Solar Cooling Research Articles

Development and application of a dynamic model for a solar assisted liquid desiccant air conditioning system

The investigation showed that there were few research works about the real dynamic performance of solar-assisted liquid desiccant air conditioning systems with an unsteady term in the governing equations. Regarding the unsteady properties of the components, a novel dynamic model was developed for a solar-assisted internally cooled liquid desiccant air conditioning system. In the model, the variable t (time) was involved in the governing equations of each component to take into consideration the influence of the previous condition on the following state of the system. The accuracy of the above mathematical model was verified partly with experimental results of some key components. Then the model was applied to a real solar-assisted internally cooled liquid desiccant air conditioning system for an office building with the capacity for eight people in Hong Kong. The transient performance of the system on a summer design day in Hong Kong was investigated. The results reflected the necessity of considering the influence of the former state on the following running of the system. In conclusion, the novel model could be a reliable tool to predicate the system operation and provide useful information for better control of the system.

Low-temperature energy conversion using a phase-change acoustic heat engine

Low-temperature heat is abundant, accessible through solar collectors or as waste heat from a large variety of sources. Thermoacoustic engines convert heat to acoustic work, and are simple, robust devices, potentially containing no moving parts. Currently, such devices generally require high temperatures to operate efficiently and with high power densities. Here, we present a thermoacoustic engine that converts heat to acoustic work at temperature gradients as low as ∼4–5 K/cm, corresponding with a hot-side temperature of ∼50 °C. The system is based on a typical standing-wave design, but the working cycle is modified to include mass transfer, via evaporation and condensation, from a solid surface to the gas mixture sustaining the acoustic field. This introduces a mode of isothermal heat transfer with the potential of providing increased efficiencies – experiments demonstrate a significant reduction in the operating temperature difference, which may be as low as 30 K, and increased output – this ‘wet’ system produces up to 8 times more power than its dry equivalent. Furthermore, a simplified model is formulated and corresponds quite well with experimental observations and offering insight into the underlying mechanism as well as projections for the potential performance of other mixtures. Our results illustrate the potential of such devices for harvesting energy from low-temperature heat sources. The acoustic power may be converted to electricity or, in a reverse cycle, produce cooling – providing a potential path towards solar heat-driven air conditioners.

Energy Saving Potential of a Combined Solar and Natural Gas-Assisted Vapor Absorption Building Cooling System

A building energy simulation study is carried out to analyze the performance of a triple-hybrid single-effect vapor absorption cooling system (VACS) operated by solar, natural gas, and auxiliary electricity-based cogeneration. A high capacity small office building subjected to different climatic conditions is considered. The system is designed to continuously maintain a specified building comfort level throughout the year under diverse environmental conditions. Simulations are done at different generator temperatures to investigate the performance in terms of total annual electric energy consumption, heating energy, and the coefficient of performance (COP). The performance of the present VACS is compared with the conventional compression-based system, which demonstrates the electric energy and cost saving potentials of the proposed VACS. Simulation outcomes are well-validated against benchmark data from national renewable energy laboratory and energy conservation building code. Interestingly, it is found that beyond a certain collector area, surplus energy savings can be acquired with the present triple-hybrid VACS as compared to the compression-based cooling. Results also show that COP of the simulated system is in line with experimental values available in the literature. Finally, recommendations are given to operate the complete system on solar and biomass resources, which provide encouraging opportunity for agriculture-based countries.

Economic Viability of Solar Absorption Cooling System in Pakistan

Economic Viability of Solar Absorption Cooling System in Pakistan

A novel scheme for torque ripple minimization of BLDC motor used in solar air conditioner

The application of BLDC motor is constrained to certain areas due to its drawback of torque ripple. This paper presents a novel scheme of reducing the commutation torque ripple of BLDC motors by injecting additional voltage in the non-commutating phase of the motor. In this work, two independent output voltages with different magnitudes are provided by single-input dual-output (SIDO) converter. One of the voltages (Vdc1) is connected to voltage source inverter which runs BLDC motor. Another voltage (Vdc2) is added to the main voltage (Vdc1) as an additional voltage at the time of commutation between any two phases. The SIDO converter is fed from PV system incorporated with MPPT scheme. The proposed configuration is developed and simulated in MATLAB/Simulink. Results prove the effective utilization of solar power for running the BLDC motor with reduced torque ripple and applicability of the proposed scheme in solar-powered air conditioner.

