Solar Cooling Research Articles

Experimental and analytical study on an air-cooled single effect LiBr-H2O absorption chiller driven by evacuated glass tube solar collector for cooling application in residential buildings

Solar cooling turns out to be a feasible method to reduce the electricity consumption of air conditioning systems in buildings. Air-cooled single effect LiBr-H2O absorption chiller has shown advantages in residential applications. It can be driven by common evacuated tube solar collectors, and save water, maintenance expense and space, due to the absence of cooling tower. However, there is no available small capacity commercial air-cooled LiBr-H2O absorption chiller yet, because of the crystallization risk under ambient conditions. In this work, an air-cooled single effect absorption chiller for which the cooling capacity is 6kW and a solar air conditioning system were developed. The air-cooled single effect absorption chiller was fabricated and tested under a broad range of steady-state conditions. The chiller was proved successful for real application without crystallization risk and the influence of different operating conditions was also analyzed. Moreover, the performance of a solar air conditioning system using the proposed chiller was investigated for residential cooling application. The results show that the studied absorption chiller can meet about 65% of the total cooling load of the building with an average COPth of about 0.61. Furthermore, 28% of the titled solar radiation is converted into cooling capacity by the solar air conditioning system.

Cooling mechanism of a solar assisted air conditioner: An investigation based on pressure–enthalpy chart

This paper reports a theoretical study of a conventional vapor compression air conditioner combined with a solar energy source. This system comprises two parts: the cooling mechanism and the solar heat source to operate it. Only the cooling machine part will be considered here, in which the refrigerant temperature leaving the immersed coil inside the storage tank can be calculated directly from the pressure–enthalpy diagram of the operating refrigerant. The investigation has been made using a new low global warming potential refrigerant that belongs to HFO family as an alternative to two high global warming potential refrigerants that belong to HFC family. These are R-1234ze(E) as an alternative to R-134a and R-410A. Comparisons between the classical vapor compression air conditioner and the solar assisted air conditioner and also between the selected refrigerants are investigated. The effects of the refrigerant temperature leaving the storage tank on the main performance parameters such as the coefficient of performance, the gain based on compression work, and the required condenser surface area are discussed.

Selection of Phase Change Material for Thermal Energy Storage in Solar Air Conditioning Systems

The selection of Phase change materials (PCMs) is crucial in the design of Latent Heat Thermal Energy Storage (LHTES) system in solar air conditioning applications. This study performs a systematic selection procedure of PCMs for LHTES in a typical solar air conditioning system. Comprising prescreening, ranking and objective function examination based on multi-criteria decision making (MCDM) tools, this procedure is able to reflect the system goals of LHTES, as well as to take into account designer's subjectivity. Results indicate the proposed approach to be a highly applicable and efficient tool in the LHTES design process.

Performance study of a quasi grid-connected photovoltaic powered DC air conditioner in a hot summer zone

The composition and principle of an air conditioner driven by a quasi grid-connected photovoltaic (PV) system are investigated by analyzing the working principle of quasi grid-connected energy-saving technology. Various aspects, including the PV properties of solar cells, the working principle of storage batteries, the working characteristics of direct current (DC) compressors, and the energy efficiency and economy of solar-powered air conditioners, are considered in the analysis. After an experimental platform is set up, experimental tests are conducted using a conventional air conditioner. Experimental results, as well as the results of the economic analysis based on the experimental platform, reveal that a solar-powered air conditioner can conserve grid electricity by more than 67% and 77% during summer daytime and summer nighttime, respectively. The comprehensive energy efficiency ratio of a solar-powered air conditioner is 4.6 times higher than that of a conventional air conditioner. The air conditioner must run for a maximum of 4h during daytime and 2h during nighttime to maximize its energy-saving ability.

Simulation of a Cold Store Driven by Solar Absorption Cooling System under Different Egyptian Climatic Conditions

Simulation of a Cold Store Driven by Solar Absorption Cooling System under Different Egyptian Climatic Conditions

Simulation of a Cold Store Driven by Solar Absorption Cooling System under Different Egyptian Climatic Conditions

Storing of products at their recommended storage temperatures in a cold store is expensive due to their cost of electricity consumption. In order to avoid the drawbacks of both fossil fuels shortage and chlorofluorocarbon refrigerants, the substitution of a conventional vapor compression refrigeration system by a solar absorption cooling system is a promising alternative to operate the cold stores. Therefore, the main objective of the present work is to simulate and evaluate the performance of solar powered absorption refrigeration system to operate the cold store under Egyptian climatic conditions. To achieve this objective, a simulation model based on the mass and energy conservation equations is developed using TRNSYS software. The results showed that this model predicts data that are very close to the available data in the literature with an average error of 6.21%. The results indicated that the maximum load is 7.12kW in 21- July. Reported results revealed that solar collector area of 100 m2 and storage tank volume of 1.8m3 are required for a maximum cold store load with solar fraction of 0.75.

