Research on a combined adsorption heating and cooling system

A combined cycle capable of heating and adsorption refrigeration is proposed, and the experimental prototype has been installed. The system consists of a heater, a water bath, an activated carbon–methanol adsorption bed and a ice box. This system has been tested with electric heating, and has been found that with 61 MJ heating, the 120 kg water in the bath can be heated up from 22 to 92 °C meanwhile 9 kg ice of −1.5 °C is made. The calculated COP_system is 0.0591 and COP_cycle is 0.41. After reconstruction to a real hybrid household water heater–refrigerator, when 55 MJ heating is added to 120 kg 21 °C water, and the condensing temperature is controlled at about 30 °C, the result is the 4 kg water contained inside the methanol refrigerant evaporator was iced to −2 °C, the cooling capacity of the ice and the refrigerant in the evaporator will maintain the 100 l cold box for about three days below 5 °C. The experiments show the potentials of the application of the solar powered hybrid water heater and refrigerator. Theoretical simulation has been done, which is in good agreement with experimental results. This research shows that the hybrid solar water heating and ice making is reasonable, and the combined cycle of heating and cooling is meaningful for real applications of adsorption systems.     

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.     

Experiments on heat-regenerative adsorption refrigerator and heat pump

A heat-regenerative adsorption refrigerator using spiral plate heat exchangers as adsorbers and an adsorption heat pump for air conditioning using plate fin heat exchangers as adsorbers have been developed and researched, experimental research results are shown. The activated carbon–methanol adsorption pair is used for the two adsorption systems, which yield a refrigeration power density of more than 2·6 kg ice per day per kg activated carbon and 150 W kg⁻¹ activated carbon for air conditioning, respectively. © 1998 John Wiley & Sons, Ltd.     

Autonomous Adsorption Cooling—Driven by Heat Storage Collected from Solar Heat

This study investigates the performance of an adsorption chiller driven by thermal heat collected from solar collectors’ panels with heat storage. The heat is reserved in a storage tank and the reserved heat is used to drive the adsorption chiller. The investigation was carried on the climatic conditions of Dhaka, Bangladesh. Heat transfer fluid goes from the collectors to the adsorption cooling unit, then from the adsorption cooling unit to the storage tank. It is seen that heat storage is more effective than direct solar coupling; however, it requires more collectors, depending on the size of the storage tank. The analysis shows that cycle time is one of the most influential parameters for the solar-driven adsorption cooling system. It is seen that the size of the collector can be reduced if the proper cycle time is adjusted. The analysis also revealed that the system with 22 collectors (each of 2.415 m²) along with 1000 s cycle time provides better performance for the base run conditions. It is also seen that the solar-driven adsorption chiller with heat storage works well beyond the sunset time.     

Charcoal-methanol adsorption refrigerator powered by a compound parabolic concentrating solar collector

A compound parabolic concentrating solar collector (CPC) of concentration ratio 3.9 and aperture area 2.0 m² was used to power an intermittent solid adsorption refrigerator and ice maker using activated charcoal (carbon) as the adsorbing medium and methanol as the working fluid. The copper tube receiver of the CPC was packed with 2.5 kg of imported adsorbent 207E3, which was only utilised when the performance of activated charcoal (ACJ1, produced from local coconut shells) was found to be inferior to the imported adsorbent. Up to 1 kg of ice at an evaporator temperature of −6°C was produced, with the net solar coefficient of performance (COP) being of the order of 0.02. Maximum receiver/adsorbent temperature recorded was 154°C on a day when the insolation was 26.8 MJ/m⁻². Temperatures in excess of 150°C are undesirable since they favour the conversion of methanol to dimethyl ether, a noncondensable gas which inhibits both condensation and adsorption. The major advantage of this system is its ability to produce ice even on overcast days (insolation 10 MJ/M⁻²).     

Thermodynamic design procedure for solid adsorption solar refrigerator

The thermodynamic design procedure for solid adsorption solar refrigeration is presented and applied to systems using activated carbon/methanol, activated carbon/ammonia and zeolite/water adsorbent/adsorbate pairs. The results obtained showed that zeolite/water is the best pair for air conditioning application while activated carbon/ammonia is preferred for ice making, deep freezing and food preservation. In all cases, the system depends strongly on adsorption and condensation temperatures and weakly on the evaporator temperature. The maximum possible net solar COP was found to be 0.3, 0.19 and 0.16 for zeolite/water, activated carbon/ammonia and activated carbon/methanol, respectively, when a conventional flat plate solar collector is used.     