Investigation on effect of indoor air distribution strategy on solar air-conditioning systems

Abstract Stratum ventilation (SV), a new indoor air distribution strategy, has been promoted for applications in different building premises in recent years. Compared to the conventional mixing ventilation (MV), the prominent advantage of SV is that indoor thermal comfort can be satisfied with a relatively high supply air temperature, hence less energy consumption in refrigeration. In solar air-conditioning, the energy performance can also be facilitated by high-temperature cooling. As such, the potential of SV to be involved in solar air-conditioning was evaluated. In this study, the solar air-conditioning systems included solar absorption cooling system (SAbCS), solar adsorption cooling system (SAdCS), solar desiccant cooling system (SDCS), hybrid solar absorption-desiccant cooling system (HSAbDCS) and hybrid solar adsorption-desiccant cooling system (HSAdDCS). Their performances using SV and MV were determined through year-round dynamic simulation. Compared to the counterpart using MV, SAbCS, SAdCS, SDCS, HSAbDCS and HSAdDCS associated with SV could have 35%, 54%, 59%, 29% and 44% saving in the annual primary energy consumption for building in subtropical climate respectively. Benchmarked with the conventional air-conditioning system, they could have primary energy saving up to 30%. Consequently, solar air-conditioning and SV can have synergetic merit in building application in hot and humid city.

Solar photovoltaic based air cooling system for vehicles

Abstract The conventional automotive air conditioning system was driven by internal combustion engine or power battery, which increased the oil consumption and vehicle carbon emission. In this study, a direct current (DC) air conditioning system powered by solar photovoltaic module (PV) has been designed to solve the problem of temperature increasing inside the vehicle when stops in the broiling summer. The purpose of this work is to design a whole DC air conditioning system with R134a as refrigerant, replacing the power source with solar energy. The result shows that the environmental condition in the vehicle has obviously improved by the DC air conditioning system, meeting the requirements of human bodies. In addition, in the experiment, the minimum refrigerating capacity should be ∼1500 W, maintaining the thermal equilibrium inside the vehicle under the sun blazing, when the vehicle stops and no person inside. The work will prompt further research of solar energy and development of solar electric vehicle air conditioning system.

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.

Feasibility Study of Self-Sufficient Solar Cooling Façade Applications in Different Warm Regions

Small-scale systems and integrated concepts are currently being explored to promote the widespread application of solar cooling technologies in buildings. This article seeks to expand application possibilities by exploring the feasibility of solar cooling integrated façades, as decentralized self-sufficient cooling modules on different warm regions. The climate feasibility of solar electric and solar thermal concepts is evaluated based on solar availability and local cooling demands to be met by current technical possibilities. Numerical calculations are employed for the evaluation, considering statistical climate data; cooling demands per orientation from several simulated scenarios; and state-of-the-art efficiency values of solar cooling technologies, from the specialized literature. The main results show that, in general, warm-dry climates and east/west orientations are better suited for solar cooling façade applications, compared to humid regions and north/south orientations. Results from the base scenario show promising potential for solar thermal technologies, reaching a theoretical solar fraction of 100% in several cases. Application possibilities expand when higher solar array area and lower tilt angle on panels are considered, but these imply aesthetical and constructional constraints for façade design. Finally, recommendations are drafted considering prospects for the exploration of suitable technologies for each location, and façade design considerations for the optimization of the solar input per orientation.

Theoretical investigation on energy storage characteristics of a solar liquid desiccant air conditioning system in Egypt

This work presents theoretical study of a standalone outdoor liquid desiccant air conditioning (LDAC) system assisted by solar energy. The liquid desiccant dehumidification cycle was integrated with a double indirect evaporative air cooler and a regenerative air heat recovery. The double indirect evaporative air cooler was used to recover heat from the return air, while air-air heat exchanger was used to recover heat from air leaving the regenerator. A water-in-glass evacuated tube solar collector was used to supply the system with solar heat. The remaining required heat is provided by natural gas fired boiler. The system was simulated by transient model under thermal energy storage, thermochemical energy storage and combined thermal and thermochemical energy storage modes.The theoretical results show that the mean daily thermal coefficient of performance (TCOP) is a strong function of the difference between absolute humidity ratio of outdoor air and saturated air. Results also show that, each tube of solar collector can deliver 30-Watt to operate the LDAC system under thermal energy storage mode for 16 h daily. While in the LDAC system under thermochemical energy storage mode, each tube would deliver 38.5-Watt for 16 h operation.It has been found that, to rise the solar fraction from 90% to 100% in the thermal energy storage mode, the required size of tubes array will be increased by 20%. Also, an analysis was carried out on the TCOP and required storage volume of the different energy storage modes. It shows that the combined energy storage method is the most energy efficient method.Finally, life cycle cost analysis (LCCA) was carried out for the LDAC system using various types of energy storage modes. The comparison indicated that 90% solar fraction LDAC system is the most economic system related to unit prices of solar collector and gas prices in Egypt. The total annual cost for the 90% solar assisted LDAC system is found to be lower than that of a vapor compression cycle (VCC) by about 50.5%. At the second order, the thermal energy storage mode by 49%. On the other side, the thermochemical energy storage mode is the least cost saving energy storage mode.