Modeling and Simulation of an Absorption Solar Cooling System Under Iraqi Weather Conditions

This work aims to model and simulate an absorption cooling system using solar flat- plate receiver with water lithium bromide (li.Br-H2O) mixture as a working fluid, and to select the optimum type for absorption cooling system, which have suitable application in Iraq. Weather conditions for Erbil city have been selected. Coefficient of performance (COP) for a single, double (series and parallel), half and triple effect of an absorption cooling system are calculated and optimized. COP Prediction, hot water temperature, and the rate of heat transfer have been simulated and represented by using TRNSYS and EES programs. Active area of the solar flat-plate receiver is calculated and optimized for five suggested areas of (140, 150, 160, 170, and 180 m 2). Average heating load, average daily - radiation and cooling load for summer months (June, July, August, and September) have been calculated. The results indicated that, the superior type of the four absorption-cooling systems is a single effect, which has COP 80% at generator temperature of (81 °C). Also the results indicated that the optimum area of solar flat-plate receiver was 160 m2 which has achieved the maximum capacity of cooling power and consumed capacity in the generator (50, and 62.5) kW respectively. I think, according to the previous studies , the current work is the first in Iraq because it approved that, single effect type is an efficient and more relevant type for good working under Iraqi climate by using solar flat–plate receiver and suitable to apply it experimentally in a wide range.

A Comprehensive Photonic Approach for Solar Cell Cooling

The heating of a solar cell has significant adverse consequences on both its efficiency and its reliability. Here to fully exploit the cooling potential of solar cells, we experimentally characterized the thermal radiation and solar absorption properties of current silicon solar cells and, on the basis of such experimental characterization, propose a comprehensive photonic approach by simultaneously performing radiative cooling while also selectively utilizing sunlight. In particular, we design a photonic cooler made of one-dimensional photonic films that can strongly radiate heat through its thermal emission while also significantly reflecting the solar spectrum in the sub-band-gap and ultraviolet regimes. We show that applying this photonic cooler to a solar panel can lower the cell temperature by over 5.7 °C. We also show that this photonic cooler can be used in a concentrated photovoltaic system to significantly reduce the solar cell temperature or required cooling power. This photonic cooler can be r...

State of the Art of Solar Absorption Cooling Technologies

State of the Art of Solar Absorption Cooling Technologies

Facades Integrated Solar-thermal Collectors – Challenges and Solutions

The Solar Heating and Cooling Roadmap (2014) set a main focus “on increasing the share of solar thermal energy for the domestic hot water and space heating demand per building, from about 25% to about 60%” with installed systems on or near the buildings. The suitable implementation area at building level is limited, and optimally oriented facades have to be considered. Facades integration adds pre-requisites to the design specifications of the solar thermal collectors, mainly related to the architectural acceptance and good conversion efficiency. A novel solar-thermal collector was developed to specifically address the main challenges brought by facades implementation. The collector with trapeze shape (0.67m2 active area, 69.42% nominal efficiency) is used as building block in arrays with various surface areas, shapes and colors, well matching the variety of the buildings facades. A comparative analysis of the solar-thermal arrays of three trapeze collectors and traditional rectangular collectors is presented in the paper. Three facades of single- and three of multi-family houses are comparatively analyzed considering architectural acceptance, functionality, durability (limited tracking) and thermal power output.

Impact of a vertical geothermal heat exchanger on the solar fraction of a solar cooling system

This paper presents the influence on the solar fraction of coupling a Solar Cooling System (SCS) with a Geothermal Heat Exchanger (GHX). The SCS analysis was made using a mathematical model and was supported by experimental data of a vertical GHX. First, the cooling capacity of the SCS was calculated, considering the cooling load required for a building of 420 m3. The results show that a 12.30 kW cooling capacity SCS would be necessary to satisfy the maximum cooling load requirement during the summer. A 1 kW PV array was considered to assist the SCS. With the constructed GHX a soil temperature model was validated to estimate the temperature of the output water at different GHX depths. The solar fraction meets between 10 and 23% of the energy demand when the condenser is air cooled. However, when a GHX of 1, 2, 4 and 10 m is implemented the solar fraction increases.

