Lithium chloride - Expanded graphite composite sorbent for solar powered ice maker

Consolidated composite material made from expanded graphite (EG) powder impregnated with LiCl salt is proposed for use in solar powered adsorption ice makers. Laboratory experiments were done to test the adsorption and desorption performance of the sorbent under different temperature conditions suitable for solar energy utilization. More than 75% of the reaction between LiCl and ammonia was completed after 30 min of synthesis at evaporation temperatures of −10 and −5 °C and adsorption temperature between 25 and 35 °C. Under the same period, it was possible to obtain 80% conversion in the desorption phase, when the generation temperatures ranged between 75 and 80 °C, and the condensation temperature varied from 25 to 35 °C. The highest average specific cooling power during the synthesis phase was 117 W per kg of the block. The calculated theoretical coefficient of performance (COP) under different cycle conditions was nearly constant at 0.47. Moreover, the new composite sorbent showed higher Specific Cooling Capacity (SCC), compared to activated carbon (AC)/methanol pair. Experiments done with blocks with different proportion of EG, showed that the proportion of EG influence the cooling capacity per unit mass of salt and had almost no influence on the cooling capacity per unit mass of the block. Moreover, the reaction enthalpy (ΔH) and entropy (ΔS) were calculated from experimental data obtained experimentally, and confirmed previous reported values.     

An energy efficient hybrid system of solar powered water heater and adsorption ice maker

A new hybrid system of solar powered water heater and adsorption ice maker has been proposed. The working principle of the combined cycles of solar refrigeration and heating is described, theoretical simulation to the thermodynamic processes has been made. Experiments have been performed in a developed prototype hybrid system; it is verified that the hybrid system is capable of heating 60 kg water to about 90°C as well as producing ice at 10 kg per day with a 2-m² solar collector.     

民用型太阳能制冰机的研究

在传统大阳能制冰机实验研究基础上,对1m^2的太阳能制冰机按产业化生产的技术要求进行了样机的设计与研发,所试制样机从外观要求,结构配置,系统操作上均克服了以往样机试验中的缺陷,使太阳能制冰机真正走入了产业化生产的流水线,所试制样机可直接进入市场。     

Design of solar powered adsorption heat pump with ice storage

The design and performance of a solar (and/or natural gas) powered adsorption (desiccant-vapor) heat pump for residential cooling (and heating) is described. The entire system is modeled and analyzed: adsorption heat pump itself, ice thermal storage reservoir, and solar collectors. The adsorption heat pump embodies patent pending improvements to the state-of-the-art which elevate coefficient of performance for cooling from a maximum of 1.2 reported in the literature to a conservatively predicted minimum of 1.5. The adsorption device utilizes economical, robust configurations (shell-and-tube) and components (helical annular finned tubes, multi-lumen tubes) commonly employed in heat exchangers in a manner heretofore untried, as well as other enhancements (metal wool to diffuse heat throughout the adsorbent). The vessel is all aluminum and the adsorbent-refrigerant pair is carbon-ammonia. The ice reservoir provides 24 h cooling. Two types of solar collector are determined to be satisfactory at the selected operating temperature of 170 °C: (1) compound parabolic concentrator with high concentration ratio (10+) and automatic tilt adjustment, and (2) evacuated (0.001 atm) flat panel, similar to atmospheric pressure versions employed for domestic water heating.     

Heat and mass transfer in a flat plate solar solid adsorption refrigeration ice maker

A uniform pressure model is presented to describe the heat and mass transfer in an adsorbent bed for a flat plate solar ice maker. This model accounts for heat and mass transfer in a porous bed in a two-dimensional transient process. An experiment has been conducted to validate this model and the calculated results are in good agreement with experiments. With the help of this model, the transient analysis and performance prediction of an intermittent solar powered solid refrigerator can be presented.     

Year round test of a solar adsorption ice maker in Kunming,China

A solar adsorption ice maker with activated carbon–methanol adsorption pair was developed for a practical application. Its main features include utilization of a water cooled condenser and removing all valves in the refrigerant circuit except the one that is necessary for refrigerant charging. Year round performance tests of the solar ice maker were performed in Kunming, Yunnan Province, China. Test results show that the COP (coefficient of performance) of the solar ice maker is about 0.083–0.127, and its daily ice production varies within the range of 3.2–6.5 kg/m² under the climatic conditions of daily solar radiation on the surface of the adsorbent bed being about 15–23 MJ/m² and the daily average ambient temperature being within 7.7–21.1 °C. The suitable daily solar radiation under which the solar ice maker can run effectively in Kunming is above 16 MJ/m².     

