Search

• Zero on-wheel emissions achieved during winter, 88 % reduction in summer. • Total lifecycle emissions by 33–47 % (1–5 gCO 2,e /km). • Potential cost savings of 0.1–0.3 € per kilometer. • The hybrid PV system is low-complexity and easy to implement. • The hybrid PV system is a viable path for decarbonising refrigerated transport. The refrigerated transportation industry's growth necessitates addressing energy consumption and greenhouse gas emissions. This study estimates a photovoltaic system's energy and environmental benefits to power a vapour compression refrigeration (VCR) system serving a light-duty commercial refrigerated van. A comprehensive energy model encompassing thermal, electrical, and battery sub-models simulating the system's dynamic behaviour is calibrated with real-world data referring to an urban single-delivery mission. The potential benefits are estimated for a long-distance single-delivery mission starting from the University of Salerno (Italy) and ending at the Jaume I University in Castellon de la Plana (Spain). The results have shown that the system can reduce fuel consumption for refrigeration by more than 88 % during summer months and allows neutral refrigeration during winter months, leading to on-wheel emission savings between 4 and 8 gCO 2 ,e/km. When considering total emissions, including electrical energy from the power grid and the increased weight due to the PV system, a 33–47 % reduction is obtained, corresponding to 1–5 gCO 2 ,e/km. In detail, PV panels can cover up to 19 % of the total energy requirements. In economic terms, the system allows a cost-saving between 0.1 and 0.3 c€/km. The low complexity and promising results suggest the hybrid PV solution is a viable path towards decarbonising refrigerated transport. [ABSTRACT FROM AUTHOR]

This work presents the results of indirectly coupling an Earth to Air Heat Exchanger to a 35 kW absorption cooling system. The study considers the weather, building, and soil conditions of a school located in the off-grid remote community of Puertecitos, Baja California, Mexico. TRNSYS simulation software was used to analyze the thermal behavior of the Earth to Air Heat Exchanger under different operation modes, in order to reduce the thermal load of the classrooms. The results show that during the months of May and June an Earth to Air Heat Exchanger with a diameter of 0.15 m, operating from Mondays to Fridays with and mass flow of 715 kg/h, is capable to reduce the thermal load of each classroom by 268.4 kWht, equivalent to 25% of the energy to be removed for maintaining the classrooms at 25 °C, which is reflected in a reduction of 12.89% and 18.25% of the electrical energy and water consumption, respectively. For the period from August to October, the thermal load was reduced by 225.2 kWht, equivalent to 15.4% of the energy to be removed for maintaining the classrooms temperature at 25 °C, causing an increase of 1.33% in electrical energy consumption, but reducing the consumption of auxiliary heat and water by 94.82% and 11.07%, respectively. The annual savings in auxiliary heat, electrical energy and water are 513.52 kWht, 136.05 kWhe and 6,084.03 kg, which represent 94.82%, 4.61% and 14.3% of the annual consumption of these resources. [ABSTRACT FROM AUTHOR]

Refrigeration plays a significant role across various aspects of human life and consumes substantial amounts of electrical energy. The rapid advancement of green cooling technology presents numerous solar-powered refrigeration systems as viable alternatives to traditional refrigeration equipment. Exergy analysis is a key in identifying actual thermodynamic losses and improving the environmental and economic efficiency of refrigeration systems. In this study exergy analyze has been conducted for a solar-powered vapor compression refrigeration (SP-VCR) system in the region of Ghardaïa (Southern Algeria) utilizing R1234ze(E) fluid as an eco-friendly substitute for R134a refrigerant. A MATLAB-based numerical model was developed to evaluate losses in different system components and the exergy efficiency of the SP-VCR system. Furthermore, a parametric study was carried-out to analyze the impact of various operating conditions on the system's exergy destruction and efficiency. The obtained results revealed that, for both refrigerants, the compressor exhibited the highest exergy destruction, followed by the condenser, expansion valve, and evaporator. However, the system using R1234ze(E) demonstrated lower irreversibility compared to that using R134a refrigerant. The improvements made with R1234ze are 71.95% for the compressor, 39.13% for the condenser, 15.38% for the expansion valve, 5% for the evaporator, and 54.76% for the overall system, which confirm the potential of R1234ze(E) as a promising alternative to R134a for cooling applications. [ABSTRACT FROM AUTHOR]

Air conditioning is vital for indoor comfort but traditionally relies on vapor compression systems, which raise electricity demand and carbon emissions. This study presents a novel thermo-mechanical vapor compression system that integrates an ejector with a conventional vapor compression cycle, incorporating a thermally driven second-stage compressor powered by solar energy. The goal is to reduce electricity consumption and enhance sustainability by leveraging renewable energy. A MATLAB® model was developed to analyze the energy and exergy performance using R1234yf refrigerant under steady-state conditions. This study compares four solar collectors—evacuated flat plate (EFPC), evacuated tube (ETC), basic flat plate (FPC), and compound parabolic (CPC) collectors—to identify the optimal configuration based on the collector area and costs. The results show a 31% reduction in mechanical compressor energy use and up to a 44% improvement in the coefficient of performance (COP) compared to conventional systems, with a condenser temperature of 65 °C, a thermal compression ratio of 0.8, and a heat source temperature of 150 °C. The evacuated flat plate collectors performed best, requiring 2 m2/kW of cooling capacity with a maximum exergy efficiency of 15% at 170 °C, while compound parabolic collectors offered the lowest initial costs. Overall, the proposed system shows significant potential for reducing energy costs and carbon emissions, particularly in hot climates. [ABSTRACT FROM AUTHOR]

