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Characterization of form-stable phase-change material for solar photovoltaic cooling
摘要： Solar PV panel cooling is essential to achieve maximum efficiency of PV modules. Phase-change material (PCM) is one of the prominent options to cool the panel and reduce the temperature, since PCMs have low thermal conductivity. Expanded graphite particles are used to enrich the structure and stability as well as to increase the thermal properties. In the present research work, polyethylene glycol (PEG) 1000 is used as a base material and expanded graphite for inclusive particle. A novel form-stable PEG1000/EG composite PCM mixture is prepared, using impregnation and dispersion method. Expanded graphite and PEG1000/EG sample phase compositions are investigated, using X-ray diffraction technique. No new peak is identified in the composite PCM sample. The surface morphology and structure of EG and PEG1000/EG are investigated, using scanning electron microscopy (SEM). Chemical stability analysis is done by Fourier-transform infrared spectroscopy. Thermal properties of the prepared composite PCMs are analysed by differential scanning calorimetry, thermogravimetric analysis (TGA) and KD2 pro analyser. Results show that addition of EG in various propositions (5%, 10% and 15%) enhances the thermal conductivity of PCM samples from 0.3654 to 1.7866 W mK?1, while melting point and latent heat of fusion of PCM samples are getting reduced. TGA thermographs are used to investigate the thermal stability of the composite PCM samples. TGA curves show that loss of mass happens above the operating temperature, and it is varied with different mass ratios of EG. Characterization of the prepared composite PCM samples is compared and found that PEG1000-85%/EG-15% is the best form-stable PCM, suitable for cooling the solar PV panel as well as to improve the electrical efficiency coupled with a decrease of temperature in the range of 35 °C to 40 °C.
关键词： PEG1000 PCM material,Solar PV cooling,Expanded graphite,Thermal storage,DSC,Characterization
更新于2025-09-23 15:19:57
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SOLAR-POWERED ADSORPTION REFRIGERATION CYCLE OPTIMIZATION
摘要： Solar energy is an attractive energy source among various renewable energy resources in Malaysia as relatively high solar radiation is available throughout the year. This solar energy can be utilized for air-conditioning by using solar-powered adsorption refrigeration cycle. Intermittent nature of the solar radiation leads to a challenge for continuous air-conditioning operation. In the present study, a combination of solar-powered adsorption refrigeration system and thermal storage is studied. Activated carbon-ammonia and activated carbon-methanol are the working pairs of the adsorption reaction. Analytical calculation results show that activated carbon-methanol pair indicates higher coefficient of performance (COP) than activated carbon-ammonia pair, while adsorption chiller system with hot water thermal storage has higher COP than the system with ice thermal storage. For the activated carbon-methanol case with hot water thermal storage, the COP is 0.79. Since this COP analysis is based on the ideal case with uniform temperature distribution within the reactor beds, which achieves equilibrium states at the end of the reactions. In more realistic situation, the reaction process will be terminated before reaching to the equilibrium states because of the non-uniform temperature distribution and the time required for the reaction. Transient simulation in which heat transfer and reaction equation are combined will be performed to model actual reactors.
关键词： Solar-powered,thermal storage,adsorption capacity,adsorption refrigeration
更新于2025-09-19 17:15:36
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Thermal and electrical performance of a novel photovoltaic-thermal road
摘要： The solar road is a new type of technology for solar energy conversion. As the solar energy utilization e?ciency of a solar road is too low, to solve this issue, a novel photovoltaic-thermal road is proposed in this paper. In addition, a mathematical model is developed to evaluate thermal and electrical performance of the photovoltaic-thermal road, and it is validated by experimental data. Moreover, the performance of a simple water system of the photovoltaic-thermal road is investigated and compared with that of a photovoltaic road. The results show that overall energy e?ciency of the photovoltaic-thermal road system is 3.95 times that of the photovoltaic road system. In addition, this study analyzed the e?ects of some meteorological and geometric parameters on the system performance. The pipe diameter was found to have little e?ect on the overall performance of photovoltaic-thermal road. Furthermore, the solar-radiation intensity, packing factor of photovoltaic cell, mass ?ow rate of circulating water, and transparent surface transmissivity have positive in?uences on the overall energy e?ciency; in contrast, the wind speed and burial depth of the pipe have negative in?uences, implying that a windless environment is conducive to the energy output of the PVTR system. An optimum thermal conductivity of asphalt concrete can maximize the overall energy e?ciency; for this study, the recommended range of this value is from 1.0 to 1.5 W/(m·K). The results of this study substantially contribute to the state of knowledge regarding photovoltaic-thermal road designs.