Experimental study on dynamic performance analysis of a flat-plate solar solid-adsorption refrigeration for ice maker

A flat-plate solid-adsorption refrigeration ice maker has been built for demonstration purposes. The working pair consists of methanol used as the refrigerant and activated carbon as the adsorption medium. The adsorbent bed is constructed of two flat-plate collectors, with a total surface area of 1.5 m². Solar radiation can be simulated with quartz lamps and some important parameters such as temperature and pressure of each subsystem can be handled by a computer. The experimental results show that this machine can produce 4–5 kg of ice after receiving 14–16 MJ of radiation energy with a surface area of 0.75 m², while producing 7–10 kg of ice after receiving 28–30 MJ of radiation energy with 1.5 m². These are the most advanced results for a solar ice maker so far. All these successful achievements will speed up the commercial processing of a solar ice maker.     

Experimental study on adsorbent of activated carbon with refrigerant of methanol and ethanol for solar ice maker

Two different working pairs, one of them activated carbon–methanol and the other activated carbon–ethanol, are used in a solar ice maker to determine ice production and refrigerant criteria in desorption and adsorption processes under similar radiation energy and environmental conditions. Experimental results show that ice can be produced with activated carbon–methanol, however, ice could not be obtained with the use of activated carbon–ethanol using the same solar ice maker with similar environments and radiation intensities. Further experiments have shown that the adsorbing and desorbing refrigerant amounts of the two working pairs gave quite different results, the activated carbon–methanol has proven to be the superior one of the two working pairs in ice production of solar adsorption refrigeration.     

太阳能与照明

介绍了国内外太阳能光电技术的发展概况,阐述了发展我国太阳能光电照明系统的重要意义,并讨论了目前存在的问题和对策。     

Aluminium maker invests in community solar power

Aluminium maker Alcoa has announced a $1,000,000 program to fund the installation of solar panels at schools and nonprofit agencies in cooperation with Chelan County Public Utility District (PUD). The aluminum maker's endowment will provide direct funds to purchase $439,740 in solar power equipment, plus arrange for labour valued at $666,810 to be donated by Alcoa employees to install the solar systems. Installation of 35 systems in Chelan County, Washington state, USA will be completed by the end of the year.This is a short news story only. Visit www.re-focus.net for the latest renewable energy industry news.     

A new conception of an adsorptive solar-powered ice maker

An experimental data base obtained from specific tests carried out on an adsorptive solar-powered ice maker using methanol/carbon pair and equipped with the collector–condenser technology is analysed and the part of the evaporator in the condensation of the methanol vapour during the desorption phase is highlighted. Consequently, a new adsorptive solar-powered ice maker equipped with a single heat exchanger playing alternatively the role of condenser and evaporator is conceived. When working as a condenser, this heat exchanger is simply cooled by natural convection by means of fins. The estimated heat transfer area of the fins needed to reach the performance of the tested machine (COPs≈12%) is 1.3 m². This new conception of the machine leads to a 30 kg lightening of the metallic mass and enables to equip the collector with airing shutters, in order to improve its nocturnal cooling, which is the limiting factor of the collector–condenser technology. A notable reduction of the manufacturing cost and more than 10% improvement of performance are expected.     

太阳电池助力“神舟七号”翱翔太空

2008年9月25日21时10分04秒,我国航天事业又迎来一个历史性时刻,我国自行研制的神舟七号载人飞船在酒泉卫星发射中心发射升空,21时19分43秒准确进入预定轨道后,飞船张开两只巨大的翅膀--飞船太阳电池阵列,它负责全飞船的用电供应,保证飞船正常飞行.     

Experimental study of a solidified activated carbon-methanol adsorption ice maker

In this paper, the experiments are performed on an adsorption ice maker driven by waste heat, which uses up to two beds. Each bed uses methanol as refrigerant and solidified activated carbon (120 kg adsorbent totally, 60 kg adsorbent per bed) as adsorbent. This system is designed to be driven by the waste heat of a 100 kW diesel engine. The experiments show that the cooling power could be enhanced by the mass recovery process up to 11%, and the heating power could be lowered by the heat recovery process up to 30%. The optimal cooling power of this prototype is about 2.0 kW and corresponds to a specific cooling power (SCP) is about 17 W/kg with both heat and mass recoveries between two beds. Considering the optimal adsorption time is much longer than optimal desorption time at the condition of ice making, the experiments are operated on a single bed (60 kg adsorbent per bed) and the adsorption time used in experiments is two times of desorption time, then the performance of a three-bed adsorption ice maker (120 kg adsorbent totally, 40 kg adsorbent per bed) is predicted by the results of experiments on this single bed. The results of prediction show that both COP and cooling power of three-bed operation could be enhanced greatly compared to the two-bed operation; optimal SCP and COP are respectively 22 W/kg and 0.239 when mass and heat recoveries proceed between three beds. Optimal ice productivity of this three-bed system is 21 kg/h when the water temperature is 25 °C and ice temperature is −7 °C.     