This paper addresses the potential of integrating a concentrating photovoltaic thermal (CPV/T) system with an absorption chiller for the purpose of space cooling in residential buildings in the United Arab Emirates (UAE). The proposed system consists of a low concentrating photovoltaic thermal (CPV/T) collector that utilizes mono-crystalline silicon photovoltaic (PV) cells integrated with a single-effect absorption chiller. The integrated system was modeled using the Transient System Simulation (TRNSYS v17) software. The obtained model was implemented in a case study represented by a villa situated in Abu Dhabi having a peak cooling load of 366 kW. The hybrid system was proposed to have a contribution of 60% renewable energy and 40% conventional nonrenewable energy. A feasibility study was carried out that demonstrated that the system could save approximately 670,700 kWh annually and reduce carbon dioxide emissions by 461 tons per year. The reduction in carbon dioxide emissions is equivalent of removing approximately 98 cars off the road. The payback period for the system was estimated to be 3.12 years. [ABSTRACT FROM AUTHOR]

Linear Fresnel reflectors are a versatile solar concentration technology, suitable for a wide range of industrial processes and thermal conditioning applications. Such collectors entail a certain footprint, generating shading on the surface where they are installed. This effect is rarely quantified but may play an indirect role on the surface below. When installed on a roof, the solar radiation heats the building less. In places where the annual heating demand is higher than the cooling demand, this constitutes an asset. However, this becomes a disadvantage when the cooling demand is higher annually than the heating demand. Essentially, the reduced solar radiation allows for the growth of plants that would not grow without the shade provided by the collector. The present paper is a quantitative analysis of such shading based on the linear Fresnel reflector of the Cyprus Institute. The work was conducted using the Tonatiuh++ ray-tracing software to determine the annual radiation blocking. A total of four years of actual meteorological measurements were applied directly to the ray-tracing model. [ABSTRACT FROM AUTHOR]

Solar cooling technology is environmentally friendly and can contribute to a significant reduction in CO2 emissions, the main cause of the greenhouse effect. At present, there is a trend to utilize solar cooling systems are those that rely on hot water-driven lithium bromide absorption chillers. Refrigeration machines have the decisive advantage that they can be operated with conventional flat or vacuum solar collectors available on the market, the suitability of which depends on the temperature range of the driving heat source. In this paper, previous literature on solar air conditioning is reviewed, discussing the absorption system, types of solar collectors, as well as types of refrigerants. literature reviewed showed that, it possible to produce an absorption air conditioning system that runs on solar energy [ABSTRACT FROM AUTHOR]

In this paper, a solar absorption cooling system with a chilled water storage tank and peak load compression system was considered for cooling the Instituto Superior Tecnico Tower building in Lisbon, Portugal. To fulfill this task, a dynamic simulation of the building was performed using the DesignBuilder software, then a solar collector field was designed. The next step was to build a computational model of the absorption chiller in the Engineering Equation Solver software, which allowed for further simulation of the annual operation of the system supported by the chilled water tank and the backup system with compressed air conditioning. The last stage of the work was the economic analysis of such a system in comparison with conventional compressed air conditioning. The simulation results and economic analysis showed that the solar absorption cooling system could be a beneficial cooling solution for the Instituto Superior Tecnico Tower building. However, it would have to operate with an energy storage system and a peak load compression backup system to be able to cool the building efficiently all year round. Additionally, such a solution could have a significant positive impact on climate through considerable annual savings in electricity consumption. Results revealed that the proposed system meets the cooling demand of the building, mainly by solar-energy-driven absorption chiller. The annual contribution of a backup compression chiller ranges from 20% to 36% depending on the size of chilled water storage tanks. Financial calculations revealed discounted payback periods in the range of 4.5 to 12.5 years depending on the system configuration. [ABSTRACT FROM AUTHOR]

The solar adsorption cooling (SAC) system driven by a flat-type solar collector was investigated in this study. The adsorber is heated by solar energy and contains activated carbon-methanol as a working pair. The modulation is based on the first law of thermodynamics to determine all forms of energy interactions at each phase of the thermodynamic cycle of the SAC system. Some assumptions are taken into consideration to develop the model. The Dubinin–Astakhov model was used to calculate the adsorbate mass in the adsorbent. Additionally, REFPROP-NIST (V 8.0, 2007) was used to determine the thermodynamic properties of the adsorbate. A numerical simulation program was developed in FORTRAN to solve the model using the Simpson method. The model is validated with published research. The results obtained from the simulation of the model were analyzed and presented to explain the effects of different operating conditions on the performance of the adsorption cycle. The system's total heat input is found to be 3377.35 kJ, while its total cold production is 1640.29 kJ, corresponding to a total daily ice produced of 3.65 kg. Furthermore, the system achieved a cycle of 0.4857. A large amount (61%) of the total heat input is used in the desorption process; about 10% is utilized by the adsorbate, the adsorbent uses 25%, and the adsorber's metal cover uses the remaining 4%. Also, an analysis of the results indicates that the thermal performance coefficient ( decreases with increased ambient and condensation temperatures. Furthermore, an increase in the evaporation temperature leads to an increase in the thermal performance coefficient. [ABSTRACT FROM AUTHOR]

Renewable cooling via absorption chillers being supplied by various green heat technologies such as solar collectors has been widely studied in the literature, but it is still challenging to get positive economic outcomes from such systems due to the large expenses of solar thermal systems. This study offers the use of a new generation of solar collectors, so-called eccentric reflective solar collectors, for driving single-effect absorption chillers and thereby reducing the levelized cost of cooling. This article develops the most optimal design of this system (based on several different scenarios) using multi-objective optimization techniques and employs them for a case study in Brazil to assess its proficiency compared to conventional solar-driven cooling methods. For making the benchmarking analyses fair, the conventional system is also rigorously optimized in terms of design and operation features. The results show that the eccentric solar collector would enhance the cost-effectiveness by 29%. In addition, using optimally sized storage units would be necessary to get acceptable economic performance from the system, no matter which collector type is used. For the case study, at the optimal sizing and operating conditions, the levelized cost of cooling will be 124 USD/MWh and an emission level of 18.97 kgCO2/MWh. [ABSTRACT FROM AUTHOR]

