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Performance Analysis of a Solar-Powered Multi-Effect Refrigeration System
摘要： The main objective of the current work is to investigate the thermodynamic performance of a novel solar powered multi-effect refrigeration system. The proposed cycle consists of a solar tower system with a heliostat field and central receiver (CR) that has molten salt as the heat transfer fluid, an absorption refrigeration cycle (ARC), an ejector refrigeration cycle (ERC), and a cascade refrigeration cycle (CRC). Energy and exergy analyses were carried out to measure the thermodynamic performance of the proposed cycle, using Dhahran weather data and operating conditions. The largest contribution to cycle irreversibility was found to be from the CR system (52.5%), followed by the heliostat field (25%). The first and second-law efficiencies improved due to the increase in the following parameters: ejector evaporator temperature, turbine inlet and exit pressures, and cascade evaporator temperature. Parametric analysis showed that the compressor delivery pressure, turbine inlet and exit pressures, hot molten salt outlet temperature, and ejector evaporator temperature significantly affect the refrigeration output.
关键词： triple effect,refrigeration,ejector,cascade,solar energy,absorption
更新于2025-09-23 15:22:29
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Energy and exergy analyses of a solar powered multi-effect cooling cycle
摘要： This study aims to assess the thermodynamic performance of a novel solar powered multi-effect cooling cycle through the cascaded utilisation of energy and exergy. The effects of parameters such as: direct normal irradiation (DNI), turbine inlet temperature, turbine back pressure, and evaporator temperature of ERC were ascertained on the energetic and exergetic performance of the cycle. Exergy destruction occurs throughout the plant components is quantified and illustrated using an exergy flow diagram, and compared to the corresponding energy flow diagram. The exergy efficiency of the cycle was significantly less than its corresponding energy efficiency. Computational analysis further revealed that the maximum exergy losses of more than 34% occur in the solar field followed by 7.25% and 6.75% in the components of ARC and CRC, respectively. Percentage of these exergy losses indicates the sites where the efforts should be made to improve the real performance of proposed cooling cycle.
关键词： ejector,solar,efficiency,refrigeration,absorption
更新于2025-09-23 15:21:21
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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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Exergy and economic analyses of a novel hybrid structure for simultaneous production of liquid hydrogen and carbon dioxide using photovoltaic and electrolyzer systems
摘要： Power-to-X technology that converts renewable electricity to chemicals and liquid fuels will be a key component of the energy turnaround. However, for a successful transition toward fossil-free energy alternatives, serious issues associated with renewable energy storage have to be addressed. Here, we report an innovative power-to-liquid hydrogen and carbon dioxide plant. The proposed integrated plant is composed of five subsystems: power generation using grid-connected solar photovoltaic (PV) subsystem, hydrogen and oxygen gas production using an electrolyzer, oxyfuel power plant for power and heat generation, carbon dioxide liquefaction using an absorption–compression refrigeration subsystem, and a hydrogen liquefaction subsystem. This hybrid structure produces 3.359 (cid:1)(cid:2)/(cid:4) (~300 ton/day) liquid hydrogen and 10.04 (cid:1)(cid:2)/(cid:4) liquid carbon dioxide. The total exergy efficiency and specific energy consumption of the hydrogen liquefaction system are 94.87% and 3.368 (cid:1)(cid:6)?/(cid:1)(cid:2)(cid:8)(cid:9)(cid:10), respectively. Exergy analysis of this integrated structure shows that the largest contribution of exergy destruction (30.58%) is associated with the photovoltaic system and the lowest exergy efficiency (25.28%) belongs to the Turbine in an oxy-fuel subsystem where it, interestingly produces over 70% of the total energy consumption of the plant. Furthermore, the economic analysis of the plant indicates that the time required for the return of capital is 4.794 years, where the prime price of the product and the value added are 0.1921 (cid:11)(cid:12)$/(cid:1)(cid:2)(cid:8)(cid:9)(cid:10) and 0.5433 (cid:11)(cid:12)$/(cid:1)(cid:2)(cid:8)(cid:9)(cid:10), respectively. This work can certainly provide a new approach to producing liquid hydrogen and carbon dioxide for long-distance transportation and CO2 reduction using solar as the renewable energy source.
关键词： Oxyfuel power plant,Renewable energy,Photovoltaic,Electrolyzer,Thermo-Economic,Liquid hydrogen,Absorption–compression refrigeration
更新于2025-09-19 17:13:59
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Solar energy harvesting potential of a photovoltaic-thermoelectric cooling and power generation system: Bidirectional modeling and performance optimization
摘要： In the present work, a comprehensive thermodynamic and exergoeconomic comparison between concentrated photovoltaic-thermoelectric cooling (CPV-TEC) and concentrated photovoltaic-thermoelectric generation (CPV-TEG) systems was introduced and explored, aiming to actively investigate the energy harvesting potential of the photoelectric-thermoelectric cooling and power generation processes. Transitional characteristics of thermoelectric conversion in concentrated photovoltaic-thermoelectric hybrid (CPV-TEH) system have been outlined through multiple evaluation indicators, including output electricity, cell temperature, thermodynamic efficiency, exergy destruction and unit exergy cost under various decision parameters. Furthermore, operating mode and conversion conditions of thermoelectric device in CPV-TEH system have been sensitively identified to obtain the dual action mechanism of cooling and power generation sequentially. Theoretical models have been compared and validated well with former published results. Results indicate that the operating mode of thermoelectric device could be fully converted from TEG to TEC when the operating current is around 0.27 A; the minimum unit exergy costs are respectively found to be 0.263 $/kwh, 0.148 $/kwh and 0.113 $/kwh for CPV-TEG system and 0.266 $/kwh, 0.152 $/kwh and 0.118 $/kwh for CPV-TEC system at CG = 1, 2, and 3 kW/m2. Present research may be helpful for the design and optimization of the CPV-TEH system to harvest the thermal and electric energy from the sunlight, thus enhancing its energy conversion efficiency.
