Solar Adsorption System Research Articles

A review on solar air conditioning systems

In order to meet the growing need for cooling in buildings, solar air conditioning systems are a creative and environmentally friendly alternative. Solar energy is the primary energy source for producing chilled air, which can be used to maintain comforting inside temperatures. The working theories and components of several solar air conditioning systems, including hybrid, adsorption, and absorption systems, are thoroughly reviewed in this research. It also discusses the performance, efficiency, and economic feasibility of these systems and their environmental impact. The review highlights the potential benefits of solar air conditioning, such as plummeting greenhouse gas emissions, reducing energy usage, and enhancing indoor air quality. However, the paper also recognizes the limitations and challenges that need to be addressed to increase the widespread adoption of solar air conditioning systems. During our analysis, we found that solar air conditioning systems require consideration in terms of design and technological aspects. Ensuring these systems perform optimally in different climates and are economically viable is crucial. While there are challenges involved such as addressing the variations in resources and the initial setup costs. However, we are witnessing progress through advancements in materials, components, and control strategies. This continuous improvement inspires and reinforces the belief that solar air conditioning can become an accessible cooling solution for applications. This review provides a valuable resource for researchers, engineers, and policymakers interested in promoting sustainable and energy-efficient cooling technologies.

Dynamic performance analysis of a solar adsorption system: the effect of operating conditions and collectors’ area

A continuous adsorption refrigerator, aiming for cold production to a fruit storage room installed in arid regions, is proposed. After cooling load estimation, a technical-economic study of different types of solar collectors was performed. Then, the dynamic performances of a solar-driven two-bed adsorption chiller are studied. Furthermore, this study shows that an optimal choice of the collector-type area and the operating conditions can reduce the global system cost and ensure better energy management. With 43.47 m 2 collectors’ area, a solar fraction of 55% is reached at cycle time (tcycle) 1600s; however, 49% is obtained at tcycle of 900s. With a total collectors’ area of 43.47 m2, a tcycle of 1600s and a cooling water inlet temperature (TCW,in) of 22°C, 60% of the cooling demand is solar produced. However, 57% is achieved at a tcycle of 900s, 50.61 m2 collectors’ area and TCW,in of 25°C. Highlights The cooling load of a storage room used for indigenous fruit preservation was estimated. A technical-economic study of different types of solar collectors is carried out to choose the most suitable one. A detailed dynamic approach to the thermodynamics of a solar adsorption refrigerator according to the time-varying solar radiation intensity and climatic data were presented. The effect of solar collectors’ area and different operating conditions has been studied to optimise the global system performance and cost.

Enhancing thermal performance of latent heat storage unit for solar cooling: A hybrid approach with C-shaped fins and nano-additives

The performance of solar cooling systems is significantly affected by the intermittent nature of solar energy. To address this problem, thermal energy storage systems such as sensible and latent heat storage systems can be a viable option. Among these, the latent heat storage systems are promising due to their high energy storage density and nearly isothermal charging/discharging characteristics. However, the low thermal conductivity of the phase change material used within the storage unit hinders heat transfer, leading to longer charging and discharging periods. To overcome this problem, a hybrid approach that uses fins and nano additives is proposed in this study. A novel C-shaped fin design is introduced that effectively utilises the natural convection current in the molten phase change material. A comprehensive geometrical and material optimisation study is performed to determine the optimal shape, position, and material of the fins. The study also investigates the effect of the inclusion of graphene nanoplatelets (GnP) on the latent heat storage units. An experimental study is conducted to characterise the composite phase change material, and empirical correlations for viscosity and thermal conductivity are developed. The performance of an optimally designed LHS stacked with nano PCM composite of varying mass fractions is also evaluated. The study reveals that the C-shaped fins can reduce melting time by up to 59% compared to conventional fin designs, while PCM dispersed with 1% GnP reduces melting time by 27% when compared to the base PCM. Finally, a two-bed solar vapour adsorption cooling system with a 500 W capacity is considered to conduct a case study for demonstrating the performance of the proposed LHS. The result shows that the solar adsorption system integrated with the proposed heat storage unit can operate up to 3.3 h longer than it currently does. Thus the study presents a promising solution to overcome the obstacles limiting the widespread utilisation of solar cooling systems.