In areas with unreliable electricity, the absorption system serves as a crucial, eco-friendly refrigeration technology. This study addresses the system's performance gaps, evaluating the 100 W NH3-H2O absorption cooling system under various conditions. The focus is on its suitability for electricity-challenged areas, employing theoretical and experimental methods. Two configurations are tested based on input heat sources, using bifacial Photovoltaic (PV) or solar parabolic troughs integrated with the absorption chiller. The Engineering Equation Solver (EES) program determines thermodynamic properties, with the model split into sections--one with the solution heat exchanger (SHX) excluding the liquid-vapor heat exchanger (LVHX) and the other incorporating both. The findings indicate a direct correlation between higher evaporator and generator temperatures and an increase in the Coefficient of Performance (COP). The theoretical and experimental cooling COP values reach 0.62 and 0.63, respectively, at 7℃ evaporator temperature and 85℃ generator temperature. Similarly, at 95℃ generator temperature, the COP values are 0.629 and 0.637 for the same evaporator temperature. The theoretical maximum COP at 3℃ evaporator temperature is 0.512 at 90℃ generator temperature, with experimental COP approaching 0.52 at generator temperatures of 96℃, 98℃, and 100℃. The integration of an LVHX into the chiller module demonstrates a notable improvement in cycle performance, enhancing efficiency by approximately 7-7.5%. In conclusion, this study offers crucial insights into optimizing the NH3-H2O absorption cooling system for off-grid scenarios, contributing to a broader understanding of absorption refrigeration technology in diverse environmental conditions. [ABSTRACT FROM AUTHOR]

This paper addresses the potential of integrating a concentrating photovoltaic thermal (CPV/T) system with an absorption chiller for the purpose of space cooling in residential buildings in the United Arab Emirates (UAE). The proposed system consists of a low concentrating photovoltaic thermal (CPV/T) collector that utilizes mono-crystalline silicon photovoltaic (PV) cells integrated with a single-effect absorption chiller. The integrated system was modeled using the Transient System Simulation (TRNSYS v17) software. The obtained model was implemented in a case study represented by a villa situated in Abu Dhabi having a peak cooling load of 366 kW. The hybrid system was proposed to have a contribution of 60% renewable energy and 40% conventional nonrenewable energy. A feasibility study was carried out that demonstrated that the system could save approximately 670,700 kWh annually and reduce carbon dioxide emissions by 461 tons per year. The reduction in carbon dioxide emissions is equivalent of removing approximately 98 cars off the road. The payback period for the system was estimated to be 3.12 years.

Linear Fresnel reflectors are a versatile solar concentration technology, suitable for a wide range of industrial processes and thermal conditioning applications. Such collectors entail a certain footprint, generating shading on the surface where they are installed. This effect is rarely quantified but may play an indirect role on the surface below. When installed on a roof, the solar radiation heats the building less. In places where the annual heating demand is higher than the cooling demand, this constitutes an asset. However, this becomes a disadvantage when the cooling demand is higher annually than the heating demand. Essentially, the reduced solar radiation allows for the growth of plants that would not grow without the shade provided by the collector. The present paper is a quantitative analysis of such shading based on the linear Fresnel reflector of the Cyprus Institute. The work was conducted using the Tonatiuh++ ray-tracing software to determine the annual radiation blocking. A total of four years of actual meteorological measurements were applied directly to the ray-tracing model.

Numerous factors affect how well a solar PV system performs, and continuous monitoring of these parameters while it is in operation is necessary to suggest improvements and attain peak optimum performance. This study examines the impacts of irradiance, cell temperature, wind velocity, water cooling, and dust deposition are examined on a 50W PV module in Rajshahi, Bangladesh. Experimental results suggest that the preferred wind velocity and water flow rate for the PV panel's top surface cooling were around 5 m/s and 0.0045 m3/min (0.113 m3/min per m2 of panel area), respectively. The cooling system's water circulation at 0.0045 m3/min boosted the PV panels' output power, energy efficiency, and exergy efficiency by 20.47%, 12%, and 37.5%, respectively, at 730–780 W/m2 irradiation. The dust deposition of the PV panel reduced the power output to 21W from 46.81W (without dust) upon applying 42 gm of dust with a 0.29 mm particle size. Wind velocity (5 m/s) increases efficiency from 14.8% to 16.5%. The findings of this study may be useful to investors and policy makers in helping them to take right actions to minimize losses associated with the effects these operational and environmental factors.

This study presents a comprehensive exergetic analysis, facilitated by computational modeling, of a solar-powered air conditioning system directly linked to a photovoltaic generator. The system, designed without an energy storage component, aims at addressing the cooling requirements of a library by harnessing the natural regulation of solar energy, under two distinct solar irradiance profiles. Simulations revealed that the photovoltaic generator necessitates a minimum solar incidence of 240 W/m² to fulfill the basal cooling capacity of the system. The results indicated that only 25% of the library's operational period on a sunny day, and a mere 12.3% on a cloudy day, met the thermal comfort standards for occupants. Furthermore, the study discerned an increase in exergy destruction in the system components over the course of the day. The photovoltaic system exhibited the highest level of exergy destruction, followed by the compressor, condenser, evaporator, and expansion valve respectively. This exergy analysis offers a holistic evaluation of the system's overall efficiency. It transcends mere energy efficiencies and incorporates power quality losses that transpire during the conversion and transport processes. With this indepth assessment, the study not only identifies the areas of greatest energy losses but also offers insights that could enhance the system's design and operational efficiency. [ABSTRACT FROM AUTHOR]

In this study, the thermodynamic behavior of a combined cycle power plant with integrated solar-driven inlet air cooling was simulated for Tehran, Phoenix, and Houston during warm-hot seasons. A considerable reduction in the output power was realized during hot ambient conditions due to the lower density of the air and lower mass flow rate to the turbines. The output power decreases from 306.6 to 260.8 MW as ambient temperature increases from 15 to 45 °C. This research focuses on utilizing solar cooling systems to achieve low inlet air temperature to generate high-electricity yields. Four different types of solar collectors and two different absorption chiller units were selected and simulated for each city to achieve the required goal. It was identified that integrating a solar inlet air cooling (SIAC) system can avert the reduction in output power with no impact on efficiency. The humid climatic condition in Houston and the low electricity cost in Tehran posed some challenges in designing a feasible SIAC system. However, by optimizing the solar collectors and cooling capacities, an optimal solution for utilizing inlet air cooling in humid climates is presented. In terms of overall impact, the evacuated flat plate collector (EFPC) coupled with a double-effect absorption chiller displayed the best economic performance among the four variants under study. In Phoenix, this combination can maintain output power during hot days with a DPR of 2.96 years. [ABSTRACT FROM AUTHOR]