关键词： Photovoltaic-thermoelectric system,Refrigeration and power generation,Thermodynamic and exergoeconomic comparisons,Dual action mechanism
更新于2025-09-19 17:13:59
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A novel solar system integrating concentrating photovoltaic thermal collectors and variable effect absorption chiller for flexible co-generation of electricity and cooling
摘要： Traditional single effect and double effect absorption chillers have relatively narrow working temperature ranges, which limits their application of solar systems. This study proposes a novel solar system integrating concentrating photovoltaic and thermal collectors, and a variable effect absorption chiller, for more flexible and efficient co-generation of electricity and cooling. In this study, variable effect chiller was optimized, showing that three working modes, combined with optimized control, make variable effect chillers a superior choice to the single effect and double effect types. Then, dynamic simulations of the solar co-generation system were performed, in order to study the effects of temperature control on system performance. The results showed that, a high turn-off temperature for the chiller generally results in higher cooling power, shorter working hours for the chiller, and in some cases, a frequent on–off cycling of chiller. With the increase in working temperature level, the cooling exergy efficiency increases, but total exergy efficiency decreases due to the photovoltaic cell’s degraded performance. The total exergy efficiency is approximately 32%–33%. A larger difference between turn-on and turn-off temperatures delays the start time of the chiller while ensuring the full use of solar energy. By adjusting the temperature control strategy, the novel solar co-generation system can offer a cooling-electricity ratio from 1.4 to 2.0, which is capable of meeting the demands in many cases. The proposed system offers flexible co-generation of cooling and electricity.
关键词： Exergy efficiency,Solar cooling,Concentrating photovoltaic and thermal (CPV/T) collector,Dynamic simulation,Variable effect absorption refrigeration cycle
更新于2025-09-16 10:30:52
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Solar Engineering of Thermal Processes, Photovoltaics and Wind || Solar Cooling
摘要： The use of solar energy to drive cooling cycles has been considered for two related purposes, to provide refrigeration for food preservation and to provide comfort cooling. In Section 15.1 we briefly review some of the literature relating to both of the applications, since there is a common underlying technology. From then on, we concentrate on problems relating to solar air conditioning. In particular, for application in temperate climates, we address questions of the use of flat-plate collectors for both winter heating and summer cooling.
关键词： flat-plate collectors,cooling cycles,refrigeration,comfort cooling,solar air conditioning,solar energy
更新于2025-09-16 10:30:52
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Experimental study of a micro-refrigeration system driven by photovoltaic power generation
摘要： A micro-refrigeration experimental system driven by photovoltaic power generation was established, and a study of the cooling capacity, load power, and system efficiency changes over time under sunny and cloudy weather conditions was carried out. The results show that the appendant battery makes the system run more stably, and the weather has no obvious effect on the operation of the indoor refrigeration system. The system exergy analysis indicates that the exergy loss of the compression process is the largest, accounting for more than 80% of the total in the refrigeration system; The exergy efficiency of the refrigeration system can reach about 28% under both weather conditions.
关键词： exergy analysis,Photovoltaic power generation,micro refrigeration system
更新于2025-09-12 10:27:22
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Study on the matching of thermal load characteristics and photovoltaic power control in typical buildings
摘要： For the Local Heat Island Effect in the building, the connection between the spatial and temporal distribution of passenger flow and heat load characteristics of the building was analyzed, and then the required cooling load at any time in each area was solved by using the functional relationship. Furthermore, the matching strategy of cooling load and photovoltaic power in the building was proposed and verified by simulation example. Due to the above method, the distribution of cooling load in space and time was rationally controlled and photovoltaic accommodation was effectively improved. At last, the problem of the contradiction between energy supply and demand of the typical building was resolved so building-integrated photovoltaic was implemented.
关键词： refrigeration load,photovoltaic accommodation,thermal load characteristics,building-integrated photovoltaic
更新于2025-09-12 10:27:22
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Laser refrigeration of gas filled hollow-core fibres
摘要： We evaluate prospects, performance and temperature limits of a new approach to macroscopic scale laser refrigeration. The considered refrigeration device is based on exciplex-mediated frequency up-conversion inside hollow-core fibers pressurized with a dopant - buffer gas mixture. Exciplexes are excited molecular states formed by two atoms (dopant and buffer) which do not form a molecule in the ground state but exhibit bound states for electronically excited states. The cooling cycle consists of absorption of laser photons during atomic collisions inducing light assisted exciplex formation followed by blue-shifted spontaneous emission on the atomic line of the bare dopant atoms after molecular separation. This process, closely related to reversing the gain mechanism in excimer lasers, allows for a large fraction of collision energy to be extracted in each cycle. The hollow-core fiber plays a crucial role as it allows for strong light-matter interactions over a long distance, which maximizes the cooling rate per unit volume and the cooling efficiency per injected photon while limiting re-absorption of spontaneously emitted photons channeled into unguided radiation modes. Using quantum optical rate equations and refined dynamical simulations we derive general conditions for efficient cooling of both the gas and subsequently of the surrounding solid state environment. Our analytical approach is applicable to any specific exciplex system considered and reveals the shape of the exciplex potential landscapes as well as the density of the dopant as crucial tuning knobs. The derived scaling laws allow for the identification of optimal exciplex characteristics that help to choose suitable gas mixtures that maximize the refrigeration efficiency for specific applications.
关键词： quantum optical rate equations,exciplex-mediated frequency up-conversion,laser refrigeration,hollow-core fibers,cooling efficiency
更新于2025-09-12 10:27:22