太阳能固体吸附式制冰机不同吸附工质对的实验研究

在构建的太阳能制冰机的基础上，选用活性炭-甲醇、活性炭-乙醇作为吸附制冷工质对，在外界环境条件及辐射能量条件相同的条件下，分别对两种不同的吸附制冷工质对进行解吸量、吸附量和制冰量的实验。通过对大量实验数据的分析与整理，所得出的结论是：对固体吸附式制冰机装置而言，活性炭-甲醇工质对仍是最佳的吸附制冷工质对，活性炭-乙醇工质对不适合于太阳能固体吸附式制冰机中。     

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.     

Experimentation of a solar adsorption refrigerator in Morocco

For countries with a high potential of solar energy, producing cold using solar energy is a promising way to sustainable development since the energy used is free and not harmful for the environment.This work proposes a solar adsorption refrigerator using the pair activated carbon–methanol, which has been totally built and is under experimental tests in the solar laboratory of the Faculty of Sciences of Rabat, the capital of Morocco with Mediterranean climate.The solar adsorption refrigerator is mainly composed of a collector containing the adsorbent, an evaporator and a condenser. The results show that the refrigerator gives good performance in Rabat. The unit produces cold even in rainy and cloudy days and the temperatures achieved by the unit can be less than −11 °C for days with a very high irradiation. The solar coefficient of performance (COP) (cooling energy/solar energy) ranges between 5% and 8% for an irradiation between 12,000 and 28,000 kJ m⁻² and a daily mean ambient temperature around 20 °C.     

Advanced solar assisted desiccant and evaporative cooling system equipped with wet heat exchangers

This work concerns an innovative solar assisted desiccant and evaporative cooling (DEC) system for building air conditioning. In this system, air-to-air packaged wet heat exchangers are used to maximize the exploitation of the evaporative cooling potential associated with the exhaust air stream.The thermodynamic cycle is first theoretically described, and then an example of a real application is shown.The system presented is an experimental DEC system originally installed at the beginning of 2008 at the Solar Laboratory of the University of Palermo and recently modified and updated. These modifications have been implemented with the aim to foster some problems related to the conventional indirect evaporative process and to increase the overall performance of the process.Different energy performance figures, such as thermal and electrical COP, are presented and discussed.The obtained results are very positive, showing that DEC systems can benefit from the use of wet heat exchangers to efficiently cool the air stream after the adsorption process in the desiccant wheel without any change in moisture content.     

An ice thermal storage computer model

In hot humid countries such as Thailand, air conditioning plant is installed in most commercial and industrial buildings. A conventional air conditioning system, which is normally operated when cooling is required, is the most favored option. Ice thermal storage on a large scale, used to provide a cool reservoir for use in peak periods, is however an attractive financial option for large buildings to supply coolness. There are two means of operating ice thermal storage systems, namely full storage and partial storage.In this paper, a computer model has been developed in order to compare energy use in conventional air cooling systems and ice thermal storage systems. Under Thailand electricity tariff rates, the results from the simulations show that the full ice thermal storage can save up to 55% of the electricity cost required for cooling per month when compared with the conventional system. It is also found that using full storage option can reduce the total energy consumption by 5% for the selected building.     

The optimum performance of a solar-assisted combined absorption–vapor compression system for air conditioning and space heating

The technique of energetic optimization is employed to investigate the optimal performance of an irreversible hybrid air-conditioning/heat pumping system consisting of a vapor compression refrigerator cascaded with a solar-driven absorption refrigerator. To get closer to a real system, the effect of internal irreversibilities on the performance of the hybrid system is considered. The optimal operating temperature of the solar collector and the maximum overall coefficient of performance (COP) of the cooling and heating modes of the system are derived. The results obtained here have more realistic meaning than those of reversible thermodynamics for the optimal design and operation of practical solar-driven hybrid systems.     

Transient analysis and performance prediction of a solid adsorption solar refrigerator

The transient analysis and performance prediction of a solid adsorption solar refrigerator, using activated carbon/methanol adsorbent/adsorbate pair are presented. The mathematical model is based on the thermodynamics of the adsorption process, heat transfer in the collector plate/tube arrangement, and heat and mass transfers within the adsorbent/adsorbate pair. Its numerical model developed from finite element transformation of the resulting equations computes the collector plate and tube temperatures to within 5 °C. The condensate yield and coefficient of performance, COP, were predicted to within 5% and 9%, respectively. The resulting evaporator water temperature was also predicted to within 5 °C. Thus the model is considered a useful design tool for the refrigerator to avoid costly experimentation.     