Solar cooling systems are widely used in the building sector, as they can utilize low-grade solar energy to reduce carbon emissions. To improve the thermodynamic performance and economic performance of solar cooling systems, solar cooling systems driven by photovoltaic–thermal (PVT) collectors have been widely studied. This paper reviews the recent research on the technological improvement of PVT collectors, the development of thermally driven cooling cycles, and the performance of solar cooling systems driven by PVT collectors. Innovative heat sink structures and the utilization of a high-thermal-conductivity coolant are employed to increase the solar-energy-conversion efficiency of PVT collectors. The use of thermal and mechanical two-stage compression and cascade cooling expands the lower temperature limit of the heat source required for the solar cooling cycle. In addition, specific examples of solar cooling systems driven by PVT collectors are reviewed to explore their thermodynamic and economic performance. Finally, the technical developments in and prospects of different types of PVT collectors and solar cooling systems are explored in an attempt to provide some insight to researchers. This study shows that the PVT collector's electrical and thermal efficiencies can be improved by 0.85–11% and 1.9–22.02%, compared to those of conventional PV systems and PVT systems based on water cooling, respectively. Furthermore, the lower limit of the heat source temperature for the new thermally driven cooling system expands by 4–20 °C. Finally, the performances of solar cooling systems driven by PVT collectors show a minimum payback period of 8.45–9.3 years, which proves favorable economic feasibility. [ABSTRACT FROM AUTHOR]

Food production in arid countries like Qatar is strongly linked to water and energy resources to grow plants or rear cattle in a protected and controlled environment. The high energy demand for air conditioning in agro-industrial communities leads to significant CO2 emissions. In a case-study on buildings that are typical in the agro-industrial sector, the reduction potential for these emissions is investigated. Therefore, greenhouses and community buildings with an insulation according to the Passivhaus standard and solar cooling with photovoltaic driven compression chillers are compared to conventional buildings. An innovative solar cooling system is developed: Power is generated in hybrid photovoltaic / thermal collectors to enhance the electric efficiency of the photovoltaic cells and to deliver heat for food processing or other purposes at a high temperature level. A compression chiller model is designed, that is based on the experimentally determined performance of the refrigeration cycle for the harsh operating conditions in Qatar. Different refrigerants are compared regarding their cycle performance and Global Warming Potential. A result of the study at hand is that greenhouses are very well suited for solar cooling since their cooling load is nearly congruent to photovoltaic power generation due to their low thermal inertia and radiative cooling during the night. The case study reveals that an insulation according to the Passivhaus standard combined with the proposed solar cooling system reduces the CO2 emissions caused by the air conditioning of greenhouses by 98% and of residential buildings by 94.7% compared to conventional buildings and air conditioning systems. [ABSTRACT FROM AUTHOR]

Today, the fastest growing end-use in the buildings sector is cooling demand, notes the International Energy Agency (IEA). In the last few years, the interest in solar cooling systems has been growing globally. Solar cooling systems are the next solution to meet the growing demand for air conditioning. The literature analysis shows that solar cooling systems mainly use single-stage absorption chillers, with water as the working fluid, and only a small fraction of them use phase change materials to improve heat storage. Based on previous studies on solar-assisted cooling systems, the use of phase change materials for thermal storage should be investigated. The paper will present a study of a solar cooling system with the optimized PCM thermal storage, with the aim of stabilizing the operation of heat storage, taking into account the volatility of solar energy, the impact of short-term operations and peak hours on the amount of heat produced. This means that the amount of electricity consumed to heat up the accumulation tank will be significantly reduced. The optimization model in simulation software will be performed to test solar cooling system with latent heat storage, with aim to investigate the efficiency of the developed latent energy storage and provide technical guidance for the implementation of such system in the practice. All indicators, including environmental impact and economic calculations, will be identified in order to determinate the specific systems for foresight market uptake.

The growing availability of low-cost electricity-driven air-conditioning systems has determined a huge increase in the electricity demand for space cooling, especially in warm and hot climates. In this framework, thermally-driven solar-assisted cooling systems are a very interesting alternative, since they are mainly fed by converting the largely available solar radiation into thermal energy: however, their economic convenience is still questionable. For this reason, many EU states have introduced suitable subsidies: in Italy, the so-called “Conto Termico” proposes cash-back incentives proportional to the thermal energy delivered by the solar field.This study investigates the suitability and consistency of these subsidies, by considering a case study including a thermally-driven solar-assisted absorption chiller that cools down an office building located in Palermo (Southern Italy). The study looks into the sizing of the system and evaluates its techno-economic feasibility by considering the incentives introduced by the Italian “Conto Termico”. The results highlight that the proposed solar-assisted absorption cooling system can reduce primary energy demand and CO2 emissions by around 75% if compared to a conventional electric chiller, under a reasonable sizing of the solar section. The subsidies are proportional to the thermal energy delivered by the solar collectors, and thus tend to favour the adoption of high collecting surfaces: for instance, installing 2 m2 of evacuated tube solar collectors per unit cooling capacity ensures relatively low payback periods of 15 years or even less. However, the energy performance of the system does not improve accordingly with higher collecting surfaces, since a non-negligible rate of delivered thermal energy is wasted, as witnessed by the decreasing seasonal COP. Moreover, Flat Plate Collectors are improperly penalized, and the real local operating conditions are not considered in the calculation. This suggests that the rationale leading Italian subsidies are not consistent, and needs being improved.

