and released almost isothermally and is used to reduce the energy consumed by conventional heating and cooling systems by reducing peak loads [17-19]. Organic and inorganic PCMs are the two types of PCMs used for construction applications. Organic PCMs are sub- classified as paraffin and non-paraffins [20, 21]. These organic PCMs are having better properties of cohesion, chemical stability, non-reactivity and recyclability as their advantages [22-27]. But these organic PCMs are comparatively low heat conductivity in the solid state. But inorganic compounds have a high latent heat absorbing capacity and also non-flammable. Inorganic PCMs have high thermalenergy store and are cheaper than organic PCMs [28, 29].
Phasechangematerials (PCMs) have long been used for thermalenergystorage due to the large amount of heat absorption/release while undergoing phase changes, with only small temperature variations [1-10]. Organic and inorganic materials are two most common groups of PCMs . Organic materials are further described as paraffin and non-paraffin. Most organic PCMs are non-corrosive and chemically stable, and have little or no sub-cooling. They are compatible with most building materials and have a high latent heat per unit weight and low vapour pressure. But they also have disadvantages in low thermal conductivities, high changes in volume on phasechange and flammability. In contrast, inorganic materials (salt hydrate and metallic) have a high latent heat per unit volume and high thermal conductivities, and are non-flammable and low in cost in comparison to organic materials. However, they are corrosive to most metals and suffer from decomposition and sub-cooling, which can affect their phasechange properties. Therefore, In order to overcome these problems, a new technique of utilising microencapsulated phasechange material (MEPCM) in thermalenergystorage system has been developed. Microencapsulated PCMs provide a means to solve the super-cooling problem and interfacial combination with the circumstance materials . The main merits of microencapsulated phasechange material (MPCM) over PCM are as follows: (1) increasing heat transfer area; (2) reducing PCMs reactivity towards the outside environment and controlling the changes in the storage material volume as phasechange occurs. The use of microencapsulated phasechangematerials (MPCMs) is one of the most efficient ways of storing thermalenergy and it has received a growing attention in the past decade [12-27]. Since MPCM was developed, it had been mainly used in the textile [19, 28-31] and building applications [32-36].
220.127.116.11. Thermo-mechanical analysis of metal foams impregnated with PCMs. The thermo-mechanical analysis of porous graphite impregnated with PCMs was also performed in order to develop of a mathematical model  of porous materials plastic behaviour. This research is focused on help understanding salt melting within the graphite matrices and for proposing reliable ways for composite materials improvement. The mathematical modelling was able to determine the relation between the pore-elastic-plastic deforma- tion versus temperature and pressure time history, as well as liquid e crystals equilibrium conditions. An important observation was that, under melting, the salt volume expansion will be con- strained by the graphite matrix and pressure in pores will thus increase. Main consequences of this pressurization are a progres- sive increase of the salt melting temperature and a progressive reduction of its latent heat. For melting progress, materials have to be heated up to a melting point which is continuously increasing. Hence, a signi ﬁ cant part of the energy supplied to the material will be used to heat it up (sensible heat instead of latent heat). Control of graphite densi ﬁ cation during materials elaboration would be an easy way for increasing porosity (voids) within the graphite matrix skeleton and hence to reduce its rigidity and to increase the pore wall thickness. However, this will also lead to a reduction of the effective thermal conductivity. Even though the porous material of this previous study slightly differs from a metal foam, the results could be considered as a preliminary approach of the interaction between the PCM and the embedded foam.
A Computational Fluid Dynamics (CFD) modelfor thermalenergystorage tank by keeping PhaseChange Material (PCM) in the capsules has been developed and validated with experimental results.The heat transfer fluid flow (HTF)in thermalenergystorage tank was developed using PCM capsules in a single arrangement during the charging and discharging processes. A Two-Dimensional CFD model using Ansys code was developed and validated with experimental results. The inlet and outlet HTF temperatures in the PCM were compared with the CFD results. This paper gives details of the CFD model and compares results from the model and experiments.
B. Studies on Paraffin wax Encapsulated GI Pipes as Heat Exchanger in a Solar Collector cum Storage Chamber. 4 liters of water was taken in the wax melting chamber. The solar heat collection and heat storage capacity of the water was studied from 10.00 AM to 5 PM and the efficiency of the heat storage system was calculated as 10%. When the system was loaded with the paraffin wax of mass 1.15 kg alone encapsulated in G.I pipes and laid as a single layer. The heat storage efficiency of the solar thermalenergystorage of the system was calculated as 16%. The heat storage capacity of the empty pipes surrounded by 4 liters of HTF was taken in the wax melting chamber are studied. Its efficiency was found as 30%. From these observations it has been found that the G.I pipes and the water was found to be a good thermalenergystorage combination. The pipes were used to encapsulate the paraffin wax and it has acted as the heat exchanger. So the heat transfer fluid charges the wax in the pipe during the morning hours in the presence of sunlight and the melting of the PCM proceeds which leads to the storage of thermalenergy. A single layer of pipe (10 pipes) encapsulated with 1.15 kg of paraffin wax laid a pool of 4 liters of water. It was subjected to collect solar energy heat storage capacity was estimated and its efficiency was calculated as 28%.
The Storage unit consists of a stainless steel cylindrical tank of 40 cm diameter and 50 cm height with a detachable lid. It is well insulated from the bottom and peripheral by Foam insulation. The top of the tank contains a steel plate of 0.2 cm thick circular disc which is bolted to the drum. There is no insulation provided for the top lid. There is an inlet and outlet provision to the HTF. Stainless steel spherical balls of 10 cm diameter are used for storing the energy. For Spherical balls the arrangements are made inside the tank so that 21 spheres of 100 mm diameter each are kept in the chamber at 7 different heights as shown in Fig. 2. From each stage thermocouple is provided to measure the temperature.