关键词： Thermal storage e?ciency,Electrical e?ciency,Solar energy,Photovoltaic-thermal road
更新于2025-09-19 17:13:59
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Solar Engineering of Thermal Processes, Photovoltaics and Wind || Energy Storage
摘要： Solar and wind are time-dependent energy resources. Energy needs for a very wide variety of applications are also time dependent but in a different fashion than the energy supply. Consequently, the storage of energy or other product of the process is necessary if these renewable resources are to meet substantial portions of our energy needs. Energy storage can be accomplished using thermal, mechanical, or chemical processes. Thermal storage is accomplished by heating or cooling a substance and recovering the energy at a later time by reversing the process. Mechanical storage and recovery can be accomplished by raising and lowering a mass, typically water, from one level to another level or by changing the rotational speed of a spinning wheel. Chemical storage is commonly accomplished through batteries but other chemical reactions are possible. Sometimes it is convenient to convert one form of energy to another before storing. The optimum capacity of an energy storage system depends on the expected time dependence of the energy source, the nature of loads to be met, the degree of reliability needed for the process, the manner in which auxiliary energy is supplied, and an economic analysis that determines how much of the load should be carried by solar or wind and how much by the auxiliary energy source. Note that auxiliary energy is assumed to be part of the process. The needed auxiliary energy could be another form of renewable energy. Consider a very large renewable energy system (like a large utility) where wind might make up temporary lack of solar (or vice versa) and hydro power is always available. In this chapter we set forth the principles of several energy storage methods and show how their capacities and rates of energy input and output can be calculated. In the example problems, as in the collector examples, we arbitrarily assume temperatures or energy quantities. In reality, these must be found by simultaneous solutions of the equations representing all of the system components. These matters are taken up in Chapter 10.
关键词： Thermal Storage,Chemical Storage,Mechanical Storage,Wind Energy,Energy Storage,Solar Energy
更新于2025-09-16 10:30:52
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Solar Engineering of Thermal Processes, Photovoltaics and Wind || Building Heating
摘要： The active systems described in the previous chapter are based on collectors and storage systems that are not necessarily integrated into a building structure. Passive systems can be distinguished from active systems on either of two bases. The first distinction lies in the degree to which the functions of collection and storage are integrated into the structure of the building; windows and the rooms behind them can serve as collectors, with storage provided as sensible heat of the building structure and contents as they change temperature. Second, many passive systems require no mechanical energy for moving fluids for their operation; fluids and energy move by virtue of the temperature gradients established by adsorption of radiation (and hence the term passive). (Mechanical energy may be used to move insulation for loss control or to move fluids to distribute absorbed energy from one part of a building to another.)
关键词： Passive systems,Collector-storage walls,Sunspaces,Hybrid systems,Direct-gain systems,Solar energy,Thermal storage,Building heating
更新于2025-09-16 10:30:52
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Transforming a residential building cluster into electricity prosumers in Sweden: Optimal design of a coupled PV-heat pump-thermal storage-electric vehicle system
摘要： Smart grid is triggering the transformation of traditional electricity consumers into electricity prosumers. This paper reports a case study of transforming an existing residential cluster in Sweden into electricity prosumers. The main energy concepts include (1) click-and-go photovoltaics (PV) panels for building integration, (2) centralized exhaust air heat pump, (3) thermal energy storage for storing excess PV electricity by using heat pump, and (4) PV electricity sharing within the building cluster for thermal/electrical demand (including electric vehicles load) on a direct-current micro grid. For the coupled PV-heat pump-thermal storage-electric vehicle system, a fitness function based on genetic algorithm is established to optimize the capacity and positions of PV modules at cluster level, with the purpose of maximizing the self-consumed electricity under a non-negative net present value during the economic lifetime. Different techno-economic key performance indicators, including the optimal PV capacity, self-sufficiency, self-consumption and levelized cost of electricity, are analysed under impacts of thermal storage integration, electric vehicle penetration and electricity sharing possibility. Results indicate that the coupled system can effectively improve the district-level PV electricity self-consumption rate to about 77% in the baseline case. The research results reveal how electric vehicle penetrations, thermal storage, and energy sharing affect PV system sizing/positions and the performance indicators, and thus help promote the PV deployment. This study also demonstrates the feasibility for transferring the existing Swedish building clusters into smart electricity prosumers with higher self-consumption and energy efficiency and more intelligence, which benefits achieving the ‘32% share of renewable energy source’ target in EU by 2030.