An efficient solar-powered adsorption chiller and its application in low-temperature grain storage

A novel solar-powered adsorption cooling system for low-temperature grain storage has been built, which consists of a solar-powered water heating system, a silica gel–water adsorption chiller, a cooling tower and a fan coil unit. The adsorption chiller is composed of two identical adsorption units, each of them containing an adsorber, a condenser, and an evaporator/receiver. The two water evaporators have been incorporated into one methanol evaporator by the use of the concept of a gravity heat pipe. In order to improve the system efficiency and achieve continuous cooling production, the adsorbers are operated out-of-phase, and heat and mass recovery processes have been used. During the period from July to September of 2004, the system was put into experimental operation to cool the headspace (i.e., the air volume above the grain) of a grain bin. Three months of operation showed promising performance. The chiller had a cooling power between 66 and 90 W per m² of collector surface, with a daily solar cooling coefficient of performance (COP_solar) ranging from 0.096 to 0.13. The electric cooling COP was between 2.6 and 3.4.     

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.     

Review of passive systems and passive strategies for natural heating and cooling of buildings in Libya

By proper passive design concepts which essentially consist of collection, storage, distribution, and control of thermal energy flow, an energy saving of 2.35% of the world energy output is possible. The basic methods of heating and cooling of buildings are solar radiation, outgoing longwave radiation, water evaporation, and nocturnal radiation cooling. A Trombe-Michel wall consists of a large concrete mass, exposed to sunlight through large, south-facing windows; it is used for heating buildings. Solar absorption cooling and solar dehumidification and evaporative cooling are two approaches that utilize solar energy for the generation of the working fluid and the cooling of dwellings. Outgoing longwave radiation is the most practical way of cooling buildings in desert climates and is effective on roof surfaces, emitting the radiations from the surface of earth to the atmosphere and to outer space. Water evaporation in desert coolers is the usual method of cooling in arid regions. Nocturnal radiation both heats in winter and cools in summer, in suitable climates, and does so with no nonrenewable energy other than a negligible amount required to move the insulation twice a day. The study of 24 different locations in Libya divides the country into regions with distinct passive strategies. The northern region and the Mediterranean coast need passive heating. The buildings in this region should restrict conductive heat flow, prevent infiltration and promote solar heat gains. The southern region, a part of the Sahara desert, needs passive cooling. The buildings in this region need high thermal mass and should promote natural ventilation, restrict solar heat gains and encourage evaporative and radiant cooling. The difficulties encountered in passive solar design are the large exposed area required with suitable orientation for the collection of energy and the large space requirement for the storage of thermal energy. This paper reviews these passive systems and discusses suitable strategies to be adopted for Libya.     

分布式能源在数据中心应用的可行性探析

介绍了分布式能源供能的特点和常见的供能方案,并结合大型数据中心的冷、电需求大及可靠性要求高的用能特点,指出“燃气轮机＋吸收式制冷机＋电制冷机＋冰蓄冷”供能方案更适合大型数据中心供能,该方案以燃气轮机产生电能和制冷量,配合市电、柴油机及中央空调为数据中心供能,提高了数据中心供能可靠性,达到节能减排的效果。     

A new type adsorber for adsorption ice maker on fishing boats

A new type of adsorber for an adsorption ice maker on fishing boats, which uses a compound adsorbent (activated carbon and CaCl₂) and ammonia working pair, is designed. This type of heat pipe adsorber solves the problem of incompatibility between ammonia, copper, seawater and steel. The heating/cooling power for the adsorption/desorption process of the adsorbent, which is required to be transferred by one heat pipe in the adsorber, is computed by the test results of the adsorbent, and the heat transfer performance of one heat pipe in the adsorber is simulated according to the theory of the two phase closed thermosyphon. The heat transfer performance of the heat pipe can meet the heat demands for adsorption/desorption of the adsorbent when the evaporating temperature is −15 °C and the cycle time is 10 min. A test unit is set up to test the heating/cooling performance of the heat pipe type adsorber, and the experimental results are coincident with the simulation. The performance of a two bed adsorption ice maker with heat pipe adsorbers is predicted, and the cooling power is about 17.1–17.8 kW at the evaporating temperature of −15 °C and cycle time of 10 min with mass recovery between two 29 kg compound adsorbent beds.