Improvement of COP with Heat Recovery Scheme for Solar Adsorption Cooling System

Heat recovery ensures optimum usage of the collected energy, and thus, minimizes heat loss for a solar adsorption chiller. Two-bed adsorption chiller with conventional single stage, run by direct solar coupling with heat recovery, has been studied mathematically. In a heat recovery adsorption refrigeration system, to facilitate heat transfer, heat transfer fluid is distributed between two adsorbers maintaining the same mass flow rate. There is no mass transfer between system components during this phase. It is a semi-continuous system performed between two adsorption beds. After completion of desorption/condensation mode, heat transfer fluid is allowed to circulate between the heated desorber and the cooled adsorber. This process distributes some heat of the desorption bed to the adsorber preparing it for the next preheating mode where heat transfer between them is done adiabatically. Consequently, the performance has been checked and a satisfactory increase in the Coefficient of Performance (COP) (approximately 15%) has been detected in the calculated results for the heat recovery operation. It is also observed that the heat recovery process enhances the working hour and overall performances of the solar heat driven adsorption chiller.

10 key principles for successful solar air conditioning design – A compendium of IEA SHC Task 48 experiences

The results of past and ongoing activities, in successive IEA SHC (solar heating and cooling) Tasks, suggest enormous potential for solar cooling technologies to reduce greenhouse gas emissions. However, solar thermal cooling still faces barriers to emerge as an economically competitive solution. IEA SHC Task 48 was introduced to gather learnings from existing installations, and to find technological and market solutions, which could enable industry to deliver solar thermal driven heating and cooling systems that are efficient, reliable and cost competitive.The selected experiences of these research activities were clustered into 10 qualitative key principles for successful design and operation of SHC systems. Three existing systems are fully discussed in a solar cooling design guide (Mugnier et al., 2017). This paper aims to introduce these key principles in its general format. The background to the qualitative statements is explained, supplemented with examples from the context of Task 48 and compared with recent literature. Furthermore, a survey was conducted among SHC experts, who provide an assessment of the importance of the principles.The result shows that all principles have their eligibility. However, it turns out that there are three main categories of principles: (i) essential, (ii) important and (iii) controversial. Following the key principles is not a guarantee, but they can support researchers, designers and contractors to implement solar heating and cooling systems successfully.

Latent Thermal Storage for Solar Cooling Applications: Materials Characterization and Numerical Optimization of Finned Storage Configurations

ABSTRACTThe present paper presents the development of a thermal energy storage system for application with non-concentrating solar plants using phase change materials (PCMs). The outcomes of an experimental analysis on commercial PCMs and laboratory-grade chemical compounds suitable for latent heat storages in a temperature range of 80–100°C is presented, with main focus on to the enthalpy and the cycle stability of the materials. Particularly, a first evaluation of possible degradation mechanisms in hydrated salts was investigated by means of nuclear magnetic resonance spectroscopy. The best performing materials have been implemented in a numerical model, based on the enthalpy method, used for the design of a thermal storage system. The configuration of the system, starting from a simple shell-and-tube layout, has been optimized by inserting asymmetric fin-and-tubes and the results with two selected materials have been compared. The analysis has shown that the most promising materials are the commercial ones belonging to the classes of paraffinic materials and hydrated salts and that, with the designed configuration, it is possible to store up to 200 kJ/m3 and get a peak power during discharge of about 1.5 kW.

Energy and Economic Performance of Solar Cooling Systems in the Hot-Summer and Cold-Winter Zone

Building energy consumption has distinctly increased in the hot-summer and cold-winter zone in China. Solar cooling technology has been developed to reduce the increasing electricity consumption for air conditioning and to shift the peak load during hot summer days. This paper presents a performance simulation and economic analysis for both photovoltaic (PV) and thermal solar cooling systems compared to a reference system, which is composed of two electric heat pumps. The results show that 30.7% and 30.2% of primary energy can be saved by using the PV and the thermal system, respectively. The payback time is 6–7 years for the PV system, but more than 20 years for the thermal system based on current conditions in China. Therefore, the PV system is more suitable for practical application in the hot-summer and cold-winter zone. The thermal system could be an alternative when middle- and high-temperature solar thermal collector technology has been further developed, as well as following mass production of small- and middle-sized chillers.