关键词： Thermal storage,Heat pump,Prosumer,Building cluster,PV optimization,Electrical vehicle
更新于2025-09-11 14:15:04
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Prefeasibility techno-economic assessment of a hybrid power plant with photovoltaic, fuel cell and Compressed Air Energy Storage (CAES)
摘要： This paper presents a hybrid power generation system comprising of Photovoltaic (PV) panels, Molten Carbonate Fuel Cell (MCFC), Gas Turbine (GT), Thermal Energy Storage (TES), Battery (Bat) and a Compressed Air Energy Storage (CAES) system. The CAES pressure was considered to be regulated using a water reservoir system located at a suitable height place. The described system was designed to supply the electricity needs of 500 households with peak electricity demand of 500kW. A set up MCFC/GT with power generation rate of 500kW was considered in the calculations, and the PV system capacity was considered to be changed from 100kW to 600kW. The optimal configuration and operational conditions of the system were conducted based on the Levelized Cost of Electricity (LCOE) definition as well as the total annual emission that is occurred by the auxiliary fossil fuel boiler and MCFC systems. The results showed that the overall system efficiency would be increased by about 25%, when the CAES is used and the compressor is switched off. Also, the optimal operational pressure of MCFC was found to be 6bar for 2000 number of PVs, 1500kWh of battery storage and CAES capacity of 685m3.
关键词： PV (Photovoltaic),TES (Thermal storage),CAES (compressed air energy system),Fuel based auxiliary system,MCFC (Molten Carbonate Fuel Cell)
更新于2025-09-09 09:28:46
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Can Nanofluids Lead to Commercial Usage in Solar Engineering
摘要： The efficiency concept has been the major concern of specialists and analysts in the vital flied of energy. The energy efficiency corresponds with the productivity of resources consumption since there is a worrying limitation on the fossil fuel reserves of the earth. Although the price of fuel has been diminished significantly in recent years, the constraint of its availability in not-too-far future has put the pressure on the governments to intend toward the renewable energies more than ever. Furthermore, nobody can really estimate that what would be occurred in the global economic market in the next years. Solar energy considered as one of the most reliable and available sources of energy which can be renewed continuously. That is why the different technologies, i.e. PV and thermal systems, have been developed and studied yet. Apart from the improvements which originated from design and technology progress, the appearance of nanotechnology caused significant advancement in solar engineering similar with the other fields of study. There are numerous researches on the field of solar energy with the applications of nanotechnology. For instance, currently the solar energy can be observed in heating, cooling, power generation, energy storage, transportation, medical etc. As long as nanotechnology proposed, the solar engineers has made their efforts to enhance the performance of solar systems and achieve the higher efficiencies. In the case of solar collector systems, nanomaterial’s can be added into absorber surfaces or heat transfer fluids which would result in enhancement of thermal and optical properties of the systems. Nanomaterial’s categorized as follows: Organic: fullerene, nanotube, electrospun nanofibers Inorganic: metal, metal oxides, quantum dots hybrid. Based on the application, nanomaterial’s can be mixed with the fluids which called Nanofluids. In other words, the suspension of nanoparticles in liquids considered as Nanofluids. Common liquids as the base fluid are water, ethylene, glycol and oil and the nanoparticles which have been used in literatures for dispersing in base fluid include carbon nanotube, alumina, titanium dioxide, silver, copper, graphite, etc. Nanofluids are made by mechanical (one-step or two-step) or chemical methods [1]. The synthesis is the main process which involved in preparation of the Nanofluids. On the other hand, the combination of nanomaterial’s with phase change materials (PCMs) known as Nano composites. Each type of Nanofluids or Nano composites exhibits the special properties. For example, the Nanofluids are more applicable in solar collectors for power generation and Nano composites are preferably considered in thermal storage projects i.e. heat or cold storage which would provide the industrial or domestic requirements of different climates. The hybrid systems exploit the most benefits of nanomaterials for simultaneous power generation and thermal storage. Furthermore, using the PCMs can increase the operating time of the system during the night or cloudy situations. Nanofluid phase change materials (NPCMs) have opened a new field of study for researchers. In fact, a NPCM is a liquid in which nanoparticles that change phase are added in order to enhance the thermal properties of this fluid. Despite the fact that all researches have been conducted theoretically and experimentally in all around the world, prove that the application of Nanofluids would lead to enhancement of optical and thermo-physical (conductive and convective) behaviour of solar systems, the applications of Nanofluids limited to the noncommercial projects [2]. Two main reasons interfere with the aim of commercializing Nanofluids application for solar power generation or solar thermal storage. Firstly, the results of remarkable achievements of numerous researchers show an inconsistency in some cases and therefore, the uncertainty of the results may necessitate more detail studies to overcome some ambiguities. Secondly, it is obvious that the optical and thermal properties of Nanofluids would be enhanced rather the base fluids, however, their application issues including durability, sedimentation, agglomeration, viscosity problems, some design complexities and operating costs have not been studied exactly and sufficiently. Hence it seems there would be a rather long way to achieve the exact, clear and unique results to smooth commercializing of Nanofluids applications in solar engineering.
关键词： Nanotechnology,Thermal Storage,Solar Energy,Nanofluids,Solar Engineering
更新于2025-09-09 09:28:46