Performance of an adsorptive solar ice maker operating with a single double function heat exchanger (evaporator/condenser)

With the help of an experimental data base, the overall heat transfer coefficient of the double function heat exchanger (condenser/evaporator) of a novel adsorptive solar ice maker (ASIM) was estimated. The calculation shows that this parameter, which is required for simulation, is not constant during the adsorption–evaporation phase and that it is higher during the water freezing phase. With the help of a predictive mathematical model the operation of the studied ASIM was simulated and the results were analysed. They showed that with a consistent design of the different components of this machine the daily ice production could exceed 5.2 kg, with a COPs of more than 0.14. This value of the COPs is very interesting in comparison with those usually obtained from the ASIMs operating with separate condenser and evaporator, i.e. 0.08–0.2, according to the meteorological conditions or technologies.     

A solar powered wireless computer mouse: Industrial design concepts

A solar powered wireless computer mouse (SPM) was chosen to serve as a case study for the evaluation and optimization of industrial design processes of photovoltaic (PV) powered consumer systems. As the design process requires expert knowledge in various technical fields, we assessed and compared the following: appropriate selection of integrated PV type, battery capacity and type, possible electronic circuitries for PV-battery coupling, and material properties concerning mechanical incorporation of PV into the encasing. Besides technical requirements, ergonomic aspects and design aesthetics with respect to good “sun-harvesting” properties influenced the design process. This is particularly important as simulations show users can positively influence energy balances by “sun-bathing” the PV mouse. A total of 15 SPM prototypes were manufactured and tested by actual users. Although user satisfaction proved the SPM concept to be feasible, future research still needs to address user acceptance related to product dimensions and user willingness to pro-actively “sun-bath” PV powered products in greater detail.     

Analysis of solar powered electric water pumps

The increased need for water pumping, especially for domestic use in remote places, together with the accelerated rise of fuel costs, brought about the development of solar powered electric water pumps (SPEWP). The SPEWP consists of a solar cell array, storage of electrical energy or water, controls, an electric motor and a pump. This paper deals with the characteristics of each element in a spewp and its mathematical model. The mathematical model of the whole system is studied and analysed. The solutions of the non-linear equations yield a method for determination of the rate of volume flow, the head of water and the efficiency of the system as a function of the radiation levels.The pump motor is studied and so is its operation point and the torque under varying conditions of the load and the solar energy available. A numerical solution of the mathematical equation is presented describing the torque of the series d.c. motor as a function of its characteristics and the non-linear nature of the solar cell array (SCA). The centrifugal pump operation is analyzed by the torque equation and its variations as a function of the pumped rate of flow and the rotation velocity is studied. A method for determination of the pump parameters is given. Finally, we discuss the principles and method for obtaining the rate of volume flow and the head of water as a function of the radiation levels. The theoretical results are compared to measured ones allowing us to examine the validity of correction factors.The authors believe that this paper contributes to better design of SPEWPs, which, in many cases, even without improvements are being chosen today over conventional water pumping systems.     

Water desalination by solar powered electrodialysis process

Solar energy is a clean source of energy that is available in all regions of the world. Bahrain, where the present research was conducted, is rich in solar energy expressed as hours of sunshine which ranges between 13 h per day in the summer months to 10 h per day in the winter months.Water desalination by solar energy can be effectively achieved by using an electrodialysis process operated with photovoltaic cells. This method is attractive because electrodialysis requires a D.C. power supply as the driving force for removing the salt ions. This experimental work involved a small-scale commercial-type electrodialysis stack powered by photovoltaic cells. The stack consisted of 24 cell pairs, arranged in four hydraulic stages and two electrical stages. The feed water was fed from two sources, the first being sodium chloride solutions prepared in the laboratory and the second was groundwater of medium salinity. The experiments were done at temperatures ranging from 10 to 40 °C and product flow rates ranging from 50 to 300 gallons/day. Increasing the flow rate resulted in lower product quality given in terms of percent salt removal. Increasing the temperature generally resulted in better product quality.