Study on Solar Liquid Desiccant Air-conditioning Systems in Xiamen

This paper mainly focuses on the applicability of solar liquid desiccant air conditioning in Xiamen area. We has carried out the following research works: the principle and the feasibility analysis of the solar liquid desiccant air conditioning; design of the solar solution liquid desiccant system; the analysis of solar energy utilization potential combined with the characteristics of Xiamen climate. Based on the economic analysis of the solar desiccant air conditioning in Xiamen, the applicability of the system was prospected.

Techno-Economic Study of PV System for Household Electricity Generation in Almadinah AlMunawwarah

The aim of this work is to study the technological feasibility and economic viability of the electrification of small house lies in a farm 50km far away from Almadinah AlMunawwarah. Nowadays, solar powered air conditioning has witnessed an increased progress because air conditioning system is almost a must in every building in Saudi Arabia where the outside temperature in summer higher than 45◦ C. therefore, this paper consists of two parts: one to investigate the design and performance of solar powered air conditioning system as a case study integrated with photovoltaic (PV) system which consists of PV panels, solar charger, inverter and batteries. The second part is to study the feasibility to provide electricity for a farm lies in the remote area far 50 km from Almadinah. The first step in this project is the load calculations for the selected space including lighting, cooling and other necessary appliances. Based on the cooling load calculations for the specified room used as a case study, it was found the estimated cooling load about 1-ton refrigeration (3.52 kW), the photovoltaic (PV) system has been constructed and built with the necessary connections. Data logging system has been used to measure the temperatures at the main components in the cycle. The input powers for the system as well as the coefficient of performance (COP) for the system under Almadinah climatic conditions were measured along the day. The COP varies between 2.16 to 4.22 for the system and are in a good agreement with conventional system performance. Economically, the PV system found to be the optimal solution to provide the required load at an initial cost of 187,267 SR. The present work shows that the PV system has the potential to provide electricity for remote homes far from the grids with additional environmental benefit that otherwise not gained when using conventional fossil fuel

The Research on Solar Photovoltaic Direct-driven Air Conditioning System in Hot-humid Regions

This research presents a design method of photovoltaic direct-drive air conditioning system, and arranges the photovoltaic direct-drive air conditioning system in an office building in hot-humid regions, the system mainly includes photovoltaic array, storage battery, confluence unit, PWM controller, and air conditioner. Through the test, we found that photovoltaic direct cur-rent air conditioning system is still able to better meet the indoor thermal environment needs even in hot weather. Besides, in the test day, the amount of photovoltaic power generation apart from meeting the demand for air conditioning and there are remaining. The excessively power generation is stored in the battery, it can be self-sufficient for the system, no municipal power grid supplement and energy efficiency is more significant.

A Solar Heating and Cooling System in a Nearly Zero-Energy Building: A Case Study in China

The building sector accounts for more than 40% of the global energy consumption. This consumption may be lowered by reducing building energy requirements and using renewable energy in building energy supply systems. Therefore, a nearly zero-energy building, incorporating a solar heating and cooling system, was designed and built in Beijing, China. The system included a 35.17 kW cooling (10-RT) absorption chiller, an evacuated tube solar collector with an aperture area of 320.6 m2, two hot-water storage tanks (with capacities of 10 m3 and 30 m3, respectively), two cold-water storage tanks (both with a capacity of 10 m3), and a 281 kW cooling tower. Heat pump systems were used as a backup. At a value of 25.2%, the obtained solar fraction associated with the cooling load was close to the design target of 30%. In addition, the daily solar collector efficiency and the chiller coefficient of performance (COP) varied from 0.327 to 0.507 and 0.49 to 0.70, respectively.

Experiment Study on Thermal Conductivity of Microcapsule Phase Change Suspension Applied to Solar Powered Air Conditioning Cold Storage System

This paper presents a novel thermal conductivity measurement of microcapsule phase change materials (MEPCM) suspension. MEPCM suspension applied to solar powered air conditioning cold storage system can significantly save electric energy and improve the system efficiency. The experiment shows that MEPCM suspension’ heat transfer capability is better than conventional cooling medium pure water. The best thermal performance of MEPCM is in the certain temperature range 16℃~17.3℃. The 30% concentration MEPCM suspension have the maximum thermal conductivity. The optimization conditions for solar powered air conditioning cold storage system is further proposed. The results of this paper provides a useful guidance of the design and improvement about solar powered air conditioning cold storage system.