Green building is a concept in sustainable development which aims to reduce energy consumption and carbon emission of buildings. This study attempts to design and introduce a novel green HVAC system which reduces both energy consumption and carbon production of buildings. This system uses solar absorption chillers to provide the cooling demands of buildings. In addition, biofuel (biogas) fired boilers are also added to provide the heating demands. By using the novel approach of the study, such HVAC system can be coupled with other renewable technologies like photovoltaics and develop green buildings. In order to design, model and simulate the operation of this system, famous energy modeling tools are compared with each other and Design Builder software is chosen as the appropriate one. The paper also introduces a plan for establishment of such systems which is applicable to any locations. The results of modeling this green HVAC system for 10 various climates indicated considerable advantages of this system over traditional systems. The green HVAC system can save the maximum energy of 50 MWh per year in a four stories building. The maximum amount of 31 tons carbon can also be saved if the said building is equipped with this novel HVAC system. The results also made it clear that the solar cooling system is a great choice for providing cooling needs in hot climates. By coupling this kind of cooling system with biofuel heaters, the sustainable HVAC system can develop green buildings even in cold or cool climates. Adding green electricity producers like photovoltaic panels to this system and the building was successful. The maximum produced green energy in buildings was calculated as the amount of 17.9 MWh/yr.

Cooling and air-conditioning systems are the primary consumers of building energy in hot and mixed climate locations. The reliance on traditional systems, driven electrically, is the main reason behind the deterioration and ever-increasing demand for energy in buildings. This is also associated with a vast amount of CO2 emissions and other environmental concerns. Solar energy has been introduced as a crucial alternative for many applications, including cooling and air-conditioning, which has been proven to be a reliable and excellent energy source. This paper presents and discusses a general overview of solar cooling and air-conditioning systems (SCACSs) used for building applications. The popular SCACSs driven by solar thermal energy are elaborated in detail, considering their operation and development aspects. A comparison among solar thermal SCACSs is performed, taking into account several technical, operational, economic and environmental indicators. Some research gaps, recommendations, and conclusions are derived from the reviewed literature to understand and further develop this essential research domain.

This study deals with the evaluation of the technical and environmental operation of solar/gas driven NH3/LiNO3 absorption chillers for malls under the environmental conditions of the city of Barranquilla, Colombia. It involves a sensitivity study on the absorption chillers performance at chilled water temperatures of 12 °C and 6 °C and different solar irradiations. It also includes the share of cooling and CO2 equivalent emissions provided by the absorption chillers considering as a base case the energy consumed by the mechanical vapour compression chillers operating in three selected malls. Results showed that solar energy could provide around 40% and 50% of the total energy required to drive the absorption chillers on a service day. This value could be increased by adding a higher solar panel area, however, the available roof area for solar equipment was a limiting factor. Moreover, the COP and SCOP of the absorption chillers were found up to 0.64 and 0.44, respectively. Additionally, the solar/gas driven absorption chillers could cover up to 83%, 100%, and 35% of the peak cooling requirements in malls 1, 2, and 3, respectively, while providing the highest reductions in CO2 equivalent emissions.

Demand for space cooling systems is growing worldwide. The main reasons are socioeconomic developments such as the growing world population and the rise of economic wealth, especially in developing countries. These developments run simultaneously with global warming effects, increasing the need for cooling. This study introduces the development of the Cooling Demand Market Index (CDMI), which indicates the demand for cooling appliances worldwide at a spatial resolution of 1 km. It is based on population density, Gross Domestic Product (GDP)/capita and Cooling Degree Days (CDD) per climate zone. The CDMI is calculated for 2020 and 2050 in four different future scenarios in accordance with the Spatial Socioeconomic Pathways (SSP) and Representative Concentration Pathways (RCP). Further, the Solar Thermal Cooling Index (STCI) was developed to spatially estimate the worldwide potential to use solar thermal cooling systems based on solar availability and limitations due to maximum heat rejection temperature. Results of the CDMI show that the economic demand for cooling solutions is increasing, especially in developing countries, and that India will be by far the largest market by 2050. Countries such as Burundi and the Democratic Republic of the Congo show the strongest national increases in CDMI. The STCI indicates that ammonia absorption chillers and zeolite adsorption chillers can serve the vast majority of the market thanks to their capability to run at high condenser temperatures. [ABSTRACT FROM AUTHOR]

Since the beginning of the third millennium, significant growth in the usage of conventional air conditioning systems was observed. This increase caused an enhancement in building electricity consumption. Therefore, the development of solar air conditioning systems applied to buildings is of great interest. However, it is essential to understand and assess this alternative solution. In this regard, this study focuses on solar cooling technology as an alternative to conventional air conditioning systems, which consume a significant amount of electricity. A mathematical model of a single-effect absorption chiller was developed using TRNSYS software to analyze the dynamic behavior of the system. The energy performance of the solar cooling system was evaluated by analyzing the solar fraction, coefficient of performance, and thermal efficiency. The optimal size of the solar panel surface and storage reservoir capacity were determined for Oujda, Morocco's climatic conditions. Simulation results showed that a 600 m2 flat plate collectors (FPC) with a 2.5 m3 storage tank could sustain a peak load of 108 kW while ensuring continuous performance. The system's efficiency was improved by maximizing useful energy and minimizing supplementary energy consumption, achieving a significant monthly average solar fraction in July to meet cooling demand. The coefficient of performance of the absorption chiller was found to be 0.53, maintaining a chilled temperature of 6.67°C. These findings demonstrate the potential of solar cooling technology as an effective and sustainable alternative for building air conditioning. [ABSTRACT FROM AUTHOR]