Smart Control System to Optimize Time of Use in a Solar-Assisted Air-Conditioning by Ejector for Residential Sector

The present work provides a series of theoretical improvements of a control strategy in order to optimize the time of use of solar air-conditioning by an ejector distributed in multiple solar collectors of vacuum tubes for the residential sector, which will allow us to reduce carbon-dioxide emissions, costs and electrical energy consumption. In a solar ejector cooling system, the instability of the solar source of energy causes an operational conflict between the solar thermal system and ejector cooling cycle. A fuzzy control structure for the supervisory ejector cycle and multi-collector control system is developed: the first control is applied to control the mass flow of the generator and the evaporator for different cooling capacities (3, 3.5, 4, 4.5 and 5 kW) and set a temperature reference according to the operating conditions; the second is applied to keep a constant temperature power source that feeds the low-grade ejector cooling cycle using R134aas refrigerant. For the present work, the temperature of the generator oscillates between 65 °C and 90 °C, a condenser temperature of 30 °C and an evaporator temperature of 10 °C. For the purpose of optimization, there are different levels of performance for time of use: the Mode 0 (economic) gives a performance of 17.55 h, Mode 5 (maximum cooling power) 14.86 h and variable mode (variable mode of capacities) 16.25 h, on average. Simulations are done in MATLAB-Simulink applying fuzzy logic for a mathematical model of the thermal balance. They are compared with two different types of solar radiation: real radiation and disturbed radiation.

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

Experimental analysis of Solar PV Panel Cooling by Using Back Water Tube Array to Improve Efficiency

Experimental analysis of Solar PV Panel Cooling by Using Back Water Tube Array to Improve Efficiency

Optimum Heat Source Temperature and Performance Comparison of LiCl–H2O and LiBr–H2O Type Solar Cooling System

This comprehensive investigation has been executed to compare the thermodynamic performance and optimization of LiCl–H2O and LiBr–H2O type absorption system integrated with flat-plate collectors (FPC), parabolic-trough collectors (PTC), evacuated-tube collectors (ETC), and compound parabolic collectors (CPC). A model of 10 kW is analyzed in engineering equation solver (ees) from thermodynamic perspectives. Solar collectors are integrated with a storage tank which fueled the LiCl–H2O and LiBr–H2O vapor absorption system to produce refrigeration at 7 °C in evaporator for Gujarat Region of India. The main objective includes the evaluation and optimization of critical performance and design parameters to exhibit the best working fluid pair and collector type. Optimum heat source temperature corresponding to energetic and exergetic aspects for LiCl–H2O pair is lower than that of LiBr–H2O pair for all collectors. Simulation shows that FPC has lowest capital cost, exergetic performance wise PTC is optimum, and ETC requires lowest collector area. On the basis of overall evaluation, solar absorption cooling systems are better to be powered by ETC with LiCl–H2O working fluid pair.

Utilization of Solar Energy for Air Conditioning System

The purposes of this research are to do a system simulation of air conditioning utilizing solar energy with single effect absorption refrigeration method, analyze the coefficient of performance (COP) for each absorbent-refrigerant variable and compare the effectivity of every absorbent-refrigerant variable used. COP is a constant that denotes the effeciency of a refrigeration system, that is ratio of work or useful output to the amount of work or energy input. The higher the number of COP, the more efficient the system is. Absorbent-refrigerant (working fluids) variables used in this research depend on its chemical and thermodynamics properties. Steps in this research are including data collection and tabulation from literature and do a simulation of air conditioning system both commercial air conditioning system (using electrical energy) and solar energy air conditioning system with Aspen Plus software. Next, run the simulation for each working fluid variables used and calculate the COP for each variable. Subsequently, analyze and compare the effectivity of all variables used from COP value and economical point of view with commercial air conditioning system. From the result of the simulation, can be concluded that solar air conditioning can achieve 98,85 % of energy savings than commercial air conditioning. Furthermore, from the calculation of COP, the highest COP value is achieved by solar conditioning system with LiNO3-NH3 as working fluid where 55% of the composition is the refrigerant and 45% of absorbent.

Environmental Assessment on Hybrid Solar Air Conditioning System in Tropical Region

Vapour compression systems are widely used in large scale of cooling application in industrial, commercial and institutional buildings. This conventional system did contribute to environmental problem; thus to overcome this issue nowadays, exploitation of solar energy for cooling purpose been studied. This paper presents a hybrid solar air conditioning system through appropriate solution for current problem of vapour compression system. However, solar air conditioning have major issue regarding an intermittence input due to unstable of daily solar radiation. Thus, introduction of thermal energy storage (TES) such as chilled water storage (CWS) foreseen to be the best solution and more economical compared to other types of storage. Through appropriate practicality in design and application, variation on solar collector area was analysed to determine optimum sizing which best suit with environmental factor. Surprisingly, the smallest collector area (150 m2) did shown highest saving on greenhouse gasses emission to environment.