The Collector Matching Analysis of Solar Cooling System Based on Three Kinds of Woking Medium

Solar collector is an important part of solar cooling system, which provides heat source for the generator. With the help of Aspen Plus software, the three working fluid systems of LiBr/H2O, NH3/H2O, and R134a/DMF are established. And this paper analyzes the corresponding collector type for the three systems.We find that When the condensing-temperature is 38℃and the range of dilute solution concentration is 54%~56%, the LiBr/H2O system can choose low solar thermal collector. When the condensing-temperature is up to 42℃, High/Medium solar thermal collector is appropriate for LiBr/H2O. NH3/H2O system can only choose High/Medium solar thermal collector. And R134a/DMF system can choose low solar thermal collector when deflated range is between 0.17 to 0.3; when deflated range is higher than 0.3, R134a/DMF system can choose high solar thermal collector.

Study of the Absorptance of a Thin Layer of the Vanadium Dioxide

Objectives: This work shows the study of the evolution of the CoeffA absorptance of a thin layer of VO2 according to the energy of the incidental photon in order to deduce its optical response in the average I.R, the close I.R, the remote I.R, the visible spectrum and the U.V. Methods/Statistical Analysis: We have used the model of Drude for the thin layer of VO2 in the metal state, and the model of Lorentz for the semiconductor state of this thin layer in order to simulate the optical functions of this material, and in particular the absorptance. An analysis of the maxima and minima of this optical function was made in the two states, semiconductor and metal, according to the model used. Findings: In the semiconductor state of the vanadium dioxide, we noticed that the number of oscillators of Lorentz influences clearly the description of the absorptance and these specific points: maxima and minima. Indeed, the model with seven oscillators is strongly maintained if compared to that of four oscillators. Whereas in the metal state of this thin layer of the vanadium dioxide, the model of Drude with only one oscillator describes the variation of CoeffA according to the energy ω (ev) of the incidental photons in the spectrum from the infra-red to the ultraviolet ray. Application/Improvements: This general study allows the incorporation of this intelligent material in various technological nano applications, like the solar air-conditioners and the thermal pumps.

Solar Heating and Cooling in Buildings – How Sustainable?

Conventional heating and cooling systems are responsible for large amounts of carbon dioxide release to the environment, as well as for the use of harmful refrigerants regarding the greenhouse effect and the ozone depletion potential. Solar radiation is a clean form of energy, which is required for almost all natural processes on earth. In South Africa, the majority of produced electricity is generated from fossil fuels and the potential of renewable energy sources is vast, solar radiation in particular is in abundance. The upper limit for Global Horizontal Irradiance (GHI) in South Africa can be as high as 2 300 kWh/m2/a, whereas the Direct Normal Irradiance (DNI) value attains a maximum of 2 900 kWh/m2/a, which is significantly higher than it is in other regions worldwide. The global air conditioning systems market has been estimated to reach 78.8 million units by 2015 due to increasing living standards, comfort expectations and global warming. South Africa is not the best performer regarding renewable energy use among African countries and there is a long way to go to achieve a sustainable environment. This paper seeks to investigate the feasibility and the sustainability of solar driven air conditioning system in South Africa based on meteological weather data. Currently, renewable energy is a topic of interest in South Africa after the 2008 energy emergency when power outages were rolled out due to inadequate maximum load planning. Solar air conditioning technology remains an untapped technology in South Africa.

Increasing the share of renewables through adsorption solar cooling: A validated case study

Tools and experience on solar thermal cooling system sizing and design are still limited, as less than one thousand plants have been built until now. In this paper, a design tool for mid-size thermal solar cooling systems is presented. The tool consists of a model realised in TRNSYS and validated using the data of a real solar air conditioning system installed in the green building of Shanghai Research Institute of Building Science. Characteristic features of the system are the use of adsorption chillers driven by low-temperature solar heat from U-type and heat pipe evacuated solar collectors. The model has subsequently been employed for a technical analysis: the most relevant parameters have been varied and figures of merit calculated. An energy analysis has been performed for 6 reference cities, differing for climates and latitudes, highlighting the possibility to use only renewable energy for cooling purposes. Eventually, the systems have been compared with reference ones. Comparison highlighted that considerable savings in primary energy and CO2 emissions can be achieved: 0.97 MWh per installed square meter of solar collectors and up to 22 tons of CO2 annually, thus indicating a great potential for increasing energy efficiency and reduce CO2 emissions.