The substitution of aluminum heat exchangers for copper ones is expected to enhance the competitiveness of solar-assisted hybrid cooling systems. However, the potential of such replacement has not been assessed exactly, which is mainly attributed to the lack of a comprehensive analysis from thermodynamic, economic, and environmental viewpoints. In this regard, an emergy-based enviro-exergo-economic model is proposed to evaluate the potential of aluminum heat exchangers at first. Subsequently, an optimization of key component size is performed. Finally, the effect of aluminum heat exchanger characteristics on the substitution feasibility and system optimization is discussed in detail. The results show that the optimal system total emergy rate of Al-20 scheme is 6.2% lower than that of the Cu-20 scheme. Additionally, both the decrease in the price ratio and the increase in the lifetime are favorable for the application of aluminum heat exchangers. When the price ratio of aluminum heat exchangers to copper ones drops from 0.85 to 0.60, the lower limit of acceptable lifetime for aluminum heat exchangers decreases from 9.5 years to 7.7 years. The work is favorable to promote the cost down of solar-assisted hybrid cooling systems by low-cost materials. Emergy-based exergo-economic-environmental assessment is proposed. Critical heat exchangers are optimized from the comprehensive view. The influences of lifetime and price of material substitution are discussed. The total emergy rate of Al-15 scheme reduces by 11.5% through optimization. The optimal total emergy rate of Al-20 scheme is 6.2% lower than that of Cu-20 one. [ABSTRACT FROM AUTHOR]

Peltier cooling systems are generally small, portable and simple in operating principle compared to conventional vapor compression cooling systems. For these reasons, Peltier cooling systems are proposed widely to use in the field. In studies on Peltier coolers presented in the literature, equipment such as pumps and fans is used and this causes noise and vibration. In order to resolve these problems and negative effects, a cooling system was designed and manufactured using completely motionless elements. Additionally, the electricity energy need of this thermoelectric cooling chamber is fully met by solar energy. This study was investigated both experimentally and numerically by using computational fluid dynamics (CFD) methods. By designing a special heat exchanger in the produced air-to-air cooler system, it has been proven that, the Peltier system can work effectively without the need for any elements such as fans. Then the effects of the voltage values applied to the system and the number of Peltier modules have been investigated. The experiments were carried out at 4 different voltage values (1.5, 2.0, 2.5 and 3.0 V) and in 3 different Peltier numbers (1, 3 and 5) in consecutive connections. According to the obtained results, the most suitable situation for reducing the temperature of the cooling chamber were obtained as the voltage was at a maximum of 3 V and the Peltier number was maximum (5 Peltiers mode), where the internal temperature of the cooling chamber decreased to 11.28 °C. It was observed that, the coefficient of performance (COP) values decreased over time in all experiments. Considering the data taken at the beginning of the experiments, the maximum COP value was obtained as 0.04 when 1 Peltier and 1.5 V voltage were applied. [ABSTRACT FROM AUTHOR]

This research presents a thermodynamic analysis of a Thermal LTC-10 single-effect absorption series cooling system using the water/LiBr pair. Four operating scenarios were modeled on an hourly basis (24h) with EES software using mass and energy balances and the environmental conditions of the city of Barranquilla, Colombia. The analysis of the results shows that the system powered only by solar energy obtains the highest COP between 8:00 and 16:00 hours and the lowest greenhouse gas (GHG) emissions, while the system powered by rice husk biogas presents stable operation throughout the day and higher SO2eq emissions. [ABSTRACT FROM AUTHOR]

[Display omitted] • A PVT-powered High Temperature Heat Pump/adsorption cogeneration system is proposed. • Performance comparison with ETC and PVT-only driven adsorption chiller is performed. • The Effect of HTHP operational parameters on system performance has been studied. • The effect of R1234ze(Z) and R134a refrigerants on system performance is examined. • A comparative economic assessment of the investigated systems has been performed. This study presents a theoretical thermoeconomic performance assessment of a novel solar-powered high-temperature heat pump (HTHP)/adsorption cogeneration system for simultaneous electricity production and cooling. Photovoltaic/thermal (PVT) solar collectors are used to capture solar thermal energy and generate electricity that is partially used to drive the HTHP compressor. The HTHP is mainly used to absorb the captured solar thermal energy through its evaporator coils to keep the collectors at lower operating temperatures for better electricity generation. Then through the HTHP compressor, the thermal energy is amplified to produce higher-temperature hot water to drive the adsorption chiller for improved cooling production. The performance of the proposed system (PVT-HTHP) is compared to the performance of the PVT-only, and evacuated tube collectors (ETC-only) powered adsorption chiller for the same solar collector area. A parametric study with different operating HTHP conditions has been performed to determine the optimal operational scenario for the proposed system. A low-GWP refrigerant R1234ze(Z) is considered for the HTHP and compared against the conventional high-GWP R134a option. A complete dynamic mathematical model is developed for the studied systems and solved by MATLAB software. Under the summer conditions of Alexandria, Egypt, the average cooling capacity is improved substantially from 3.91 kW for PVT-only to 8.6 kW for ETC-only and 10.21 kW for proposed PVT-HTHP configuration with R1234ze(Z) and operating evaporator and condenser temperatures of 35 °C and 90 °C, respectively. The best-performing configuration from the energy efficiency perspective is the proposed PVT-HTHP with R1234ze(Z) refrigerant at a value of 46.8% when the operating HTHP evaporator and condenser saturation temperatures of 35 °C and 80 °C, respectively. The economic assessment of the proposed PVT-HTHP system proves that the system can be applied feasibly with a payback period (PBP) of 7.5 years. [ABSTRACT FROM AUTHOR]

Photovoltaics has emerged as a crucial and progressively significant contributor to renewable energy generation. Nevertheless, its effectiveness is limited to daylight hours when sunlight is available. This research paper presents an approach to promote dual usage of solar panels beyond daytime operations to facilitate water production. An AWGPV (Atmospheric water generation on PV modules) system is built and operated for nearly a year. During this period, several prototypes were built to produce up to 2.5 L/panel per day without optimizing the energy consumed during direct cooling. A techno-economic assessment was done for the prototype AWGPV system. The prototype system consisting of 3 AWGPV panels connected to the grid was able to produce water at 33 USD cents per liter in Dubai, UAE. If the electricity for direct cooling is reduced, the cost of water can be reduced further. The results point to new avenues to explore methods for reducing the electricity consumption for cooling for achieving further cost reduction. A parameter n-MHI (night Moisture harvesting index) is introduced to evaluate the feasibility and energy demands of harvesting atmospheric moisture through direct cooling. Through a climate-based analysis of various locations, the global potential of this process is explored. The collected water can be used for dust cleaning of solar panels, agrophotovoltaic systems, and other applications where water and electricity generation needs to be decentralized.