Evaluation and Design of Large-Scale Solar Adsorption Cooling Systems Based on Energetic, Economic and Environmental Performance

In hot and dry regions such as the Gulf Cooperation Council (GCC) countries, the cooling demand is often responsible for more than 70% of electricity consumption, which places a massive strain on the electricity grid and leads to significant emissions. Solar thermal driven Silica-Gel/Water adsorption chillers, used for space cooling, could provide low carbon emission cooling and reduce the reliance on grid electricity. However, a meticulous design is required to make this both economically and environmentally beneficial. This paper aims to evaluate the solar thermal adsorption chiller performance based on large-scale cooling demand through a TRNSYS simulation for 1 year of operation. The proposed system consists of two main parts: first, the solar loop with evacuated tube solar collectors; and second, the adsorption cooling system with a silica-gel/water adsorption chiller. A neighbourhood of 80 typical 197 m2 villas in Riyadh, the capital city of the Kingdom of Saudi Arabia (KSA), was taken as a case study. The solar adsorption cycle’s performance has been compared to the conventional vapour compression cycle in terms of energy, economic and environmental performance. In addition, a parametric study has been performed for the main design parameters. Results reveal that the system can reach a solar fraction of 96% with solar collector area of 5500 m2 and a storage tank volume between 350 and 400 m3. Furthermore, the annual energy cost can be reduced by 74% for the solar adsorption system compared to the conventional vapour compression cycle. Meanwhile, the CO2 saving percentage for the solar adsorption cycle was approximately 75% compared to the conventional vapour compression cycle. Carefully designed solar thermal cooling systems can reduce greenhouse gas emissions while covering a large scale of cooling demands. This can reduce the strain on the electricity grid as well as greenhouse gas emissions.

Desalination of Agricultural Wastewater by Solar Adsorption System: A Numerical Study

There are still areas around the world suffer from severe shortage of freshwater supplies. Desalination technologies are not widely used due to their high energy usage, cost, and environmental damaging effects. In this study, a mathematical model of single-bed adsorption desalination system using silica gel-water as working pair is developed and validated via earlier experiments. A very good match between the model predictions and the experimental results is recorded. The objective is to reveal the factors affecting the productivity of fresh water and cooling effect in the solar adsorption system. The proposed model is setup for solving within the commercially-available software (Engineering Equation Solver). It is implemented to solve the mass and heat balance equations for the adsorbent bed, condenser, and evaporator components. At a typical temperature of 89 °C and flow rate of 30 m3/sec for the hot water entering the bed, the following results are reported: (a) the specific daily water production of 1.89 m3 /ton of silica gel/ day, (b) coefficient of performance of 0.32, and (c) specific cooling power of 40.82 W/kg of silica gel. The concentration of salt (X) in the product (desalinated water) has been set with value of 0.5 gm/kg to be suitable for drinking and irrigation. The salt concentration in the evaporator is estimated to be 4.611 gm/kg during the overall adsorption process. The results from this study should be of wide interest for the field of solar water desalination and air-conditioning.

Performance Analysis of a Solar Cooling System with Equal and Unequal Adsorption/Desorption Operating Time

In solar-thermal adsorption/desorption processes, it is not always possible to preserve equal operating times for the adsorption/desorption modes due to the fluctuating supply nature of the source which largely affects the system’s operating conditions. This paper seeks to examine the impact of adopting unequal adsorption/desorption times on the entire cooling performance of solar adsorption systems. A cooling system with silica gel–water as adsorbent-adsorbate pair has been built and tested under the climatic condition of Iraq. A mathematical model has been established to predict the system performance, and the results are successfully validated via the experimental findings. The results show that, the system can be operational at the unequal adsorption/desorption times. The performance of the system with equal time is almost twice that of the unequal one. The roles of adsorption velocity, adsorption capacity, overall heat transfer coefficient, and the performance of the cooling system are also evaluated.