Solar cooling technologies have become essential, especially in tropical countries due to the amount of solar radiation and the growing need for cooling. Gigantically, this study aims to depict a hybrid solar cooling system driven by a photovoltaic/thermal unit. The PV cells are used to power a Vapor Compression Refrigeration (VCR) cycle; whereas the waste thermal energy that has been utilized from cooling the PV modules is applicably used to run the Ejector Cooling Refrigeration (ECR) cycle. A mathematical model of the system has been generated to simulate this hybrid solar cooling system. The electrical energy derived from the PV cells was used to run the (VCR) cycle, resulting in a cooling capacity that ranges from a minimum of 3.215 kW to a maximum of 3.99 kW. Meanwhile, the heat utilized by cooling the PV modules was used to run the ECR resulting in an additional cooling capacity arranges from a minimum of 1.85 to a maximum of 2.46 kW. Consequently, as a result, the total cooling capacity of the hybrid system arranges from 5.14 kW to 6.4 kW with a COP of 5.8 and a maximum of 6.9 have been occupied during the period of study. Compared to the conventional VCR cycle powered by a solar non-cooled PV unit, the hybrid system has produced 24.8% increasingly more cooling capacity while using the same (25 m2 ) area of panels in July privately when running the system for 18 hours. Based on the economic viability of the system, crucially the payback period of the added cost from combining the VCR with the ECR systems will be returned within 7.3 years. [ABSTRACT FROM AUTHOR]

Electricity generated by photovoltaic (PV) modules can be converted into cooling using well-known refrigeration technologies based on vapor compression refrigeration cycles. One of the most critical issues arising when using PV modules is elevated temperatures in sunny and hot conditions, resulting in a corresponding decrease in electrical efficiency. Therefore, this work aims to enhance the performance of a solar compression refrigeration system using a single PV-thermal (PVT) collector fully integrated with a refrigeration system employing a low GWP refrigerant (R290) instead of the R134a. Furthermore, zinc oxide (ZnO) nanofluid is used to absorb thermal energy from the PVT collector and to improve its electrical efficiency. The outlet fluid from the PVT collector is used to subcool the refrigerant at the outlet from the condenser of the cycle. The impacts of varying the nanofluid flow rate, nanoparticle concentration, evaporator, and condenser temperatures on the performance of the system are thermodynamically evaluated. The theoretical analysis based on the first and second laws of thermodynamics indicates that using ZnO nanoparticles enables an enhanced Solar Cooling Efficiency (SCE) and Coefficient of Performance of the system by more than 30%, from 21 to 28% and from 9 to 12%, respectively, for various nanoparticle concentrations ranging from 0 to 6%. The use of the nanofluid results in a 1–6% decrease in the total heat exchanger area compared to pure water in the solar-collector circuit. Finally, it is reported that using R290 enhances the SCE by 3%, compared to a system employing R134a as the refrigerant. [ABSTRACT FROM AUTHOR]

• A dynamic model of a falling film water evaporator with recirculation is presented. • The evolution of wetted area is characterized via experimental tests. • The wettability factor is correlated to film Reynolds and Prandtl numbers. • The model can be integrated in the dynamic simulation of adsorption cycles. The objective of the present study was to develop a dynamic model to simulate a prototype falling-film evaporator that is part of a single-bed adsorption chiller test bench located at the Department of Energy of the Politecnico di Milano. The model is based on the evaporator energy and mass balances and was calibrated and validated using experimental data coming from realistic operating conditions in a range of inlet chilled water temperatures (T i n , c h w) from 15 to 25°C. From the experimental data, it was obtained that the average overall heat transfer conductance (U A) was approximately 530 W/K for all temperatures during the quasi steady-state section of the process. A correlation to calculate the wetted surface through a variable called wettability factor (f w e t) was developed from experimental data. The f w e t factors were identified using the model and were in the range of 0.80 – 0.20 (T i n , c h w = 15°C) and 0.60 – 0.20 (T i n , c h w = 25°C). It was seen that, the higher the T i n , c h w , the lower the f w e t values. The U A and saturation temperature (T r e f , s a t) values from the model were in good accordance with experimental data during the quasi steady-state section of the process. Nevertheless, the final transition stage (i.e., a situation in which the evaporator's refrigerant pool is empty) required an additional hypothesis due to the uncertain process' dynamics. The mass and energy balances that are part of the hydrodynamics and heat transfer sections of the model use Nusselt's classic theory for falling-film. [ABSTRACT FROM AUTHOR]

[Display omitted] • A characterization of each component within a solid desiccation plant is carried out. • An experimental investigation was conducted on desiccant plant installed for the 1st liver on the Algerian coast. • The system was simulated with TRNSYS and validated against experimental data collected under Algerian climatic conditions. An experimental investigation of a solid desiccant cooling system for a research laboratory on the Algerian coast has been carried out. The system utilized flat-plate solar collectors for regeneration and was evaluated through a combination of individual component characterization, system modeling (using TRNSYS), and experimental validation. The results obtained have been validated and show that the efficiency of the rotary heat exchanger reached 65 %, the evaporative humidifier efficiency reached 94 %, and the desiccant wheel achieved efficiencies of 73 % on the process side and 66 % on the regeneration side. This translates to a significant dehumidification effect, reducing absolute humidity in the treated air by 9 g/kg, for the supply air temperature effectively maintained at a comfortable 24 °C. The close agreement between the simulated and experimental COP values (1.13 and 1.08, respectively) validates the chosen approach and confirms the potential of this technology for energy-efficient building cooling in the hot and humid Mediterranean climate of northern Algeria. [ABSTRACT FROM AUTHOR]

• Numerical analysis of Solid-solid PCM storage integration with absorption chiller. • Customized solar collector and storage sizes for modern and outdated buildings. • Innovative tree-shaped storage enhances latent heat exploitation and heat rate. • Storage capacity set at 487.8 kg for modern buildings, 382.0 kg for outdated ones. • Thermal storage achieves up to 97.70% − 98.21% efficiency during discharge. This manuscript presents a comprehensive analysis of a solar cooling system, integrating a latent heat thermal energy storage (LHTES) with an absorption chiller, alongside a solar collectors' field. The LHTES employs solid–solid phase change material (PCM), while the solar collectors belong to the parabolic type. Real-case boundary conditions are derived through the thorough examination of the overall system, encompassing user demands and operational dynamics. In particular, the study evaluates two distinct building scenarios, i.e., modern, and outdated buildings, considering both existing and new structures, to assess the flexibility and adaptability of the LHTES system to varying cooling demands. The preliminary system analysis gives a set of boundary conditions for the subsequent storage sizing and numerical simulations. Building upon these insights, the manuscript introduces a novel storage design inspired by tree-shaped configurations. This design – numerically simulated through a finite element code – aims to enhance heat spreading throughout the solid–solid PCM and maximize latent heat exploitation, thereby improving overall system efficiency and performance. The sizing of the storage system results in 487.8 kg, and 382.0 kg, for the modern and outdated building, respectively, and storage efficiency reaches a value of 86.15 % and 71.84 % for the charging phase and 97.70 % and 98.21 % for the discharging one, respectively. These results demonstrate the high instantaneous heat rate of the proposed LHTES, leading to high efficiencies in the charging and discharging phases. [ABSTRACT FROM AUTHOR]

Today, the fastest growing end-use in the buildings sector is cooling demand, notes the International Energy Agency (IEA). In the last few years, the interest in solar cooling systems has been growing globally. Solar cooling systems are the next solution to meet the growing demand for air conditioning. The literature analysis shows that solar cooling systems mainly use single-stage absorption chillers, with water as the working fluid, and only a small fraction of them use phase change materials to improve heat storage. Based on previous studies on solar-assisted cooling systems, the use of phase change materials for thermal storage should be investigated. The paper will present a study of a solar cooling system with the optimized PCM thermal storage, with the aim of stabilizing the operation of heat storage, taking into account the volatility of solar energy, the impact of short-term operations and peak hours on the amount of heat produced. This means that the amount of electricity consumed to heat up the accumulation tank will be significantly reduced. The optimization model in simulation software will be performed to test solar cooling system with latent heat storage, with aim to investigate the efficiency of the developed latent energy storage and provide technical guidance for the implementation of such system in the practice. All indicators, including environmental impact and economic calculations, will be identified in order to determinate the specific systems for foresight market uptake. [ABSTRACT FROM AUTHOR]

Maintaining mechanical ventilation has been identified as a potential strategy for reducing the risk of virus infections. However, in hot and humid climatic conditions, delivering fresh air to a building comes at an energy cost and could impact occupant comfort due to the persistent need for simultaneous cooling and dehumidification. In this paper, the performance of a novel hybrid air conditioning system that handles fresh air is studied. In this system, dehumidification is accomplished by a solid desiccant dehumidifier coupled with a cooling coil integrated with the cooling tower of an existing chiller system. Using the data available from an operational desiccant cooling system, a system-level model has been developed and validated to study the potential application of the system in hot and humid climates. The study found that such a system is effective in delivering sensible cooling in all types of climates; thanks to the two-stage cooling in cooling coil and chilled water coils, respectively. However, the system is effective in delivering thermal comfort in regions where the climate has a relatively moderate ambient humidity. For the tropical cities of Darwin, Kuala Lumpur and Bangkok, the system can provide comfortable temperatures, but faces challenges in keeping the humidity within the comfort zone. The system electrical coefficient of performance (COP) is higher than that of refrigerative systems. This system also has the benefit over the refrigerative system of the supply air, which is entirely fresh ambient air and is expected to improve the indoor environmental quality largely. [ABSTRACT FROM AUTHOR]

This paper proposes a solar jet-compression composite cooling system with phase change microcapsule storage and build a cooling storage-type solar composite refrigeration system and operational performance test platform. A microencapsulated suspension with a base solution of deionized water was prepared, and sodium dodecyl sulfate (SDS) 0.2%, xanthan gum 0.2%, and sodium chloride (NaCl) 0.5% were added. The operating characteristics of the solar cooling system and the variation in the storage performance of the phase change material under evaporation temperatures of −5 °C and −10 °C and suspension mass fractions of 10% and 15% were investigated. It was found that the temperature of the suspension with a 15% mass fraction decreased by 7.34 °C when the storage time reached 100 min and that of the suspension with a 10% mass fraction decreased by 8.20 °C in the same storage time. The storage capacity of the microencapsulated suspension was greater than that of water within the same storage time. The storage capacity of the 10% suspension at 33 min is 2765.01 kJ, which is 63.1% more than that of water, indicating that the suspension has better storage performance. [ABSTRACT FROM AUTHOR]

Solar cooling systems, specifically solar absorption cooling systems, are becoming an attractive subject since they are great alternatives to the conventional cooling systems which lead to high electrical consumption. In addition, this system can provide cooling without greenhouse gas emissions. Hence, many combinations of different components might be adopted to apply the solar absorption cooling system. This paper will discuss the absorption chiller working cycle, the absorption chiller working fluids, the solar collectors to be combined with solar cooling systems and the single-effect absorption chiller. Furthermore, the variation of the coefficient of performance, the solar fraction and the economic study will be discussed. The goal of this review is to present previous studies and analyze their results; highlight the environmental, energetic, and economic viability of such systems and tackle future challenges regarding solar absorption cooling system and discuss the application of this system on new climates and more specifically on Lebanon.