Dynamic and Economic Investigation of a Solar Thermal-Driven Two-Bed Adsorption Chiller under Perth Climatic Conditions

Performance assessment of a two-bed silica gel-water adsorption refrigeration system driven by solar thermal energy is carried out under a climatic condition typical of Perth, Australia. A Fourier series is used to simulate solar radiation based on the actual data obtained from Meteonorm software, version 7.0 for Perth, Australia. Two economic methodologies, Payback Period and Life-Cycle Saving are used to evaluate the system economics and optimize the need for solar collector areas. The analysis showed that the order of Fourier series did not have a significant impact on the simulation radiation data and a three-order Fourier series was good enough to approximate the actual solar radiation. For a typical summer day, the average cooling capacity of the chiller at peak hour (13:00) is around 11 kW while the cyclic chiller system coefficient of performance (COP) and solar system COP are around 0.5 and 0.3, respectively. The economic analysis showed that the payback period for the solar adsorption system studied was about 11 years and the optimal solar collector area was around 38 m2 if a compound parabolic collector (CPC) panel was used. The study indicated that the utilization of the solar-driven adsorption cooling is economically and technically viable for weather conditions like those in Perth, Australia.

Comparison of the Thermal Performance of Solar Adsorption Cooling System between Egypt and Morocco

This paper presents the thermal performance of a single stage solar adsorption system. The study includes a thermal performance comparison between two different locations in North Africa (Cairo and Casablanca) under different climate conditions. It was found that the solar fraction of the adsorption system is better under Cairo climate due to the relatively low daily solar radiation of Casablanca compared to Cairo. The solar fraction of the cooling plant was investigated theoretically for six months. The effect of the solar collector area and the mass flow rate of the solar loop on the solar fraction were investigated. The solar fraction was computed for 40 and 20 kW auxiliary heater capacity. The required solar collector area for optimum solar fraction was reduced from 140 to 88 m2 with using 20 kW auxiliary heater and reduced to 46 m2 with the 40 kW auxiliary heater using. The results proved that with the mass flow rate of the solar loop increasing from 0.18 to 1.5 kg/s the collector area required decreases from 110 to 60 m2. This study was performed by the TRNSYS simulation using.

Feasibility of solar adsorption air-conditioning in the region of Biskra: Reflection on the government support for electricity bills

In this paper, the feasibility of solar adsorption air conditioning system in the region ofBiskra (Algeria) is studied. The main objective is to give a reflection on the current governmentsupport for electricity bills. A comparison between three air conditioning systems was made bytaking into account economic and environmental constraints: classical mono-split system (A),classical centralized air conditioning chiller (B) and solar adsorption system (C). In the context ofthe current government support for electricity bills, results show that system A is actually thebest choice from the total investment costs, electrical consumption and maintenance point ofview. This is observed even with the gain of the electrical consumption obtained in the case ofsolar adsorption air conditioner (C). From an environmental point of view, the system (C) is moreadvantageous than the classical systems (A) & (B) especially for its use of the solar energy, its lowelectrical consumption, low CO2 emissions and low heat rejected to the outside. It can beconcluded that the current state policy do not encourage the transition to the use of airconditioning systems operate by renewable energies. Thus, the redirection of the current supportfor electricity bills to the support of the investment cost of the solar adsorption air conditioner(C) will make it more competitive in the Algerian market. In this case, system (C) can replace, inthe long-term, the system (A) used actually.

Solar Cooling – A Green Energy Solution for Reducing Food Losses

According to the recent reports of the Food and Agriculture Organization (FAO) of the United Nations, roughly one third of the food produced in the world for human consumption every year get lost or wasted globally, while 800 million people are going into hungry. Saving ¼ of the food which is been wasted will provide the opportunity to feed this 800 million people. Food waste refers in to throwing perfectly edible food into trash at the consumption level while food loss refers to the losses which occur along the food chain that is at the production, harvesting, post-harvest activities and processing phases. Poor handling transport, storage facilities and lack of correct infrastructure cause post-harvest food losses in developing countries. Fresh products like fruits, vegetables, meat and fish straight from the farm or after the harvest can be spoilt in hot climates due to lack of infrastructure for correct transportation, storage, cooling and marketing. Sri Lankan scenario is not much different to the rest of the world where there is about 10-40% loss in fruits and vegetables within food supply chain. There are no country wide valid estimates of looses among other food commodities. Sri Lanka located close to the equator, receives an abundant supply of solar radiation throughout the year. Solar radiation over the island does not show a marked seasonal variation. Due to these reasons, solar cooling is a promising technology to address reducing food losses in Sri Lanka. Solar cooling technology can be applied for food preservation by using it to generate ice or for refrigeration. Different types of ice (blocks or flakes) are typically used to keep fish or milk within the conservation temperature range. These types of ice making facilities are globally available and managed by a community or a cooperative. Solar refrigerators are used for the purpose of conserving fruits and vegetables which operates at a temperature below 100 C. There are many solar refrigeration technologies available such as well known solar photovoltaic systems, solar absorption systems and, solar adsorption systems. Each of these technologies have their own advantages and limitations and most of these technologies are still at the developing stage. There is a global trend towards harnessing solar energy for food preservation and this will be a promising technology to reduce food losses in Sri Lanka. Keywords: Solar cooling, Solar refrigeration, Food losses

Reduction in Auxiliary Energy Consumption in a Solar Adsorption Cooling System by Utilization of Phase Change Materials

This study investigates the efficiency of application of phase change materials (PCMs) in a solar cooling system. The proposed system consists of an adsorption chiller and a latent heat storage unit (LHSU) containing PCMs. The PCM stores solar energy during daytime and at nighttime, the thermal energy stored in the PCM is utilized to drive the adsorption chiller. An auxiliary heater is also used to provide the required energy in addition to the LHSU. To verify the accuracy of the obtained results, the modeling of the solar adsorption system and the PCM unit are validated separately. Moreover, the whole system performance is verified by evaluation of the conservation of energy in the system. The performance of the system is compared with a similar solar adsorption chiller lacking LHSU. Also, the parameters which affect the performance of the LHSU are studied. It is found that application of LHSU decreases auxiliary energy consumption and increases solar fraction. Solar fraction goes up more if larger amount of PCM is used. However, there exists a maximum mass of PCM which can be charged during the sunshine hours. The maximum chargeable mass of PCM goes up by increasing the solar collector area, which leads to decreasing auxiliary energy consumption and increasing solar fraction. The results also show that enlargement of the hot water storage tank reduces auxiliary energy consumption and enhances solar fraction, but decreases thermal storage efficiency. In order to achieve higher thermal storage efficiency and also less auxiliary energy consumption, it is suggested to use average-sized hot water storage tanks.

Performance of a dual-purpose solar continuous adsorption system

A conceptual design and performance of a dual-purpose solar continuous adsorption system for domestic refrigeration and water heating is described. Malaysian activated carbon and methanol are used as the adsorbent–adsorbate pair. The heat rejected by the adsorber beds and condensers during the cooling process of the refrigeration part is recovered and used to heat water for the purpose of domestic consumption. In a continuous 24-h cycle, 16.9 MJ/day of heat can be recovered for heating of water in the storage tanks. In the single-purpose intermittent solar adsorption system, this heat is wasted. The total energy input to the dual-purpose system during a 24-h operation is 61.2 MJ/day and the total energy output is 50 MJ/day. The latter is made up of 44.7 MJ/day for water heating and 5.3 MJ/day for ice making. The amount of ice that can be produced is 12 kg/day. Using typical value for the efficiency of evacuated tube collector of water heating system of 65%, the following coefficient of performances (COP's) are obtained: 44% for adsorption refrigeration cycle, 73% for dual-purpose solar water heater, 9.1% for dual-purpose solar adsorption refrigeration and 82.1% for dual-purpose of both solar water heater and refrigerator.

Thermodynamic analysis and optimization of a combined adsorption heating and cooling system

This paper presents the description and operation of a solar-powered hybrid adsorption ice-maker with activated carbon fibre and methanol as the working pair. The analysis indicates that for the given amount of adsorbent/adsorbate, by adapting more adsorbers instead of conventionally used single adsorber bed, the performance of the adsorption system can be improved. Also, the results show that compared to the change in mass of the adsorbent, the amount of water in the tank influences the system performance to a greater extent. Hence, in the present work, an optimum design has been outlined for a solar hybrid adsorption system employing an evacuated vacuum tube collector with an exposed area of 2 m2 as the heat source. It is shown that, an optimized adsorption system could achieve a coefficient of performance (COP) of about 0.56 and produce around 6 kg of ice a day. Copyright © 2003 John Wiley & Sons, Ltd.